Found in documentation from the 1980s, this circuit can have several adaptations to use modern transistors and LEDs instead of the lamp. The power supply voltage can also be changed.
This circuit was found in an old American documentation on telecommunications. It is suitable for...
This circuit for discharging NiCad batteries limits the current to a value that can be adjusted in the...
This circuit was found in a 1997 publication, but it uses few common components and is very...