Transmission Controls And Indicators, Model 1; Local/Communicate Key; Standby (S) Light; Transmit (T) Light - IBM 2740-1 System Reference Manual

These controls and indicators are located directly
adjacent to the left and right of the typing keyboard,
as shown in Figure 2. They provide additional con­
trols required for operating in communicate mode.
Certain keys are associated with special features
(as indicated) and are provided only when that fea­
ture is installed.

Local/Communicate Key

P ress the Local, bottom portion of this two-position
key (Figure 3), for local mode (normal typing). If
your terminal is addressed to receive a message
while in this mode, an alarm sounds automatically.
If the alarm sounds, press the Com (Communicate)
portion of the Local/Communicate key to receive
the incoming message from the calling terminal or
multiplexer.
Pressing the Com (Communicate) portion of this
key places the terminal in communicate mode and the
terminal can alternately transmit and receive from
the communication line. However, the terminal is
switched to a receive status only when signaled to
do so by another terminal or computer.

Standby (S) Light

This light (Figure 3) is on when your terminal is in
the communicate mode, in a ready status, and
neither transmitting nor receiving (standby status).
The typewriter motor is not running when the te r­
minal is in this status. If the Bid key is operated,
or the terminal receives a signal to receive, the
terminal automatically shifts to either transmit or
receive status and the typewriter motor is automati­
cally turned on. When the terminal changes status,
the Standby light is automatically turned off, and
either the Transmit or Receive light turns on.

Transmit (T) Light

This light (Figure 3) is on during the time one can
transmit information from the keyboard to the com­
munications line and consequently to other terminals
or a multiplexer. During this time the keyboard is
unlocked and the terminal is controlling the com­
munications line. This light also turns on when the
terminal transmits the answerback to an EOB/LRC
sequence when the Checking special feature is in­
stalled.

TRANSMISSION CONTROLS AND INDICATORS, MODEL 1

Receive (R) Light

This light (Figure 3) is on when your terminal is
ready to receive a character from another terminal
on the line, or from a multiplexer in the communi­
cations system. During this time your terminal can
receive characters only from the terminal or
multiplexer which initiated the call, and your key­
board is locked. When the checking feature is in­
stalled, this light also turns on while the terminal
is awaiting an answerback to an EOB/LRC sequence.

Bid Key and Light

Point-To-Point Operation
P ress this key to obtain the line to transmit a mes­
sage (Figure 3).
only when your terminal is in a standby status
(Standby light on). Operating this key places your
terminal in transmit status (Transmit light on),
turns the typewriter motor on, and causes a signal
to be transmitted to the other terminal on the line.
The other terminal recognizes this signal and auto­
matically shifts from standby status to receive
status. If a terminal is without paper, without data
set status, or operating in local mode, it does not
shift to receive status, but does sound an alarm
alerting the operator that corrective action is r e ­
quired. The Bid light (located to the right of the Bid
key) is not operative in a term inal-to-term inal type
of operation.
Broadcast Operation
When operating in broadcast mode (more than one
other terminal on the same communications channel)
press the Bid key to obtain the communications line
to transmit a message.
only when your terminal is in standby status and the
Bid light is on. The Bid light on indicates that the
terminals in the broadcast network are in contention
for the line; that is, no other terminal in the broad­
cast network is on the line and sending a message.
Operating the Bid key shifts your terminal to trans­
mit status (Transmit light on, Standby light off),
turns the typewriter motor on, and turns the Bid
light off (see Broadcast Operation under " Principles
of Operation, 2740 Model ÜÏ
Transmission Controls and Indicators, Model 1
The Bid key can be operated
The Bid key can be operated
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