Recommended for automotive applications, this circuit was found in an April 1982 Radio Electronics magazine. The transistor supports equivalents. Sensitivity adjustment is made by R1.
This circuit is from a Japanese magazine from 1967. The circuit uses transistors from that time,...
This circuit produces 1 kHz square signals using the CMOS IC 4070. The frequency is given by the...
Found in an old Radio Electronics, this circuit applies to frequency meters for frequencies up to 100 MHz....