I/O devices use coded languages. These languages
are:
ASCII Code —American Standard Code for
Information Interchange, eight-level paper tape;
and
ITA #2 Code —American version of
international TTY alphabet, five-level paper
tape.
Message Header Programming
At the beginning of each AUTODIN message is a
header (format line 2) containing pertinent information
on the destination of the message. The originator can
address a message either to a single addressee or to
multiple addresses. This system saves time and
requires fewer communications facilities, since only
one message is prepared by the originator and sent to the
switching center.
The timing system contained in AUTODIN
equipment briefly connects a switching center to each
subscriber terminal in turn. Computer memories act as
reservoirs for the incoming messages of each subscriber
terminal. The computer is programmed to connect each
terminal in turn during a cycle. Messages received in
their entirety are scheduled for output to the addressees’
charnels as their turns arrive in the cycle.
AUTODIN has built-in safeguards that can detect
almost any type of hardware or format error.
Additionally, a complete (reference) copy of all relayed
messages is kept on AUTODIN computer tape. A
separate (journal) copy is made of only the addressee(s).
Using this journal copy as an index enables the system
to locate the reference copy of any message.
AUTODIN Tape Messages
The AUTODIN system is programmed to accept
properly cut tapes and route them through the various
switching centers and terminals en route to their
ultimate destination. The system is then able to produce
a tape and hardcopy for the designated addressee(s).
When preparing a message tape for the AUTODIN
system, you must adhere to certain tape-cutting
procedures. For example, format lines 1, 2, and 4 must
not deviate; otherwise, the ASC will reject the message.
The next paragraphs discuss the most important points
on proper preparation of tape messages for transmission
in the AUTODIN system.
ROUTING INDICATORS. —Within the
AUTODIN network, a message tape is routed through
the AUTODIN system to the addressee(s) by a routing
indicator. Routing indicators are combinations of not
less than four nor more than seven letters.
A routing indicator begins with the letter R or Q.
The letter R indicates that the routing indicator is part of
the worldwide tape relay system. The letter Q indicates
that the routing indicator is within a self-contained
network within a command or theater.
The second letter of the routing indicator identifies
the nation or international alliance to which the
indicator belongs. For example, the letter U refers to the
United States. Therefore, RU indicates that the
message tape is part of the worldwide network and is
destined to a station in the United States.
The third letter of the routing indicator identifies the
geographical area in which a particular station is located
or from which it is served. This is necessary for relay
purposes because the second letter may indicate a large
nation within which there are a number of subdivisions
or stations. For example, many stations in the United
States are designated by the third letter C. Therefore,
the first three letters of “RUC” indicate that the tape is
part of the worldwide network, destined for the United
States, and to a certain geographical area within the
United States.
The fourth and subsequent letters of a routing
indicator designate relay and tributary stations within
the tape relay network. Like the first three letters, the
fourth and subsequent letters may vary, depending upon
location, area, and other factors.
TRANSMISSION IDENTIFICATION
(FORMAT LINE 1). —As a means of maintaining
traffic continuity, TTY terminals (modes II, IV, and V)
must prefix each message header with a message
transmission identification (TI). The ASC validates the
elements in the TI. Modes I and III do not require format
line 1. The TI is constructed without spaces and must be
accurately prepared without corrections. For example,
a correctly prepared TI might appear as follows:
VZCZCJTA (FIGS) 123 (LTRS) (2CR 1LF)
The elements of the TI and their meanings are as
follows:
l V —Ensures that the first character of
intelligence is not lost or garbled;
l ZCZ —Indicates the start of the message;
1-6
