I wonder if there is an old Western Union hand in the group. I'm looking at a diagram for an operating table which says it is Class C, and I see there is a Class CT for use over telephone circuits, so I assume that Class C is a particular transmission scheme. I can see that there is a single wire line, and that the table transmits positive for mark and negative for space. I see the receiving relay has a bias current at all times. I don't know what goes on at the other end of this circuit, what it transmits and how it receives. I see that this can be a terminal station at the end of the wire or an intermediate station in series with the wire.
I guess I need to find a W.U. relay and do some experiments to figure out the meaning of D, U, circle-D, circle U, A, O, A' and O'
-- jhhaynes at earthlink dot net***** Moderator's Note *****
I think we need some more detail to help you, but I'll publish this in hopes that someone from WU will recognize the device and/or system you're working on. It sounds like a duplex circuit, but I'll defer to the WU veterans.
Bill Horne Temporary Moderator
Please put [Telecom] at the end of your subject line, or I may never see your post! Thanks!
We have a new address for email submissions: telecomdigestmoderator atsign telecom-digest.org. This is only for those who submit posts via email: if you use a newsreader or a web interface to contribute to the digest, you don't need to change anything.