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.
The operational amplifier used in this configuration is uncommon today, but more modern types can...
This 600-ohm line driver was found in a 1980s documentation. The integrated circuit used is not...
Two comparators are used to indicate the status of a 9 V battery. The circuit is from Electronics Now...