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.
We found this circuit in a 1998 documentation. It is based entirely on relays that must have...
This traditional complementary symmetry circuit provides 20 W of rms power at a load of 8 ohms...
Assembled with SMD components this circuit can be very small. The range is a few tens of meters. We...