Table 1. Line Sets Per Line Base and Per 2703. FEATURE NAME per Sis per SIS per Sync Base Type per 2703 Base Base
Type I Type II 1A 1B 2A
Data Line Set (inc!. expanders) 11 (5 exp.) 3 (1 exp.) -
- - 22 (10 exp.)
Telegraph Line Set (inc!. expo )* 11 (5 exp.) 3 (1 exp.) ---22 (10 exp.)
IBM Line Set IA 9 3 ---12
IBM Line Set IB 9 3 ---12
IBM Line Set 2 4 3
- - - I 4
2712 Modell Adapter (incl. expo ) 8 (4 exp.) 3 (or 2 and 1 exp.)
- - -
8 (4 exp.)
2712 !vlodel 2 Adapter (incl. expo ) 8 (4 exp.) 3 (or 2 and 1 exp.) I - I - I - I 8 (4 exp.) I Sync Line Set Sync Line Set with Sync Clock
speed operates al11ines of that speed within anyone 2703. The speed options available are: 45.5 bps, 50 bps, 56.9 bps, 74.2 bps, 100 bps, 110 bps, 134.5
bps, and 600 bps.
2712 Modell and Model:? Adapter Features
The 2712 Adapter features, when used in conjunction
with an IBM 2712 Remote Multiplexer, provide for
concentration of a number of low-speed lines over
one voice-grade (high-speed) line. Figure 9 shows
a typical Gonfiguration. Half-duplex low-speed lines
are brought into the 2712 Remote Multiplexer, which
bit-multiplexes data from the terminals onto a full­
duplex voice-grade line. The data is separated
at the 2703 and fed into the individual 2712 Adapters
in the 2703. Data going to the terminals is multiplexed at the 2703 by the 2712 Adapter and sent over the other
half of the full-duplex voice-grade line. The remote
2712 separates the data and sends it to th terminals
over the lower speed lines. To the CPU it appears
to be working with a number of low-speed lines.
Thus, no programming changes are required.
Two models of this feature are available. Model 1
operates with up to 10 lines (using a Modell
Expander feature to provide for lines 9 and 10) at
* includes W. T. single current and double current line sets
38
6 4 3 12
3 <) - D. U v
speeds of 134.5 bps. This model permits attachment
of such terminals as the 1050, 1060, 2740, and 2741.
Model 2 operates at 74. 2 bps with WU Plan 115A,
AT&T 83B2, or AT&T 83B3 line control (Model 28
teletypewriter terminal) and can have up to 14 lines
(using a Model 2 Expander feature to provide for
lines 9 to 14). A block of eight addresses must be
assigned for each expander, as well as for each
adapter feature. However, the 1\lodel 1 Expander
utilizes only two of the eight assigned addresses,
while the Model 2 Expander utilizes six of the eight
assigned addresses.
Figure 10 shows the various configurations using
the 2712 Model 1 and Model 2 Adapter features (with
the Expander features) on the 2703 with maximum
lines for each configuration. There can be a max­
imum of four expanded 2712 Adapter features (any
combination) on one 2703. NOTE: The 2712 Attachment feature is required for installa­
tion of either the 2712 Modell or Model 2 /\dapter. Modell requires a Type 3002 with C2 conditioning
full-duplex private-line data channel, while the
Model 2 requires a Type 3002 with C 1 conditioning
full-duplex private-line data channe 1. The 2703 is
connected to the communications channel \'ia Western Electric Data Set 202D2 or equivalent. I

IBM 2712
Remote
Multiplexer
Model 1
2 Full duplex • voi ce-grade • • • • Communication • Channel 10 Figure 9. Typical 2712 Configuration
TERMINAL CONTROL OPERATIONS The 2703 operates with the following terminal
controls:
IBM Terminal Control Type I
IBM Terminal Control Type II
Telegraph Terminal Control Type I
Telegraph Terminal Control Type II
At least one such feature is required; a maximum
of four start/stop terminal-control features is
possible for anyone 2703. IBM Terminal Control Type I
This feature provides controls necessary for the
attachment of 2740, 2741, 1050, 1060, and 1070 terminals at 14.8 cps (134.5 bps); 1070 terminals
at 66.6 cps (600 bps); or 1050 terminals (with the
Telegraph Attachment feature) at 75.0 bps. The
transmission code is six bits plus parity, with the
following relation to the System/360 channel inter­
face:
o 2 3 4 5 6 7 System/360 Byte Shift • S B A 8 4 2
Check Six-Bit BCD IBM 2703 Transmission Control
2
2712 Model 1
Adapter 3
Feature • 2712
Multiplexer
Line
Channel • To
Adapters II CPU 8
2712 Model 1
9
Expander
Feature 10 In the six-bit BCD transmission code, ® represents
the shift bit. A logical one identifies the upper case;
a logical zero represents the lower case. The @ bit is the first bit transmitted after the start bit.
An odd-parity (check) bit is transmitted following the
1 bit. Each received character i's checked for odd
vertical parity.
Shifted-character-set conversion, a standard
feature, automatically deletes the upshift and down­
shift characters from the received data stream,
notes the last shift character received, and inserts
an eighth bit, ® , to indicate the appropriate shift
character to the System/360. On outgoing data, the <ID (shift) bit is removed and noted. A change in this ® bit automatically causes insertion of the appro­
pritate shift character (upshift or downshift) into the
outgoing data stream before sending the data
character. Start B A 8 4 2 Ch;f< 1 C
{
Outgoing Data Stop Character
The © (check) bit in the character indicates the
correct odd-parity count: a logical one if the bit
39