Richard Gagnon wrote:

> I work in industry

So do I.  :-)

> in the USA that uses 20ma and it is 4ma to 20ma with
> regulated power supplies. The signal can be any value between those two
> numbers, quite often 0 signal is 4ma and maximum signal is 20ma. Machine
> computer control is very effective at sending the exact values via a d/a
> module.
> This may have nothing to do with this thread but I wanted to comment on the
> technology.

Yes, that is the analog extension of the old digital 20 mA teletype 
current loop.
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