Metal locator (CB7506E)

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

Balanced Modulator (CB4224E)
This circuit was found in a 1980s telecommunications publication. The circuit uses a diode bridge to...
High Quality Headphone Amplifier (CB11998E)
This circuit is from an English magazine from 1980, but it can be easily assembled with more...
Two 555 Siren (CB16400E)
The indicated circuit is an intermittent one in which we use two 555 integrated ones, one as a low...