This circuit was obtained in a 1967’s EEE. Transistors and integrated circuits can be replaced by modern equivalents. The FET is for general use.
This detector or window comparator was suggested by Harris in documentation from the 90's. The...
This circuit was found in the April 1971 Radio Electronics magazine. It uses common transistors and can...
Found in Radio Electronics from the 90s, this circuit uses a thermistor or NTC. The resistance of the...