Metal detector receiver (CB22457E)

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

Flowing LED VU (CB18718E)
We found this VU circuit with special effects in an LED array in a 1991 documentation. The circuit...
Electronic Roulette (CB24471E)
This game with digital logic circuits was found in the December 1976 issue of Radio Electronics magazine....
Four Way Call Warning Light (CB17693E)
This 2009 circuit is a bilateral call warning. Easy to build, using light communication between two...