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AUTODIN Prologue
Part 1
Overview of the AUTODIN History TimeLine
By Bob Pollard - Editor
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The intention of this overview is to present a brief version of the History of the Automatic Digital Network (AUTODIN) System. If further and/or detailed information is your goal, please click on the ALP Contents button for a listing of all the historical categories and pictures.

Early Communications (Military)

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 was a system with point-to-point circuits between field organizations and their parent commands. It was an effective means of communications; however, as time went on, commands and field organizations needed to communicate with other commands and field organizations. Realizing how impractical and uneconomical it was to provide additional circuits and equipment for each specific requirement, a manual relay system for card traffic was developed.

Manual Data Relay System

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 cases.

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 was sent.

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).

The advent of transistors changed the computer environment and communications capability forever.

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