Status Byte. The status-byte field contains the
ending-status information that is presented to the
channel at the completion of the command. (See "Status-Byte Conditions!! under "Commands. It) Word-Parity Indicator. This bit is set when a parity
error is detected during an access to MCW-2. When this bit is ON with Channel End and Device End, it
is reset; Equipment Check is then set to indicate the
occurrence of a core-storage parity error. Parity. This bit is set to provide odd parity for MCW-2. Main Data Words 1 and 2 MDW-1 and MDW-2 (see Figure 4) store the data
bytes for receive or transmit type operations. Data
is transferred to and from the channel in bursts of
up to four bytes to reduce I/O-interface time. MDW-2 is employed only when synchronous type
operation3 are performed.
Data Byte. The eight data-byte fields store the
channel data bytes. I/O Character Count. The character-count field
defines the number of characters received from the
channel on a transmit data service, or the number
of characters to be sent to the channel on a receive
data service. The character count in conjunction
with the condition of the data bit (ON or OFF) indi­
cates the full or empty condition of the main data
words for a transmit operation.
Data. The data bit is set ON if data is stored in MDW-1 for a transmit operation. The data bit ON with a character count of 3 means MDW-1 is full.
The data bit OFF with an I/O character count of 3
means there is no data in MDW-l. The same is true
for MDW -2. The data bit is not used for receive­
data ope ra tions . Parity. This bit is set to provide odd parity for
each main data word (MDW-1 and MDW-2). SPECIAL FEATURES SUMMARY Following is a summary of all special features
offered for the 2703. These features are listed in
three distinct groups: general--pertaining to both
start/ stop and synchronous type operations; start/
stop type operations exclusively; and synchronous
type operations exclusively. The feature number is
provided with each feature as a means of positive
identification, as well as for future reference
In addition, the features within the general group
are described in detail. For detailed information
pertaining to features exclusive to either start/stop
or synchronous operations, check the special­
features paragraphs in the start/stop and synchronous
portions of this manual.
General (both Start/Stop and BSC) Autocall, first--#1340 (Automatic calling for
eight lines)
Autocall, second--#1341 (Automatic calling for an
additional eight lines)
Two- Processor Switch--#8110 (Permits two System/360 processors to share one 2703) Start/Stop Type Communications
Terminal-Control Features
IBM Terminal Control Base--#4619 (for Terminal
Control Type I and II)
IBM Terminal Control Type 1--#4696 (for 1050, 1060, 1070, 2740/2741)
2741 Break--#8055 (for 2741 with Interrupt feature)
Type I Terminal Interrupt--#8200 (for either IBM
1 O!)O Data Communication Systems or IBM 2741
Communication Terminals equipped with Interrupt
IBM Terminal Control Type II--#4697 (for 1030) Telegraph Terminal Control Base--#7905 (for
Telegraph Terminal Control Type I and II and
for World Trade Telegraph Terminal Control.
Telegraph Terminal Control Type 1--#7911 (for
AT&T 83B2/83B3 or Western Union Plan 115A
Telegraph Terminal Control Type II--#7912 (for
Model 33/35 TWX stations) World Trade Telegraph Terminal Control--#2795
(for World Trade teleprinters)
Telegraph Attachment--#7876 (to attach Telegraph
Line Sets) Line-Base Features Start/Stop Base Type 1--#7505 (88 maximum) Start/Stop Base Type II--#7506 (24 HDX--600-J:lps maximum)
Base Expansion--#1440 (to attach more than one Start/Stop Base Type I or II) Line-Set Features
Data Line Set--#3205 (eight lines using common­
carrier data sets--for 1030, 1050, 1060, 1070 2740, 2741, and Model 33/35 TWX stations)
Data Line Set Expander--#3206 (eight additional
IBM Line Set 1A--#4686 (eight two-wire mM Line
Adapters for up to 4.75 miles--for 2740/2741)
IBM Line Set 1B--#4687 (eight four-wire IDM Line Adapters for up to 4. 75 miles--for 2740/ 2741)
IBM Line Set 2--#4688 (eight two-wire IBM Line
Adapters for up to 8 miles--for 1030, 1050, 1060, 1070, 2740/2741)
Telegraph Line Set--#7897 (eight lines for leased
common-carrier private-line telegraph
service--for AT&T 83B2/83B3 and Western
Union Plan 115A terminals, or 1050 terminals)
Telegraph Line Set Expander--#7898 (eight
additional lines)
World Trade Telegraph Single Current Line Set-­ #2829 (eight simplex or half-duplex single­
current telegraph lines)
World Trade Telegraph Single Current Line Set Expander--#2830 (eight additional simplex
or half-duplex lines)
World Trade Telegraph Double Current Line
Set--#2831 (eight simplex or half-duplex
double current telegraph lines via IBM 3945
Model 11 Telegraph Line Termination (serial #200 or above)
World Trade Telep-raph Double Current Line Set Expander--#2832 (eight additional simplex or
half-duplex lines) Speed Options Line-Speed Option 45.5 bps--#4873 (common-carrier telegraph
service) 20 50 bps--#2334 (World Trade teleprinters)
56.9 bps--#4874 (common-carrier telegraph
74. 2 bps --#487 5 (common -carrier telegraph
75 bps--#4876 (1050 via telegraph channels
or World Trade teleprinters) 100· bps--#2835 (World Trade teleprinters) 110 bps--#4877 (common-carrier TWX) 134.5 bps--#4878 (1050, 1060, 1070, 2740/274] 600 bps--#4879 (1030, 1070) 2712 Attachment Features
2712 Attachment--#8043 (for Modell and/or 2)
2712 Model 1 Adapter--#8047 (for eight lines to
a 2712 Modell)
2712 Modell E:x-pander--#8048 (for two additional
2712 Model 2 Adapter--#8057 (for eight lines to a
2712 Model 2)
2712 Model 2 Expander--#8058 (for six additional
Synchronous Type Communications (BSC) Terminal-Control Features
Synchronous Terminal Control:
EBCDIC code--#7715 USASCII code--#7716 Six-Bit Transcode--#7717 Station Selection--#7473 (required for any BSC­ equipped 2703 using a leased line and operating
as a remote--tributary--station in a centralized
multipoint network)
Line-Base Features
Base Expansion--#1440 (permits use of the Synch­
ronous Attachment)
Synchronous Attachment--#7702 (permits attach­
ment of communications lines for synchronous
operation) Synchronous Base Type l.A--#7703 (up to 24 lines
for Synchronous Terminal Control using either
EBCDIC or USASCII) Synchronous Base Type 1B--#7704 (up to 16 lines
for Synchronous Terminal Control using Six­ Bit Transcode, EBCDIC, or USASCII) Synchronous Base Type 2A--#7706 (up to 12 lines
for Synchronous Terminal Control using EBCDIC or USASCII) Line-Set Features
Synchronous Line Set--#7710 (up to four lines of
voice-grade quality for synchronous operation) Synchronous Clock--#7705 (for attachment of
Western Electric Data Sets 202C1 or 202D1 or
World Trade Line Set--#2902 (for attacru'Ttent of
up to four synchronous lines controlling data
transfer between System/360 and synchronous
data devices, except with Japanese NTT
modems. For operation of Synchronous Line Set--#2902 on the Switched Telephone Network
in Sweden or United Kingdom, Attachment Fea­
ture #2975 is required for attachment of PTT
modems. ) Synchronous Line Set--#2974 (for attachment of
up to four synchronous lines controlling data
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