[GreenKeys] Differences between US Army & Navy TTY communications

[Nick England]

Just for clarity - the Teletype terms were LESU and ESA-

LESU - model 28 Electrical Service Unit located in back of the motor in RO,
KSR, and ASR cabinets. Could have line relay, autostart relay, internal
loop supply, selector magnet driver, etc. In NON-TEMPEST units the external
high-level (current loop) signals went through the LESU and then to
selector magnets and keyboard contacts. In TEMPEST units, the LESU handled
AC circuits but not any signals.

ESA - Electrical Service Assembly was a double shielded gold-colored box
used in TEMPEST units. Contained cards to convert external low-level
(+/-6v) signals. Included a selector magnet driver (SMD) connected via
shielded cable to shielded selector magnets. For KSR and ASR it included a
low-level keyer (LLK) to convert very low current keyboard signals (via
shielded cable) to +/-6v signals. The LLK connected to the outside world
and also to a second SMD input so that the printer would echo the keyboard.
This low-level link was wired inside the ESA box. There was also a separate
clutch magnet driver (CMD) ESA for driving the keyboard and TD clutches to
sync with crypto equip pulses if necessary.

https://www.navy-radio.com/tty-tempest.htm

Shipboard, the black side ran high-level 60ma current loops and the red
side ran low-level +/-6v signals.

All this would be much easier if we were drawing on paper napkins over a
beer…..

Cheers
Nick at NAVCOMMSTA Chapel Hill

On Sun, Apr 9, 2023 at 11:32 AM Duncan Brown <duncanancy at earthlink.net>
wrote:

> On Sat, Apr 8, 2023 at 7:43 PM Duncan Brown <duncanancy at earthlink.net>
> wrote:
> >Low-level signalling!  There is another variable and reason you can't put
> >TX & RX all on one loop.
>
> On 08-Apr-23 21:04, Nick England wrote:
>
> Normal low-level connection was with the keyboard feeding one of two
> inputs to the printer.
>
>
> At first, I didn't understand Nick's statement.
> But then I realized it is another Army/Navy, Kleinschmidt/Teletype Corp.
> difference.
>
> A M28 KSR/ASR always had a an ESU with a local loop and a line relay for
> isolation from the line. So you could have a low level "loop" feeding the
> M28 and then the ESU converted the low level to high level to feed the
> selector magnets.
>
> Kleinschmidt machines never included a isolating line relay. Except at the
> large comm centers, they normally connected directly to a wire line modem
> or FSK converter. A low-level TX signalling  connection was made directly
> to to the crypto equipment which would typically be only a few away.  There
> was no low-level signalling on the RX side from the crypto gear. From the
> 1950s through the 1980s, crypto gear was KW-9 (until mid 1960s), KW-7, &
> KW-26.
>
> Duncan
> K2OEQ
>
> --
Nick England K4NYW
www.navy-radio.com
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