[GreenKeys] TTY loop interface

[Nick England]

Well perhaps Jim is the father of low level +/-6v signaling that was
implemented for TEMPEST purposes. The TH-83 hubbing repeater is exactly
what he describes. See
https://www.navy-radio.com/tty-tempest.htm
And
https://www.navy-radio.com/manuals/tty/tty_ctl-391-6010.pdf


Nick



On Wed, Aug 11, 2021 at 9:30 PM Jim Haynes <jhhaynes at earthlink.net> wrote:

> Many years ago I tried (unsuccessfully) to sell a concept of how to
> hook up Teletype gear in a station.  The idea was that every selector
> magnet would have an electronic driver, and every signal generator would
> produce a signal, and the standard signal would be a voltage of + or - 6V.
> This was before RS-232 came out (and was intended for a different purpose)
> and probably before MIL-STD-188.  At the time I had in mind low voltage
> selector circuits that could be keyed with power transistors rather than
> 120V circuits, but today even the latter are easily handled with solid
> state relay ICs.
>
> The problems this solves, compared to current loops, are that you don't
> have to keep current in the loop to keep something from running open,
> and you don't have to keep the loop closed when you disconnect something.
> (Also you don't have 120V loops running around your jack panels or
> whatever that can give you nasty shocks.)  The selector magnet drivers
> can be biased so that the selector circuit is closed when there is nothing
> connected to the driver input.
>
> Think of the signal circuit as a hub rather than a loop.  You can connect
> as many printers, reperfs, etc. to the hub as you want, so long as their
> drivers are designed not to draw too much current from the hub.  You can
> connect as many keyboards and other signal sources to the hub as you
> want by putting in diode or transistor gates so that any one of them can
> drive the hub spacing when the rest are marking.  You can, if you wish,
> have separate receive and send hubs with a regenerative repeater between
> them.
>
> Jim W6JVE
>
>         ---
>
>         "Ya can argue all ya wanna, but it's dif'rent than it was."
>         "No it ain't! No it ain't!  But ya gotta know the territory."
>                 Meredith Willson, The Music Man
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-- 
Nick England K4NYW
www.navy-radio.com
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