This circuit is from an 80's technical newsletter. The circuit can use any general purpose transistor and its power supply can be changed with a resistive divider to use a single 9V battery.
Found in an Electronics Now from the 90s, this circuit appears elsewhere in this section and...
This 3, 5, 6, 9 and 12 V power supply selected by a switch has a digital indicator of the selected...
This circuit is from a Radio Electronics from December 1964. The components are from the time and...