We find this circuit in American documentation from the 1980s. It consists of a frequency folder using a varicap. The capacitors and coils depend on the frequency of operation.
This circuit is from Radio Electronics from February 1987. The frequency is given by the crystal that...
In this circuit, a light-sensitive SCR or Light Activated SCR determines the operation of an...
This 3-transistor circuit was found in a Mullard manual from 1960. The transistors are germanium of the...