Found in American documentation from the 90s, this circuit uses a high voltage relay and has no grid isolation. The high values of R1 and R2 prevent the shock when it touches the sensors.
This circuit, obtained from the component manual used, has an ultra narrow 1 kHz range given by...
Utilizing the MAX4172 or MAX495 integrated circuit, this circuit increases the sensitivity of a...
This circuit uses an unusual component today which is the integrated circuit. We found this...