This regulator can be controlled by a logic signal. The circuit is from an Electronics Now from the 90s. Note that the switching transistor is before the integrated circuit.
The power supply shown has protection against short circuits and can eventually be mounted with...
This circuit with germanium transistors was found in a 1980s documentation. The circuit makes use...
This photocell circuit was found in Radio Electronics magazine from July 1959. The transistor used...