This simple 5.6 V regulator circuit was found in a 1966’s Philips. The zener can be changed to obtain other voltages.
This circuit from a Popular Electronics from the 90's can generate signals from 0.03 Hz to 3 kHz...
Found in the November 1986 issue of Radio Electronics magazine, this circuit can generate signals of...
This anti-theft circuit was found in a 1985 documentation. It uses common components that can...