This circuit was obtained from a National Semiconductor manual from the 1990s. The circuit employs a pair of matched transistors, and the indicator is analog.
This sensor was published in Radio Electronics magazine in April 1962. The two-transistor circuit...
Another of the many similar configurations we have in this section. This one is from a Radio...
This circuit like the previous one is intended for 24V x 3W solenoids being connected from the...