It actually consists of a tunable field strength meter. The circuit is of an old documentation and the circuit must be tuned to the frequency to be monitored. The circuit offers the option to use a headset.
I found this simple circuit in an English magazine from 1984. The circuit can be assembled easily...
This RS flip-flop uses two type 4N26 optical couplers and is characterized by the very high...
August 2017 - Mouser Electronics is stocking the new Molex optical EMI shielding adapters. These...