Paul, I don't understand much about phone system but I know that in britain too, they use 2 wires in residential phone sockets. About 10 years ago I worked on a phone system in Britain and it used 3 wires. One, I believe was for the ringing. Can you explain to me more about the differences, how it works and why it changed to 2 wires?
Belgian,
The current British arrangement (introduced about 20 years ago) still needs 3 wires to each phone, although as in practically every other country the line from the house back to the exchange is only 2 wires.
Two of the lines to each jack are connected directly to the tip and ring of the incoming line (called the "A" and "B" wires here). The third line is wired to the B-wire via a capacitor and provides a separate feed to the ringer on each phone, the other side of each ringer being commoned to the A-wire.
Telephone jacks in residential work are most commonly wired with 4-core cable. The fourth wire is generally connected at the jacks, but is spare.
Have a look
here for the wiring diagrams and some pictures of the plugs and sockets.
Prior to this system, single phones were most often hardwired to a junction box. Where a phone needed to be used at more than one location, we had a system of 1/4-inch Post Office jacks (follow the "Plug 420" link from the above link).
The wiring on these was different to that used in the modern system.
[This message has been edited by pauluk (edited 11-04-2002).]
