This circuit was found in the March 1992 issue of Radio Electronics magazine. The circuit has several adjustments and uses an operational amplifier. Note the supply voltage.
This circuit was obtained in a 1994 documentation. The assembly is very critical, and the circuit...
This circuit is from the 80's documentation. The integrated circuit is from the time but can be...
This sensitive sound or noise activated key can be used in an alarm system. The circuit is from an...