PRIVATE CIRCUIT
MAGNETO WORKING WITH TELEPHONES
The GPO designed many circuits and systems and one of the more obscure was an end to end generator circuit using telephones.

This was a simple telephone at each end, that used generator signalling to call each other.  They designed two versions: one was for two wire working, which could be used internally or via long lines off a local exchange, whilst the other was four wire connected and this would have been used for long distance working.

In both instances batteries are required at each telephone to power the transmitter.  A Telephone No. 706 or 710 would be used as the regulator could be removed to defeat the regulator circuit.  An "Adaptor, Local Battery" would be installed in the transmitter circuit.

Originally a hand generator (Generator No. 26AN) would be used but in the 1970's a mains powered ringing generator was specified.

Diagram - N4404 (4 wire working).

Diagram - N4560 (2 wire working).

 

 
 
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Last revised: October 27, 2023

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