[russell_w_b]

This confirms my earlier post.

Old english telephone connections are:
ZE = Zinc and earth (negative of battery and earth, or return line).
C = Carbon (positive of battery).
MC = Microphone carbon (being the carbon in the microphone).
L = Line.

You'll need a battery in each telephone. Attached is a circuit diagram from Herbert G. White's book 'Telephone Erection and Maintenance' (3/6 net, October 1922). The other end is wired similarly, i.e: L to L; ZE to ZE. Note that the mic is tapped down the battery. 9V may be too much for it, so use three 1.5V cells with a tap off a couple - or simply experiment - the tap may be un-necessary depending on the length of your line.