Voltage Monitor MC34064 (CB14536E)

The component used in this circuit is uncommon today. The circuit is from Motorola's 1990 Linear Databook.

Light Alarm (CB24237E)
In this circuit found in the December 1972 Radio Electronics magazine. R can be from 1k to 22k,...
Field Strength Meter (CB19193E)
This circuit can operate between frequencies from 1 to 15 MHz depending on the coil. For 3.5 MHz...
Simple Metal Detector (CB5335E)
This metal detector circuit uses an AM radio as an indicator. The radio is placed off-station and tuned...