Type 4 light curtains provide a multiple beam array of infrared light. If any of the beams are blocked by an object, such as a finger or a hand, the light curtain signals the machine to a safe state. The curtains come in protective heights 160–1,510 mm, and in 150 mm increments with optional muting and blanking. Installation doesn't require software or control boxes, and meets highest maximum achievable safety level requirements of SIL3, SILcl3 and PL e per IEC61496.