This elementary receiver with a crystal earphone was found in Japanese documentation from the 1960s. The coil has 60 + 40 turns of wire 28 to 32 in a ferrite rod.
This simple amplifier uses a microphone attached to the telephone. The 3-transistor circuit was...
This toy organ was found in Popular Electronics from January 1967. It can be constructed from...
The circuit below was found in the March 1990 issue of Radio Electronics magazine. The circuit...