World Trade Telegraph Terminal Control
This terminal control provides controls for opera­
ting WT teleprinter attachments at transmission
speeds of 50, 75, or 100 bps. The transmission
code is ITA2, with the following relation to the
I/o interface and the 2703 serial data field.
o 23456 7 ::'hut 5 2 3. 4 5 System/360 Byte Shifted Code S represents the case. A logical one identifies
upper case; logical zero, lower case. The one bit
is the first bit transmitted following the start bit.
Shifted character set conversion, a standard
feature, automatically deletes LTRS and FIGS char­
acters from the received data stream, notes the last
shift character received, and inserts a sixth bit in
the code set to indicate the case to the processor. On outgoing data, the S (case) bit is removed and
noted. A change in the S (case) bit automatically
causes insertion of the appropriate shift character
in the outgoing data stream before sending the data
character.
Attachment to the World Trade Telegraph Ter­
minal Control is point to point with contention.
For transmitting, the programmer inserts from
4 to 20 LTRS characters before the start of message
character (line feed) to insure that the terminal is
able to receive properly. If the terminal bids for
the line simultaneously with the processor, an echo
check occurs, terminating the write operation at the CPU. For receiving, the Prepare command is issued
to the terminal line to wait for the completion of
the first character from the terminal. Command
chaining to a Read command can be used to accept
the message. This terminal control does not have
a short timeout to pre-empt the normal 28-second
timeout.
Character Recognition
End of Transmission (EOT) format is FIGS, CHAR­
AcTER' LTRS, with the character assigned on a
per system basis. EOT sets channel end, device
end, and unit exception status.
End of block (EOB) format is FIGS, CHARAC­
TER, with the character assigned on a per system
basis. EOB sets channel end and device end status.
Message Restriction
Terminal to Processor:
1. The characters used in EOB and EOT must
not be the same.
2. A space character received by the 2703 will
not downshift (FIGS to LTRS) unless the "Un­ Shift on Space" option is installed.
3. Although text following t...H EOT or EOB is not
transferred to the processor, the receive
type command is not ended until the trans­
mission line is quiet for one character time.
Text immediately tollowing FIGS, CHARAC­
TERS, LTRS is lost. EOT must not be sent
between blocks of data.
Processor to Terminal:
The terminal control automatically inserts the
proper shift character in outgoing data when a
change of case is encountered.
44.1

World Trade Telegraph Terminal Control
This terminal control provides controls for opera­
ting WT teleprinter attachments at transmission
speeds of 50, 75, or 100 bps. The transmission
code is ITA2, with the following relation to the I/O interface and the 2703 serial data field.
o 234 567 ShUt 5 234 5
System/360 Byte
Shifted Code S represents the case. A logical one identifies
upper case; logical zero, lower case. The one bit
is the first bit transmitted following the start bit.
Shifted character set conversion, a standard
feature, automatically deletes LTRS and FIGS char­
acters from the received data stream, notes the last
shift character received, and inserts a sixth bit in
the code set to indicate the case to the processor. On outgoing data, the S (case) bit is removed and
noted. A change in the S (case) bit automatically
causes insertion of the appropriate shift character
in the outgoing data stream before sending the data
character.
A ttachment to the World Trade Telegraph Ter­
minal Control is point to point with contention.
For transmitting, the programmer inserts from
4 to 20 LTRS characters before the start of message
character (line feed) to insure that the terminal is
able to receive properly. If the terminal bids for
the line simultaneously with the processor, an echo
check occurs, terminating the write operation at the
CPU.
For receiving, the Prepare command is issued
to the terminal line to wait for the completion of
the first character from the terminal. Command
chaining to a Read command can be used to accept
the message. This terminal control does not have
a short timeout to pre-empt the normal 28-second
timeout.
Character Recognition
End of Transmission (EaT) format is FIGS, CHAR­
A CTER, L TRS, with the character assigned on a
per system basis. EOT sets channel end, device
end, and unit exception status.
End of block (EOB) format is FIGS, CHARAC­
TER, with the character assigned on a per system
basis. EOB sets channel end and device end status.
Message Restriction
Terminal to Processor:
1. The characters used in EOB and EOT must
not be the same.
2. A space character received by the 2703 will
not downshift (FIGS to LTRS) unless the "Un­ Shift on Space" option is installed.
3. A lthough text following an EOT or EOB is not
transferred to the processor, the receive
type command is not ended until the trans­
mission line is quiet for one character time.
Text immediately following FIGS, CHARAC­
TERS, LTRS is lost. EOT must not be sent
between blocks of data.
Processor to Terminal:
The terminal control automatically inserts the
proper shift character in outgoing data when a
change of case is encountered.
Type I Terminal Interrupt Feature
The Type I Terminal Interrupt feature is a modifi­
cation to the IBM Terminal Control Type I. This
feature, in conjunction with the IBM Terminal Con­
trol Type I, is effectively a new terminal control.
It provides the neces sary control to operate either
an IBM 1050 or IBM 2741 equipped with interrupt
features. Terminal Control Type I capabilities are
expanded to re.cognize a 'break' Signal from a termi­
nal and to transmit a 'break' signal to the terminal.
The Interrupt feature is mutually exclusive with
the 2741 Break feature. It is not considered another
terminal control when maximum configuration is
considered. However, when present, 'it prevents
use of the IBM Terminal Control Type I in its
non-modified form. The Type I Terminal Interrupt
feature is program-supported by the Time Sharing Option (TSO) of the System/360 Operating System.
When the Type I Terminal Interrupt feature is
present, each set of lines assigned to IBM Terminal
Control Type I operation must be assigned to one of
the two following types of operation:
1. IBM Terminal Control Type I with Break.
2. IBM Terminal Control Type I with Break
(Inhibit Unit Exception on © ).
Line control assignment is by hard-wire plugging
in the 2703, with each assignment pertaining to an
entire set of eight lines. Line assignment appearf
on the 2703 specification sheet, and lines are plug:;ed accordingly at installation or in the factory. Assign­
ment may be changed later by altering the specifi­
cation sheet and the plugging. Only one Type I
Terminal Interrupt feature may be installed on each 2703. It provides control functions for any number
of line sets.
The IBM Terminal Control Type I equipped with
this feature performs all the functions of the IBM
Terminal Control Type I with the following differences
and similarity.
45