AUTODIN means Automatic Digital Network. Formerly, it was a worldwide data communications network of the U.S. Defense Communications System, now replaced by the DMS (Digital Messaging System).

Autodin Mode 5 Terminal. (From L-R)  Kleinschmidt teletype,  tape reperforator including an externally affixed paper tape reader and the Autodin Mode 5 unit in the rack.  The Mode 5 unit had no crypto capabilities. It was the automated tech control for a teletype circuit encrypted by the KW-26 send/receive system. (Photo courtesy Fort Monmouth Historical Office. Submitted by George Mace)

The main Autodin station would send out polling data to the various sites around the world.
When traffic was originated or received, the Autodin took care of the routing procedures.  It was designed to signal if there was incoming FLASH precedent traffic (via the Sonalert on the front panel of the Mode 5 unit) which alerted the operator who generally had less than 5 minutes to acknowledge receipt.

It numbered traffic messages so that the Autodin switch would know if it missed any from the station.   Operators would prepare the messages and the Mode V unit would automatically create header and routing data based on the data it read from the transmit punched tape.  In itself, it did no encryption of any sort.

An operator could sit at the keyboard, cut a tape and have hard copy at the same time then use the reader to send the message. Alternately, one could receive hard copy and a tape copy at the same time.  You could send or receive but not simultaneously because it was  a half-duplex unit . Usually, the message preparation was done on a separate machine.

Messages would be sent via keyboard when setting up circuits at HJ time or whenever any end-to-end  coordination was required but generally all sending was through the reperforator  with pre-punched tape.

Many Autodin installations used Kleinschmidt teletypes that were upgraded from 45 wpm to 75 wpm. Although the modification seemed to work well, the machine  would shake and shudder while printing almost as if it was trying to destroy itself.  By 1970, the Kleinschmidts were phased out and replaced by Teletpye Corp. machines.

Autodin Ancedote from Doug Eyre

While stationed at RAF Welford, England  our Autodin broke once in the entire time I was there.  We were down about 48 hours before a technical representative was dispatched. This guy had to be seen
to be believed - bowler hat, pin striped suit with vest, black shiny shoes and an umbrella.  The only thing he was worried about was the directions to the local post office because he was a stamp collector.

This tech opened up the front of the equipment and for two days all he did was turn schematic pages in the TO and point his little penlight inside the machine. After two days, he received a phone call from European HQ that said there was a problem with another circuit at a higher priority site.  So he
left with the TO open on the work bench and the equipment open in the rack. Once of our maintainers, a SSgt by the name of Tad Phillips, decided to try tracing the schematic.  To the best of my recollection  this was still a discrete component type of machine with transistors but no ICs.

Anyway, Tad traced the circuit and then pulled out a small sub-unit and found a cracked resistor.  We were told that this resistor was a part classed as NRTS (not reparable this station) and that it
would have to be sent to the repair depot.  Our circuit had now been down for about five full days.  I told Tad to call the local TV repair shop in the small town of Newbury and see if they had a resistor of that value, wattage, and physical size.  They did, so he went down town, bought it and installed it.
Voila! -The circuit came up.

Did we get a thank you and well done praise from HQ?  Heck no! We were "chewed out" because a   non-milspec part was installed into the unit to fix it!  We offered to remove the part nut HQ thought that probably wasn't a good idea. Then all went back to normal!
 

July 24//05