Multiple power source automatic switching circuitry

Abstract From the Canadian patent

Circuitry is provided for automatically selectively switching a load from a primary power source to a secondary power source and back again, including switch means connected between the primary and secondary power sources, and control circuit means which controls opening and closing of the switch according to the sensed voltage level of the primary source. Once the secondary power source has been switched on at such time as its voltage, level drops below a predetermined level the switch can be adapted to automatically disconnect the secondary power source (e.g. battery) from the load.