This simple circuit can work with either 4.5 V or 6 or 9 V if a 1k resistor is added in series with the set of LEDs. The circuit is from an old French publication.
Found in Raytheon's 1960s transistor circuit manual, this circuit employs the CK722, one of the...
Found in Electronics now, this circuit generates signals given by the formulas next to the...
Found in Popular Electronics from the 90s, this circuit can be used as a warning shield for...