Table of Contents
Advertisement
• When the buffer is filled while in Enter mode.
• During a carrier-retu rn or tab operation.
• If terminal is in buffer print mode.
To return the ca rrie r to the left margin, when
the keyboard is locked; shift to local mode, and
press the Reset and Return keys.
Station Control (Multiplexer Addressing and Polling)
Station Control provides the terminal with the ability
to be addressed indicating "Prepare to receive", or
to be polled (a signal indicating "Prepare to send")
from the multiplexer (Figures 22, 23, 24, and 25).
NOTE: Each 2740 master terminal (either group or all call), re
quires its own local loop when using a 4-w ire IBM leased or
shared line IBM Line Adapter.
be the communication line between the comm on-carrier
connecting office and the customer's 2740 term inal installa
tion.
This local loop cannot be shared by other 2740 ter
minals.
Subordinate 2740 terminals will fail to print the
first text character following an EOB/LRC sequence if they
are on the same local loop as the master terminal.
All communication in the multiplexer operation
is centralized both to and from the multiplexer to
the terminal. The multiplexer does all the necessary
polling and addressing. Anytime there is no trans
mission from a terminal (in transmit status) for a
fifteen second time period, a time-out occurs and
the terminal shifts to standby status.
Each terminal is assigned a single character
identification code (either alphabetic A-Z, numeric
0-9, or any of five additional characters).
five additional characters are:
This identification character is specified by the
customer and wired by IBM personnel at installation
time.
Figure 23.
Addressing Operation (With Record Checking Special Feature Only)
36
A local loop is considered to
The
and &.
Polling
The polling sequence is an identification code followed
by the Space character.
a (
) if it is not ready to transmit data and a (§)
n
followed by text if it is ready to transmit (Figures
22 and 24).
Addressing
Each 2740 Model 2 terminal can be addressed by
three different means: an Individual address, a
Group address, or an A ll-Call address. The Indi
vidual address consists of an identification code,
selected at time of installation, followed by the Space
character. Only the addressed terminal responds
to an individual address.
A group address consists of the group identifica
tion code, selected at time of installation is followed
by the Space character. This character cannot be one
that is used as an individual address. The group
address is used for addressing only and allows all
terminals in the group (wired for the particular
identification code) to receive the message trans
mitted from the CPU. Only one terminal (designated
Master terminal) of the group responds to the group
addressing sequence.
The A ll-Call address is the slash (/) character
followed by the Space character.
dress enables all terminals on the line (in Standby
status) to accept the transmitted message. Only one
terminal (Master terminal) responds for the group.
The Group or A ll-Call Master terminal is designated
by the user at the time of installation and wired by
an IBM Customer Engineer.
minal is not ready to receive data, it responds with
a (N), or if ready, with a © (Figures 22, 23, and
25). An A ll-Call or Group Master terminal responds
for the group with (
) or (
n
condition.
The terminal responds with
The A ll-Call Ad
If the addressed te r
), depending upon the
y
Advertisement
Table of Contents
