2210 lines
99 KiB
Plaintext
2210 lines
99 KiB
Plaintext
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What You Need To Know About Modems
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December 25, 1991
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Version 1.0
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------------------------------------------------------------------------------
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Copyright (c) 1991 Patrick Chen. All rights reserved.
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Distribution Notice: This document may be distributed by electronic bulletin
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boards and commercial on-line services. This document may not be edited or
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changed in any way for redistribution.
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This article is Part One of a three-part report entitled "The Joy of
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Telecomputing." As a plain ASCII file, it cannot contain any of the
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illustrations and graphic elements provided in the printed version. For
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further information about "The Joy of Telecomputing," see Appendix C.
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This article should be useful to anyone interested in high-speed modems (or
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2400 bps modems with MNP-5 or V.42bis). Most modems mentioned in this article
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are external units. These modems can be used on any microcomputer system, be
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it a PC, a Macintosh or an Amiga. Although only certain communication programs
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are used as examples, the discussions about setting up software apply to
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packages not covered herein.
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It is assumed that the reader knows the basics about going online. For
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example, we would not discuss how to connect an external modem to your
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computer, nor would we explain what 8-N-1 means.
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This file is in the IBM ASCII format. Each line ends with a linefeed and a
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carriage return. If you use a Macintosh, open the file with a text editor and
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get rid of the linefeeds. (I recommend McSink, a shareware text editor widely
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available. Just launch McSink and open the file, then choose the Convert menu
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and select Strip Linefeeds.)
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To print this document, use a 10-pitch (12 characters per inch) mono-spaced
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font such as Courier.
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Every effort has been made to supply complete and accurate information.
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However, information contained herein is subject to change without notice and
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should not be construed as a commitment by the author who assumes no
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responsibilities for any errors that may appear.
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Trademarks: The author has attempted throughout this document to distinguish
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proprietary trademarks from discriptive terms by following the capitalization
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style used by the manufacturer.
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-----------------------------------------------------------------------------
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CONTENTS
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Introduction
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Modulation Protocols
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2400 bps modems
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High-speed modems
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V.32
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V.32bis
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U.S. Robotics HST
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Telebit PEP
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Hayes Express 96
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CompuCom CSP
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Things to come
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V.fast
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ISDN
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Error Control Protocols
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V.42 and MNP-4
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V.42 & MNP-4 can provide error-free connections
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V.42 and MNP-4 can improve throughput
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Are MNP 4/V.42 useful?
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Data Compression Protocols
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MNP-5 & V.42bis
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Are MNP-5 & V.42bis useful?
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Compression by Software vs. MNP-5/V.42bis
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Local Flow Control and Data Buffering
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Macintosh and high-speed modems
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PC and UART
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Profiles of High-speed modems
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ATI 9600etc/e
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CompuCom SpeedModem Champ/Star/Storm
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Hayes modems
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Image Communications: Twincom 96/42
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Intel 9600EX & 14.4EX
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Practical peripherals PM9600SA & PM9600
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Prometheus modems
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Telebit modems
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U.S. Robotics modems
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Zoom V.32 Turbo Modems
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Things to come
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Buying a High-speed Modem
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Should you pay the extra for a V.32bis modem?
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Should you buy a modem with a proprietary modulation protocol?
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Should you buy a 2400 bps modem with V.42bis?
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Beware of the ads
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Setting Up Software to Work with High-speed Modems
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The Proper Software Setup
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Does Your Software Initialize the Modem Properly?
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Does Your Software Configure Itself to Match the Modem Settings?
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Why You May Need to Change the Initialization String
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Editing the Initialization String
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Match Software Settings To the Modem Settings
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Configuring Popular Communications Software to Work with High-speed Modems
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Procomm 2.0
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Telix
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Qmodem
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HyperAccess 5
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Crosstalk for Windows
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MicroPhone II (for Macintosh)
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ZTerm (for Macintosh)
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Other Settings for Your Communications Software
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Telephone Number
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Dial String: ATDT
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8-N-1 or 7-E-1 (data bits-parity-stop bits)
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Half vs. Full Duplex: Local Echo
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Terminal Emulation
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Comm Port
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File Transfer Protocols
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ASCII
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Xmodem
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Xmodem-1K
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Ymodem
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Ymodem-g
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Zmodem
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Kermit
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Sealink
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Which file transfer protocol should you use?
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Appendix A: Resources
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Appendix B: How to reach the author
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Appendix C: About "The Joy of Telecomputing"
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-------------------------------------------------------------------------
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Introduction
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Buying and using a modem used to be relatively easy. Not so long ago,
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almost all modems are 1200 or 2400 bps units and they are all compatible
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with the Hayes Smartmodems (although some are more Hayes-compatible than
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others). How time has changed.
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Today, modems not only run faster, they are also loaded with features
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like error control and data compression. Suddenly, you are confronted
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with all the buzzwords: V.32, V.32bis, V.42, V.42bis, MNP-5, LAP-M, etc.
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What do they mean? And what do they mean to you?
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To make the most of a high-speed modem, you need to understand three
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different kinds of protocols and the relationships among them. They are
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the modulation protocols, error control protocols and data compression
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protocols.
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Modulation Protocols
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Modem stands for MOdulator/DEModulator. A modem converts digital signals
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generated by the computer into analog signals which can be transmitted
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over a telephone line and transforms incoming analog signals into their
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digital equivalents.
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The specific techniques used to encode the digital bits into analog
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signals are called modulation protocols. The various modulation
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protocols define the exact methods of encoding and the data transfer
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speed. In fact, you cannot have a modem without modulation protocols. A
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modem typically supports more than one modulation protocols.
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The raw speed (the speed without data compression) of a modem is
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determined by the modulation protocols. High-speed modems are modems
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that feature modulation protocols at 9600 bps or higher. A 2400 bps
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modem with data compression that can theoretically yield a 9600 bps
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throughput is not a high-speed modem.
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"CCITT" is a French acronym for the International Telegraph and
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Telephone Consultative Committee. CCITT, a United Nations agency, is an
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international telecommunications standards committee that makes
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recommendations on a broad range of subjects concerning data
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communications.
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2400 bps Modems
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A 2400 bps Hayes-compatible modem typically supports the following
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modulation protocols:
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Bell 103 (300 bps U.S. Standard)
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Bell 212A (1200 bps U.S. Standard)
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CCITT V.22 (1200 bps standard used outside the U.S.)
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CCITT V.22bis (2400 bps International Standard)
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Some 2400 bps modems also support the following protocols:
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CCITT V.21 (300 bps standard used outside the U.S.)
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CCITT V.23 (1200/75 and 75/1200 bps, used in Europe)
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In the past, most 2400 bps modems do not support any error correction or
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data compression protocols. Recently, however, many modem manufacturers
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have introduced 2400 bps modems with extra features like data
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compression, error correction and fax capability.
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High-speed Modems
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There are two standard modulation protocols for high-speed modems: V.32
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and V.32bis. Both are standards established by the CCITT.
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V.32
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This is the standard for 9600 (and 4800) bps modems. CCITT V.32 is
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adopted by the CCITT in 1984. But the market has not taken off until
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recently. V.32 modems used to cost more than modems using proprietary
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modulation protocols (Hayes introduced the Smartmodem 9600, a V.32
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modem, in 1988 with a $1999 price tag). But it is no longer true. At
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present, street prices for most V.32 modem are below $500. Every modem
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manufacturer is making V.32 modems now. Packet-switching networks like
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Sprintnet (Telenet) and CompuServe are also starting to support V.32
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modems. Companies that make modems with proprietary modulation protocols
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are making modems with "dual standard." U.S. Robotics, Telebit, Hayes
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and CompuCom all have modems that support V.32 and their own proprietary
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protocols.
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V.32bis
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V.32bis, established in early 1991, is the CCITT standard for 14400 bps
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modems. A V.32bis modem also can fall back to 12000, 9600, 7200 and 4800
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bps. V.32bis is downwardly compatible with V.32.
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Unlike 2400 bps modems where a single modulation protocol (V.22bis) is
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supported by all modem makers, there are several proprietary modulation
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protocols used by modems from different manufacturers.
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U.S. Robotics HST (High Speed Technology)
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Until the recent surge of V.32 modems, the U.S. Robotics HST was the de
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facto standard in the PC-based BBS community. U.S. Robotics introduced
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the Courier HST modem in 1986 and pioneered the market for high-speed
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modems in the IBM PC environment. The immense popularity of the HST
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modems was partly due to the generous discount program U.S. Robotics
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offered to the BBS Sysops (SYStem OPerators). Many modem manufacturers
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have implemented similar Sysop discount programs, but most BBS sysops
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remain loyal to the U.S. Robotics modems.
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The original Courier HST modem ran at 9600 bps. U.S. Robotics later
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improved the speed of the Courier HST to 14400 bps.
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Although U.S. Robotics remains committed to the HST modems, there are
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now three different high-speed Courier modems available: the Courier HST
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(which only supports the HST protocol), the Courier V.32bis (which only
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supports V.32bis) and the Courier HST Dual Standard (which supports both
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the HST and the V.32bis protocols).
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Telebit PEP (Packetized Ensemble Protocol)
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Telebit introduced the TrailBlazer in 1985 that employed a proprietary
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modulation protocol called PEP. While the Courier HST is popular among
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BBS, Telebit modems dominate the UNIX UUCP and Usenet communities.
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(Usenet, UUCP and the Internet are discussed in Part II of "The Joy of
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Telecomputing").
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The TrailBlazer Plus owes its success partly to its built-in support for
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the UUCP g-protocol, thus allowing efficient and flawless UUCP session.
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PEP also performs well even with noisy telephone lines. The actual
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throughput is around 14400 bps. The TrailBlazer Plus has an installed
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base of more than 120,000 units.
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Telebit also introduced a cheaper (and slower) PEP modem, the T1000, in
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1988.
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Hayes Express 96
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Hayes entered the high-speed modem arena in 1987 with the introduction
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of the V-series Smartmodem 9600. The modem used a proprietary modulation
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protocol called Express 96 (also known as Hayes "Ping Pong" protocol).
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The V-series modems have not been as successful as the U.S. Robotics or
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the Telebit modems.
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CompuCom CSP (CompuCom Speed Protocol)
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While every modem manufacturer is jumping on the V.32 bandwagon,
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CompuCom bucked the trend and came out with the SpeedModem Champ in
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early 1991. It's a 9600 bps modem with a proprietary modulation
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protocol called CSP. The SpeedModem Champ has one strong selling point.
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It is the only modem with a proprietary protocol that costs less than a
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generic V.32 modem. The internal SpeedModem Champ is priced at $169. An
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external version is available for $199. Hundreds of PC-based bulletin
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board systems have installed the SpeedModem Champ. The Champ also works
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as a Hayes-compatible 2400 bps modem with MNP 2-4 error control and
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MNP-5 data compression.
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Two modems can establish a connection only when they share a common
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modulation protocol. To connect at high speed, two modems have to
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support the same high-speed modulation protocol. Therefore, a modem with
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a proprietary modulation protocol can only establish a high-speed
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connection with another modem from the same manufacturer. A U.S.
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Robotics HST modem can only establish a high-speed connection (at 9600
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or 14400 bps) with another HST or an USR Dual Standard modem. A Courier
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HST modem cannot establish a high-speed connection with a Courier
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V.32bis modem. They can only connect at 2400 bps. (All high-speed modems
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in the market support the CCITT V.22bis modulation protocol).
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On the other hand, two V.32 modems can talk to each other at 9600 bps.
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They do not have to be from the same manufacturer. Two V.32bis modems
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can talk to each other at 14400 bps. A V.32 modem can talk to a V.32bis
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modem at 9600 bps.
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Things to come
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V.fast
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CCITT is working on a new modem standard, dubbed V.fast. If all goes
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well, the next modem standard can materialize before 1993. A V.fast
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modem is expected to reach a raw speed of 19,200-24,000 bps over
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standard dial-up telephone lines.
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ISDN
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In a couple of years we may not need modems at all. Integrated Services
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Digital Network (ISDN) has been coming for years. When will ISDN really
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become available for the rest of us? It depends on your local telephone
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company. It is estimated that by the end of 1994 about half the
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telephone connections in the U.S. will has access to it. With ISDN, you
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won't need a modem since no modulation or demodulation will be
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necessary. You will need an ISDN adapter instead.
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An ISDN line carries three digital channels: two "B" channels that carry
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various kinds of data at 64,000 bps and a "D" channel at 16,000 bps that
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can carry control signals or serve as a third data channel.
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A single ISDN channel can transfer uncompressed data bidirectionally at
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64,000 bps. Combine that with a data compression scheme and you will be
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able to transfer data at hundreds of kilobits per second.
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Eventually, ISDN will provide widely available, low-cost digital
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communications for voice and data communication. Until ISDN is firmly in
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place, high-speed modems will be with us for a while.
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Error Control (Error-Correcting, Error Correction) Protocols
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Besides high-speed modulation protocols, all current models of
|
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high-speed modems also support error control and data compression
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protocols.
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V.42 and MNP-4
|
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There are two standards for error control protocols: MNP 4 and V.42. The
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Microcom Networking Protocol, MNP, is developed by Microcom. MNP 2 to 4
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are error correction protocols. MNP-5 is a data compression protocol.
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V.42 is established by CCITT. V.42 actually incorporates two error
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control schemes. V.42 uses LAP-M (Link Access Procedure for Modems) as
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the primary scheme and includes MNP-4 as the alternate scheme.
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Therefore, a V.42 modem will be able to establish an error-controlled
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connection with a modem that only supports MNP 4.
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A modem that uses a proprietary modulation protocol may also use a
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non-standard error control protocol. For example, Hayes V-series
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Smartmodem 9600 supports an error control protocol called LAP-B.
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CompuCom's SpeedModem Champ also uses a non-standard error control
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protocol.
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V.42 & MNP-4 can provide error-free connections
|
||
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|
|
||
|
|
Modems without error control protocols, such as most 2400 bps
|
||
|
|
Hayes-compatible modems, cannot provide error-free data communications.
|
||
|
|
The noise and other phone line anomalies are beyond the capabilities of
|
||
|
|
any standard modem to deliver error-free data.
|
||
|
|
|
||
|
|
V.42 (and MNP 2-4) copes with the phone line impairments by filtering
|
||
|
|
out the line noise and automatically retransmitting corrupted data. If
|
||
|
|
you have used a standard Hayes-compatible modem, you probably notice
|
||
|
|
some garbled characters (like "@8d_\nw`[ce") show up on your screen from
|
||
|
|
time to time. When two modems establish an error-controlled connection,
|
||
|
|
they are said to have a reliable link and are capable of filtering out
|
||
|
|
those garbled characters caused by the line noise. Notice that the line
|
||
|
|
noise is still there, it just does not show up on your screen or the
|
||
|
|
screen on the remote system.
|
||
|
|
|
||
|
|
The filtering process used by V.42 (and MNP 2-4) is similar to the error
|
||
|
|
correction scheme used by file transfer protocols (such as Xmodem). The
|
||
|
|
two modems use a sophisticated algorithm to make sure that the data
|
||
|
|
received match with the data sent. If there is a discrepancy, the data
|
||
|
|
is resent.
|
||
|
|
|
||
|
|
What is the difference between error control protocols (such as V.42)
|
||
|
|
and file transfer protocols (such as Xmodem)?
|
||
|
|
|
||
|
|
For one thing, file transfer protocols provide error detection and
|
||
|
|
correction only during file transfers. File transfer protocols do not
|
||
|
|
provide any error control when you are reading e-mail messages or
|
||
|
|
chatting with other people online. In other words, an error control
|
||
|
|
protocol is "on" all the time during your online session and file
|
||
|
|
transfer protocols are "on" only some of the times, namely when you are
|
||
|
|
sending or receiving files.
|
||
|
|
|
||
|
|
Even though an error control protocol is "on" all the time, we still
|
||
|
|
need file transfer protocols when two modems establish a reliable link.
|
||
|
|
A modem works with bit streams, timing and tones. It does not understand
|
||
|
|
what a file is. When you download or upload a file, your communications
|
||
|
|
software needs to take care of the details related to the file: the
|
||
|
|
filename, file size, etc. This is handled by the file transfer protocol
|
||
|
|
which does more than error-checking.
|
||
|
|
|
||
|
|
Some file transfer protocols, most notably Ymodem-g and Imodem, are
|
||
|
|
developed to handle file transfer without performing any error-checking.
|
||
|
|
The idea of using a protocol like Ymodem-g is to eliminate the
|
||
|
|
redundancy thus improve the transfer speed. Ymodem-g and Imodem should
|
||
|
|
only be used with modems that provide built-in error control protocols.
|
||
|
|
These file transfer protocols do not provide any error-detection or
|
||
|
|
recovery capability. If a problem occurs during the file transfer, the
|
||
|
|
transfer session will be aborted.
|
||
|
|
|
||
|
|
Protocols like Ymodem-g or Imodem depend on the modems to provide
|
||
|
|
assurance for the integrity of data being transferred. However, you
|
||
|
|
should know that a reliable link between two modems does not provide
|
||
|
|
absolute guarantee for the data integrity during file transfer. When you
|
||
|
|
call a remote computer, there are really three links involved in the
|
||
|
|
process. Besides the link between the two modems, there are still one
|
||
|
|
link between your computer and your modem and another link between the
|
||
|
|
remote modem and the remote computer. When two modems make a reliable
|
||
|
|
connection using V.42 or MNP 4, only the data integrity between the two
|
||
|
|
modems is ensured. It is still possible for errors to occur at either
|
||
|
|
end between the serial port and the modem (in the cable) or in the
|
||
|
|
computer itself. (Fortunately, such errors are rare.)
|
||
|
|
|
||
|
|
For extra protection, you may still want to use a file transfer protocol
|
||
|
|
- such as Zmodem - which also performs error checking even if you have a
|
||
|
|
reliable link with the remote system. There is a common misconception
|
||
|
|
that Ymodem-g is much faster than other file transfer protocols.
|
||
|
|
Although Ymodem-g is significantly faster than Ymodem, it offers little
|
||
|
|
over Zmodem. Zmodem has proven to be extremely efficient. (See benchmark
|
||
|
|
below)
|
||
|
|
|
||
|
|
|
||
|
|
Filename Ymodem Ymodem-g Zmodem
|
||
|
|
-------------------------------------------------------
|
||
|
|
the-wave.txt 1527 cps 3261 cps 3296 cps
|
||
|
|
dayrpt.arc 761 1042 1025
|
||
|
|
dayrpt.wks 1244 2314 2337
|
||
|
|
sunset.arc 745 987 965
|
||
|
|
sunset.pic 1297 2594 2588
|
||
|
|
text109k.arc 814 1089 1064
|
||
|
|
text109k.txt 1351 2812 2885
|
||
|
|
|
||
|
|
|
||
|
|
Note: The seven test files used throughout this article are available
|
||
|
|
on the Hayes BBS (800-874-2937). It is an excellent source for
|
||
|
|
information about Hayes products. The BBS also provides a database
|
||
|
|
for thousands of BBS in the U.S. Best of all, it is free.
|
||
|
|
|
||
|
|
Unless noted otherwise, the results are obtained by using the
|
||
|
|
following:
|
||
|
|
|
||
|
|
Computer: Mac SE with Mobius Two Page Display with 68030 accelerator
|
||
|
|
Modem: ATI 9600etc/e (the modem is set as V.32 with V.42bis enabled)
|
||
|
|
Operating System: System 7.0
|
||
|
|
Communication Software: ZTerm (Comm port speed set to 38400 bps)
|
||
|
|
File Transfer Protocol: Zmodem
|
||
|
|
|
||
|
|
All results are reported by ZTerm. (I use several communication
|
||
|
|
programs on both IBM PC and Mac. All of them show the average
|
||
|
|
throughput while file transfer is in progress, but ZTerm actually
|
||
|
|
produces a report after the transfer is completed).
|
||
|
|
|
||
|
|
|
||
|
|
V.42 & MNP-4 can improve throughput
|
||
|
|
|
||
|
|
The other benefit of V.42 (or MNP 4) is that it can improve throughput.
|
||
|
|
Before sending the data to a remote system, a modem with V.42 (or MNP 4)
|
||
|
|
assembles the data into packets and during that process it is able to
|
||
|
|
reduce the size of the data by stripping out the start and stop bits.
|
||
|
|
|
||
|
|
A character typically takes up 1 start bit, 8 data bits and 1 stop bit
|
||
|
|
for a total of 10 bits. When two modems establish a reliable link using
|
||
|
|
V.42 or MNP 4, the sending modem strips the start and stop bits (which
|
||
|
|
subtracts 20% of the data) and sends the data to the other end. The
|
||
|
|
receiving modem then reinserts the start and stop bits and pass the data
|
||
|
|
to the remote computer.
|
||
|
|
|
||
|
|
Therefore, even without compressing the data you can expect to see as
|
||
|
|
much as 1150 characters per second on a 9600 bps connection. (Although
|
||
|
|
the modem subtracts 20% of the data, the speed increase is less than 20%
|
||
|
|
due to the overhead incurred by the error control protocol.) Here are
|
||
|
|
the test results obtained by downlaoding the same file (1) without any
|
||
|
|
error control protocol, (2) with MNP-4, and (3) with V.42. No data
|
||
|
|
compression protocol is used.
|
||
|
|
|
||
|
|
|
||
|
|
Filename No EC MNP-4 V.42
|
||
|
|
------------------------------------------------------------------
|
||
|
|
the-wave.txt 935 cps 1151 cps 1128 cps
|
||
|
|
dayrpt.arc 863 1023 1002
|
||
|
|
dayrpt.wks 898 1071 1052
|
||
|
|
sunset.arc 838 971 953
|
||
|
|
sunset.pic 903 1080 1065
|
||
|
|
text109k.arc 908 1085 1064
|
||
|
|
text109k.txt 937 1150 1127
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
Are MNP4 and V.42 useful?
|
||
|
|
Absolutely. Anyone that has ever used a standard modem can appreciate
|
||
|
|
the benefit of an error-free connection. And the increase in data
|
||
|
|
throughput, though modest, is nothing to sneeze at.
|
||
|
|
|
||
|
|
|
||
|
|
Data Compression Protocols
|
||
|
|
|
||
|
|
Besides error control protocols, all current high-speed modems also
|
||
|
|
support data compression protocols. That means the sending modem will
|
||
|
|
compress the data on-the-fly and the receiving modem will decompress the
|
||
|
|
data to its original form.
|
||
|
|
|
||
|
|
MNP-5 and V.42bis
|
||
|
|
|
||
|
|
There are two standards for data compression protocols, MNP-5 and CCITT
|
||
|
|
V.42bis. Some modems also use proprietary data compression protocols.
|
||
|
|
|
||
|
|
A modem cannot support data compression without utilizing an error
|
||
|
|
control protocol, although it is possible to have a modem that only
|
||
|
|
supports an error control protocol but not any data compression
|
||
|
|
protocol. A MNP-5 modem requires MNP 4 error control protocol and a
|
||
|
|
V.42bis modem requires V.42 error control protocol.
|
||
|
|
|
||
|
|
Also note that although V.42 include MNP-4, V.42bis does not include
|
||
|
|
MNP-5. However, virtually all high-speed modems that support CCITT
|
||
|
|
V.42bis also incorporate MNP-5.
|
||
|
|
|
||
|
|
The maximum compression ratio that a MNP-5 modem can achieve is 2:1.
|
||
|
|
That is to say, a 9600 bps MNP-5 modem can transfer data up to 19200
|
||
|
|
bps. The maximum compression ratio for a V.42bis modem is 4:1. That is
|
||
|
|
why all those V.32 modem manufacturers claim that their modems provide
|
||
|
|
throughput up to 38400 bps.
|
||
|
|
|
||
|
|
Are MNP-5 and V.42bis useful?
|
||
|
|
|
||
|
|
Don't be fooled by the claim. It is extremely rare, if ever, that you
|
||
|
|
will be able to transfer files at 38400 bps. In fact, V.42bis and MNP-5
|
||
|
|
are not very useful when you are downloading files from online services.
|
||
|
|
Why?
|
||
|
|
|
||
|
|
How well the modem compression works depends on what kind of files are
|
||
|
|
being transferred. In general, you will be able to achieve twice the
|
||
|
|
speed for transferring a standard text file (like the one you are
|
||
|
|
reading right now). Decreasing by 50% means that you can double the
|
||
|
|
throughput on the line so that a 9600 bps modem can effectively transmit
|
||
|
|
19200 bps.
|
||
|
|
|
||
|
|
V.42bis and MNP-5 modem cannot compress a file which is already
|
||
|
|
compressed by software. In the case of MNP-5, it will even try to
|
||
|
|
compress a precompressed file and actually expand it, thus slow down the
|
||
|
|
file transfer! Here are the test results obtained by downloading the
|
||
|
|
three compressed files using (1) MNP-4 without data compression, (2)
|
||
|
|
MNP-5, (3) V.42 without data compression, and (4) V.42bis.
|
||
|
|
|
||
|
|
|
||
|
|
Filename MNP-4 MNP-5 V.42 V.42bis
|
||
|
|
-------------------------------------------------------------------
|
||
|
|
dayrpt.arc 1023 cps 946 1002 1010
|
||
|
|
sunset.arc 971 935 953 950
|
||
|
|
text109k.arc 1085 988 1064 1053
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
If you have ever downloaded files from a BBS or online service, you know
|
||
|
|
that almost all files are in a compressed format. Therefore, you should
|
||
|
|
only expect to see an actual throughput between 950 to 1100 cps even if
|
||
|
|
your V.32/V.42bis modem is supposed to offer throughput "up to" 38400
|
||
|
|
bps.
|
||
|
|
|
||
|
|
Most PC files are in the ZIP format. Macintosh files are typically in
|
||
|
|
the .SIT (Stuffit) or .CPT (Compact Pro) format. Amiga files are usually
|
||
|
|
in the ZOO, ARC or LZH format. Note that GIF files are also in a
|
||
|
|
compressed format.
|
||
|
|
|
||
|
|
|
||
|
|
Compression by Software vs. MNP-5/V.42bis
|
||
|
|
|
||
|
|
There are several reasons why compression software programs (such as
|
||
|
|
PKZIP or Stuffit) are superior to MNP-5 or V.42bis.
|
||
|
|
|
||
|
|
1. Compressed files save disk storage space.
|
||
|
|
|
||
|
|
2. Compression software programs are more versatile. Most of them allow
|
||
|
|
you to group several files in a compressed file archive to ensure
|
||
|
|
that all the related files get transferred at the same time.
|
||
|
|
|
||
|
|
3. Software compression is more efficient than on-the-fly modem
|
||
|
|
compression. In the case of a small file, this may not make much
|
||
|
|
difference. But the difference can be significant when you are
|
||
|
|
transferring large files.
|
||
|
|
|
||
|
|
Filename Size Time Throughput
|
||
|
|
-----------------------------------------------------------------
|
||
|
|
the-wave.txt 143579 bytes 43 seconds 3296 cps
|
||
|
|
dayrpt.arc 8423 bytes 8 seconds 1010 cps
|
||
|
|
dayrpt.wks 19712 bytes 8 seconds 2337 cps
|
||
|
|
sunset.arc 5084 bytes 5 seconds 950 cps
|
||
|
|
sunset.pic 16391 bytes 6 seconds 2643 cps
|
||
|
|
text109k.arc 29775 bytes 28 seconds 1053 cps
|
||
|
|
text109k.txt 111386 bytes 39 seconds 2822 cps
|
||
|
|
|
||
|
|
|
||
|
|
As we can see from the test results, it is about 30% faster to transfer
|
||
|
|
the compressed file text109k.arc than to download the text file with
|
||
|
|
V.42bis.
|
||
|
|
|
||
|
|
Hayes BBS does not provide a compressed version for the file
|
||
|
|
the-wave.txt. Using PKZIP (for PC) and Stuffit (for Macintosh), we
|
||
|
|
obtain the following results:
|
||
|
|
|
||
|
|
the-wave.zip: 6812 bytes (PKZIP)
|
||
|
|
the-wave.sit: 6081 bytes (Stuffit)
|
||
|
|
|
||
|
|
Assuming a transfer speed of 1000 cps, the compressed file can be
|
||
|
|
downloaded in 7 seconds. That's six times faster than downloading the
|
||
|
|
text file with V.42bis!
|
||
|
|
|
||
|
|
Here is another example. Spider Island Software BBS (714-730-5785) has a
|
||
|
|
test file called One-Minute Max. It is a Macintosh TIFF file (file size
|
||
|
|
206,432 bytes). According to Spider Island Software, the file can be
|
||
|
|
downloaded in 56 seconds (with an effective throughput of 3745cps) with
|
||
|
|
a V.32/V.42bis modem.
|
||
|
|
|
||
|
|
The result may seem impressive at first. However, the file can be
|
||
|
|
compressed to 6065 bytes (with Compact Pro) or 7385 bytes (with
|
||
|
|
Stuffit). Assuming a transfer speed of 1000 cps, it would only take 6-8
|
||
|
|
seconds to transfer. Again, it is seven to nine times faster than
|
||
|
|
downloading the file with V.42bis.
|
||
|
|
|
||
|
|
On-the-fly modem compression does have one advantage. It is more
|
||
|
|
convenient. You can send a file without compressing it first and the
|
||
|
|
recipient does not need to decompress the file.
|
||
|
|
|
||
|
|
Local Flow Control and Data Buffering
|
||
|
|
|
||
|
|
To get the most from a modem with data compression, you'll want to send
|
||
|
|
data from your PC to the modem as quickly as possible. If the modem is
|
||
|
|
idle and waiting for the computer to send data, you are not getting the
|
||
|
|
maximum performance from the modem.
|
||
|
|
|
||
|
|
For example, you have a V.32/V.42bis modem and you want to send a text
|
||
|
|
file to a remote system which also has a V.32/V.42bis modem. Let's
|
||
|
|
assume the modem is able to send the file at 20000 bps using V.42bis. If
|
||
|
|
your computer is sending data to your modem at 9600 bps, your modem will
|
||
|
|
have to stop and wait to receive data from your computer.
|
||
|
|
|
||
|
|
To get the maximum performance, you want to set the computer to send
|
||
|
|
data to the modem at 38400 bps (the maximum a V.32/V.42bis modem can
|
||
|
|
achieve). Since the modem can only send the file to the other modem at
|
||
|
|
20000 bps, it will never have to wait.
|
||
|
|
|
||
|
|
Here are the test results for downloading the text file the-wave.txt by
|
||
|
|
setting the communication port at different speeds:
|
||
|
|
|
||
|
|
the-wave.txt: 946 cps (modem port speed 9600 bps)
|
||
|
|
1885 cps (modem port speed 19200 bps)
|
||
|
|
3296 cps (modem port speed 38400 bps)
|
||
|
|
|
||
|
|
|
||
|
|
However, there is a new problem. Since your computer is sending data
|
||
|
|
faster than the modem can handle, there needs to be some ways for the
|
||
|
|
modem to ask the computer to stop sending data. Otherwise, data loss is
|
||
|
|
sure to occur. This is where local flow control comes into play.
|
||
|
|
|
||
|
|
A high-speed modem typically supports two kinds of local flow control:
|
||
|
|
hardware handshaking (CTS/RTS) and software handshaking (XON/XOFF). Of
|
||
|
|
the two, hardware flow control is the preferred method.
|
||
|
|
|
||
|
|
We have mentioned earlier that there are three links involved when you
|
||
|
|
are connected to a remote system:
|
||
|
|
|
||
|
|
1. The link between your computer and your modem
|
||
|
|
2. The link between the modems
|
||
|
|
3. The link between the remote modem and the remote computer
|
||
|
|
|
||
|
|
Local flow control is used for the first and third links. Notice that
|
||
|
|
the first link may not use the same kind of flow control as the third
|
||
|
|
link.
|
||
|
|
|
||
|
|
Hardware flow control (or hardware handshaking) works by altering
|
||
|
|
voltage levels on the RTS (Request To Send) and CTS (Clear To Send)
|
||
|
|
signal lines at the RS232 serial interface between the modem and the
|
||
|
|
computer.
|
||
|
|
|
||
|
|
CTS is used by the modem on the sending end of a transmission. When the
|
||
|
|
local modem is ready to receive data, it sends the CTS signal to the
|
||
|
|
local computer and the computer starts transferring data. If the modem
|
||
|
|
is unable to accept the data as fast as it is received from the
|
||
|
|
computer, the modem will disable the CTS to inform the computer that the
|
||
|
|
modem buffer is almost full (A high-speed modem typically contains a
|
||
|
|
small amount of RAM which is used to provide data buffers). The computer
|
||
|
|
will then suspend data transfer. Once the local modem has emptied its
|
||
|
|
buffer by transmitting data to the remote modem, it will enable CTS
|
||
|
|
again.
|
||
|
|
|
||
|
|
RTS is used by the computer on the receiving end of a transmission. When
|
||
|
|
the computer cannot accept data at the rate at which the modem is
|
||
|
|
passing data, it will disable RTS. The computer enables RTS again when
|
||
|
|
it is ready to resume receiving data from the modem.
|
||
|
|
|
||
|
|
Software flow control (or software handshaking) is achieved by embedding
|
||
|
|
control character in the data stream. XON and XOFF are the most commonly
|
||
|
|
used control characters. XON is also known as Control-Q or DC3 (ASCII
|
||
|
|
19) while XOFF is known as Control-S or DC1 (ASCII 17).
|
||
|
|
|
||
|
|
The use of XON and XOFF during data transfer can create problem when a
|
||
|
|
binary file contain the Control-S (^S) character as a legitimate part of
|
||
|
|
the data. Do not use this method if ^S and ^Q are part of the
|
||
|
|
transmitted data.
|
||
|
|
|
||
|
|
|
||
|
|
Macintosh and High-speed Modems
|
||
|
|
|
||
|
|
If you use a Macintosh with a high-speed modem, you will need a special
|
||
|
|
modem cable that is wired correctly to support hardware handshaking. You
|
||
|
|
can order the cable from most mail-order companies that sell high-speed
|
||
|
|
modems. I got mine from Maya Computer (800-541-2318) for $10 (plus $2.50
|
||
|
|
for shipping & handling).
|
||
|
|
|
||
|
|
Unfortunately, the cable did not work with my SE. The cable is good
|
||
|
|
since it worked fine on a Mac IIsi. It just refused to work on my SE. I
|
||
|
|
was disappointed but not surprised. After all, my SE is equipped with a
|
||
|
|
25 Mhz 68030 accelerator. (Well, it is actually both an accelerator and
|
||
|
|
a video adapter for a 19 inch dual-page monitor.) Since I will never
|
||
|
|
want to run my SE without the accelerator, I have no choice but to use
|
||
|
|
software handshaking.
|
||
|
|
|
||
|
|
PC and UART (8250, 16450, 16550)
|
||
|
|
|
||
|
|
Your PC's serial port has a UART (Universal Asynchronous
|
||
|
|
Receiver/Transmitter) chip to control the input/output. The XT usually
|
||
|
|
has an 8250 UART, the AT usually has a 16450 UART. If you are running
|
||
|
|
Windows, Desqview, OS/2 or any other multitasking environment, you
|
||
|
|
should upgrade your UART with the 16550 (if your PC does not already
|
||
|
|
have one). The 16550 is standard in most IBM PS/2 and many 386-based
|
||
|
|
computers. The 16550 UART has a 16 bytes FIFO (first in, first out)
|
||
|
|
buffer that helps to prevent degradation when several programs are
|
||
|
|
running at the same time.
|
||
|
|
|
||
|
|
If you use an external modem, the UART is in your computer (either on
|
||
|
|
the motherboard or on an I/O card that has the serial port). If you use
|
||
|
|
an internal modem, the UART is on the modem. (Both internal modems from
|
||
|
|
Practical Peripherals and Zoom use the 16550 UART. The Twincom 96/42
|
||
|
|
uses a 16450. The CompuCom SpeedModem Champ, due to its unique design,
|
||
|
|
does not use a standard UART.)
|
||
|
|
|
||
|
|
Even if you have a 16550 UART, the communication software that you use
|
||
|
|
will need to support it. Fortunately, the most recent versions of
|
||
|
|
popular communications programs are all designed to support the 16550
|
||
|
|
UART.
|
||
|
|
|
||
|
|
Hayes ESP (Enhanced Serial Port)
|
||
|
|
Hayes makes an adapter called Enhanced Serial Port (ESP) that has two
|
||
|
|
serial ports complete with an on-board coprocessor. The ESP can save
|
||
|
|
your PC's CPU from having to manage the work load. If a 16550 UART is
|
||
|
|
not good enough for you, the ESP may be the only answer.
|
||
|
|
|
||
|
|
|
||
|
|
Profiles of High-speed Modems
|
||
|
|
|
||
|
|
Here are profiles of some high-speed modems. The list is not comprehensive,
|
||
|
|
nor is it intended to be. Unless noted otherwise, the street price quoted are
|
||
|
|
from PC Connection (800-243-8088) in PC Magazine (12/31/91). PC Connection
|
||
|
|
generally does not offer the lowest price, but the service is excellent. I
|
||
|
|
have dealt with PC Connection and MacConnection (800-800-4444) for years
|
||
|
|
and have yet to be disappointed with their services.
|
||
|
|
|
||
|
|
Unless noted otherwise, a V.32/V.42bis modem supports V.32, MNP2-5,
|
||
|
|
V.42/V.42bis. And a V.32bis/V.42bis modem supports V.32bis, MNP 2-5,
|
||
|
|
V.42/V.42bis. Most modems listed here are introduced in the past eighteen
|
||
|
|
months.
|
||
|
|
|
||
|
|
|
||
|
|
ATI 9600etc/e
|
||
|
|
|
||
|
|
ATI Technologies is well known for their video adapters. But they also
|
||
|
|
make a V.32/V.42bis external modem. As of this writing, it is the least
|
||
|
|
expensive external modem from an established manufacturer. It is a
|
||
|
|
generic high-speed modem that works well. The street price for the ATI
|
||
|
|
9600etc/e is $379.
|
||
|
|
|
||
|
|
I have been using an ATI 9600etc/e for several months now and I am very
|
||
|
|
pleased with it. I will not hesitate to recommend it to anyone looking
|
||
|
|
for an affordable V.32/V.42bis modem.
|
||
|
|
|
||
|
|
There are two things I really like about the ATI modem:
|
||
|
|
* It has a slide volume control on the outside so you can easily adjust
|
||
|
|
the volume by hand.
|
||
|
|
* It has factory settings for three different modes: V.32 only, V.32
|
||
|
|
with MNP-5, V.32 with V.42bis. It is very convenient if you need to
|
||
|
|
initialize the modem in different ways.
|
||
|
|
|
||
|
|
|
||
|
|
CompuCom SpeedModem Champ/Star/Storm
|
||
|
|
|
||
|
|
The SpeedModem Champ is a 9600 bps high-speed modem with CompuCom's
|
||
|
|
proprietary CSP modulation protocol. It is introduced in early 1991. It
|
||
|
|
can be ordered from CompuCom directly at a discount price of $169. The
|
||
|
|
CompuCom Champ is supported by hundreds of BBS in the U.S., including
|
||
|
|
heavyweights such as EXEC-PC and Channel 1.
|
||
|
|
|
||
|
|
CompuCom also markets the SpeedModem Combo which is a SpeedModem Champ
|
||
|
|
with fax and voice mail capabilities. The current price is $269.
|
||
|
|
The SpeedModem Storm is a dual-mode modem. It supports both CSP and
|
||
|
|
V.32/V.42bis. The discount price is $299 (internal) and $339 (external).
|
||
|
|
The Storm is also available with fax and voice mail options for an
|
||
|
|
additional $90.
|
||
|
|
|
||
|
|
The SpeedModem Star is also a dual-mode modem. It supports both CSP and
|
||
|
|
V.32bis/V.42bis. The discount price is $499 (internal) and $539
|
||
|
|
(external). The Star is also available with fax and voice mail options
|
||
|
|
for an additional $90.
|
||
|
|
|
||
|
|
|
||
|
|
Hayes Modems
|
||
|
|
|
||
|
|
V-series Smartmodem 9600. Introduced in 1987, this is a high-speed modem
|
||
|
|
that supports the proprietary Hayes Express 96 modulation protocol. The
|
||
|
|
V-series Smartmodem 9600 is still available from various mail order
|
||
|
|
vendors. There is also an internal unit called V-series Smartmodem
|
||
|
|
9600B.
|
||
|
|
|
||
|
|
Smartmodem 9600. Introduced in 1988, the Smartmodem 9600 is a V.32
|
||
|
|
modem. It does not support any error control or data compression
|
||
|
|
protocol. Don't confuse this unit with the V-series Smartmodem 9600.
|
||
|
|
|
||
|
|
Ultra 96 is a dual-mode modem from Hayes. Introduced in 1990, the Ultra
|
||
|
|
96 supports both V.32/V.42bis and the Hayes Express 96 modulation
|
||
|
|
protocol. Ultra 96 has many unique features that are not needed if you
|
||
|
|
are calling BBS or online services. The current street price is $669.
|
||
|
|
|
||
|
|
Introduced in Fall 1991, Ultra 144 is a dual-mode modem that supports
|
||
|
|
both V.32bis/V.42bis and the Hayes Express 96 protocol. The current
|
||
|
|
street price is $799.
|
||
|
|
|
||
|
|
Optima 96 is a plain vanilla V.32/V.42bis modem. This is Hayes' answer
|
||
|
|
to the "generic" V.32/V.42bis modem. The current street price is $479.
|
||
|
|
|
||
|
|
|
||
|
|
Image Communications: Twincom 96/42
|
||
|
|
|
||
|
|
The Twincom 96/42 is an internal V.32/V.42bis modem. It lists for $299.
|
||
|
|
(Don't expect to get discount on the price.) It just won a 1991 Best Buy
|
||
|
|
Award from Computer Shopper. Notice that it has a 16450 UART, not a
|
||
|
|
16550. Furthermore, you cannot replace the 16450 with a 16550, the
|
||
|
|
Twincom 96/42 will not support a 16550 UART at all.
|
||
|
|
|
||
|
|
|
||
|
|
Intel 9600EX & 14.4EX
|
||
|
|
|
||
|
|
The 9600EX is a V.32/V.42bis modem. The 14.4EX is a V.32bis/V.42bis
|
||
|
|
modem. PC Connection is selling the 9600EX for $499 and the 14.4EX for
|
||
|
|
$549. If you decide to buy an Intel modem, the 14.4EX is obviously a
|
||
|
|
better deal.
|
||
|
|
|
||
|
|
|
||
|
|
Practical Peripherals PM9600SA & PM9600
|
||
|
|
|
||
|
|
The PM9600SA is a V.32/V.42bis modem. It is designed to be compatible
|
||
|
|
with the Hayes Ultra 96. That means you can tell your communications
|
||
|
|
software that you have a Hayes Ultra 96. However, the PM9600SA only
|
||
|
|
responds to a subset of the commands supported by the Hayes Ultra 96.
|
||
|
|
Any commands specific to the Hayes Ultra 96 that are not implemented in
|
||
|
|
the PM9600SA will be ignored.
|
||
|
|
|
||
|
|
Some early PM9600SA units have quite a few problems connecting to other
|
||
|
|
V.32 modems. (Make sure you send in the warranty card.) Practical
|
||
|
|
Peripheral has since sent out several ROM upgrades and the current
|
||
|
|
shipping units seem to be working fine.
|
||
|
|
|
||
|
|
Practical Peripherals also makes an internal modem that features a 16550
|
||
|
|
UART. You can get the PM9600SA for $469 and the internal PM9600 for
|
||
|
|
$399.
|
||
|
|
|
||
|
|
|
||
|
|
Prometheus Modems
|
||
|
|
|
||
|
|
Prometheus modems are available from many Macintosh mail order
|
||
|
|
companies. Until recently, Prometheus is the only manufacturer that
|
||
|
|
makes high-speed modems with fax capability.
|
||
|
|
|
||
|
|
Promodem 9600 Plus is a V.32/V.42bis modem. It can also send and receive
|
||
|
|
Group III fax at 9600 bps.
|
||
|
|
|
||
|
|
Prometheus Ultima is a V.32bis/V.42bis fax modem. It can also send and
|
||
|
|
receive Group III fax at 9600 bps. MacConnection sells the Ultima for
|
||
|
|
$689.
|
||
|
|
|
||
|
|
|
||
|
|
Telebit Modems
|
||
|
|
|
||
|
|
Telebit makes several modems. The prices quoted for the Telebit modems
|
||
|
|
are their new list prices.
|
||
|
|
|
||
|
|
TrailBlazer Plus. $849. Introduced in 1985, the Trailblazer has been the
|
||
|
|
de facto standard in the UNIX UUCP and Usenet communities. With the new
|
||
|
|
pricing, you should consider the T2500 or the T3000 instead of the
|
||
|
|
TrailBlazer Plus if you need to connect to a Telebit PEP modem.
|
||
|
|
|
||
|
|
T1000. Introduced in 1988, the T1000 is the little brother of the
|
||
|
|
TrailBlazer Plus. The T1000 supports PEP at a slower speed. The actual
|
||
|
|
throughput is about 9600 cps. The current list price is $699. Unlike the
|
||
|
|
TrailBlazer Plus, the T1000 does not have callback or password security.
|
||
|
|
|
||
|
|
T2500. $949. Introduced in 1989 when V.32 modems started to enter the
|
||
|
|
market, the T2500 supports both V.32/V.42bis and PEP. The maximum
|
||
|
|
throughput is 19,200 bps due to the limitation imposed by the older
|
||
|
|
Rockwell chipset used.
|
||
|
|
|
||
|
|
T1600. $699. The T1600 is a V.32/V.42bis modem introduced in 1991. It
|
||
|
|
provides built-in support for UUCP and offers password and callback
|
||
|
|
security.
|
||
|
|
|
||
|
|
T3000. $949. This is the top of the line model from Telebit. The T3000
|
||
|
|
is a V.32bis/V.42bis modem. PEP upgrade is available for $99 until
|
||
|
|
3/31/92. After that date, the upgrade will be $199.
|
||
|
|
|
||
|
|
QBlazer. $745. If I am going to buy another high-speed modem today, this
|
||
|
|
will be it. (I use a notebook computer). QBlaser is the first portable
|
||
|
|
V.32/V.42bis modem (2.3"x2.4"x2.4"). It works with a 9-volt battery for
|
||
|
|
about two hours.
|
||
|
|
|
||
|
|
Note that T1600, T2500, T3000 all offer the following features:
|
||
|
|
* Built-in support for UNIX UUCP, Xmodem, Ymodem, Kermit file transfer
|
||
|
|
protocols
|
||
|
|
* Two types of dial-access security: password security and callback
|
||
|
|
security
|
||
|
|
* Remote management and diagnostics
|
||
|
|
|
||
|
|
|
||
|
|
U.S. Robotics Modems
|
||
|
|
|
||
|
|
Courier HST. This is the modem that made U.S. Robotics the king of
|
||
|
|
PC-based BBS communities. Unless you are only going to communicate with
|
||
|
|
other USR HST modems, it is probably not a good idea to purchase this
|
||
|
|
unit. The street price for a 14400 bps HST is $550-$600. Telemart
|
||
|
|
(800-521-1973) sells either the internal or the external version for
|
||
|
|
$559.
|
||
|
|
|
||
|
|
Courier V.32bis. Introduced in 1990, this is a V.32bis/V.42bis modem. It
|
||
|
|
does not support HST. Telemart offers the external version for $565 and
|
||
|
|
the internal version for $535.
|
||
|
|
|
||
|
|
Courier HST Dual Standard. This unit is introduced in 1990. If you need
|
||
|
|
to connect to HST modems and also want to be able to talk to other
|
||
|
|
V.32/V.32bis modems, this is the modem to buy. Its current street price
|
||
|
|
is around $800. Telemart sells the HST Dual Standard for $799. (Note
|
||
|
|
that earlier HST Dual Standard modems only support V.32 and not
|
||
|
|
V.32bis.) The HST Dual Standard is considered by many PC users as the
|
||
|
|
best modem money can buy.
|
||
|
|
|
||
|
|
The only reservation I have about the Courier modems is their size. The
|
||
|
|
external Courier modems are rather bulky: 8.3" wide, 12.65" deep, 1.57"
|
||
|
|
tall. I would not want to carry one of these with me when I travel.
|
||
|
|
(It's bigger than my notebook computer.)
|
||
|
|
|
||
|
|
Sportster 9600 V.42bis. This unit is introduced in 1991. The Sportster
|
||
|
|
9600 is an entry level V.32/V.42bis modem from U.S. Robotics. The list
|
||
|
|
price is $645 for the external version. ($595 for the Internal version).
|
||
|
|
|
||
|
|
WorldPort 9600 V.32. The WorldPort 9600 is a portable pocket modem.
|
||
|
|
Originally made by Touchbase Systems, the WorldPort 9600 is a V.32/MNP-5
|
||
|
|
modem. It does not support V.42/V.42bis. The WorldPort 9600 works with a
|
||
|
|
9-volt battery. The list price is $699.
|
||
|
|
|
||
|
|
|
||
|
|
Zoom V.32 Turbo Modems
|
||
|
|
|
||
|
|
Zoom has been making Hayes-compatible modems for a long time. The V.32
|
||
|
|
Turbo is their entry into the high-speed modem arena. The V.32 Turbo is
|
||
|
|
a V.32/V.42bis with a 12000 bps turbo mode which is compatible with a
|
||
|
|
V.32bis modem at 12000 bps. Zoom also makes an internal version of the
|
||
|
|
V.32 Turbo that features a 16550 UART. PC Connection sells the internal
|
||
|
|
model for $399.
|
||
|
|
|
||
|
|
|
||
|
|
Things to come
|
||
|
|
|
||
|
|
Every modem manufacturer makes at least one V.32/V.42bis modem now. And
|
||
|
|
soon every manufacturer will also make a V.32bis/V.42bis modem. The
|
||
|
|
price for V.32 and V.32bis modems will continue to drop.
|
||
|
|
|
||
|
|
In fact, Supra has announced an external V.32 fax modem (SupraFaxModem
|
||
|
|
V.32) for $299 and an external V.32bis fax modem (SupraFaxModem V.32bis)
|
||
|
|
for $399. These prices are for the modems only. Communication and fax
|
||
|
|
software will be bundled with the modem for an additional $50-$70.
|
||
|
|
(These modems won't be available at least until January 1992.)
|
||
|
|
|
||
|
|
|
||
|
|
Buying a High-speed Modem
|
||
|
|
|
||
|
|
V.32 and V.32bis modems are clearly the standards of high-speed modems
|
||
|
|
today. You should buy a V.32 or a V.32bis modem unless
|
||
|
|
|
||
|
|
1. Your application requires a high-speed modem with a proprietary
|
||
|
|
modulation protocol. In this case, you should consider a dual-mode
|
||
|
|
modem that support both the proprietary protocol and V.32 (or
|
||
|
|
V.32bis).
|
||
|
|
|
||
|
|
2. You cannot afford a V.32 modem. In this case, your only choice for a
|
||
|
|
high-speed modem is the CompuCom SpeedModem Champ.
|
||
|
|
|
||
|
|
|
||
|
|
Should you pay the extra for a V.32bis modem?
|
||
|
|
|
||
|
|
A V.32bis modem is faster than a V.32 modem but it also costs more.
|
||
|
|
Should you pay the extra for the speed difference? That depends on two
|
||
|
|
factors: what's the price difference and how do you want to reach the
|
||
|
|
remote system. If the price difference is $50, I would buy the V.32bis
|
||
|
|
modem. But what if the price difference is $200?
|
||
|
|
|
||
|
|
Assuming the remote system support V.32bis, a V.32bis modem will pay for
|
||
|
|
itself rather quickly if you are placing long distance calls to the
|
||
|
|
remote system. However, it may be more cost-effective for you to use
|
||
|
|
some packet-switching networks to reach the remote system by calling a
|
||
|
|
local number. A V.32bis modem will be wasted since none of the
|
||
|
|
packet-switching networks currently support V.32bis. In fact, they are
|
||
|
|
just starting to offer 9600 bps access service. Part III of "The Joy of
|
||
|
|
Telecomputing" provides a comprehensive discussion of the issues
|
||
|
|
involved.
|
||
|
|
|
||
|
|
|
||
|
|
Should you buy a modem with a proprietary modulation protocol?
|
||
|
|
|
||
|
|
With the exception of the CompuCom SpeedModem Champ, it is generally not
|
||
|
|
a good idea to purchase a modem which only supports a proprietary
|
||
|
|
modulation protocol. If you have to connect to a modem that uses a
|
||
|
|
proprietary modulation protocol, you should consider getting a modem
|
||
|
|
that supports dual modulation protocols (USR Courier Dual Standard,
|
||
|
|
Telebit 2500 or 3000, Hayes Ultra).
|
||
|
|
|
||
|
|
Should you buy the SpeedModem Champ? It certainly costs much less than
|
||
|
|
even the least expensive generic V.32 modem in the market today.
|
||
|
|
Assuming the systems you are calling support both V.32 and the CompuCom
|
||
|
|
Champ modems, should you save the money and buy the Champ?
|
||
|
|
|
||
|
|
Unfortunately, there is no clear-cut answer to the question. The answer
|
||
|
|
again depends on how you are going to reach the remote systems. If you
|
||
|
|
want to reach the remote systems via a packet-switching network, the
|
||
|
|
CompuCom Champ may not be a good choice.
|
||
|
|
|
||
|
|
The CompuCom Champ is generally not supported by packet-switching
|
||
|
|
networks (The only company that supports the CompuCom Champ is
|
||
|
|
Connect-USA). As a result, you will only be able to connect at 2400 bps
|
||
|
|
with the packet-switching networks. You would be forced to place a long
|
||
|
|
distance call if you want to connect at 9600 bps. See Part III of "The
|
||
|
|
Joy of Telecomputing" for the various issues involved.
|
||
|
|
|
||
|
|
|
||
|
|
Should you buy a 2400 bps modem with V.42bis?
|
||
|
|
|
||
|
|
If you are thinking of purchasing a 2400 bps modem with V.42bis data
|
||
|
|
compression, think again.
|
||
|
|
|
||
|
|
We have mentioned earlier that V.42bis and MNP-5 are useless for
|
||
|
|
downloading compressed files. There is one more reason why a 2400 bps
|
||
|
|
with V.42bis is generally not useful when you are calling commercial
|
||
|
|
online services or BBS.
|
||
|
|
|
||
|
|
Online services and BBS usually have separate phone numbers for 2400 bps
|
||
|
|
and high-speed modems. Most of them do not support V.42bis on their 2400
|
||
|
|
bps lines. Therefore, you won't be able to make a connection with
|
||
|
|
V.42bis if you call their 2400 bps modem lines.
|
||
|
|
|
||
|
|
Couldn't you call their 9600 bps lines? Well, not really. Commercial
|
||
|
|
online services, as well as many bulletin board systems, typically do
|
||
|
|
not allow you to call their high-speed modem lines with a 2400 bps
|
||
|
|
modem. You won't be able to make a connection even if you try.
|
||
|
|
|
||
|
|
You should seriously consider the CompuCom SpeedModem Champ instead of a
|
||
|
|
2400 bps modem with V.42bis. The CompuCom Champ will probably give you
|
||
|
|
much more for your money (especially if you need to pay more than $100
|
||
|
|
for the V.22bis/V.42bis modem).
|
||
|
|
|
||
|
|
|
||
|
|
Beware of the Ads
|
||
|
|
|
||
|
|
Current V.32 modems typically support MNP 2-5 and V.42/V.42bis. However,
|
||
|
|
there are still some earlier models of V.32 modems in the market which
|
||
|
|
1. may not support any error control or data compression protocol (Hayes
|
||
|
|
Smartmodem 9600).
|
||
|
|
2. may support MNP 2-5 but not V.42/V.42bis.
|
||
|
|
3. may support proprietary data compression protocol (Microcom MNP-9).
|
||
|
|
4. may support V.42 but not V.42bis (Prometheus).
|
||
|
|
|
||
|
|
|
||
|
|
When a modem is said to offer a 38400 bps speed (or throughput), it may
|
||
|
|
mean that
|
||
|
|
1. it is a V.32 or V.32bis modem with V.42bis
|
||
|
|
2. it is a V.32 modem with proprietary data compression protocol (some
|
||
|
|
Microcom modems)
|
||
|
|
3. it is a high-speed modem with proprietary modulation protocol and
|
||
|
|
V.42bis (U.S. Robotics Courier HST)
|
||
|
|
4. it is a high-speed modem with proprietary modulation protocol and
|
||
|
|
proprietary data compression protocol (CompuCom Champ)
|
||
|
|
|
||
|
|
An ad that says "USR modem, 38400 bps throughput, V.42bis" does not tell
|
||
|
|
us anything except that the modem is made by U.S. Robotics. It could be
|
||
|
|
any one of the three Courier modems. It could even be a Sportster 9600.
|
||
|
|
|
||
|
|
|
||
|
|
When a modem is said to offer a 9600 bps speed (or throughput), it may
|
||
|
|
mean several things:
|
||
|
|
1. it is a V.32 modem
|
||
|
|
2. it is a high-speed modem using proprietary modulation protocol (Hayes
|
||
|
|
V-series Smartmodem 9600, Telebit 1000, etc).
|
||
|
|
3. it is a 2400 bps modem with V.42bis data compression.
|
||
|
|
4. it is a 2400 bps modem with 9600 bps fax
|
||
|
|
5. it is a 2400 bps modem both V.42bis and fax
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
Setting Up Software To Work With High-speed Modems
|
||
|
|
|
||
|
|
Getting a high-speed modem is only half the battle. You will need to get
|
||
|
|
it to work with your communications program. Most communications
|
||
|
|
programs still come with settings configured for standard 2400 bps
|
||
|
|
modems.
|
||
|
|
|
||
|
|
Since all 2400 bps modems are Hayes-compatible, it is relatively easy to
|
||
|
|
set up the software. You simply install the software as if you had a
|
||
|
|
Hayes modem. The software usually will work flawlessly. And you don't
|
||
|
|
really have to worry about things like the initialization string.
|
||
|
|
|
||
|
|
Getting a high-speed modem to work with your software is a different
|
||
|
|
story. There is no longer a Hayes standard that everyone follows. Here
|
||
|
|
are some of the reasons why you need to know how to configure your
|
||
|
|
high-speed modem to work with your communications program.
|
||
|
|
|
||
|
|
First, your high-speed modem may not be supported by your software.
|
||
|
|
|
||
|
|
Secondly, even if your software supports your high-speed modem, the
|
||
|
|
software may not be set up properly.
|
||
|
|
|
||
|
|
Finally, even if your software is set up properly, the settings may not
|
||
|
|
work all the times.
|
||
|
|
|
||
|
|
|
||
|
|
The Proper Software Setup
|
||
|
|
|
||
|
|
When we say that the software is set up properly, we mean that
|
||
|
|
|
||
|
|
1. the modem is initialized properly by the communications software, and
|
||
|
|
2. the settings of your software match those of the modem
|
||
|
|
|
||
|
|
What is the proper way to initialize a high-speed modem? In general,
|
||
|
|
your modem needs to be initialized to:
|
||
|
|
|
||
|
|
* Enable V.42bis Data Compression
|
||
|
|
* Enable hardware flow control
|
||
|
|
* Handle the DTR and CD signals properly (by adding &C1&D2 to the modem
|
||
|
|
initialization string)
|
||
|
|
|
||
|
|
We'll use the ATI 9600etc/e modem as an example for our discussions
|
||
|
|
below. The initialization string described here is for the ATI modem
|
||
|
|
only. Refer to your modem manual for the equivalent initialization
|
||
|
|
string for your modem.
|
||
|
|
|
||
|
|
The ATI modem is supported by two popular communications programs:
|
||
|
|
Qmodem and HyperAccess 5. Qmodem initializes the modem and also
|
||
|
|
configures itself to use hardware flow control. HyperAccess 5 also
|
||
|
|
initializes the modem properly, however it does not configure itself to
|
||
|
|
use hardware flow control.
|
||
|
|
|
||
|
|
All modems come with default settings pre-configured from the factory.
|
||
|
|
Many V.32 high-speed modems are preset to use V.42bis and hardware flow
|
||
|
|
control when they are turned on. This optimal configuration enables the
|
||
|
|
modem to automatically negotiate a connection with either another V.32
|
||
|
|
modem supporting V.42bis or MNP protocols (or even a standard modem).
|
||
|
|
|
||
|
|
Interestingly enough, not all high-speed modems are configured this way.
|
||
|
|
The ATI 9600 etc/e modem, for example, is preset to use V.32 without
|
||
|
|
error control or data compression at power-on. (Why? Good question.)
|
||
|
|
|
||
|
|
As a result, your communications program needs to issue the appropriate
|
||
|
|
initialization string (AT&F2) to set up the ATI modem to use V.32 with
|
||
|
|
V.42bis and hardware flow control.
|
||
|
|
|
||
|
|
There is another change required. And it has to do with the parameters
|
||
|
|
controlling how the modem deals with two of the RS232 signals: DTR (Data
|
||
|
|
Terminal Ready) and CD (Carrier Detect).
|
||
|
|
|
||
|
|
CD is a signal generated by the modem which is used to indicate its
|
||
|
|
connection status. DTR is a signal generated by your computer. DTR is
|
||
|
|
used to enable the modem to accept commands from your communications
|
||
|
|
program, it is also used by most modems to determine when to disconnect
|
||
|
|
a call.
|
||
|
|
|
||
|
|
The factory default setting for DTR tells the modem to ignore change in
|
||
|
|
DTR (&D0), and the setting for CD forces CD always on (&C0). These
|
||
|
|
specific settings are required by some dedicated dumb terminals in order
|
||
|
|
to communicate with the modem. (Virtually all modems use &C0&D0 as the
|
||
|
|
default setting.) However, these settings will often cause problems when
|
||
|
|
hanging up the phone lines or produce an error message which says the
|
||
|
|
modem is online when it is not.
|
||
|
|
|
||
|
|
Most communications software programs expect the modem to follow DTR and
|
||
|
|
expects CD to follow carrier. &C1&D2 set the parameters for the modem to
|
||
|
|
handle the DTR and CD signals as expected by most communications
|
||
|
|
programs.
|
||
|
|
|
||
|
|
Therefore, the proper initialization string to use for the ATI modem
|
||
|
|
should be AT&F2&C1&D2.
|
||
|
|
|
||
|
|
|
||
|
|
Does Your Software Initialize the Modem Properly?
|
||
|
|
|
||
|
|
Let's take a look at the initialization strings used by Qmodem and
|
||
|
|
HyperAccess 5 for the ATI 9600etc/e modem.
|
||
|
|
|
||
|
|
HyperAccess 5 use the following initialization string
|
||
|
|
|
||
|
|
AT&F2E1V1L0Q0W2X4&C1&D2S11=55
|
||
|
|
|
||
|
|
This string is longer than the one we suggest. But does it do more?
|
||
|
|
Actually it doesn't. Many of the commands in the string are redundant or
|
||
|
|
not necessary. Only AT&F2&C1&D2 are crucial.
|
||
|
|
|
||
|
|
Four of the commands - E1, V1, Q0 and X4 - are redundant since they are
|
||
|
|
duplications of the factory default settings. (Check your modem manual
|
||
|
|
to find out what they mean. Since you would most likely need to read it
|
||
|
|
sooner or later, you might as well get started now.)
|
||
|
|
|
||
|
|
L0 does not apply to the ATI modem. L0 normally is used to set modem
|
||
|
|
speaker volume to the lowest level. However, the ATI 9600etc/e modem
|
||
|
|
does not respond to the L0 command. Unlike most modems, the ATI modem
|
||
|
|
has a slide volume control on the right side for adjusting the volume
|
||
|
|
level.
|
||
|
|
|
||
|
|
The other two commands (W2 and S11=55) are not redundant, but they are
|
||
|
|
not necessary.
|
||
|
|
|
||
|
|
W2 sets the modem to report Negotiation result codes in single line
|
||
|
|
format instead of the default three line format (W1).
|
||
|
|
|
||
|
|
Three line format: Single line format:
|
||
|
|
----------------- ------------------
|
||
|
|
CARRIER 9600 CONNECT 9600/LAP-M
|
||
|
|
PROTOCOL: LAP-M
|
||
|
|
CONNECT 38400
|
||
|
|
|
||
|
|
|
||
|
|
S11=55 (default is 95) sets the modem to dial at a faster speed than the
|
||
|
|
factory setting.
|
||
|
|
|
||
|
|
Despite the fact that its initialization string contains some redundant
|
||
|
|
commands, HyperAccess 5 does properly initialize the ATI modem.
|
||
|
|
|
||
|
|
Although HyperAccess 5 will initialize the modem with the string every
|
||
|
|
time you dial a remote system, the program does not change the factory
|
||
|
|
default settings for the ATI modem (which is V.32 without error control
|
||
|
|
or data compression). Every time you turn the modem off and back on, the
|
||
|
|
modem will revert to its factory defaults.
|
||
|
|
|
||
|
|
Unlike HyperAccess 5 (and other communications programs), Qmodem does it
|
||
|
|
in a different way. It actually replaces the old factory default setting
|
||
|
|
(AT&F) of the ATI modem with a new default configuration (AT&F2&C1&D2).
|
||
|
|
|
||
|
|
When you first install Qmodem to work with an ATI 9600 etc/e modem, the
|
||
|
|
program sends the following two strings to the modem (make sure the
|
||
|
|
modem is connected to your PC and is turned on):
|
||
|
|
|
||
|
|
AT&F2^M
|
||
|
|
AT&C1&D2&W^M
|
||
|
|
|
||
|
|
The first string sets the modem as V.32 with V.42bis enabled, hardware
|
||
|
|
flow control enabled (among other things). Note that ^M is equivalent to
|
||
|
|
sending a Carriage Return to the modem.
|
||
|
|
|
||
|
|
The second string changes the factory settings of the CD and DTR
|
||
|
|
(&C0&D0) and then write (&W) all the new active configuration settings
|
||
|
|
to the nonvolatile memory of the modem. The new settings are now stored
|
||
|
|
by the modem and become the new default configuration when the modem is
|
||
|
|
powered on (or when it received the ATZ command).
|
||
|
|
|
||
|
|
Thus, Qmodem simply sends the initialization string "ATZ^M" (which
|
||
|
|
resets the modem to its default state, now AT&F2&C1&D2) to the modem
|
||
|
|
whenever you load the program.
|
||
|
|
|
||
|
|
Although the two programs use different techniques, the result is the
|
||
|
|
same. The modem is initialized as V.32/V.42bis with hardware flow
|
||
|
|
control enabled, which is normally the optimum setting.
|
||
|
|
|
||
|
|
|
||
|
|
Does Your Software Configure Itself to Match the Modem Settings?
|
||
|
|
|
||
|
|
Besides sending the right initialization string to the modem, the
|
||
|
|
communications software will also need to match the modem setting.
|
||
|
|
Specifically, the communications software should also use hardware flow
|
||
|
|
control since the modem is initialized with hardware flow control
|
||
|
|
enabled.
|
||
|
|
|
||
|
|
One would expect that when a software initializes the modem to use
|
||
|
|
hardware flow control, the software itself would also use hardware flow
|
||
|
|
control. But it is not always true. As we mentioned earlier, HyperAccess
|
||
|
|
5 initializes the modem with hardware flow control enabled, but expect
|
||
|
|
you to change the flow control settings in each individual dialing
|
||
|
|
entry.
|
||
|
|
|
||
|
|
|
||
|
|
Why You May Need to Change the Initialization String
|
||
|
|
|
||
|
|
In general, the string AT&F2&C1&D2 should work without any problem. But
|
||
|
|
there is no guarantee that it will always work. When it does not work,
|
||
|
|
you'll normally need to change the initialization string to solve the
|
||
|
|
problems.
|
||
|
|
|
||
|
|
Here are a few reasons why the initialization string used by your
|
||
|
|
communications program may not work:
|
||
|
|
|
||
|
|
1. The settings need adjustments to work with the system you are
|
||
|
|
calling.
|
||
|
|
|
||
|
|
Case 1: When I called the Hayes BBS, the modem would abort and failed
|
||
|
|
to make a connection. It turned out that the default setting (30
|
||
|
|
seconds) of the S7 register is not long enough for the ATI modem to
|
||
|
|
make a connection with the Hayes Ultra 96 modem on the other end.
|
||
|
|
|
||
|
|
Solution: To establish a connection to the Hayes BBS, I need to add
|
||
|
|
"S7=60" to the modem initialization string and also change the
|
||
|
|
setting in the communications software to wait 60 seconds for a
|
||
|
|
connection.
|
||
|
|
|
||
|
|
By initializing the modem with the string AT&F2&C1&D2S7=60, I was
|
||
|
|
able to connect without any problem. (The default setting for the S7
|
||
|
|
register is not universal, the Hayes Ultra and Practical Peripheral
|
||
|
|
use 50 seconds as the default value.) Note that there is nothing
|
||
|
|
special about the number 60. In my particular case, any number larger
|
||
|
|
than 45 will work.
|
||
|
|
|
||
|
|
Case 2: When I call a system that uses the Telebit T1600 modems, I
|
||
|
|
cannot make a connection if the ATI modem is set to use V.42bis or
|
||
|
|
MNP-5. The ATI modem will only connect reliably when it is set to use
|
||
|
|
MNP-4.
|
||
|
|
|
||
|
|
Solution: To connect successfully, I have to set up the modem as V.32
|
||
|
|
with MNP-4 by sending the string AT&F1&U0 to the ATI modem. (AT&F1
|
||
|
|
sets the ATI modem as V.32 with MNP-5, &U0 turns off data
|
||
|
|
compression.)
|
||
|
|
|
||
|
|
2. Your communication software may not be compatible with the setting.
|
||
|
|
For example, America Online implemented an error-correcting scheme in
|
||
|
|
the software (both the PC and the Mac versions) which is not
|
||
|
|
compatible with the modem's error correction protocol.
|
||
|
|
|
||
|
|
Solution: To use America Online, you need to turn off error control
|
||
|
|
on the modem. AT&F configures the ATI modem as V.32 without error
|
||
|
|
control.
|
||
|
|
|
||
|
|
3. Your computer hardware may not work with the setting. As I mention
|
||
|
|
earlier, you need a properly wired cable for the Mac to use hardware
|
||
|
|
flow control. If you do not have the right cable or if your Mac
|
||
|
|
simply won't work with the cable, you will need to use software flow
|
||
|
|
control. (&K4 tells the ATI modem to use software flow control.)
|
||
|
|
|
||
|
|
Solution: To use the ATI modem in V.32/V.42bis mode with my Mac, I
|
||
|
|
need to disable hardware flow control and use XON/XOFF software flow
|
||
|
|
control instead. The string AT&F2&K4&C1&D2S7=60 sets up the modem
|
||
|
|
properly (again, S7=60 is for calling the Hayes BBS).
|
||
|
|
|
||
|
|
4. You may need to change the setting to achieve better performance. It
|
||
|
|
is advisable that you turn off MNP-5 while downloading pre-compressed
|
||
|
|
files from a remote system that has a MNP-5 modem. You can initialize
|
||
|
|
the ATI modem to turn off MNP-5 data compression with the string
|
||
|
|
AT&F1&U0.
|
||
|
|
|
||
|
|
|
||
|
|
Again, the initialization string used here is for the ATI modem only. If
|
||
|
|
you use a different modem, you would need to check with the modem manual
|
||
|
|
to find out the equivalent commands to use.
|
||
|
|
|
||
|
|
|
||
|
|
Editing the Initialization String
|
||
|
|
|
||
|
|
If the initialization string provided by your software does not work (or
|
||
|
|
if your software does not support your modem at all), you'll need to
|
||
|
|
edit the initialization string in your communications program.
|
||
|
|
|
||
|
|
The modem initialization string consists of a series of commands (called
|
||
|
|
the AT commands). They can be divided into three groups:
|
||
|
|
|
||
|
|
1. A capital character followed by a digit. For example, M1.
|
||
|
|
2. An ampersand & and a capital character followed by a digit. For
|
||
|
|
example, &M1. Note that M1 is different from &M1.
|
||
|
|
3. Sr=n where "r" is the number of the register to be changed and "n" is
|
||
|
|
the new value that is being assigned. For example, S7=60.
|
||
|
|
|
||
|
|
There are some other characters that may also appear in the modem
|
||
|
|
initialization string. These characters normally should not be changed.
|
||
|
|
|
||
|
|
AT tells the modem that modem commands follow.
|
||
|
|
|
||
|
|
Z resets the modem to default state
|
||
|
|
|
||
|
|
~ makes your software pause for half a second. You can use
|
||
|
|
more than one ~ in a row. For example, ~~~~ tells the
|
||
|
|
software to pause two seconds.
|
||
|
|
|
||
|
|
^M sends the terminating Carriage Return character to the
|
||
|
|
modem. This is a control code that most communication
|
||
|
|
software translate as a "carriage return."
|
||
|
|
|
||
|
|
|
||
|
|
Let's assume that the appropriate initialization string to use is
|
||
|
|
AT&F2&C1&D2S7=60 (for the ATI modem). You'll need to replace this string
|
||
|
|
with the one provided by your communications software.
|
||
|
|
|
||
|
|
If your software does not support your modem, you can install the
|
||
|
|
program by telling it that you have a Hayes modem. After the
|
||
|
|
installation, you'll simply edit the initialization string with the
|
||
|
|
appropriate one. Please make sure you do not delete any ~ or ^M.
|
||
|
|
|
||
|
|
Here are some examples,
|
||
|
|
|
||
|
|
1. To change the string provided by Procomm Plus
|
||
|
|
|
||
|
|
ATE1 S7=60 S11=60 V1 X1 Q0 S0=0^M
|
||
|
|
|
||
|
|
Use the string
|
||
|
|
|
||
|
|
AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
2. To edit the string used by Telix
|
||
|
|
|
||
|
|
ATZ^M~~~AT S7=45 S0=0 V1 X4^M
|
||
|
|
|
||
|
|
change it to
|
||
|
|
|
||
|
|
ATZ^M~~~AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
3. To replace the initialization string provided by ZTerm (Macintosh)
|
||
|
|
|
||
|
|
ATE1M1 V1^M
|
||
|
|
|
||
|
|
use the following string
|
||
|
|
|
||
|
|
AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
|
||
|
|
Match Software Settings To the Modem Settings
|
||
|
|
|
||
|
|
Besides using the right initialization string, you also need to make
|
||
|
|
sure that the settings in your communications program match those of the
|
||
|
|
modem.
|
||
|
|
|
||
|
|
Speed setting
|
||
|
|
|
||
|
|
If you have a modem that supports data compression. You want to make
|
||
|
|
sure that the speed setting for the entries in your dialing directory is
|
||
|
|
the maximum throughput. Here are the general rules of thumb:
|
||
|
|
|
||
|
|
For a V.32bis/V.42bis modem, set speed to 38400 or 57600 bps (check your
|
||
|
|
modem manual).
|
||
|
|
For a V.32/V.42bis modem, set speed to 38400 bps.
|
||
|
|
For a V.32/MNP-5 modem, set speed to 19200 bps.
|
||
|
|
For a V.22bis/V.42bis modem, set speed to 9600 bps.
|
||
|
|
For a V.22bis/MNP-5 modem, set speed to 4800 bps.
|
||
|
|
|
||
|
|
Note: Your computer may not be fast enough to work reliably at 38400 or
|
||
|
|
57600 bps. Also, the communications programs you use may not support
|
||
|
|
speed higher than 19200 bps.
|
||
|
|
|
||
|
|
|
||
|
|
Hardware flow control
|
||
|
|
|
||
|
|
Note that you will need to configure your software to use hardware
|
||
|
|
handshaking if the modem is initialized to use hardware flow control.
|
||
|
|
|
||
|
|
|
||
|
|
Dialing Time-out Value
|
||
|
|
|
||
|
|
Independent from your modem setting, your software may also impose a
|
||
|
|
limit on how long it will wait for a connection. If you initialize the
|
||
|
|
modem with the command S7=60, you'll need to change the time-out value
|
||
|
|
used by your software to 60 seconds accordingly.
|
||
|
|
|
||
|
|
|
||
|
|
Configuring Popular Communications Software to Work with High-speed Modems
|
||
|
|
|
||
|
|
Below are brief instructions for configuring some popular communications
|
||
|
|
programs to work with a high-speed modem. The particular initialization
|
||
|
|
string is for the ATI 9600etc/e modem. It is assumed that the
|
||
|
|
appropriate initialization string to use is AT&F2&C1&D2S7=60.
|
||
|
|
|
||
|
|
Make sure you save the changes you make.
|
||
|
|
|
||
|
|
|
||
|
|
Procomm Plus 2.0
|
||
|
|
|
||
|
|
To change the modem initialization string: (Global, i.e. it works with
|
||
|
|
every dialing entry)
|
||
|
|
1. Load Procomm, press Alt-S
|
||
|
|
2. Select Modem Options
|
||
|
|
3. Select Modem Commands
|
||
|
|
4. Press A
|
||
|
|
5. Change the initialization string to AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection: (Global)
|
||
|
|
1. Load Procomm, press Alt-S
|
||
|
|
2. Select Modem Options
|
||
|
|
3. Select General Options
|
||
|
|
4. Press A
|
||
|
|
5. Type 60 and press Return
|
||
|
|
|
||
|
|
To enable hardware flow control: (Global)
|
||
|
|
1. Load Procomm, press Alt-S
|
||
|
|
2. Select Terminal Options
|
||
|
|
3. Press D (hardware flow control)
|
||
|
|
4. Press Space Bar to toggle, press Return to accept
|
||
|
|
5. Press C (software flow control)
|
||
|
|
6. Press Space Bar to toggle, press Return to accept
|
||
|
|
|
||
|
|
|
||
|
|
Telix
|
||
|
|
|
||
|
|
To change the modem initialization string: (Global)
|
||
|
|
1. Press Alt-O
|
||
|
|
2. Select Modem and dialing
|
||
|
|
3. Select A (Init String)
|
||
|
|
4. Change the initialization string to ATZ^M~~~AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection: (Global)
|
||
|
|
1. Press Alt-O
|
||
|
|
2. Select Modem and dialing
|
||
|
|
3. Select K (Dial time) and enter 60 press Return
|
||
|
|
|
||
|
|
To enable hardware flow control (Global)
|
||
|
|
1. Press Alt-O
|
||
|
|
2. Select Terminal options
|
||
|
|
3. Press J (XON/XOFF software flow control)
|
||
|
|
4. Select Off
|
||
|
|
5. Select K (CTS/RTS hardware flow control)
|
||
|
|
6. Select On
|
||
|
|
7. Press ESC to exit
|
||
|
|
|
||
|
|
|
||
|
|
Qmodem
|
||
|
|
|
||
|
|
To change the modem initialization string: (Global)
|
||
|
|
1. Press Alt-N
|
||
|
|
2. Press M to select Modem menu
|
||
|
|
3. Select Modem Commands
|
||
|
|
4. Press Return
|
||
|
|
5. Change the initialization string to AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection: (Global)
|
||
|
|
1. Press Alt-N
|
||
|
|
2. Press M to select Modem menu and Press Return to select Communication
|
||
|
|
Parameters
|
||
|
|
3. Press H to select Timeout delay
|
||
|
|
4. Type 60 and press Return
|
||
|
|
5. ESC to exit
|
||
|
|
|
||
|
|
To enable hardware flow control: (Global)
|
||
|
|
|
||
|
|
1. Press Alt-N
|
||
|
|
2. Select Toggles
|
||
|
|
3. Press Return to toggle XON/XOFF flow
|
||
|
|
4. Select CTS/RTS flow
|
||
|
|
5. Press Return to toggle
|
||
|
|
6. ESC
|
||
|
|
7. ESC
|
||
|
|
8. Press E for Exit
|
||
|
|
9. Save Changes
|
||
|
|
|
||
|
|
|
||
|
|
HyperAccess 5
|
||
|
|
|
||
|
|
Note: HyperAccess 5 supports the ATI 9600etc/e. However, HyperAccess 5 does
|
||
|
|
not let you edit the initialization string directly. You can add additional
|
||
|
|
setup commands to change the modem settings for each individual dialing
|
||
|
|
entry.
|
||
|
|
|
||
|
|
To change the modem initialization string: (Individual, i.e. it works
|
||
|
|
only with the particular dialing entry)
|
||
|
|
1. Select Define system settings from the Main menu
|
||
|
|
2. Select Modify
|
||
|
|
3. Use cursor to select the system to modify and press Enter
|
||
|
|
4. Select Hardware from the System settings menu
|
||
|
|
5. Select Modem
|
||
|
|
6. Select Additional modem setup commands
|
||
|
|
7. Type S7=60
|
||
|
|
8. Press ESC twice to go back the Main menu
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection:
|
||
|
|
N/A
|
||
|
|
|
||
|
|
To enable hardware flow control: (Individual)
|
||
|
|
1. Select Define system settings from the Main menu
|
||
|
|
2. Select Modify
|
||
|
|
3. Use cursor to select the system to modify and press Enter
|
||
|
|
4. Select Hardware from the System settings menu
|
||
|
|
5. Make sure that Data terminal ready signal is output on DTR, delete
|
||
|
|
RTS if it is listed
|
||
|
|
6. Select Communications port
|
||
|
|
7. Select Incoming hardware handshaking and type CTS
|
||
|
|
8. Select Outgoing hardware handshaking and type RTS
|
||
|
|
|
||
|
|
|
||
|
|
Crosstalk for Windows
|
||
|
|
|
||
|
|
To change the modem initialization string: (Global)
|
||
|
|
1. Pull down Setup menu and select Modem...
|
||
|
|
2. Select Custom and click on Settings
|
||
|
|
3. Change the initialization string to ^M~AT&F2&C1&D2S7=60^M
|
||
|
|
4. Click OK
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection: (Individual)
|
||
|
|
1. Pull down File menu and select Open a phone book entry
|
||
|
|
2. Open the phone book entry
|
||
|
|
3. Pull down Setup menu and select Session
|
||
|
|
4. Click on More
|
||
|
|
5. Change the value in Allow xx seconds for the host to answer
|
||
|
|
|
||
|
|
To enable hardware flow control: (Individual)
|
||
|
|
1. Pull down File menu and select Open a phone book entry
|
||
|
|
2. Open the phone book entry
|
||
|
|
3. Pull down Setup menu and select Device
|
||
|
|
4. Click on RTS/CTS and click OK
|
||
|
|
|
||
|
|
|
||
|
|
MicroPhone II (for Macintosh)
|
||
|
|
|
||
|
|
To change the modem initialization string: (Individual)
|
||
|
|
1. Choose Settings Menu
|
||
|
|
2. Select Communications
|
||
|
|
3. Choose V.32 Standard from the Modem Driver list box
|
||
|
|
4. Click OK
|
||
|
|
5. Hold down the Command key and choose Scripts menu
|
||
|
|
6. Select Modify Script
|
||
|
|
7. Click the Modem Scripts button
|
||
|
|
8. Double-click on Modem_Init
|
||
|
|
9. Double-click on the first line that says
|
||
|
|
Set Variable * mcmd from Expression "'AT....'"
|
||
|
|
10. Change the initialization string in the lower right box to
|
||
|
|
'AT&F2&C1&D2S7=60^M'
|
||
|
|
11. Double-click on the second line that says
|
||
|
|
Set Variable * mcmd from Expression "'AT....'"
|
||
|
|
12. Change the initialization string in the lower right box to
|
||
|
|
'AT&F2&C1&D2S7=60^M'
|
||
|
|
13. Click OK
|
||
|
|
14. Press the Option key and choose the File menu
|
||
|
|
15. Select Save Modem Driver (If you want to save the driver under a new
|
||
|
|
name, select Save Modem Driver As... in the File Menu. Name the new
|
||
|
|
driver, and save it into the Modem Folder.)
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection:
|
||
|
|
N/A
|
||
|
|
|
||
|
|
To enable hardware flow control: (Individual)
|
||
|
|
1. Pull down Settings Menu
|
||
|
|
2. Select Communications
|
||
|
|
3. Click on the Hardware Handshake box
|
||
|
|
|
||
|
|
|
||
|
|
ZTerm (for Macintosh)
|
||
|
|
|
||
|
|
To change the modem initialization string: (Global)
|
||
|
|
1. Choose Settings Menu and select Modem
|
||
|
|
2. Change Init String to AT&F2&C1&D2S7=60^M
|
||
|
|
|
||
|
|
To set the software to wait 60 seconds for connection: (Individual)
|
||
|
|
1. Choose Settings Menu and select Modem
|
||
|
|
2. Edit Dial Timeout
|
||
|
|
|
||
|
|
To enable hardware flow control: (Global)
|
||
|
|
1. Choose Settings Menu and Select Flow Control
|
||
|
|
2. Uncheck Xon-Xoff Receive
|
||
|
|
3. Uncheck Xon-Xoff Send
|
||
|
|
4. Check HW Handshake
|
||
|
|
|
||
|
|
|
||
|
|
Other Settings for Your Communications Software
|
||
|
|
|
||
|
|
Telephone Number
|
||
|
|
|
||
|
|
Online services use different phone numbers for different kinds of
|
||
|
|
modems. To get the best throughput, make sure you dial the right phone
|
||
|
|
number. Note that many bulletin board systems do not allow calling their
|
||
|
|
high-speed modem lines with 2400 bps modems. You would be disconnected.
|
||
|
|
|
||
|
|
For example:
|
||
|
|
EXEC-PC, the largest BBS in the United States, has the following
|
||
|
|
telephone numbers:
|
||
|
|
|
||
|
|
#1: Standard 2400 bps modems 414-789-4210
|
||
|
|
#2: US Robotics HST 9600 MNP5 414-789-4337
|
||
|
|
#3: US Robotics HST 14400 & V.32/V.42bis/MNP5 414-789-4352
|
||
|
|
#4: US Robotics V.32bis/V.42bis & HST 414-789-4360
|
||
|
|
#5: CompuCom Speedmodem 9600 MNP5 modems 414-789-4450
|
||
|
|
#6: Hayes 9600B V-series modems, NON-V.32 414-789-4315
|
||
|
|
|
||
|
|
|
||
|
|
If you have a 9600 bps HST modem, call #2.
|
||
|
|
If you have a 14400 bps HST modem, call #3 or #4. You can also call #2
|
||
|
|
but you won't be able to get the best throughput.
|
||
|
|
If you have a V.32 modem, call #3 or #4.
|
||
|
|
If you have a V.32bis modem, call #4. You can also call #3 but you won't
|
||
|
|
get the best throughput.
|
||
|
|
If you have a CompuCom SpeedModem Champ, call #5
|
||
|
|
If you have a CompuCom SpeedModem Storm, call #3 or #4 (V.32), #5 (CSP)
|
||
|
|
If you have a CompuCom SpeedModem Star, call #4 (V.32bis), you can also
|
||
|
|
call #3 or #5 but you can only connect at 9600 bps.
|
||
|
|
If you have a Hayes V-series Smartmodem 9600 (or 9600B) modem, call #6.
|
||
|
|
|
||
|
|
|
||
|
|
Dial String: ATDT
|
||
|
|
|
||
|
|
You don't have change the dialing string unless you use a PBX system or
|
||
|
|
have call waiting service.
|
||
|
|
|
||
|
|
|
||
|
|
PBX
|
||
|
|
|
||
|
|
If you have to dial the digit 9 to obtain an outside line, Use ATDT9,
|
||
|
|
(the comma , instructs the modem to pause two seconds). This allows
|
||
|
|
enough time for the dial tone to occur before the modem dials. You can
|
||
|
|
use as many commas as you like.
|
||
|
|
|
||
|
|
|
||
|
|
Call Waiting
|
||
|
|
|
||
|
|
Call waiting service will disrupt modem sessions. If your telephone
|
||
|
|
company supports the ability to disable call waiting, use the dial
|
||
|
|
string ATDT*70, (make sure you add the comma ,) instead of ATDT.
|
||
|
|
|
||
|
|
ATDT*70,123-4567
|
||
|
|
|
||
|
|
Also, adding 1170 after the ATDP dial command can be used to disable
|
||
|
|
call-waiting on some pulse-dialing phone systems. Check with your phone
|
||
|
|
company to see if these features are supported.
|
||
|
|
|
||
|
|
|
||
|
|
8-N-1 or 7-E-1 (data bits-parity-stop bits)
|
||
|
|
|
||
|
|
In general, set the parameters to 8-N-1. If you are calling a commercial
|
||
|
|
online service (such as GEnie), you may need to set the parameters to
|
||
|
|
7-E-1.
|
||
|
|
|
||
|
|
|
||
|
|
Half vs. Full Duplex: Local Echo
|
||
|
|
|
||
|
|
The only popular on-line service that uses half duplex is GEnie.
|
||
|
|
|
||
|
|
|
||
|
|
Terminal Emulation
|
||
|
|
|
||
|
|
If you are using an IBM compatible, choose IBM PC or ANSI.
|
||
|
|
Otherwise, try VT102, VT100, VT52, TTY.
|
||
|
|
|
||
|
|
|
||
|
|
Comm Port
|
||
|
|
|
||
|
|
For your computer to talk to your modem, you need to tell the software
|
||
|
|
where to find the modem. If you use a PC with an external modem, you
|
||
|
|
need to specify which serial port the modem is connected to. If you have
|
||
|
|
an internal modem, you need to configure the modem and tell the software
|
||
|
|
which COM port the modem is configured for.
|
||
|
|
|
||
|
|
If you use a Macintosh, specify whether your modem is connected to the
|
||
|
|
modem port or the printer port.
|
||
|
|
|
||
|
|
|
||
|
|
File Transfer Protocols
|
||
|
|
|
||
|
|
Errors that occur during file transfer are automatically detected and
|
||
|
|
corrected by file transfer protocols. If a block of data is received
|
||
|
|
incorrectly, the receiving system sends a message to the sending system
|
||
|
|
and requests the re-transmission. This process is automatic. When errors
|
||
|
|
occur during file transfer, the communication program shows an error in
|
||
|
|
the file transfer status window.
|
||
|
|
|
||
|
|
|
||
|
|
ASCII
|
||
|
|
|
||
|
|
This is designed to work with ASCII text files only. Notice that you do
|
||
|
|
not have to use this protocol when transferring text files. The ASCII
|
||
|
|
protocol is useful for uploading a text file when you are composing
|
||
|
|
e-mail online.
|
||
|
|
|
||
|
|
|
||
|
|
Xmodem
|
||
|
|
|
||
|
|
Xmodem is one of the most widely used file transfer protocols. The
|
||
|
|
original Xmodem protocol uses 128-byte packets and a simple "checksum"
|
||
|
|
method of error detection. A later enhancement, Xmodem-CRC, uses a more
|
||
|
|
secure Cyclic Redundancy Check (CRC) method for error detection. Xmodem
|
||
|
|
protocol always attempts to use CRC first. If the sender does not
|
||
|
|
acknowledge the requests for CRC, the receiver shifts to the checksum
|
||
|
|
mode and continues its request for transmission.
|
||
|
|
|
||
|
|
|
||
|
|
Xmodem-1K
|
||
|
|
|
||
|
|
Xmodem 1K is essentially Xmodem CRC with 1K (1024 byte) packets. On some
|
||
|
|
systems and bulletin boards it may also be referred to as Ymodem. Some
|
||
|
|
communication software programs, most notably Procomm Plus 1.x, also
|
||
|
|
list Xmodem-1K as Ymodem. Procomm Plus 2.0 no longer refers to Xmodem-1K
|
||
|
|
as Ymodem.
|
||
|
|
|
||
|
|
|
||
|
|
Ymodem
|
||
|
|
|
||
|
|
Ymodem is essentially Xmodem 1K that allows multiple batch file
|
||
|
|
transfer. On some systems it is listed as Ymodem Batch.
|
||
|
|
|
||
|
|
|
||
|
|
Ymodem-g
|
||
|
|
|
||
|
|
Ymodem-g is a variant of Ymodem. It is designed to be used with modems
|
||
|
|
that support error control. This protocol does not provide software
|
||
|
|
error correction or recovery, but expects the modem to provide the
|
||
|
|
service. It is a streaming protocol that sends and receives 1K packets
|
||
|
|
in a continuous stream until instructed to stop. It does not wait for
|
||
|
|
positive acknowledgement after each block is sent, but rather sends
|
||
|
|
blocks in rapid succession. If any block is unsuccessfully transferred,
|
||
|
|
the entire transfer is canceled.
|
||
|
|
|
||
|
|
|
||
|
|
Zmodem
|
||
|
|
|
||
|
|
This is generally the best protocol to use if the electronic service you
|
||
|
|
are calling supports it. Zmodem has two significant features: it is
|
||
|
|
extremely efficient and it provides crash recovery.
|
||
|
|
|
||
|
|
Like Ymodem-g, Zmodem does not wait for positive acknowledgement after
|
||
|
|
each block is sent, but rather sends blocks in rapid succession. If a
|
||
|
|
Zmodem transfer is canceled or interrupted for any reason, the transfer
|
||
|
|
can be resurrected later and the previously transferred information need
|
||
|
|
not be resent.
|
||
|
|
|
||
|
|
|
||
|
|
Kermit
|
||
|
|
|
||
|
|
Kermit was developed at Columbia University. It was designed to
|
||
|
|
facilitate the exchange of data among very different types of computers
|
||
|
|
(mainly minicomputers and mainframes). You probably will not need to use
|
||
|
|
Kermit unless you are calling a minicomputer or mainframe at an
|
||
|
|
educational institution.
|
||
|
|
|
||
|
|
|
||
|
|
Sealink
|
||
|
|
|
||
|
|
Sealink is a variant of Xmodem. It was developed to overcome the
|
||
|
|
transmission delays caused by satellite relays or packet-switching
|
||
|
|
networks.
|
||
|
|
|
||
|
|
|
||
|
|
Which file transfer protocol should you use?
|
||
|
|
|
||
|
|
In general, I recommend Zmodem. If Zmodem is not supported by the system
|
||
|
|
you are calling, use Ymodem-g. (If you are connecting to a UNIX system
|
||
|
|
in a university, you may have to use Kermit or Xmodem to transfer
|
||
|
|
files.)
|
||
|
|
|
||
|
|
Here are the test results obtained by downloading the files using
|
||
|
|
various file transfer protocols. The number before the parentheses is
|
||
|
|
the transfer speed (in cps) and the number in the parentheses is the
|
||
|
|
time elapsed (in seconds).
|
||
|
|
|
||
|
|
Protocol Xmodem Xmodem-1K Ymodem Ymodem-g Zmodem
|
||
|
|
---------------------------------------------------------------------
|
||
|
|
the-wave.txt 429(334) 1508(95) 1527(94) 3261(44) 3296(43)
|
||
|
|
dayrpt.arc 314(26) 758(11) 761(11) 1042(8) 1025(8)
|
||
|
|
dayrpt.wks 415(47) 1252(15) 1244(15) 2314(8) 2337(8)
|
||
|
|
sunset.arc 337(15) 771(6) 745(6) 987(5) 965(5)
|
||
|
|
sunset.pic 399(41) 1337(12) 1297(12) 2594(6) 2588(6)
|
||
|
|
text109k.arc 343(86) 817(36) 814(36) 1089(27) 1064(27)
|
||
|
|
text109k.txt 410(271) 1379(80) 1351(82) 2812(39) 2885(38)
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
************************************************************************
|
||
|
|
Appendix A: Resources
|
||
|
|
Here is a list of selected modem manufacturers.
|
||
|
|
Manufacturer Information Tech Support Support BBS
|
||
|
|
--------------------------------------------------------------------------
|
||
|
|
ATI Technologies (416) 756-0718 (416) 756-0711 (416) 756-4591
|
||
|
|
Cardinal (800) 233-0187 (717) 293-3124 (717) 293-3074
|
||
|
|
Compucom (800) 228-6648 (408) 732-4500 (408) 738-4990
|
||
|
|
Hayes (404) 441-1617 (404) 441-1617 (800) 874-2937
|
||
|
|
Image Communications (201) 935-8880 (201) 935-8880 n/a
|
||
|
|
Intel (800) 538-3373 (503) 629-7000 (503) 645-6275
|
||
|
|
Microcom (800) 822-8224 (617) 551-1313 (617) 551-1655
|
||
|
|
Multi-Tech (800) 328-9717 (800) 328-9717 (612) 785-9875
|
||
|
|
Practical Peripherals (800) 442-4774 (818) 991-8200 (818) 706-2467
|
||
|
|
Prometheus (800) 477-3473 (503) 624-0571 (503) 691-5199
|
||
|
|
Supra (800) 727-8772 (503) 967-2440 (503) 967-2444
|
||
|
|
Telebit (800) 835-3248 (800) 835-3248 n/a
|
||
|
|
U.S. Robotics (800) 342-5877 (800) 982-5151 (708) 982-5092
|
||
|
|
Zoom (800) 666-6191 (617) 423-1076 (617) 451-5284
|
||
|
|
Support BBS for Communications Programs
|
||
|
|
--------------------------------------------------------------------------
|
||
|
|
Procomm Plus (Datastorm Technologies, Inc.) (314) 875-0523
|
||
|
|
Telix (Exis Inc.) (416) 439-9399
|
||
|
|
Qmodem (The Forbin Project, Inc.) (319) 233-6157
|
||
|
|
HyperAccess 5 (Hilgraeve Inc.) (313) 243-5915
|
||
|
|
Crosstalk for Windows (DCA) (404) 740-8428
|
||
|
|
MicroPhone II (Software Ventures) (415) 849-1912
|
||
|
|
ZTerm n/a
|
||
|
|
************************************************************************
|
||
|
|
Appendix B: How to reach the author
|
||
|
|
If you have any comments or suggestions, I'll love to hear from you. You can
|
||
|
|
reach me via
|
||
|
|
America Online: Pat Chen
|
||
|
|
CompuServe: 70754,3162
|
||
|
|
DELPHI: POC
|
||
|
|
FidoNet: 1:161/444.38
|
||
|
|
GEnie: p.chen2
|
||
|
|
MCI Mail: 445-6669
|
||
|
|
Internet: 445-6669@mcimail.com
|
||
|
|
70754.3162@compuserve.com
|
||
|
|
pchen@cup.portal.com
|
||
|
|
U.S. Mail: Patrick Chen
|
||
|
|
P.O. Box 5325
|
||
|
|
Irvine, CA 92716
|
||
|
|
|
||
|
|
************************************************************************
|
||
|
|
Appendix C: About "The Joy of Telecomputing"
|
||
|
|
What is "The Joy of Telecomputing?"
|
||
|
|
|
||
|
|
"The Joy of Telecomputing" is a 200-page (and growing), three-part
|
||
|
|
report consisting of the following articles: "What you need to know
|
||
|
|
about modems,""Life beyond CompuServe" and "Is AT&T the right choice?" A
|
||
|
|
glossary and an index are also provided.
|
||
|
|
|
||
|
|
The discussions in "The Joy of Telecomputing" are devoted to the
|
||
|
|
following online activities: file transfer (downloading shareware,
|
||
|
|
exchanging files with colleagues or friends), electronic mail,
|
||
|
|
conferences (forums, newsgroups, SIGs), chatting. You won't find
|
||
|
|
discussions on stock quotes, shopping malls, online databases, etc.
|
||
|
|
|
||
|
|
Going online has become a way of life for many computer users. It is
|
||
|
|
undeniably fascinating, fulfilling and fun. But there is also a down
|
||
|
|
side to it: the cost can be prohibitive. I have yet to meet an avid
|
||
|
|
modem user who didn't wish that he could afford to be online longer.
|
||
|
|
|
||
|
|
To get the most mileage from your online dollars, you need to know the
|
||
|
|
answers to the following three questions:
|
||
|
|
|
||
|
|
1. What is the right modem to use?
|
||
|
|
2. What online services are available and how do they compare?
|
||
|
|
3. What is the most cost-effective way to reach those services?
|
||
|
|
|
||
|
|
These are not isolated questions. The answers to these questions will
|
||
|
|
help you decide what online systems are right for you.
|
||
|
|
|
||
|
|
People live in different cities, use different kinds of computers and do
|
||
|
|
different things online. It should come as no surprise that there isn't
|
||
|
|
a single online system that is right for everyone.
|
||
|
|
|
||
|
|
The goal of "The Joy of Telecomputing" is to help you get the most from
|
||
|
|
telecomputing. Our goal is not to tell you that so-and-so is the best
|
||
|
|
but to present you with enough information so that you will be able to
|
||
|
|
determine what is right for you. We'll provide you a survey that is both
|
||
|
|
comprehensive and specific.
|
||
|
|
|
||
|
|
To be comprehensive, we'll cover the three main groups of online
|
||
|
|
systems: commercial online services (CompuServe and others), bulletin
|
||
|
|
board systems and the Internet.
|
||
|
|
|
||
|
|
To be specific, we'll present you all the necessary information to help
|
||
|
|
you make a decision. Take electronic mail, for example. Virtually all
|
||
|
|
online systems offer electronic mail service. However, listing dozens of
|
||
|
|
services and saying that they all offer e-mail would do little to help
|
||
|
|
you make an intelligent decision. We'll also provide specific details
|
||
|
|
about each service such as
|
||
|
|
|
||
|
|
* How much does it cost?
|
||
|
|
* How fast does a message get delivered?
|
||
|
|
* Is the e-mail message protected? (Can someone else besides the
|
||
|
|
recipient read your mail messages?)
|
||
|
|
* Can you send e-mail to people that are not subscribers of the
|
||
|
|
service?
|
||
|
|
* Can you send a file with your message?
|
||
|
|
* Is there a limit on the size of the file you can send with your
|
||
|
|
message?
|
||
|
|
* How can you reach the service?
|
||
|
|
* Can you read and reply messages offline?
|
||
|
|
|
||
|
|
I use MCI Mail, CompuServe and the Internet for e-mail on a daily basis.
|
||
|
|
Do I need all these accounts? Not really. Theoretically I only need one
|
||
|
|
of them. (Yes, you can send e-mail from MCI Mail to a CompuServe or an
|
||
|
|
Internet user, and vice versa.) Why do I have three accounts then?
|
||
|
|
Because each has its pros and cons. And I use e-mail so much so that the
|
||
|
|
three accounts combined offer me the best solution.
|
||
|
|
|
||
|
|
(Note: CompuServe is a good deal for e-mail only if you join the Basic
|
||
|
|
Service Plan. To join this experimental program, type GO NEWBASIC at any
|
||
|
|
! prompt. For $7.95 per month, you are allowed to send 60 messages. Each
|
||
|
|
message can have up to 7500 characters. Note that there is a surcharge
|
||
|
|
for sending e-mail to MCI Mail users. Also, reading e-mail sent to you
|
||
|
|
from Internet also count against your monthly allowance.)
|
||
|
|
|
||
|
|
For the past eight years, I've worked as a computer consultant. I
|
||
|
|
decided to pursue my career as a computer writer a few months ago. In
|
||
|
|
the past three months, I have signed contracts for two computer books to
|
||
|
|
be published in 1992.
|
||
|
|
|
||
|
|
"The Joy of Telecomputing" is a project that I believe is sorely needed.
|
||
|
|
Initially I have considered submitting it to the computer book
|
||
|
|
publishers. However, I have learned that it can easily take six to nine
|
||
|
|
months (if no longer) to get a book published. As a result, by the time
|
||
|
|
the book gets to the readers, it is probably obsolete. (It may not be
|
||
|
|
too bad if this is a book on C programming. But a book on the
|
||
|
|
online world?) Therefore, I decide to try it on my own to see whether
|
||
|
|
the online community would support such a project.
|
||
|
|
|
||
|
|
The online world is constantly changing and it will remain one of the
|
||
|
|
hottest growing area in microcomputing for many years to come. By
|
||
|
|
keeping the project under my own control, I'll be able to provide you
|
||
|
|
the information you need on a timely basis.
|
||
|
|
|
||
|
|
"The Joy of Telecomputing" is an ongoing project. It will be updated
|
||
|
|
every quarter. Future updates of "What you need to know about modems"
|
||
|
|
will remain available on BBS and other online services.
|
||
|
|
|
||
|
|
If there are enough supporters for this project, I would like to set up
|
||
|
|
a BBS. (What else?) You will be able to exchange informations, download
|
||
|
|
files and participate in discussions about the ever evolving online
|
||
|
|
world.
|
||
|
|
|
||
|
|
|
||
|
|
What's in "Life Beyond CompuServe?"
|
||
|
|
|
||
|
|
Part II of "The Joy of Telecomputing" provides a comprehensive survey of
|
||
|
|
the online world. It covers the three major groups of online systems:
|
||
|
|
|
||
|
|
* Commercial online services (America Online, BIX, CompuServe, DELPHI,
|
||
|
|
GEnie, MCI Mail, Prodigy, etc).
|
||
|
|
* BBS (including discussions on FidoNet, RIME, etc)
|
||
|
|
* The Internet (including discussions on UUCP, Usenet, Bitnet, etc).
|
||
|
|
|
||
|
|
|
||
|
|
Commercial Online Services
|
||
|
|
|
||
|
|
In general, commercial online services do not offer good
|
||
|
|
price/performance, though some of them excel in certain areas (such as
|
||
|
|
e-mail). We'll look at the major commercial online services (CompuServe,
|
||
|
|
GEnie, Prodigy, etc.) and see what they offer and what they are good
|
||
|
|
for. Major topics covered are:
|
||
|
|
|
||
|
|
* What are the major commercial online services?
|
||
|
|
* How much do they cost?
|
||
|
|
* How can you access those services?
|
||
|
|
* What do they offer? How do they compare with each other?
|
||
|
|
* How do they compare with BBS?
|
||
|
|
|
||
|
|
|
||
|
|
The World of BBS
|
||
|
|
|
||
|
|
It is estimated that more than 30,000 bulletin boards exist in the
|
||
|
|
United States. If you live in a metropolitan area, you'll probably find
|
||
|
|
hundreds of BBS that are local. Most BBS operate as a hobby by their
|
||
|
|
owners and without charge to their users. There are many BBS that have
|
||
|
|
members all over the United States (and the world).
|
||
|
|
|
||
|
|
The world of BBS has become a phenomenon. BBS are no longer isolated
|
||
|
|
systems. Fidonet, the network linking thousands of BBS around the world,
|
||
|
|
allows users on one BBS to communicate with those on other BBS.
|
||
|
|
Recently, with gateways to the UUCP network, many BBS has allowed their
|
||
|
|
members to exchange e-mail with users of the Internet and to participate
|
||
|
|
in Usenet newsgroups.
|
||
|
|
|
||
|
|
We'll cover the following topics:
|
||
|
|
|
||
|
|
* How many BBS are there? How do they compare?
|
||
|
|
* How much does it cost to become a member?
|
||
|
|
* What are the limitations?
|
||
|
|
* How to find BBS numbers?
|
||
|
|
* Which BBS offers the latest and greatest files for PC users?
|
||
|
|
Macintosh users? Amiga users?
|
||
|
|
* Which BBS are good for chatting? Which are good for conferences?
|
||
|
|
* What is Fidonet? How does it work? What does it offer?
|
||
|
|
* How to join Fidonet as a node?
|
||
|
|
* How to become a point on Fidonet?
|
||
|
|
* How to send e-mail from Fidonet to Internet (and from Internet to
|
||
|
|
Fidonet)?
|
||
|
|
* What is RIME?
|
||
|
|
* What are the major BBS software available?
|
||
|
|
* How to use BBS effectively?
|
||
|
|
* What software tools you need and where to find them?
|
||
|
|
* BBS Etiquette
|
||
|
|
* Why ZTerm is the best program to use for calling BBS? (For Macintosh
|
||
|
|
users only)
|
||
|
|
* What are MacBinary files? How to download a Macintosh file to a PC?
|
||
|
|
How to download a PC file to a Macintosh? (For Mac users or people
|
||
|
|
who use both Mac and PC.)
|
||
|
|
|
||
|
|
|
||
|
|
Internet
|
||
|
|
|
||
|
|
If you want someone to learn UNIX, show him the Internet. (You don't
|
||
|
|
need to be a UNIX expert to use the Internet though. Besides, UNIX is
|
||
|
|
not really that hard.)
|
||
|
|
|
||
|
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Internet is a global computer network linking hundreds of thousands of
|
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computers (mainly UNIX computers) at universities, research institutions
|
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|
|
and government agencies. Internet is unsurpassed for e-mail and
|
||
|
|
conferences (called newsgroups in the UNIX world). It is also an
|
||
|
|
invaluable resource for free software. Some major topics covered are:
|
||
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||
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|
* What is Internet
|
||
|
|
* What is UUCP? What is Usenet? What is Bitnet?
|
||
|
|
* What can you do on the Internet?
|
||
|
|
* How to send e-mail on the Internet?
|
||
|
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* How to send e-mail from Internet to CompuServe, MCI Mail, Fidonet
|
||
|
|
(and vice versa)?
|
||
|
|
* How to send binary files?
|
||
|
|
* What newsgroups are available?
|
||
|
|
* How to participate in a newsgroup?
|
||
|
|
* Etiquette
|
||
|
|
* What is FTP?
|
||
|
|
* What is Anonymous FTP?
|
||
|
|
* How to use FTP?
|
||
|
|
* What are the FTP sites available?
|
||
|
|
* How to find the files you need?
|
||
|
|
* What is telnet?
|
||
|
|
* What can you do with telnet? (Read "The Cuckoo's Egg" by Cliff Stoll
|
||
|
|
for a first-hand account on how a German hacker use telnet to break
|
||
|
|
into computers on Internet.)
|
||
|
|
* How to use telnet?
|
||
|
|
* How can you get an Internet account?
|
||
|
|
* What services are available? What kind of access level do they offer?
|
||
|
|
* How much do they cost?
|
||
|
|
* How to transfer files from a UNIX host to your personal computer?
|
||
|
|
* What are uuencode and uudecode?
|
||
|
|
* What are compress, tar and shar?
|
||
|
|
|
||
|
|
|
||
|
|
What's in "Is AT&T The Right Choice?"
|
||
|
|
|
||
|
|
Part III of "The Joy of Telecomputing" provides detailed discussions on the
|
||
|
|
various ways you can reach a remote system (i.e., a system which is not
|
||
|
|
local to you). What is the most cost-effective way to reach those systems?
|
||
|
|
|
||
|
|
There are generally two options you have to reach a remote system:
|
||
|
|
|
||
|
|
1. You can place a distance call using AT&T, MCI, etc.
|
||
|
|
2. You can reach the system via some packet-switching networks by
|
||
|
|
dialing a local number (the system you are calling may already have a
|
||
|
|
deal with a packet-switching network and charge you accordingly, or
|
||
|
|
you may subscribe to one of the packet-switching networks yourself).
|
||
|
|
|
||
|
|
However, packet-switching networks differ widely in what they offer, how
|
||
|
|
much they charge, and how well they perform. We'll look at some of the
|
||
|
|
services available (PC Pursuit, Connect-USA, Accu*Link, Tymnet,
|
||
|
|
REDI-Access, etc.).
|
||
|
|
|
||
|
|
* How many ways can you reach a remote system? What are the pros and
|
||
|
|
cons?
|
||
|
|
* What are packet-switching networks?
|
||
|
|
* How do they work?
|
||
|
|
* What services are available?
|
||
|
|
* What do they offer?
|
||
|
|
* What kinds of modems do they support?
|
||
|
|
* What are the differences in performance among different
|
||
|
|
packet-switching network?
|
||
|
|
* How much do they cost?
|
||
|
|
* Are packet-switching networks cost-effective?
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
==============================================================================
|
||
|
|
|
||
|
|
How to order "The Joy of Telecomputing"
|
||
|
|
|
||
|
|
30-Day Money-Back Guarantee: If you are not satisfied with your purchase
|
||
|
|
of "The Joy of Telecomputing," return it in resalable condition with all
|
||
|
|
the original packaging within the guarantee period for a refund check.
|
||
|
|
Shipping cost is not refundable.
|
||
|
|
|
||
|
|
To order a printed copy of "The Joy of Telecomputing," send a check or
|
||
|
|
money order to the following address:
|
||
|
|
|
||
|
|
Patrick Chen
|
||
|
|
P.O. Box 5325
|
||
|
|
Irvine, CA 92716 (USA)
|
||
|
|
|
||
|
|
|
||
|
|
"The Joy of Telecomputing"..................................$19.95
|
||
|
|
Shipping & Handling (see below).............................$_____
|
||
|
|
California residents please add 7.75% tax ($1.55)...........$_____
|
||
|
|
|
||
|
|
Total.......$_____
|
||
|
|
|
||
|
|
|
||
|
|
Note: Shipping to 48 continental states is $5.00. Alaska, Hawaii, and
|
||
|
|
Canada is $10.00. Other countries, please send e-mail before ordering.
|
||
|
|
Please allow 2-4 weeks for delivery.
|
||
|
|
|
||
|
|
There is no need to fill out the order form if you are sending a check
|
||
|
|
with your name and address printed on it.
|
||
|
|
|
||
|
|
Non U.S. residents: please send checks or money orders drawn on U.S.
|
||
|
|
Banks in U.S. Funds.
|
||
|
|
|
||
|
|
|
||
|
|
Name: Phone:
|
||
|
|
______________________________________ ______________________________
|
||
|
|
Company:
|
||
|
|
________________________________________________________________________
|
||
|
|
Address:
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
Comments/Suggestions:
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
|
|
|
||
|
|
________________________________________________________________________
|
||
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