We found this circuit in the July 1971 Radio Electronics magazine. The circuit activates a Sonalert or a relay for a higher power warning system.
This old receiver (1967) uses germanium transistors from the time and coupling transformers,...
This circuit was found in old documentation. D1 can be a diac. | Clique na imagem para ampliar...
This oscillator takes advantage of the 2000 ohms headphone inductance as the oscillator circuit coil....