In article , Alan
writes

Similarly, I would question the reliability of ring on a single line
referencing
ground, since party lines tended to be out longer distances -- the ground
resistivity
would make it more difficult to get ring current to the phone(s).

It did work though. The mechanical bells in older phones in the UK had
a lower impedance (500 ohm coils vs. 2000 ohm coils in newer phones), so
the ringer would draw more current. The ringer was also two bells
either side of a balanced clapper, so it took little to make it ring -
the more current it was able to draw from the line, the louder it rang.

I remember a neighbour with a party line whose phone had problems -
calling her would give a ring tone in the earpiece, but she would claim
that she had never heard the phone ring. Several visits from the GPO
(as was BT) engineers found no fault, the phone always working when they
visited.

Eventually it was discovered that her party line was grounded via the
waste pipe (lead pipe into a cast iron stack disappearing into the
ground) of her cloakroom toilet, which was little used, and in the
summer, when the ground dried out and the water in the toilet pan
evaporated and ran low, the phone lost its earth and failed to ring.
Flushing the toilet restored normal operation to the phone

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