This circuit that we found in a 1990 documentation uses an LED as a sensor. The operational amplifier is equivalent to the 741 and the trigger adjustment is made in the potentiometer.
This circuit was found in Motorola documentation from 1966. The lamps are according to power and...
This circuit divides the grid 60 Hz frequency to obtain 20 Hz to drive mechanical watches used at...
We found this circuit in a Mullard manual from 1960. The transistor is a phototransistor of the...