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.
The circuit below was suggested by the Motorola Linear Databook of 1990. The component used is...
This circuit is intended for testing small capacitors. What we have is an astable multivibrator, which works...
This circuit was found in an American 1980s documentation. The transistorized step is the...