This simple indicator circuit was found in a documentation from the 90s. Trimpots can have values between 2k and 10k, a series resistor is recommended to limit the current to the minimum setting.
This circuit is from 1968 documentation. We can assemble it with more modern components such as a...
Found in a 90s Silicon Chip documentation this circuit is intended to protect a speaker system in...
The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from...