Quote:
Originally Posted by ct92404
When the magneto is not being cranked, it's removed from the circuit, probably just so that current from an incoming ring doesn't go through it.
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That is indeed the reason.
Quote:
Originally Posted by ct92404
The only thing that still kind of confuses me is what was the purpose for the normally closed contacts? It seems like the way this telephone is wired, they don't really do anything.
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The magneto would probably be a general purpose one, and that contact may be used in other circuits. For instance, in the GPO magnetos I mentioned in an earlier post, the NC contact allows a through path between the local 'phone and the line, which is broken while the magneto is being cranked so that the magneto output is not fed back into the local 'phone.
It looks as though it would be possible to wire your 'phone so that this contact would disconnect the local ringer while the magneto is cranked if you didn't want it ringing while you crank.