This circuit uses an LED (called SSL) to regulate current in a configuration with complementary transistors. The circuit is from 1970 General Electric documentation.
This circuit was obtained in the manual of the used integrated circuit. Equivalents may be used...
This source whose voltage depends only on the zener diode used, can supply currents up to about 3 A....
This highly sensitive circuit was found in a 1967 General Electric SCR manual. Equivalent...