Suggested by Raytheon in 1967 documentation this circuit uses a lightbulb and LDR optical coupler of the time. The transistor determines the maximum current.
The circuit illustrated in Figure allows external loads (8) to be driven from parallel port...
This circuit uses two transistors to simulate the action of an SCR on a regenerative switch....
The filter presented is from 1994 but can be implemented with a more modern equivalent. We found...