This frequency triple oscillator circuit was found in an American publication in 1967. The FET is current and more detailed information about the coils is not given.
This detector uses an unusual sensor today. The circuit is from an 80s documentation. Its...
This circuit was found in the December 1976 issue of Radio Electronics magazine. The circuit...
For inductive loads we have the configuration shown in the figure. Note that the opto-coupler...