Found in an Electronics World of 1966, this circuit makes use of FETs of the time. Modern equivalents can be used. The high voltage supply suggests its use with tube amplifiers.
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
This sensitive circuit for triggering relays was found in an old English publication. It works with...
This circuit was obtained from a 90’s Linear Technology documentation. The circuit provides...