... Immunity 3.Durable life 4.Good anti-vibration and easy to use 5.Self-locking function STQ seriesProtection range, 0- ... 80,240,400,560,3120mmThe product uses the separate emitter, receiver design, the structure is reliable, the contour is artistic, ... a controller and two signal cables.The emitter launches light to mirror, through reflecting to receiver, forms two or three protection light curtains