This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
This circuit can reduce the voltage of a source by providing regulated adjustable output. The...
Figure bellow shows how one of the two separated counters found inside the 4518 is used as a...
This circuit for very long-time intervals was found in the March 1993 Radio Electronics magazine. Times...