An "electric eye" alarm detects a break in the beam of light not with a simple "electric" cell but with this type of cell
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Grant ... breaks the beam between the light source and the light sensor, and .... a 
photoelectric cell system or "electric eye" with a paired light source... [DOC] [TLE] Choosing and Using Fire and Burglar Alarms - Garage Door Remote [PAR] A simple rule of thumb is that if you're not using your key every time you leave ...