This benchtop power supply with various output voltages from 1.5 to 12 V was found in Radio Electronics magazine from August 1960. The circuit uses power transistors of the time.
The figure shows how to implement the AND function with a Norton LM3900 operational amplifier. The number of...
This source, from a 1982 documentation, uses a triac to control the power and voltage applied to...
This circuit applies to small gearboxes with motors that do not exceed 200 mA. The circuit is from...