We found this circuit with duty cycle adjustment in the May 1988 Radio Electronics magazine. The source must be symmetrical, and the frequency given by R3 and C1.
A 3-terminal voltage regulator can be used as an efficient temperature regulator for a current...
Connected to the output of an audio amplifier or radio this circuit indicates the level of the...
This two-transistor circuit was found in a 1966 US documentation. The power transistors are of the...