This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made at R6. Supply voltage is matched to that of the relay.
This circuit allows you to find two diodes with equal characteristics. The circuit was found in a...
This small amplifier with the fraction-watt LM4862 was found in the November 1999 issue of...
The output of this circuit must be connected to the input of an audio amplifier. The microphone is a small...