This low power circuit was obtained from an American 80's documentation. The circuit indicates the voltage of a battery being trimmed by the trigger point. The transistors can be the BC549.
The battery charger suggested in the figure has its current limited by resistor R1. This component can...
The operation of this circuit is not common today, but equivalents can be experienced. The circuit is...
This circuit generates various types of sounds and can be used as a toy. The circuit is from Radio...