The Banner Engineering EZ-Screen is a two-piece (two-box) system comprising an emitter and a receiver but no external controller. The external device-monitoring (EDM) function ensures the fault detection capability required by EN ISO 13849-1 Categories 3 and 4 without a third box, a controller or a smart (self-checking) safety module required of systems without EDM. In typical operation, if any part of an operator’s body (or any opaque object) of more than a predetermined cross-section is detected, the solid-state output signal switching device (OSSD) safety outputs turn off.