The IBM 2702/2703 Transmission Control Units:
Permit combining data processing and data com-
• Direct and control data flow between the processor
and remote terminals.
o Operate in byte-interleaved mode.
• The 2702 can operate from 1 to 31 half-duplex
The 2703 can operate from 1 to 176 half-duplex
The 2702 provides speeds up to 180 bps, or up to
600 bps with added features.
The 2703 provides speeds up to 600 bps, or up to
2400 bps with added features.
In addition, the 2702/2703:
e Receives and transmits data serially by bit.
o Transfers data to and from channel by byte.
Does not restrict message length.
The 2702/2703 Transmission Control Units (from
now on referred to as multiplexers) provide for the
on-line attachment of various
devices via private
and commercial common-carrier communications
facilities to a channel that conforms to the standard
Channel Interface (Figure 1-1).
Data communications equipment that can be attached
to the multiplexers inclUde the following:
IBM 1030 Data Collection System.
IBM 1032 Digital Time Unit (2702 only).
IBM 1050 Data Communication System,
IBM 1060 Data Communication System.
IBM 1070 Process Communication System.
IBM 2712 Remote Multiplexer, Models 1 and 2,
IBM 2740 and 2741 Communications Terminals.
CHAPTER 1. INTRODUCTION
AT&T 83B2/83B3 Type Selective Calling Ter-
Western Union Plan 115A Terminals.
Common Carrier TWX Stations (8-level code).
European Teleprinters (World Trade attachments).
Another IBM System/360 via an IBM 2701 Data
Adapter Unit equipped with appropriate Syn-
chronous Features (2703 only).
Another IBM System/360 via an IBM 2703 Trans-
mission Control equipped with the appropriate
Synchronous Features (2703 only).
IBM 2780 Data Transmission Terminal (2703 only),
IBM 1130 Computing System equipped with the
Synchronous Communications Adapter feature
Each multiplexer occupies one of eight allowable
control-unit positions in a multiplexer channel. Data
transfers between the multiplexers and the multi-
plexer channel are in the byte-interleaved mode,
each byte consisting of eight data bits and one parity
Each multiplexer is flexible in line capacity, trans-
mission code, and speed. The basic 2702 can have
15 half-duplex lines and operates at speeds up to
134.5 bps for any or all attached communications
lines. (Optional features enable the 2702 to operate
up to 15 lines in a start-stop mode at transmission
rates up to 600 bps.) The 2703 can operate 1 to 176
half-duplex lines at speeds up to 134.5 bps for any
or all attached communications lines (as an optional
feature up to 72 lines at 600 bps).
available enable the 2703 to operate in a synchronous
mode at transmission rate up to 2400 bps.
On input messages (data being sent to the channel),
the mUltiplexer accepts data serially by bit from the
remote terminal via the communications line, assem-
bles this data into characters and transfers the char-
acters serially to the channel. On output messages
(data being sent to the mUltiplexer from the channel),
the multiplexer accepts the data serially by byte and
transfers it serially by bit to the remote terminal.
The multiplexer does not impose restrictions on
message length. All 2702/2703-channel message
buffering is done by the processor. All necessary
bit-byte conversion, data control, and signal match-
ing to common-carrier equipment are accomplished
by the multiplexers.