Found in a 1968 American documentation, this circuit generates 1 kHz signals. The SCR used is not a common component today.
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...