simple transmitter - receiver

judith submitted this idea :

In the 50's you could buy war surplus field telephones. They were un-powered, but used a cranking generator to ring the bell. They used either a moving coil or moving magnet microphone, which generated the voltage needed to make the earpiece at the far end produce sound.

Yes!

They would work over several miles of cable, but they were not very loud.

Think those were called Tele F and had an internal battery. Old telephones used carbon mics and these don't actually generate a signal, unlike say a moving coil device.

This might provide some more info:-

Jan Wysocki expressed precisely :

R1155 being the receiver of the 1155/ 1154 pair.

many thanks to all who responded - particularly for links and photos.

cheers

They were made for the hobbyist / crystal set / 2 transistor radio / etc market Ca. 1960.

They were Piezoelectric and are still available.

Their main advantage is low power requirement, meaning you could make a crystal set with only a ferrite rod aerial, and they didn't load down the tuned circuit too much.

Derek