[GreenKeys] TTY protocol

[wa2hwj at att.net]

ZCZC

On switched TTY systems, ZCZC was used as a "broadcast" code to turn on all
machines ("turn on" meaning the machines would go into the "print" mode). Other
codes could be designated as the broadcast code, depending on the how the system worked.
The Bell 83B3 systems used two-letter call directing codes and two-letter TD control
codes. The end of message code was typically a FIGS H LTRS. Obvisouly, these systems
depending on the Model 28's stuntbox to do all of the selection/control work.
I do not recall ever seeing a setup that actually turned the motor on and off in these
systems (how could it turn back on when the stuntbox is doing the work and
it's turned off?). Simpler point-to-point TTY networks used the motor control relay in
the 28 or an external "Idle Line Motor Control" box to turn the machine on and
off. The 28's internal version used the FIGS H LTRS to shut down and any
mark-to-space transition would then turn it back on. The external boxes would
turn off the motor if the line was idle for a set amount of time (anywhere from
1 to 15 minutes). A mark-to-space transition would turn the motor on.
The only time I saw the ZCZC and NNNN used together was on weather TTY circuits and 
TTY systems used by the airlines.

73,
Jack K0TTY

NNNN

-------------- Original message from Sheldon Daitch <sdaitch at kuw.ibb.gov>: -------------- 


> I suppose you could use codings to turn on and off equipment as desired. 
> 
> When VOA ran an HF RTTY system, we used FAXFAX to start 
> the tape punches and NNNN to stop the tape punches for our torn tape 
> relay. 
> 
> FAXFAX was our term for the message traffic between the stations and 
> Washington HQ, and even today, the "official" messages are still slugged 
> FAXFAX, even though we have gone long past the paper tape. (But 
> running the RTTY shift was a lot more fun!!) 
> 
> Actually, I think the machines were really coded for NNN to stop, and 
> normally, three of the four Ns in a series would stop the reperf. 
> 
> We never used ZCZC, but maybe no one ever thought about that. 
> 
> 73 
> Sheldon 
> 
> H.W.Hall wrote: 
> > I seem to recall reading somewhere (long ago) that NNNN was used to signal 
> > the receiving equipment to turn off the teleprinter motor. If that is true, 
> > the I suppose the ZCZC must have been to restart it. Does that jive with 
> > anyone else's recollections? 
> > --Wayne 
> > WB4OGM 
> > _______________________________________________ 
> > GreenKeys mailing list 
> > GreenKeys at mailman.qth.net 
> > http://mailman.qth.net/mailman/listinfo/greenkeys 
> > 
> _______________________________________________ 
> GreenKeys mailing list 
> GreenKeys at mailman.qth.net 
> http://mailman.qth.net/mailman/listinfo/greenkeys