A motion detector system including first and second pairs of pyro- electric elements, electrical interconnections between the pyro-electric elements in the first pair providing a first signal output and local temperature compensation for the elements in the first pair, electrical interconnections between the elements in the second pair providing a second signal output and local temperature compensation for the pyro- electric elements in the second pair, wherein the compensation for the first pair is independent of the compensation for the second pair, a housing enclosing the two pairs of pyro-electric elements and defining a window, only one of the pyro-electric elements in each pair viewing a motion detection field of view through the window, and a signal processor receiving the first and second signal outputs and providing an output indication of crossing the field of view by an object having a temperature different from the ambient in the field of view.