Metal locator (CB7506E)

This simple metal detector was found in a 1960 Sylvania transistor manual. The phone must be high impedance or crystal.

Voice Controlled Switch (CB12169E)
This circuit of a voice-controlled switch, Vox or sonic switch was obtained in a Popular...
Light-Operated Lamp (CB23961E)
This circuit appeared in the July 1969 issue of Radio Electronics magazine. The sensor is an LDR....
Simple Timer (CB18452E)
This circuit of two transistors was found in a Japanese magazine in 1967. The transistors are made...