Abstract: Intrusion detection apparatus including a microwave transmitter comprising a generally unshielded dielectric resonating oscillator, whose parasitic field is radiated within a volume and Doppler detection apparatus for sensing received Doppler signals reflected by a moving object within the volume.

Abstract: A passive infra-red sensor comprising a housing including a mounting base and a lens mounting cover element, detector support apparatus selectably positionable with respect to said mounting base along a first axis, an infra-red detector and a beam locator illuminator mounted on the detector support apparatus, a multi-faceted focusing lens including a first array of beam defining lenses arranged for optical coupling to the infra-red detector and a second array of beam defining lenses arranged for optical coupling to the beam locator illuminator.