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.
An excellent signal generator for the audio track was found in a 1983 documentation. Its complete...
CMOS inverters can be used as amplifiers, obtaining a flat response up to approximately 20 kHz....
This circuit uses BCD switches to program the frequency to be divided. The circuit is from a Radio...