This circuit was obtained in a 1964 Electronic Design. The components used are from that time. Observe the high voltage used in the supply.
This 1964 Electronic Design circuit uses a photo-FET as a sensor. The component is rare today. |...
Operational amplifiers or comparators like those in the LM139 series can be used on this circuit,...
This sensitive electrostatic charge detector uses only common discrete components. The circuit can be...