On Sat, 17 Apr 2021 11:15:53 +0100, The Natural Philosopher
wrote:

On 17/04/2021 10:06, Peter Able wrote:
If all of your extensions are simply connected across the incoming pair,
then induced hum won't just affect one extension.

I thought about that, and then decided as a statement of fact it was
********.

Consider a set of telephone wires all starred from a single point where
they are all shorted together. Telephones are oin te end of each pair.

One of the wires goes through a transformer that is designed to induce
current in it. The telephone on that wire and that wire alone will see
'hum'.

Except that mine are wired as a spur. I am quite surprised the hum
does not go back the way to number 2.