498 lines
20 KiB
Plaintext
498 lines
20 KiB
Plaintext
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DATAPAC SERVICE DESCRIPTIONS
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Service - DATAPAC 3101 (ASYNC/ITI)
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DATAPAC 3101 (ASYNC/ITI)
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------------------------
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Datapac 3101 is a network access service which enables teletypewriter
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compatible devices, such as time-sharing terminals, to access the Datapac
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Network.
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Low speed, asynchronous devices are supported through an Interactive Terminal
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Interface (ITI) in a Packet Assembler/Disassembler (PAD), which allows the
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devices to access the Network over dial-up (DDD) or Dedicated Access Lines.
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ITI, the end-to-end protocol for Datapac 3101, conforms to the CCITT
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recommendations X.3, X.28 and X.29 and supports access to the Datapac Network
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for asynchronous, start-stop character mode terminals.
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X.3 specifies the operation of the PAD. It contains the specifications
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for the twenty-two International parameters and their operation.
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X.25 specifies the command language between the terminal and the PAD. It
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also specifies the conditions which define the command mode and the data
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transfer mode.
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X.29 specifies the procedures to be followed by an X.25 DTE to access and
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modify the parameters in the PAD as well as the data transfer procedure.
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The Datapac 3101 service provides for terminal to Host (user's computer) and
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terminal to terminal communication. The Host access should conform with the
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X.25 protocol, using the Datapac 3000 access service, and also support the
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higher level protocol conventions for ITI. Host access may also be provided
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via the Datapac 3101 service for some applications. The Datapac 3101 service
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also provides block mode and tape support.
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INTERNATIONAL PAD PARAMETERS
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----------------------------
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1) Ability to Escape from Data Transfer State*
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The setting of this parameter allows the user to interrupt the
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communication of his or her application (data transfer mode) and interact with
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the PAD (common mode). The character to do this is "Control-P". To return to
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data transfer mode, press the carriage return or enter a blank command line.
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If the user wants to send a "Control-P" to the Host, with this parameter set
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set to one, simply hit Control-P twice and the second Control-P will go to the
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Host and the user will remain in data transfer mode. This also applies to the
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user data field in the call request command line.
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Parameter Number: 1
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Possible Values: 0 = Escape not possible.
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1 = Escape is possible.
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*Note: Escape from Data transfer mode may also be
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possible using the break signal if parameter seven is set to eight.
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2) Echo*
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This parameter indicates to the PAD whether or not the terminal input
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data must be echoed. This may be required if the user's terminal cannot echo
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back what is being entered.
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Parameter Number: 1
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Possible Values: 0 = No echo.
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1 = Echo.
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*Note: Echo will also be affected by the setting of Parameter 20.
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3) Selection of Data Forwarding Signal
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This parameter indicates to the PAD the set to terminal generated
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characters or conditions that will cause data to be forwarded to the
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destination. For example, (CR) can be used as a data forwarding signal on
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receipt of a (CR) from the local DTE Y, the PAD will forward all characters in
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its buffer to the remote end, including the (CR). If P13 is set to 6.7, 22 or
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23, a (LF) will be included in the packet and will delimit it. Data is also
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forwarded when the buffer is full whether or not a forwarding character is
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received.
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Parameter Number: 3
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Possible Values: 0 = No data forwarding signal.
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2 = Forward on carriage return.
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2 = Carriage return.
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126 = All characters in columns 0 and 1
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of ASCII table and the character
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del of International alphabet #5.
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(See Appendix 1.)
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4) Selection of Idle Timer Delay
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This parameter is used to determine the idle timer limit value when data
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forwarding is based on timeouts. To optimize packetizing of data, no data
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forwarding signal need be specified. The PAD will then packetize data based on
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packet size specified (256 or 128 characters). The idle timer is used to send
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any packets that are not fully filled. If idle timer is activated and the Host
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requires the (CR) to input data, it still must be provided before the data send
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is accepted by the Host. The idle timer does not send any empty packets.
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Parameter Number: 4
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Possible Values: 0 = No data forwarding on timeout is
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required.
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1-255 = Indicates value of the delay in
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twenties of a second. (i.e., a
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value of 250 makes the time wait
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10 seconds)
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*Note: When editing is on (P15:1), the idle timer is inactive. If this is
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the only data forwarding condition, turning the editing function on could cause
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a user terminal to hand or data not to be forwarded.
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5) Auxiliary Device Control*
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This is used for flow control of data coming from either a PC or
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auxiliary device, e.g.: a paper tape machine. When set to 1 it indicates to
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the PAD that the data is to be read an auxiliary I/O device connected to the
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terminal. This parameter set to 2 indicates that the data is coming from an
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intelligent device, i.e., a PC, and that the PAD must exert flow control
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differently.
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Parameter Number: 5
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Possible Values: 0 = No use of X-on/X-off.
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1 = Use of X-on/X-off for auxiliary
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devices.
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2 = Use of X-on/X-off for
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intelligent terminals.
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*Note: A value of 2 is recommended for PC's.
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6) Suppress Network Messages
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This parameter indicates to the PAD whether or not Network generated
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messages are to be transmitted to the terminal.
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Parameter Number: 6
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Possible Values: 0 = Suppress message.
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1 = Transmit message.
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5 = PAD prompt (*) follows Datapac
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service signals.
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7) Procedure on Break
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This parameter is used to indicate how the PAD should process a break
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signal that is received from the terminal while the terminal is in data
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transfer state.
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Parameter Number: 7
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Possible Values: 0 = Nothing. (remain in data transfer
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mode)
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1 = Interrupt. (remain in data
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transfer mode)
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2 = Reset. (remain in data transfer
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mode)
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4 = Send an "indication of break"
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message to the packet mode DTE.
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(remain in data transfer mode)
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8 = Escape from, data transfer ,mode
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(i.e., enter command mode)
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16 = Discard output to terminal
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activate Parameter 8 (P8:1)
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(remain in data transfer mode)
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21 = A combination of 1, 4 and 16.
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*Note: The break signal is ignored if the virtual circuit is not established
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while in command state. The break signal will delete the current line.
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The valid values for P7 are 0, 1, 2, 8 and 21.
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8) Discard Output
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This parameter is used in conjunction with Parameter 7. Depending upon
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the break procedure selected, this parameter may be set by the PAD when the
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terminal user requests that terminal data be discarded. This parameter must
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then be reset by the destination computer to allow normal delivery. The PAD
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will discard all packets destined for the terminal from the time the PAD sets
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this parameter (i.e., it receives a break signal when Parameter 7 is set to 21)
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to the time the parameter is reset by the destination. It can only be reset by
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the destination.
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Parameter Number: 8
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Possible Values: 0 = Normal delivery of output to
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terminal.
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1 = Discard output to terminal.
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9) Padding after Carriage Return
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This parameter is used to specify the number of padding characters to be
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inserted by the PAD following a CR R transmitted to the terminal. Padding
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allows time for the carriage to return on mechanical printing devices.
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Parameter Number: 9
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Possible Values: 0 = 2 padding characters will be
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inserted at 110 bps and 4
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padding characters will be
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inserted at higher speeds, in
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command mode only. (no padding
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is done in data transfer mode)
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1-255 = The number of padding characters
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to be inserted in both data
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transfer and command mode.
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10) Line Folding
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This parameter indicates the maximum number of printable characters that
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can be displayed on the terminal before the PAD must send a format effector
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(i.e.., <CR><LF>). This permits more data to be transmitted in one packet
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while still letting the user print out more than one line, i.e., printing out
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forms.
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11) Transmission Speed (Read only)
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This parameter is set by the PAD as a result of transmission speed
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detection if the terminal accesses an autobaud port. When a private port with
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fixed speed is used, this parameter is set based on the pre-stored information
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selected at subscription time.
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Parameter Number: 11
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Possible Values: 0 = 110 bps
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2 = 300 bps
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3 = 1200 bps
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4 = 2400 bps
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12 FLOW CONTROL
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This parameter allows the terminal user to signal the PAD that the
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terminal cannot receive any more data, i.e., to flow control data coming from
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the network. When it is set to 1, the terminal user can request that the PAD
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stop sending data by transmitting a "Control S". the PAD then suspends
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transmission of the data until a "control Q" is received.
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Parameter Number: 12
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Possible Values: 0 = No use of X-on/X-off for flow
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control.
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1 = Use X-on/X-off for flow control.
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13) Linefeed Insertion
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(Similar to National Parameter 126
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This parameter specifies when the PAD should insert linefeeds <LF>
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receipt of a carriage return <CR> from the terminal, PAD or the destination
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Host.
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Parameter Number: 13
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Show Possible Values: 0 = Insert no <LF>.
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1 = Insert <LF> to terminal upon
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receipt of a <CR> from Host.
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4 = Insert < > to terminal after a
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<CR> from terminal or on PAD
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generated <CR>.
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5 = Insert <LF> to terminal on <CR>
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from PAD terminal or Host.
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6 = Insert <LF> to terminal on <CR>
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from terminal and insert <LF> in
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data Host on <CR> from terminal.
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7 = Insert <LF> to terminal on <CR>
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from PAD, terminal or Host and
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insert <LF> in data to Host on
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<CR> from terminal..
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16 = Insert <LF> to terminal after
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a PAD generated<CR>.
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17 = Insert <LF> to terminal after
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a PAD generated<CR> or Host
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generated <CR>.
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20 = Insert <LF> to terminal on <CR>
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from terminal.
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21 = Insert <LF> to terminal on <CR>
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from terminal to host
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22 = Insert <LF> to terminal on <CR>
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from terminal. Insert <LF> in
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data to Host <CR> from terminal.
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23 = Insert <LF> to terminal on <CR>
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from terminal or Host. Insert
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<LF> in data to Host on <CR>
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from terminal
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14) Padding Characters after Linefeed
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To allow for mechanical paper feed, this parameter is used to specify the
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number of padding characters to be inserted by the PAD following <LF>
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transmitted to the terminal in data transfer mode only.
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Parameter Number: 14
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Possible Values: 0-255 = Number of padding character
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(NUI) sent to the terminal
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after transmission of a <LF>
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to the terminal.
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15) Control of Editing Functions*
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This parameter specifies whether or not editing is allowed in data
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transfer mode. It is always available in command mode. This controls
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parameters 16, 17 and 18.
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ParameterNumber: 15
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Possible Values: 0 = Editing only in command mode.
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1 = Editing in command and data
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transfer mode.
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*Note: Setting Parameter 15 to 1 will cause the operation of the idle timer
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(Parameter 4) to become disabled.
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16) Character Deletion
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(Similar to National Parameter 118)
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This parameter specifies the ASCII character to be used as a "character
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delete" character for local editing by the PAD. The default value is set to
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127 (the delete or del key).
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Parameter Number: 16
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Possible Values: 0 = Turn off the character
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editing (command and data
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transfer mode).
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1-127 = Character delete character
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(Appendix K).
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17) Line Deletion
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(Similar to National Parameter 119)
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This parameter specifies the ASCII character to be used as a "line
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delete" character for local editing by the PAD. The default value is set to 24
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(Control X). On some older terminal the Control X key will clear the screen as
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well as delete the line.
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Parameter Number: 17
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Possible Values: 0 = No key will delete a character
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1-127 = ASCII code for the "line
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delete" character.
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18) Line Display
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(Similar to National Parameter 120)
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This parameter specifies the ASCII character to be used as a "line
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display" character for local editing by the PAD. The default value is set to
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18 (Control R).
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Parameter Number: 18
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Possible Values: 0 = No key will delete a character
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1-127 = ASCII code for the "line
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display" character.
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19) Editing Service Signals*
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This parameter defines the format of the service signal sent to terminal
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upon execution of the editing functions (P16 or P17).
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Parameter Number: 19
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Possible Values: 0 = No service on editing
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1 = Backslash is displayed for
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each character deleted,
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"***" is displayed for each
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line deleted.
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2 = <BS> <SP> <BS> is displayed
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for each character deleted,
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<BS> <SP> <BS> is repeated
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"***" is repeated for each
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character on the line deleted.
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32-126 = The specified character is
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displayed for each character
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deleted, "***" is displayed
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for each line deleted.
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*Note: Value 1 is recommended for printing terminals and Value 2 when PAD
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echo is off (P2 = 0) and the character "delete" character is defined as <BS>
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(P16 = 8). The PAD does not send an editing service signal to the terminal
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upon execution to the character delete editing function; however, the character
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will still be deleted from the PAD buffer.
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For video display terminal product a <BS>, but the character will
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still be deleted from the PAD.
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20) Echo Mask*
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This parameter specifies a set of characters not to be echoed to the
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terminal.
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Parameter Number: 20
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Possible Values: 0 = All characters echoed (except)
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X-on/X-off which depend on the
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setting of P5, P12 and P22).
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1 = No echo of <CR>
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2 = No echo of <LF>
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4 = No echo of <VT>, <HT>, <FF>
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8 = No echo of <BEL>, <BS>
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16 = No echo of <ESC>, <ENQ>
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32 = No echo of <ACK>, <NAK>,
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<STX>,<SOH>, <EDT><ETB>, <ETX>
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128 = No echoing of all other
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characters in Column 0 and 1
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of ASCII table in Appendix 1
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Plus <DEL>
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*Note: This parameter is only active when echo in on (P2 - 1).
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21) Parity Detected or Checked
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(Similar to National Parameter 123)
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This parameter specifies whether or not the PAD should detect, check and
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generate parity. This parameter is set to 0 when the user wishes to transmit
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8-bit data.
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Parameter Number: 21
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Possible Values: 0 = No detected or checked.
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3 = Parity checked and detected.
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22) Page Wait
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This parameter controls the ability to set a terminal page size which,
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when reached, causes the PAD to stop all further output to the terminal.
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Parameter Number: 22
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Possible Values: 0 = No page wait.
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1-255 = Page wait size.
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The PAD will resume normal transmission when any of the following occurs:
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- on receipt of the page wait cancellation (X-on); or
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- on resetting Parameter 22 to zero.
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NATIONAL PARAMETERS
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The following parameters are specific to the Datapac interactive terminal
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interface (Datapac 3101 Service).
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P118 Character Deletion
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P119 Line Deletion
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P120 Line Display
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P12, 122 Additional Data Forwarding Signals
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These parameters 121 and 122 allow the definition of one or two additional
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data forwarding signals. These signals are in addition to any that are
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specified by Parameter 3 and 4.
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Parameter Number: 121, 122
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Possible Values: 0 = None.
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1-127 = ASCII code of additional data
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forwarding signal.
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P123 Parity Treatment
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This parameter specifies whether or not the PAD should detect and check parity
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and performs the same function as International Parameter 2.
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Parameter Number: 123
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Possible Values: 0 = No detected or checked.
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1 = Parity checked and detected.
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125) Output Pending Timer
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This parameter specifies the length of time, if any, that terminal output will
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be blocked by terminal input.
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Parameter Number: 125
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Possible Values: 0 = Output.
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1-255 = Value of delay in seconds..
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126) Linefeed Insertion
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Parameter Number: 126 See International Parameter 13
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GENERAL NOTES ABOUT PARAMETERS
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The setting of any of parameters 16 (118), 17 (119), or 18 (120) to a non-zero
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value will also set Parameter 15 to 1 when Parameter 4 is zero. In the 1984
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software level, setting both editing (P15) is off. This operation is according
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to CCITT 1984 standards.
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If the character chosen for a certain parameter has already been selected to
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be used with another parameter, then the function with the highest priority is
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selected upon receipt of the character. This priority scheme is as follows:
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1) escape from command state;
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2) flow control;
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3) line display;
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4) line delete;
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5) character delete;
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6) packet forwarding.
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All of the above parameters are changeable by the user. However, it should be
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noted that the Host computer can also change these parameters.
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