The concept of AUTODIN began
because of the need to upgrade the "point to point" IBM data card system and the
associated "teletypewriter" switching system network.
Point to Point
The use of the IBM card as a means of communications between various military activities
has existed for many years; however, in the beginning, cards were limited primarily to
logistical support in the form of supply transactions. When only a few cards were used,
they were sent by mail. As the number of activities using cards increased so did the
volume of cards. Therefore, mailing became a slow and bulky process. As a tape method of
relay was already established, it was decided that card information could be perforated on
tape and transmitted over the Teletype network (TTYNET). This plan did not prove
satisfactory as the transforming of information from card to tape and tape back to card
was a slow and tedious job, with the volume of cards continuing to Increase daily.
Therefore, a system was established whereby cards were used in their original form. The
IBM Corporation provided the equipment, for transmitting and receiving card information.
This system consisted of eleven
manual data relay stations within the United States, three in Europe, and four in the
Pacific area. The relays were interconnected to make possible the exchange of card traffic
between the manual relay and its tributaries on a transceiver basis; that is, a tributary
station could transmit to and receive from the relay, but not simultaneously. If a
tributary was sending traffic, it could not receive traffic; likewise, when traffic was
being received by the tributary traffic could not be transmitted.
Still, the manual data relay system was a
great improvement over the point-to-point type communications. Operations, through the use
of a patch panel, were able to connect various tributaries, thereby providing better
communications to all activities concerned.
This system served quite effectively for
awhile; however, like the previous system, it became obsolete. It could not provide the
speed and accuracy and support the ever-increasing amount of card traffic.
In addition to the manual data card relay
system there existed a perforated tape switching system, which was used in conjunction
with the card system. The manual perforated tape switching system used the Baudot (or
similar) five bit code set. The center utilized reperforators (paper tape character punch
machines) for receiving the message and a tape transmitter for sending the message. The
data card and perforated tape system existed within the same switching center in many
All input messages (data) to the center
were received via a paper tape reperforator, which punched a tape, corresponding to the
data received. A message start indicator(s) (SOM), address field, text and an End of
Message indicator(s) (EOM) would be necessary to compose a complete message. Other
information (fields), such as a priority indicator could also be included in the message.
When a complete message was received it would be manually routed for transmission to the
appropriate destination. Depending on the age of the system this manual routing could be
accomplished through the use of a patch cord or by pushing a button, which accomplished an
electrical/mechanical relay connection. Also some reperforators printed the Baudot
characters on the tape and others did not. If the characters were not printed it was
necessary for the operator to learn the Baudot Code in order to read the punched
characters across the tape. It was necessary to read the address in order to route the
message, in addition to other control characters.
Normally each tributary, served by the
center, was connected (electrically) to a reperforator (receive) and a transmitter (send).
Therefore, it was usually necessary to provide a reperforator for each tributary, but a
transmitter could be shared because of the manual connection methods. It was also possible
for a tributary to be a send or receive only site.
The Plan 51 was the latest semi-automatic
(manual routing) paper tape reperforator system prior to the automatic Plan 55 system. The
Plan 51 system used the button switch panel matrix for connecting the transmitter to the
appropriate destination. Once a complete message was received via the reperforator and fed
into the transmitter, stopped for operator action, the operator pushed the button
associated with the correct destination and then the transmitter started and the message
The transition from Plan 51 was an upgrade
to a more up-to-date system, Plan 55, which was an automatic perforated tape system. This
system is described in the glossary under Plan 55 or, in greater detail, in the AUTODIN
Legacy Project (ALP) section "Plan 55".
This system was followed by the
computerized Communications Logistics Network (COMLOGNET) system, the beginning of
AUTODIN. COMLOGNET was designed to handle the punched card traffic for the Air Material
Command. As the system requirements grew, which included the Plan 55 Teletype system, the
name was changed to AFDATACOM (Air Force Data Communications), followed by AUTODIN, which
included all military services and the Department of Defense (DOD).