Instructables

How do old-fashioned hand-crank telephones work?

I was wondering how old fashioned hand crank phones work, in particular: Does the cranking provide power to the phone, or does it just ring the bell on the other end? I always thought that the cranking rang the bell on the other end of the line, and that the phone itself used a transformer to amplify the input from the microphone, without using power? Also, how do duplex coils keep the user from hearing their own voice through the speaker? Thanks!

orksecurity5 years ago
The crank just generated voltage to ring the for the operator's attention. Normal conversation was powered from the central office, as is true for modern analog phones.
waightka4 years ago

First answer is correct, of course.  The crank was attached to a magneto which generated the ring current.  I have one in the garage, but it's COLD out there (This is The Great White North, after all!!)  I'll get it later today and send a picture.  Still works, tool