[GreenKeys] jackfields

[Jeffrey Angus]

> There's an awful lot of TS stuff out there for loop current use.
> 
> Back when I worked for UCSC we did an awful lot of switching at
> the RS-232 level and used TRS hardware, but that was strictly
> my own decision, not guided by anything the industry does.

Take the following bit as opinion, not "this is how it's done".

A month or so ago, I downloaded the huge AT&T "green book" and
one of the more interesting things in it was how a manual switch
board was wired.

ALL the phone pairs were (surprise) Tip and Ring, and the sleeve
was used for local signaling (Ie. making relays close or lamps light.)

As to TTY connections, again, we have a floating pair, could be 
any polarity, either side grounded or not. As such, using the sleeve
of the connectors (to me) sounds like a bad idea just on general
princibles.

I like to have all of my cables, either shielded or at the minimum
a chassis ground tieing all the equipment together. The sleeve
fits the bill quite nicely.

So, at least at my end of the cable, I'll be using Tip and Ring 
for the TTY loops and the Sleeve as safety ground..

Jeff-1.0
wa6fwi