Type B1 non-contact devices (such as photo-beams) and / or Type B2 contact sensors (such as reversing edges) are required for most automatic gate system applications. DKS gate operators require a minimum of 1 device to be connected in each direction of travel; otherwise, the operator will not run. All entrapment devices used with DKS gate operators are monitored per the requirements of the UL 325 Standard for Safety.