118 lines
5.1 KiB
Plaintext
118 lines
5.1 KiB
Plaintext
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|| Circuit Switched Digital ||
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|| Capability ||
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|| ------------------------- ||
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|| Written by ||
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|| The Executioner ||
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|| and the ||
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|| [+] PhoneLine Phantoms [+] ||
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|| - - - ||
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][==================================][
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The Circuit Switched Digital Capability feature provides for the end-to-end
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digital transmission of 56 kilobits per second (kb/s) data and, alternately,
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the transmission of analog voice signals on a circuit switched basis. The CSDC
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feature was formerly known as PSDC (Public Switched Digital Capability). Both
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terms are used in practice because of translations, set cards and etc.
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requiring the PSDC term. The CSDC term is used for customer identification and
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explanation. The CSDC feature provides an alternate voice/data capability. If
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the loop is a wire loop, CSDC utilizes time compression multiplexing (TCM)
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which allows for the transmission of digital signals over a common path using a
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separate time interval for each direction. During a CSDC call the caller may
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alternate between voice and data as many times as desired. CSDC can support
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subvariable data rates but a 56 kb/s is used in the network.
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Some applications for CSDC:
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1. Audiographic teleconferencing
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2. Secure voice
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3. Facsimile
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4. Bulk data
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5. Slow scan television
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A typical CSDC call is originated over a 2-wire loops which can be used for
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message telecommunications service (MTS) and touch tone is required. Calling
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can be done by automatic calling equipment (ACE) or manually. Digit reception,
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transmission, and signalling follow the same procedures used for MTS outgoing
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calls on CCIS or non-CCIS trunks. However, CSDC calls are always routed over
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digital transmission facilities.
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=================
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=Long term plans=
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=================
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The long term plan allows for Equal Access Multi-frequency (EA-MF) signalling
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and improved AMA. A CSDC call attempt is screened to ensure that the calling
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party has CSDC and the carrier used provides 56 kb/s alternate voice/data at
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the office. A blocked call is routed to a special error message. A CSDC call is
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routed directly to the carrier or indirectly via the access tandem (AT) or
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signal conversion point (SCP). The call is terminated directly from the carrier
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to the end office or indirectly via the AT or SCP. Signalling for direct
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routing is either CCIS or EA-MF and is assigned on a trunk group basis.
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The AT is a 1A ESS switch which allows access to carriers form and end office
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without requiring direct trunks. Signalling between the end office and the AT
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is either EA-MF or CCIS, Trunk groups using EA-MF signalling can have combined
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carrier traffic. Separate trunk groups for each carrier are required for CCIS
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signalling.
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The SCP is a 1A ESS switch which allows access to carriers using only CCIS
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signalling from offices without the CCIS capability. Separate trunk groups for
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each are used between the originating end office and the SCP. Separate trunk
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groups are optional between the SCP and the terminal end office. Signaling
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between the end office and the SCP is MF. The SCP must have direct connection
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to the carrier using CCIS.
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CSDC is also available for Centrex/ESS X-1customers. Most of the capabilities
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of centrex service can be applied to the CSDC feature. CSDC provides the
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following for the centrex group:
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1. Message Network Basis
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2. Intracentrex group basis
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3. Intercentrex group basis
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4. Any combo of above
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=========
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=Dialing=
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=========
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To establish a CSDC call, a user dials the following:
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#99 AB (1+) 7 or 10 digits (#)
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The user dials '#99' to access CSDC and AB is the carrier being used. The '#'
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is used optional for end of dialing indicator. The long-term dialing plan is as
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follows:
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#56 (10XXX) (1+) 7 or 10 (#)
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Dialing 56 means 56 kb/s. The 10XXX identifies the carrier. If 10XXX is not
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dialed on an Inter-LATA call, the primary subscriber is used. If 10XXX is not
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dialed on an Intra-LATA call then the local Telco handles it.
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=================
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=Switching Modes=
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=================
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Suppose Party A wants to switch from voice to data. Party A issues a mode
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switch command and then receives a signal called a far end voice (FEV) bipolar
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sequence (2031 hz at 60 ipm). Party A can now hang up any time. Party B
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receives a far end data tone at 2031 hz at 39 ipm indicating that Party A wants
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to do some data transfer. Then Party B must initiate a mode switch command.
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Party B then hangs and transmission is possible.
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TO switch back to voice, Party A initiates a mode switch command and this
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time receives an FED tone, and B gets an FEV tone. Party B then picks up and
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does a switch then the voice is established.
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=====================================
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= (C) 1985 Sexy-Exy & The PLP =
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=====================================
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Dedicated to The Guardian Demon.
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