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.
In the figure we have a simple timer with two voltage comparators of the four of an LM339. The...
This circuit can be used in a signal level indicator with LEDs. The circuit is from an Electronics Now...
This circuit, found in an old magazine of the year 1968, uses a Power germanium transistor. This...