We found this circuit in a 1998 documentation. It tests common household appliances to see if they are shorted by lighting an incandescent lamp.
In the absence of a modulation signal, the carrier of this simple short-range transmitter is cut...
This circuit was obtained from an 80's Electronic Engineering. The circuit detects ice formation...
Other operational amplifiers series operatives, such as MC34072, MC34074, MC35071, MC35072,...