This circuit was obtained in a 1969 Mullard manual. The transistors are from that time. The input sensitivity is 300 mV.
This circuit was obtained in the manual of the used integrated circuit. Equivalents may be used...
The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from...
This circuit was suggested by Popular Elecronics from the 90's. The circuit has high input...