wait mode to await the answer-back message from the
data
processing center.
Output Mode: When the answer-back message is
received on the ouput data line, the 1ca is in this mode.
Upon recognition of the answer-back, the 1ca returns
to input mode.
Retransmission Mode: After
a predetermined time
interval, if no answer-back
arrives from the data
processing center, the 1ca retransmits the message pre-
viously stored while it was in input mode. Immediately
upon finishing the retransmission of the message, it
once more enters wait mode to again await an answer-
back. This process is described
further under “Wait
for Response from the Data Processing Center.”
Use of the Data Register and Core Storage
The data register has many functions in the 1ca. All
input data pass through this register en route from the
telegraph equipment to the terminal interchange. Out-
put data (answer-backs) are temporarily stored here.
The register also acts as an
input-output device to the
core storage.
The core storage contains positions for 96 characters.
Translated characters minus
edited characters (from
telegraph equipment) are stored here. They are held
until, during retransmission
mode, the 1ca again trans-
mits the contents of its storage
to the terminal inter-
change, or until, during input
mode, the next message
replaces them.
Translating, Editing,
and Recognizing
Telegraph
End-of-Message
Sequence
The translating
portion
of the 1ca
is composed
of two
sections, the decoder
and the encoder.
The decoder allows
all 64 combinations
of the five-
level code (with
shifts) to be recognized.
Decoded
alphabetic and numeric
characters are
wired directly
to the encoder. Punctuation
and special characters are
wired to a control
panel by
the 15m customer
engineer.
The encoder
is partially wired
directly
to the de-
coder and partially
wired to the
control panel. Its
function is to
generate the
9000 series
scp character
for the corresponding
five-level
code character.
By use
of the control
panel, the punctuation
and
special char-
acters can be
encoded to
any scp character
desired.
Also, any of these
characters
can be used
for telegraph
end-of-message
recognitions
or be edited
out of the
input
message.
An editing
control allows
the 1ca
to edit any
special
character or
punctuation
character
from the
input tele-
graph message.
To do
this, outputs
from the
decoder
are directed to
the edit-control
portion of
the control
panel. Editing
is done
merely by
preventing
both stor-
age and transmission
of the unwanted
character.
28
The
telegraph end-of-message recognition control is
able to recognize any character sequence up to four
telegraph characters, if they are directed to the tele-
graph-Eom portion of the control panel.
Character Generation
Certain
control characters are generated in the Ica
during input mode.
Terminal Identifying Character 1 (TIC,): This char-
acter
is generated when the input message is a normal
message.
It is the first character; its bit configuration is:
START CBA S42 1 stor
1
0:10 diel 0 20
Terminal
Identifying Character 2 (TIC,): This char-
acter
is generated when no
answer-back arrives within
the
predetermined time limit or when manual interven-
tion has been necessary for re-entering a message from
the
telegraph equipment. The bit configuration for
this character is:
START CBA8421= STOP
1 1.0 Ll ld: 0
End
of Message Incomplete (EOM,): This character
is
generated when the 1ca has transmitted 95 characters
(unless
the character following
the 94th telegraph char-
acter is to be edited, in which case only 94 characters
are transmitted) and the telegraph end-of-message se-
quence
has not been recognized.
The bit configuration
for this character is:
START .C B.A 8 472.1. srop
aL 10-0 12041 0
End of Message Complete (EOM¢): This character
is
generated when the telegraph end-of-message se-
quence is recognized in the incoming message. (If the
95th character is the last character of the telegraph
end of message, the EOM, is generated.) The bit con-
figuration for this character is:
START CBA 8 4
1
0:00 gl
271
2STOr
Onle 20
Wait for Response from the
Data Processing Center
When the ica enters the wait mode, a predetermined
time interval control is activated. This control is adjust-
able to compensate for different response times from
the data processing centers. It is after this predeter-
mined time interval has expired that the input message
is retransmitted, if the answer-back message has not
been received. Figure 28 shows this operation in flow-
chart fashion.
Message Formats
A message sent from the ica to the terminal inter-
change can be in one of four formats, depending upon
the length of the telegraph message and the presence
or absence of alarm conditions.
ieee
Start
Operator
depresses stop,
sending
a reset char to
Terminal Interchange.
Op
backs up tape to
beginning
of last message
Op
pushes re-enter and
Message
is read
from
Stark
telegraph
equip
into
|
ICA
storage
and is
simultaneously
trans-
mitted
(preceded
by a
TIC})to Terminal
Interchange
Message
is read from
telegraph
equip into
ICA storage and is
simultaneously
sent
(preceded
by TIC)
to the Terminal
Interchange
Message (preceded
by
TIC)
is sent
to
Terminal
Interchange
Stored message
(preceded
by TIC)
is sent to Terminal
Interchange
No Answer
- XY‘
back? Proceed
Alarm
sounds
Call the IBM
and re-enter Customer
light
comes on Engineer
Figure
28. No-Answer-Back Routine for the 1ca
1.
If the telegraph message, excluding edited char-
acters
(and the end-of-message characters may be
edited
), is no more than 95 characters and contains the
end-of-message
sequence, the format is:
Tic}, body of message (maximum 95 characters'),
EOMc
2.
If the message from the
telegraph equipment is
longer
than 95 characters (excluding edited char-
acters),
the 1ca will divide it into segments. All seg-
ments
except the last will have
the following format:
TIC,, body of message (95 characters” ), EOMy;
The
last segment will conform to format 1.
3.
If the telegraph message (excluding edited char-
acters)
is no more than 95
characters and contains a
‘Note
that the number of data characters included in the 95-
character
message depends upon
the telegraph end-of-message
sequence used.
*See
preceding explanation of EOM1.
telegraph
end-of-message
sequence
and if
the message
is
being retransmitted, its format is:
TIC2,
body of
message (maximum
of 95
characters’),
EOMc
4.
If an incomplete-message
segment
is being re-
transmitted,
its format is:
TIC2,
body of message
(95 characters”), EOMy
If the last segment
of the
long message
is being re-
transmitted,
however,
its format will be:
TICy,
body of message
(maximum of
95 characters’),
EOM¢
The
only output
message to the 1ca
is the answer-
back
from the
data processing
center. This
is a one-
character
message: EOMc.
In
addition to normal message
formats, a “reset”
character
is sent to
the terminal interchange
when the
stop
key is depressed.
This
character has
the following
bit
configuration:
START
Input
Communication
Adapter
Operator’s
Panel
The
operator’s
panel is used
to control the
1ca and to
place
it in normal
operating
condition. The
switches,
keys,
and lights, and
their functions
are (Figure 29):
Power
Off/On:
This switch
controls the
ac power.
It
must be in
the on position
for normal
operation.
Start:
Depressing
this key
resets the 1ca
so that it is
able
to receive
input
messages and
operate
normally.
Stop:
Depressing
this key
stops all 1ca
operations
except
a retransmission
and sends
a reset character
to
the
terminal
interchange.
Re-enter:
Depressing
this
key causes
a TIC: char-
acter
to be generated
as the
first character
of the input
message.
This
key is pressed
after
a message
has been
re-entered
manually in
the telegraph
equipment.
The
start
key must
be pressed
after the re-enter
key.
Power
On: This
light indicates
that
ac power is
present
in the ica.
System
Available:
This light
is normally
on. It signi-
fies
that the
9000 series
system is
available.
Re-enter:
This
light indicates
that an input
message
was
in error when
it was transmitted
by
the ica, and
MAIN}
OFF POWER
SYSTEM
ALARM READER
LINE ON AVAILABLE} RE-ENTER | CHECK
BLANK
BLANK START
STOR RE-ENTER BLANK
Figure 29. 1ca Operator’s Panel
Communication Adapters 29
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