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.
Found in Electronics now, this circuit generates signals given by the formulas next to the...
This source was found in the National Semiconductor's Linear Applications Handbook of 1994....
This circuit is another practical idea for places where they still receive signals from analog TV. The...