US Patent 7897277 Reversible battery cartridge

A lighting apparatus includes an electrical contact that receives power from an external power source, a battery receiving region, and a battery backed light source. A user interface receives an input indicative of a first desired operation of the lighting apparatus when power is available from the AC power source and a second desired operation of the battery backed light source in the absence of power from the AC power source. Electrical circuitry uses battery power to operate the battery backed light source in the absence of power from the AC power source based on the second desired operation.