BTH Type C Crystal Set Radio Receiver

Crystal set made in 1922, has a twin crystal but only used one crystal at a time.

The crystal set was a simple radio receiver which did not need any power to make it work. It only received AM, amplitude modulated, signals. The crystal, with a point contact, called a cats whisker as that was what was sometimes used, on its surface, created a diode action rectifying the carrier wave so making it possible to hear the audio signal which was modulated onto it.