The Siemens PBR-1191 retroreflecting prism has the shape of a pyramid whose lateral faces are form by isosceles orthogonal triangles. Also, the light beams entering through the base are completely reflect twice on the lateral faces and reflected back through the base.
The Siemens PBR-1191 prism is install in a housing that is identical to the one use for the detector base. Besides, the reflector is equip with a reflector heater. If condensation is possible, connect the heater to a 24V supply. Retroreflectors reflect the received light beam back along the path of incidence. Furthermore, the design of all the reflectors minimizes the effect of vibration and structural movement.