This frequency triple oscillator circuit was found in an American publication in 1967. The FET is current and more detailed information about the coils is not given.
We found this trebble booster circuit in a 1990 documentation. The components are current, and the...
This circuit was found in an 80s Hands On Electronics. It senses the water level in a reservoir by...
This circuit was found in General Electric documentation from the 1980s. The circuit is intended...