This circuit is from a July 1970 Radio Electronics magazine. The sensors are metal probes. The 18 V power source must be isolated from the mains.
We found this circuit in a 1977 radio documentation. The circuit uses TTL frequency dividers from...
In figure we have a three-phase AC motor control for voltages up to 600 V or 1200 V depending on...
The oscillator shown in the figure can generate signals up to 500 kHz and has good stability. Coil...