We found this circuit in a 90s Popular Electronics. The circuit uses a pickup coil that consists of 100 to 200 turns of wire 28 around the cable to be monitored.
This circuit can be used in demonstrations or science fairs. The circuit uses headphones and can...
We found this wiretapping circuit in a publication from the 90s. The circuit allows the cable...
This circuit uses a resonant reed switch at the trigger frequency. The circuit is from General...