This audio oscillator is from a 1957 Raytheon publication. The tone generated depends on C2 and C2 and the handset must be high-impedance magnetic. Equivalent transistors can be tested.
This signal generator found in Japanese documentation of 1973 uses an unusual integrated circuit...
This circuit was obtained in the publication 101 Electronics Projects of 1979. The circuit can be...
We found this circuit in an old European publication. Integrated circuits are not common today and the...