Metal detector receiver (CB22457E)

Found at Popular Electronics this receiver is used with a transmitter for quadrature-coil signals.

Radio Compass or Goniometer (CB18338E)
This goniometer for the medium wave range was found in a 1967 documentation. It can be adapted to work...
Astable with Inverters (CB13813E)
We found this astable configuration in a technical documentation from the 1970s. In it we have the way...
Magnetic Field Meter (CB23690E)
We found this circuit in a Radio Electronics from October 1965. The pickup coil can be of the...