Terminal Identification Feature; Operator Identification Card Reader Feature - IBM 3742 Reference Manual

Terminal Identification Feature
The terminal identification feature transmits a 4-character
terminal identification sequence and compares a received
identification sequence with a keyed-in sequence.
Transmitting the Terminal Identification Sequence
The BSC terminal transmits a 4-character identification
sequence when initiating a line bid or when responding to
a line bid on a switched network.
If the 3741 is the calling station, the first transmission on
a switched network after a connection has been established
is the following sequence:
PPPSS EP
AAAYYTABCNA
DDDNN QD
If the 3741 is the called station, the first transmission after
receiving a line bid is the following sequence:
PPPSS A P
AAAYYTABCCOA
DDDNN K D
If the terminal is not prepared to receive a line bid, the
following sequence is transmitted:
PPPSS NP
AAAYYTABCAA
DDDNN KD
The terminal type character T is the lowercase v (hex' A5').
A 3-character sequence will be a factory-installed sequence
assigned by I BM from a master list. The master list con-
sists of characters from all positions of the EBCDIC code
set with the exception of SOH, STX, ETX, EOT, ENQ,
ACK, OLE, NAK, SYN, ETB, US, NUL, DEL, and EO.
Remote Terminal Identification Compare
This function compares an operator keyed sequence of
characters to a terminal identification sequence received on
the communications line. The transmission or reception of
data begins after the received terminal identification sequence
matches character for character and has the identical length
as the keyed sequence.
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The operator keys the remote terminal identification
sequence while the station is in the update or read index
mode. A sequence of up to 15 characters must be positioned
with the first character in position 1 of the current record
buffer and the cursor in the next position followi ng the
last character of the sequence. If the cursor is left in the
first position, indicating that no characters have been
keyed, the BSC terminal accepts any remote terminal
identification sequence of up to 15 characters, and the
transmission or reception of data occurs as though the
terminal identification feature were not installed. If the
cursor is left in a position indicating that more than 15
characters have been keyed, an error is displayed after
FUNCT SEL and COMM are pressed.
After the identification sequence is completed, the BSC
terminal is placed in one of the communication modes by
pressing FUNCT SEL, COMM, and the desired mode key.
The keyed remote terminal identification sequence is trans-
ferred to another buffer and erased from the display. This
sequence is stored as long as the terminal is in a communi-
cations mode.
When the terminal is the calling station, the identification
sequence of the response to its I ine bid is compared with
the operator keyed sequence. If the sequences match and
the response is positive, the terminal prepares to transmit
or receive data blocks. If the sequences match and the
response is negative, the terminal disconnects. If the
sequences do not match, the terminal retransmits its line
bid up to 14 times before disconnecting.
When the terminal is the called station, the remote terminal
identification sequence of the received line bid is compared
to the operator keyed sequence. If the sequences match,
the terminal gives a positive response and prepares to trans-
mit or receive data blocks. If the sequences do not match,
the terminal does not respond, but does continue to look
for a valid sequence.
Operator Identification Card Reader Feature
This feature is used to read an operator identification card
and transmit the information to a CPU that is programmed
to accept only valid sequences. This feature can be by-
passed if the 3741 terminal is transmitting to another
terminal.
When the 3741 terminal is in one of the transmit modes, a
letter B is displayed next to the mode indicator. The opera-
tor must then insert the identification card into the card
reader. After the card has been read, the B is erased and
the terminal is ready to transmit; if an error is detected, no
action is recorded and the card may be read again.
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