[GreenKeys] Nems-Clarke Teletypewriter Switching Unit

[Jim Haynes]

On Sun, 3 Dec 2023, John, W9DDD wrote:

> Thanks Jim for some enlightenment.
>
> First time I understood what practical use there was for the solenoid and 
> switch.  Probably never saw the combination together at once before.  I have 
> an RO with the switch, but the printer with it didn't have the solenoid.  
> Printers I've seen with the solenoid weren't with keyboards with switches.  I 
> suppose I should have inferred it from WDs, but didn't.
>
> So one could program the stunt box to only print when your call sign was 
> received or switch to print everything.

Numerous uses for the stunt box.  Perhaps there were a number of private
wire systems where all the stations were on the same line and you could
prefix a message with selection characters to select one or a group of
printers to copy.  In the CAA/FAA service I think it was Service B
about flight plans that used selective calling so as not to bother
stations with traffic they did not need to see.  Whereas in Service A,
the weather broadcasts, you wanted to print everything and let pilots
choose which messages they wanted to look at.  And in Service A the
stunt box was also programmed to recognize your station's own call
sign to tell it when to send the weather message the operator had
punched into tape.

Going way back in time, the operators had to watch the printer until
their stations were polled to transmit and then switch on the TD to
send their reports.  So the operators had to waste a lot of time
just watching the printers.  Then there was a thing called ASID -
Automatic Station Identification Device - that would send the station
call sign at the right time to be sure the operator didn't botch it.
Then the SOTUS and system called SECO to recognize station polling and
start the TD automatically when the station was polled.  Then Model 28
stunt box made the SOTUS unnecessary, the system was upgraded from
60 wpm to 100 on the area circuits, and a high-speed circuit spanned
the U.S. to get traffic from one area circuit to the others.  (Brought
on by jet travel, so it was just too slow to have traffic relayed
from one area circuit to another.)  This was ADIS - Automatic Data
Interchange System circa 1960.  Then there was BDIS, sort of a pun on
ADIS for Service B.  Somewhat similar to ADIS, but dealing with messages
addressed to specific stations and groups of stations.

There was to be a CODIS for services C and O, but FAA dumped Teletype
and all its paper tape in favor of computer technology switching being
offered by Collins and other computer companies.