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.
This circuit allows the division of the frequency generated by an oscillator with the 4069 by two,...
Found in ancient documentation, this circuit uses a high voltage transistor of the time. Observe...
This circuit with TTL compatible output was found in a 1968 US documentation. The circuit is...