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.
We found this trebble booster circuit in a 1990 documentation. The components are current, and the...
This circuit was found in an 80s Hands On Electronics. It senses the water level in a reservoir by...
This circuit was found in General Electric documentation from the 1980s. The circuit is intended...