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.
When this circuit is activated the LED flashes for a moment indicating that the function has been...
This 1970 Electronic Design circuit uses a varactor or varicap. The circuit divides the frequency...
Found in a 1993 Electronics Hobbyst Handbook, this passive circuit can be used with common...