This circuit was obtained from American documentation from 1966. It triggers when the two input voltages are within a pre-established range. The circuit can be mounted with modern transistors.
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...