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 is from a 1995 publication. The components are all common and the number of LEDs may...
This circuit, found in a 1995 documentation, is intended for switching composite RGB video signals...
This circuit is from Motorola's Linear Interface ICs of 1993. The integrated circuit is not common...