[GreenKeys] RS-232 to 60mA current loop conversion for Model 15 TTY?

[Jim Haynes]

Take at look at the Fairchild HSR312, an opto-isolated FET switch,
takes 2ma to turn it on, good for 250 volts and 190 ma.  Of course you
have to use some kind of snubber to limit the inductive kick, such as
an R-C or a Zener diode or a MOV device.  Costs $1.72 at Mouser.
Add a 1N5956 200V Zener diode for 24 cents.

I haven't used any of these yet, but sure looks like a good tool
for the purpose.




jhhaynes at earthlink dot net