[GreenKeys] Current limiting

[Chris Elmquist]

I'm a little green on current loop fundamentals-- having grown up in
the RS232 age...  but is the high voltage really neccessary if you are
not running a long distance with the loop?

In other words, could a modern constant current source using say, LM317
be built that provides a nice stable 20 or 60mA but with only 12, 24 or
48v DC source?

Is there something in the older TTYs that requires a higher voltage on
the loop?

My ASR-33 runs with 20mA sourced from 12v but that is pretty "modern"
compared to the 5-level stuff you guys are working with I am sure.

Chris
-- 
Chris Elmquist
mailto:chrise at pobox.com