This sensitive circuit was found in the August 1971 issue of Radio Electronics magazine. The SCR is equivalent, and the transistor may be a BC548. The load may be a relay.
The presence of a low resistance between the terminals of the sensor causes this modulated...
The frequency of this oscillator depends on R and C (see math section for electronics). The...
This circuit was found in a 1980s documentation from the manufacturer of the integrated. The...