Thread: Incorrect bell?
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Old 28th May 2019, 3:26 pm   #1
PickleRick63
Triode
 
Join Date: May 2019
Location: London, UK.
Posts: 13
Default Incorrect bell?

Hi all - I set myself a project on the weekend - to resuscitate an old telephone I bought at a market and connect to my BT landline at home to allow incoming calls - and got on quite well, but I can't get the bell to ring! I'd be grateful if you could help me.

It's an old unidentified telephone but has the following etched on the back-plate:
Circuit Operateur S63
Sous licence de la
Societe Francais des
telephones Ericsson
I believe it used to be positioned in public locations to allow direct communications with the fire brigade in France. There is no dial/pulse facility, and there's an external bell (which is marked 6-12v 50 ohm).

The wiring to it is quite peculiar: a 3 pair cable provides:
  • 1 pair connected directly to the bell
  • 1 pair connected to the terminal board (line I assume)
  • 1 pair connected to the hook

I guess that this is something similar to a Socotel S63 telephone. In any technical documents I can find, a bell with a completely different resistance value is mentioned as suitable.

I have connected the terminals to A/B from my BT line (as per photos) and tested the phone fine with incoming calls. I've wired the bell onto effectively pins 3 and 5 of the BT plug (again, as per photos) while plugged directly into a BT master socket and the bell rings only very faintly...

I wonder if the installed bell is completely inappropriate to be operated by the bell voltage on a BT line?

Any help/pointers would be much appreciated!

Many thanks
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