Found in an Electronics World of 1966, this circuit makes use of FETs of the time. Modern equivalents can be used. The high voltage supply suggests its use with tube amplifiers.
In the figure we have the way to use the LM3914 as a scale of bar LEDs or moving point. The...
We found this circuit in a European publication of the 1980s. The transistor could be the BC549. The...
We found this simple continuity tester in a 1995 documentation. It uses two LEDs to indicate...