[GreenKeys] W.U. transmission question

[Jim Haynes]

Wonder if there is an old W.U. hand around who knows about this.  I'm
looking at a schematic for an operating table which says it is Class C
operation, and also something about Class CT for operation over telephone
company circuits.  So I assume Class C means a certain kind of
transmission.  It's clear that it sends positive on mark and negative
on space, if the relays are labelled the way I think they are.  I'm
not clear on what happens at the other end of the wire to receive
this, or what the other end sends to affect this end.  The receive
polar relay has a bias current , but I'm not clear if that biases toward
mark or space.  Guess I need to do some experimenting to show the
meaning of the markings A, A', O, O', D, U, D-in-a-circle, and O-in-a
circle.



jhhaynes at earthlink dot net