An "electric eye" alarm detects a break in the beam of light not with a simple "electric" cell but with this type of cell
... Foil tape costs only pennies per foot, but it breaks easily even when 
you .... of electric-eye motion detectors, which use a photoelectric cell to detect an
... [DOC] [TLE] FED-STD-800 - GSA [PAR] Most optical systems use infrared lights to read the code so the spots are not 
visible ....