This circuit was found in a Popular Electronics from the 90's. The components used are common and instead of the buzzer we can use an LED or a relay.
We found this circuit in a 1975 publication. The circuit can be made with more modern equivalent...
August 2016 - It can be obtained from Mouser Electronics the power factor controller NCP1602 from...
This is a traditional circuit in which a 741 operational amplifier is used as an audio amplifier with...