[GreenKeys] 60 ma current loop to RS232 converter

[Jim Haynes]

On Sat, 24 Feb 2018, Pete Lancashire wrote:

> From time to time on Ebay you can find Black Box 323/CL-E boxes at quite
> good prices, I bought 3 new on the boxfor $50 included shipping.
> 
> http://ftp.blackbox.com/manuals/C/CL051A(E)(C)%20Manaul.pdf
> 
> The spec is 20 or 60 mA. I've not tried one at 60 mA but is in the spec
> 
> -pete

And here we always warn that most such devices are designed to work with
low-voltage current loops as in the Teletype Model 32/33/35 family, and
not with the older equipment that uses 120 volts at 20 or 60 ma.  For
the latter you need something like a high-voltage transistor or a solid
state relay IC.