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 556 integrated circuit is actually a double 555. This circuit can be assembled from an...
The transducer used in this configuration that appears elsewhere on this site is a piezoelectric...
This modern XTAL radio replaces the galena crystal for a germanium diode as the 1N34 or...