This indicator or logic probe was found in the April 1979 Radio Electronics magazine. The integrated circuit is the 555 and the FET can be any general-purpose type.
This 6V microsupply with just 2mA current uses a common 1N34 germanium diode. The circuit was...
This circuit for a frequency of 100 kHz was found in documentation from the 60's. The circuit can...
This preamplifier for record players with crystal capsules was found in Radio Electronics magazine...