Found on an 80's Radio Electronics, this circuit is designed to pass the 300 to 34,000 Hz voice range using standard operational amplifiers.
This circuit was found in a Mullard transistor manual from 1960. Note the symmetrical power...
With the shadow over the sensor, it is possible to interrupt the sound of your amplifier using this...
This circuit puts the battery in the circuit when the voltage of a source is cut, preventing it...