View Single Post
  #84   Report Post  
Posted to uk.d-i-y
Scott[_17_] Scott[_17_] is offline
external usenet poster
Posts: 1,904
Default *Five* wire overhead mains cables

On Tue, 20 Apr 2021 19:21:09 +0100, Peter Able wrote:

On 20/04/2021 16:26, Scott wrote:
On Sun, 18 Apr 2021 09:03:28 +0100, Peter Able wrote:

On 17/04/2021 12:01, Scott wrote:
On Sat, 17 Apr 2021 11:15:53 +0100, The Natural Philosopher

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

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

Philosopher, starting with a false assumption is always a bad start, but
star, daisy-chain or hybrid. Would you describe the path(s) of the
induced currents for no handsets lifted and for each handset in turn lifted?

Scott, have you tried swapping around the handsets? Just a bit more

No, but I thought of that as I was watching Netflix. I also found out
if I hold the line the buzzing increases !!! Maybe I am acting as an

OK - are you going to try swapping? Is that you holding the 'phone or
the power cable? It'd be interesting to see a sketch of the network of
phones - showing any broadband filters. Is each extension used for
phone only, broadband only, or both? Does any of the network still
include a third, "bell" wire?

I'll try the swapping tonight. The phone has a headset and I was
holding the cable to the headset.

Master socket (filtered) ext 1 ext 2. I had to reconnect the bell
wire as ext 2 does not ring without it. The only broadband filter is
contained in the master socket. The route from ext 1 to ext 2 runs
under the floor close to a ring main and my TV set, which I assume is
the source of the problem.