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.
This circuit is from the National Semiconductor's Linear Applications Handbook of 1994. The...
This RF signal meter has a switch position that allows calibration and comparison of low intensity...
T We found this circuit in the 1960 Mullard transistor application manual. The circuit can be...