Capacitors C2, C3 and C4 determine the frequency of this simple oscillator. Transistor can be general purpose equivalent.
We found this source with the CI 723, common at the time, in a 1989 paper. Power transistors must be...
This old voice circuit suitable for telephones of the time was found in a Radio Electronics from...
We found this frequency meter circuit in a 1974 documentation. The circuit is powered by 12 V and...