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.
Found in an old Elektor, this circuit uses two 7-segment displays to indicate the volume of an...
L1 and C1 determine the frequency of this Colpitts Oscillator. Refer to our section Mathematics...
This circuit is from Mullard 1969 documentation. The circuit operates at a relatively high supply...