Found in a 1965’s Electronic Design, this circuit operates with a voltage of 1.5 V. The relay can be of a reed relay or other type.
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...