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.
Phase and amplitude can be controlled in this circuit found in the May 1988 Radio Electronics...
The purpose of the circuit of the figure is to control a servomotor remotely using a simple signal...
We found this circuit in a 90s Popular Electronics. The circuit can be implemented with modern...