[GreenKeys] Western Union 7C tape transmitter?

[Jim Haynes]

I have a book here, "Classic Reprint Series" The Western Union Telegraph
Company Specifications for the Multiplex Printing Telegraph System, Theory
and Operation, publisher Forgotten Books.  It's hard to imagine why
there would be a market for such a book, but I must have bought a copy.
www.ForgottenBooks.com   One section of that book covers the 1-A tape
transmitter, which is probably quite similar to the 7C.