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.
The transducer of this circuit is a small ceramic capsule or crystal earpiece and the frequency given...
This circuit was found in an American documentation from 1968. The circuit generates ladder-shaped...
The circuit shown in the figure generates a rectangular signal whose frequency depends on C1. For...