photoelectric cell - definition and synonyms

noun [countable] 

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/ˌfəʊtəʊɪˌlektrɪk ˈsel/
singularphotoelectric cell
pluralphotoelectric cells
  1. 1
    a piece of equipment that reacts to light and is used in machines such as burglar alarms (=machines that make a loud noise if a thief tries to get into a building)