[GreenKeys] jack field polarity?

[Harold Hallikainen]

The TU-170 uses a TRS jack with the positive loop supply on tip, the
keying transistor collector on ring, and ground on sleeve.

Ideally, I'd like all equipment to be the same. In my DSP TU (
https://w6iwi.org/rtty/DspTU/ ), I'm using an SSR to key the loop and an
AC optocoupler to sense loop current. It is floating and polarity
agnostic, just as my model 15 and 14 stuff is.

Right now, I have two TRS patch boxes as shown at https://w6iwi.org/rtty/
. One is driven by the TU-170, and the other by a loop supply. I can plug
any piece of equipment (including the DSP TU) into either of these. Also,
the positive end of the loop supply is on the tip of the connector.

Harold
https://w6iwi.org