The Bosch DS453Q Quad Beam Photoelectric Detector features with separate transmitters and receivers. The transmitter emits an invisible infrared beam to the receiver. If the beam is broken, the receiver signals an alarm. The DS453Q use four pulsed infrared beams that are designed to activate an alarm only when all four beams are simultaneously blocked. It also features interlocked upper and lower beams, signal voltage LED, and selectable environmental discrimination circuitry.
