Metal detector receiver (CB22457E)

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

Modulated Oscillator 4093 (CB17577E)
Photometer (CB7360E)
This 1964 Electronic Design circuit uses a photo-FET as a sensor. The component is rare today. |...
Limit Detector (CB5163E)
This two-input limit detector was found in an American 1980s documentation. The circuit can be...