This circuit with the CA3059 was found in the July 1995 Elexctronics Now magazine. The signal must be DC, and the circuit is not isolated from the mains.
This simulation shows how to use an operational amplifier as a voltage comparator. The sample uses the...
This circuit automatically activates the relay when the phone is answered, closing the record...
This car alarm was found in an American '80s documentation. The circuit automatically activates...