GPO 312 Causing other phones to Ring (not tinkle)

[Millay_2010]

This is an interesting one, I've wired the 312 as per Bob's instruction and it works fine, rings on incoming can answer it and talk OK. Dial out to 1471 fine, but if I call somebody else, when they answer the other telephone connected to the same line as the 312 rings?! I can stop this by depressing the call exchange button. So obviously a fix can be arranged by shorting the button. But what is going on? Am I doing something incorrect?

[Station X]

Some line faults, such as low insulation within a phone socket, will cause a modern phone "bell" to ring continuously. However in this case it's DC line current and not ringing current which causes the bell to ring.

Some exchange systems reverse the caller's line current polarity when a call is answered. You could check for this with a meter.

Possibly a combination of the above two scenarios is causing your problem.

The call exchange button applies an earth to one leg of the line to indicate which customer on a shared service (party line) is initiating a call. It needn't be wired in and won't apply an earth unless you have an earth connection, which is highly unlikely.

I would certainly double check your phone wiring.

Perhaps you could try the phone on a another line to see if the fault is unique to your installation

[Millay_2010]

Thank you for the ponters, I am starting to wonder looking at the diagram if there is a continuity issue between Terminal 1 and Terminal 3 of Key 302b, as Really the key should have no affect over the phones operation after the wiring has been updated

[Millay_2010]

It would appear that this is an early set with Key 302b Terminal 3 coming out to T7 instead of T1, I think strapping t7-t1 should sort the issue