[GreenKeys] Station Control Circuit

[Jim Haynes]

81C1 is an earlier (1930s) and 81D1 is a later fully automatic store
and forward message switching system.  As I recall 81C1 allowed for
only one switching center, while 81D1 allowed for multiple centers.
These systems were used by big companies like the airlines, steelmakers,
internally in the Bell System, etc.  All were based on punched tape for
storage.  In its last days 81D1 was brought up to 100 wpm with Model
28 equipment.

It was a mixed-architecture system, in that there were multistation
circuits for the out stations as well as single station per circuit
facilities.  And of course there was a provision for message orgination
and delivery right at the switching center itself.

So what you have is presumably the version of an ASR set that works
with an 81D1 system as an out station, probably on a multistation
line circuit.  It can probably be polled for traffic incoming to the
switching center and is probably arranged to suppress printing on
messages on the line not intended for that station.  It would use the
M28 stunt box to detect the polling signals and print selection
activity.

As a student of old switching systems I would be interested to know
more about what you have.

jhhaynes at earthlink dot net