Automatic Eob (Prerequisite, Checking Feature) - IBM 2740-1 System Reference Manual

addressing responses for the group.
A ll-call addressing (transmitting to all stations
on the line simultaneously) is accomplished by the
transmission of a special two-character code (/
space).
NOTE: The / (slash) ch aracter is used w ith the PTTC/BCD and
PTTC/EBCD codes. A lower case x is used w ith the Corre­
spondence code. However, in each case the transmission
bit value (AC1) is the sam e.
When this code is received, all terminals shift to
receive status. One terminal is preselected to pro­
vide the addressing and checking responses for all
term inals.
NOTE: The S tatio n Control feature cannot be used if the D ial-
Up Adapter special feature is installed.

Automatic EOB (Prerequisite, Checking Feature)

This feature provides a three-position switch located
on the left side of the 2740 cabinet (see Figure 1).
The three positions of the switch are: Term (termi­
nal), Mplx (multiplexer), and Off. The switch is set
to the Term position when transmitting to another
terminal and set to the Mplx position when trans­
mitting to a multiplexer.
When this switch (on the transmitting station) is
set to the Term or Mplx position, an EOB code
followed by an LRC character is automatically trans­
mitted directly after the CR/LF code each time a
ca rrie r return is keyed.
At the receiving station, the EOB/LRC sequence
is received and either a positive
Figure 14. Station Control (Multiplexer Polling, without Checking)
answer is returned to the transmitting terminal. In
the first instance, normal transm ission continues.
If, however, an erro r is detected in this message
block, a hyphen is printed below the message block
just completed (receiving 2740 terminal only), and
a negative answer (
terminal. This (N) signal causes a hyphen to print
below the message block just completed at the trans­
mitting terminal.
board at the transmitting terminal, turns on the
Restart light, and sounds the audible alarm .
The message can be retransmitted by initially
pressing the R estart key. This unlocks the keyboard
and turns the Restart light off. Operating this key
also causes a CR/LF to occur at the transmitting
terminal, and a CR/LF to occur at the receiving
terminal, if the switch at the transmitting terminal
is set to the Term position. If the switch is set to
the Mplx position, the CR/LF code is not transmitted
to the multiplexer. The CR/LF operation positions
the ca rrie r on a new line (below the hyphen). The
message can now be keyed again.
When the switch is off, the EOB/LRC sequence can
be initiated only by manually pressing the EOB key.
If the receiving terminal does not have the Auto­
matic EOB feature installed, the printing position
of the hyphen is altered at this terminal. In this
case, the hyphen is printed at the receiving terminal
during the carrier return (in-flight printing).
places the hyphen within two inches of the right
margin (or point of ca rrier return initiation). The
printing position of the hyphen character at the
or negative transmitting terminal is not altered.
A
D
D S
R P
E A
) is returned to the transmitting
n
The ( ) signal also locks the key­
n
Special Features, Model 1
This
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