Quote:
Originally Posted by Dave Moll
Incidentally, the switch of the GPO magneto 26N/26P works to make the magneto electrically invisible when at rest, but with the handle off-normal (I don't think it needs to be turning) disconnects the local end and connects itself across the line to send its ringing current.
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As opposed to the Soviet TAI-43 field telephone, which has the magneto shunted until the handle is turned. Cranking the handle shorts the local bell and speech cct and puts the ringing supply on line via a key. If the key is pressed, the short is opened and the local bell rings as well, as long as there is a load at the other end (or a locally-applied strap): a handy test to see if the generator works!
It means, though, that if there is muck on the magneto switch contact the call will be routed via the magneto winding impedance, and if inadvertently cranked during a call, the speech path will be shorted out.
I can't see any advantage to the way the Kellogg magneto is wired (according to the drawing). Perhaps it's just economy of wiring with the same terminal arrangement being provided for different telephones? Or maybe it's been drawn incorrectly (as suggested)?