These line sets provide for the attachment of up
to four data sets. The following data sets, or
equi valent, can be attached via the Synchronous
Line Set without a Synchronolls Clock Western Electric Data Set 201A3 (2000 bps)
Western Electric Data Set 201B1 (2400 bps)
Synchronous Clock Feature. This feature is sup­
plementary to the Synchronous Line Set and provides
for the attachment or up to four data sets (or IBM
Line Adapters), where clocking for bit synchroni­
zation is not provided by the data set (or line
adapter). This feature requires the installation of
synchronous line speeds (see "Synchronous Line Speed Option"), and accommodates the following
data sets (modems) or their equivalent:
IBM 3977 Modem (WTC only)
IBM 3976 Model 3 (WTC only) GPO Datel 1 Model 5 (WTC only)
NTT DT1203 (WTC only) PTT D1200S (WTC only) PTT GH2002 (WTC only--Model has an optional
clock. Either the modem clock or the machine
clock feature may be used, but not both; nor
can both be intrrmixed on the same communi­
cations facility.)
Western Electric Data Set 202C1 Western Electric Data Set 202D1 Table III summarizes the number of synchronous
lines that can. be attached per 2703 by Synchronous Base.
Synchronous Line Speed Option These options provide the pulses to drive the Synch­ ronous Clock feature, which is required whenever
the data set or line adapter does not provide timing
or clocking pulses needed for external bit sampling.
The Synchronous Line Speed Option is available for
operation of the SF at 600, 1200, 2000, or 2400 bits
per second for World Trade Corporation applications
and at 1200 bps for domestic use. Only one speed
can be specified per Synchronous Line Set, and this
speed is preset. If the Synchronous Clock feature is
specified for one line, the other station(s) on the net­
work serviced by this line must have the Synchronous Clock feature installed, and all stations must have
the same bit rate.
Data Set (Modem) Features
A variety of transmission facilities can be attached
to the BSC -adapted 2703, depending on the type
facility used, transmission configuration, trans-
mission speed employed, country of use, and so
forth. Refer to Figure 13 for details.
54
Table m. Synchronous Line Sets Synchronous Transmission Number of Number of
Base Code Synchronous Synchronous
Line Sets Line Sets without Yi,.ith Syn- Synchronous chronous Clock Clock Base Mach. Base Mach.
1A EBCDIC, 6 12 3 6
2A USASCn 3 6 IB SBT 4 8 3 6 Station -Selection Feature
The Synchronous Features in a 2703 may be opera­
tionally used as the BSC portion of a master station,
or the SF may be used in a BSC-equipped multi­
point network as a tributary (remote) station. The
basic synchronous-equipped 2703 is designed to
operate as a master station on a point-to-point
basis; however, with the installation of the Station­ Selection feature, a synchronous-equipped 2703 can
be used as the tributary station--thus permitting a
number of low-traffic-volume stations to be effec­
tively combined to fully utilize the throughput capa­
bility of a multipoint line.
A multipoint network could typically be configured
as shown in Figure 14.
The Station-Selection feature causes the elimina­
tion of interference that would otherwise be caused
by interstation transmission on the line. Thus, the CPU (with a 2703 containing Station-Selection­ adapted SF) is interrupted only when the SF's selec­
tion or polling address is received and transferred
to main storage, at which point main storage can be
interrogated for proper programmed action.
The Station-Selection feature is required when the SF is attached to a multipoint network and the station
is operating as a remote (tributary) station and all
transmission operations are directed to or from the
central (master) station. BSC-adapted stations can operate on the same
multipoint line. provided they:
1. All use the same transmission code;
2. All utilize the same checking features;
3. All are able to handle, if not employ, the same
optional features and special operations re­
specting their compatibility supplements: ,1. All operate at the same line speed.
The Station-Selection feature implements two
additional commands: Address Prepare (Adprep),
and Search.

Communication SPEED DATA SET COUNTRY Facil ity NETWORK CONFIGURATION in Bits Per Second or MODEM 1200 W.E. 20201* ® Leased Voice Point-to-Point
Grade and 2000 W.E. 201A3*
U.S.A. Multi-Point
and 2400 W.E. 201BI* Canada
Modems may be attached by the
customer under the provisions of 4800 the "Multiple Supplier System Pol icy";consult your IBM Marketing Representive.
Switched 1200 W.E. 202CI* , ffi Telephone Point-to-Point W.E. 20201 A , B , ©
Network 2000 W.E. 20IA3*@, ©
World Trade** Leased Voice Paint-to-Point*** 600 or 1200 IBM 3977 Model 1 or 2 @ Grode Lines or or
in Countries Multi -point *** IBM 3976 Model 3 @ where Approved ® Point-to-Point Up to 2400 IBM 3977 Model 2 4800 Consult your IBM Marketing
Representive for Modem
i nformat i on.
United Kingdom Point-to-Point*** 600 or 1200 GPO Datel 1 GPO Leased Lines or Model 5
Multi-point
Germany Point-to-Point*** 600 or 1200 PH DI200S PH leased lines or (GH-201 I, Model 5)
Multi-point
Sweden Multi-Point 600 or 1200 PTT GH-2002B PTT leased li nes PTT GH-2oo2C
Point-to-Point*** 600 or 1200 PH GH-2002B Japan Point-to-Point 600 or 1200 NTT DTl203 NH Leased Lines
Switched Point-to-Point 600 or 1200 IBM 3976. Model 3
Telephone
Network
United Kingdom GPO Datel 1
Model 5
Germany
PTT DI200S (GH 2011 Model 5)
Sweden PH GH2002A NOTES Or equivalent
** Must be approved by PH Administrations. For use of other than named modems, consult your IBM Marketing Representive.
*** Point-to-Point configurations use 2 or 4 wire facil ities
Multi-point configurations use 4 wire facilities
®Synchronous Clock Feature required.
® If Autocall feature is installed, W.E. Automatic Calling Unit 801AI/A6 or 80lC2/C4 *
is required. 80lAI/A6 serves rotary pulse dialing; 801C2/C4 serves push button dialing. See common-carrier representive for type of dialing facilities available.
© Requires Western Electric Data Auxiliary Set 804AI *
Figure 13. Communications Facilities for BSC
55