Metal detector receiver (CB22457E)

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

Photocontroller (CB17202E)
This circuit activates an incandescent garden, balcony or showcase lamp when it gets dark, turning it...
Overvoltage Indicator (CB12210E)
This circuit is from an old publication of 1972 but can be mounted with BC548 transistors for 12 V...
Complete FET Test (CB19255E)
This circuit is intended for the testing of junction FETs, providing several reading options...