IR1000/HD50 - Retro-reflective photobeam
Some applications have no facility for getting a cable to one side of the opening. Retro reflective photobeams shoot a beam from one side to a reflector on the other side.
Range is up to 10m, but alignment is critical for the longer distances. A 5m opening is relatively easy to protect. These photobeams can take from 12Vdc to 240Vac, and provide a volt free changeover output contact