We find this circuit in an Electronic Design of the 90s. The used integrated circuit admits equivalents and next to the diagram are given the formulas for the calculation of the components used.
This circuit is from a July 1970 Radio Electronics magazine. The sensors are metal probes. The 18 V...
This commercial medium and short-wave radio was manufactured in Japan in the 60s. The circuit has...
General Electric suggests this circuit in an 80's documentation. The circuit makes use of PUTs...