Metal locator (CB7506E)

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

LM3914 Moving Point Voltmeter (CB25450S)
We found this circuit in the March 1992 issue of Radio Electronics magazine. The circuit has a...
Adjustable Field Strength| Meter (CB5188E)
The circuit presented may use any general purpose transistor. The indicator is an LED and...
5 W Class Amplifier (CB13674E)
This unusual audio amplifier configuration was obtained in a 1974 documentation. The PNP...