We found this circuit with JFETs in a Radio Electronics magazine from June 1969. The circuit has its assembly described in a complete article. Equivalent transistors can be used.
Based on an integrated circuit CA31062 which consists of a photosensor, this circuit was obtained from...
This ultra-simple meter uses an output transformer and a small speaker as a microphone. The...
The frequency of this oscillator depends on the crystal used and the transistors. The circuit was...