A sensor having: a housing extending from a front to a back, where the front has a transparent cover glass; an infrared (IR) beam emitter within the housing that emits a first beam along a first path; a visible light beam emitter within the housing that emits a second beam along a second path that is noncongruent with the first path; and a beam guide within the housing that engages the first and second beams so that the first and second beams are coaxial or parallel and exit the front of the housing.

An elevator system has an elevator car with a roof on which roof a balustrade is arranged as a fall protection for delimiting an accessible inner region on the roof. The balustrade includes a guide rail engagement means via which the balustrade can be brought into engagement with a guide rail by a latching mechanism for a secure position such that the balustrade is supported inwardly and outwardly on the guide rail in the secure position.