[GreenKeys] Interesting WU film on You Tube

[John Nagle]

> I had no idea that such a tape based messaging system existed and was so
> automated. It seems like the precursor to the
> internet: https://en.wikipedia.org/wiki/Interface_Message_Processor
>
> I’m curious how they knew how/where to route the message on to the next
> center. Was there some kind of indication at the beginning of the tape
> that had the destination address, and somehow something (a stunt box)
> read that and connected to the proper onward circuit?
>
> Paul

     See

       https://en.wikipedia.org/wiki/Plan_55-A

for an overview, and its references, especially

      http://www.webcitation.org/5gOoc3dQf

Each message had a SOM sequence (the military used ZCZC)
followed by 4 to 6 characters.  Incoming messages
went to a paper tape punch feeding a paper tape reader.
That was the input buffer.  Messages were switched across
the switching center via a telephone-type switch, to an
outgoing station with another paper tape punch and reader.
That was the output buffer.  Traffic within the office
ran faster than the baud rates used for incoming and
outgoing lines, to reduce internal bottlenecks.

The last message sent through that system was on December 11, 1976, at 
3:30 AM, Central Standard Time, handled by Late Night Traffic Chief 
DeEtte Sopczyk at the Minneapolis switch.

				John Nagle