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.
With this circuit, obtained from an American publication for radio amateurs in 1976, it is...
Small variations in the resistance of the skin of a person holding the electrodes can be detected by...
This circuit was found in a 1967 American documentation. The circuit uses components of the time,...