At 07:04 PM 12/2/2014, John Ferrell wrote:
>We may be thinking about different conditions. In the 20 ma teletype
>loop a mark was 4 ma, a space was 20 ma. A line that is 20 ma and open
>has unsafe transients due to the unknown inductance in the line. Neither
>the 20ma condition or the 4ma condition is high impedance or saturated
>logic.

Hi there.

I'm pretty sure the above is not correct, at least for Canada.  I'm=20
positive that a mark was 0 ma (open) and space was 20 mA=20
(ish).  Might you be confusing this with industrial 4-20 mA current=20
loops for analog data transmission?

dwayne


--=20
Dwayne Reid   <dwayner@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

--=20
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