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!
Question by mad magoo 9 years ago | last reply 2 months ago