Metal detector 4001 (CB21723E)

This is one of many metal detector versions of this type found on this site. This one uses a small headphone and an explorer coil.

Ceramic Phonocaptor Preamplifier (CB15817E)
This circuit uses only one transistor and has an excellent gain for the type of signal source...
1.2 V Zener Diode (CB20458E)
Zener diodes of approximately 1.2 V can be obtained from common diodes. In fact, given the...
Sequential relay control 4017 (CB25370E)
This circuit was found in the February 1991 Radio Electronics magazine. The circuit must be...