This circuit with zener diodes was found in documentation from the 90s. The zener diodes determine the lighting point of the LEDs. The circuit is for 12 V automotive batteries.
I found this circuit in an English magazine from July 1982. The circuit is still viable by using...
The circuit shown was found in the 1994 National Semiconductor's Linear Application Handbook. The...
This solar powered circuit was found in a 1991 documentation. The transistor is a general purpose...