21 Feb
2013
21 Feb
'13
8:53 p.m.
On Thu, Feb 21, 2013 at 02:49:15PM -0800, Chuck Guzis wrote:
I believe those were 60ma current loop.
Yes -- and it really was a loop. You'd hook all your stuff up in series
(insulated 1/4" jacks since the sleeve isn't necessarily ground) so the loop
supply could be pretty substantial. I think MJE340s were fairly standard
for solid-state switching in TUs (modems) since they could take the voltage.
Before that it was Western Electric bipolar relays (which are things of
beauty).
I seem to remember that it was also common
practice for RTTY operators to send something like "LTRS LTRS LTRS"
when beginning a message to make certain that the receiving end was
in the correct mode.
One LTRS is enough to reset the carriage, *but* the carriage-return dashpots
were pretty big and were slow to react or else might bounce (depending on
which way they were misadjusted) so people would end lines with something
like CR CR LF LTRS LTRS just to be safe (the LTRSes were just fill
characters). Luckily those keys were all near each other.
There was an option for some models called "USOS" (unshift on space) which
would ... well, unshift on space. But since you never know whether the
other guy has it, you can't count on it.
But anyway a model 15 etc. would be terrible for computer use since it's
missing most of the math characters. Too bad because the type was beautiful...
John Wilson
D Bit