This resistive sensor was found in a 1969 US documentation. The circuit uses transistors of the time, but current equivalents can be employed.
This 10-transistor radio was found in Radio Electronics magazine from December 1964. The...
This oscillator uses one of the four ports of a 74C14 integrated circuit and can generate 100 kHz...
This simple humidity alarm circuit includes a timed warning oscillator whose time is set to R4....