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Figure 3.
IBM 2740 Model 1 Transmission Controls (Right Side of Keyboard)
Check-Loop Test
The Bid key is also used to test a portion of the
electronic circuitry of the terminal (see nTest Pro
cedures" section in the IBM 2740/2741 Communication
Terminal—Operator's Guide, Form A27-3001).
Set the local/communicate switch to the local position
to perform the test.
While holding the Bid key down,
a single operation of any one of the character keys
on the keyboard (except Shift key) causes that char
acter to print repeatedly.
electronic circuitry associated with the printing of
the character is functioning properly. Releasing
the Bid key stops the repeat printing.
Station Control (Special Feature)
When the Station Control special feature is installed,
operating the Bid key sets up a circuit to notify the
multiplexer of a message to be transmitted when
the multiplexer polls the terminal.
turns on to indicate a request to transmit the next
time your terminal is polled (called) by the multi
plexer.
When your terminal is polled and shifts to
transmit status, the Bid light turns off, the Trans
mit light turns on, and an alarm sounds to notify
you that transmission can begin from your terminal
(see Station Control under Special Features, Model
1
).
8
This indicates that the
The Bid light
R estart (RST) Key and Light (Checking Special
Feature)
The R estart light is located to the right of the Re
start key (Figure 3). When in transmit status,
the R estart light at your terminal turns on when
you perform a checking sequence (press EOB key)
and remains on if the message you transmitted was
received incorrectly at the receiving terminal.
When in transmit status, pressing the Restart key
turns the light off, unlocks the keyboard, and allows
message transmission to continue, or the error
message to be retransmitted.
status, the R estart light turns on as soon as an
erro r is detected and turns off automatically when
your terminal sends a negative answer to the trans
mitting terminal.
Dial-Disconnect (Disc) Key and Dial-Connect Light
(Dial-Up Adapter Special Feature)
Use this key to disconnect the line in a dial-up line
connection (Figure 3).
EOT key must be operated before operating this key.
Pressing this key, following the operation of the
EOT key, releases both terminals from the com
munications line (provided both data sets have the
Automatic Disconnect feature installed). Otherwise,
this key must be operated at each terminal following
the operation of the EOT key.
When in receive
If in transmit status, the
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