Found in an Elektor from the 90s, this circuit can be powered directly by the power grid. The circuit uses a rectifying bridge that can be replaced by 4 common diodes.
This simple electroscope with bipolar transistors is not the most sensitive, but can detect static...
This oscillator for various frequencies was obtained from a 1980s telecom documentation. The...
This circuit is from a July 1970 Radio Electronics magazine. The sensors are metal probes. The 18 V...