This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay is 12 V. The circuit is from Radio Electronics magazine, April 1975.
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....