This circuit is from a 1980s Motorola documentation. The circuit can be made with modern equivalent components. The original circuit is for the 115 Vac (110 V) grid and has two settings.
Found in American documentation from 1968 this circuit is based on discrete components in addition...
This simple circuit indicates, through an LED, when the water level of a filter (or other kind of...
This circuit appears in similar versions elsewhere on this site. The transformer is 110 V or 220 V...