cofty,
My first job when I left school was as a trainee technician with what is now Telecom New Zealand. (Where I remained for barely 12 months, because some idiot of a local elder made me throw it in - a story for a later telling!)
The exchange I worked at was of a variant somewhere in between a "crank-handle" (i.e. Magneto) manual exchange and an automatic one. They called it a "Central Battery" exchange, in which you lifted the hand-piece off its "cradle" to alert the exchange operator - with the resulting low resistance loop pulling in your number's Line Relay and illuminating your line's "Call Lamp" on the operator's console. (From that, the generic term used to describe either an earth fault or a short circuit on the line was "PG", for "Permanent Glow").
Even then (1972), that thing should have been long pensioned off, yet they retained this museum piece right up until the late 1980s.