Abstract: A method of operation of a light curtain system for sensing the intrusion of objects into detection planes which define a protected zone. A group of light beams are strobed from one transmitter in a first direction across a zone to a receiver, and another group of light beams are strobed from another transmitter across the zone to another receiver. Light beams within each group which intersect a desired entry area are deactivated for penetration of a permitted object, and other beams in the groups are enabled to detect intrusion into the objects in portions of the zone which lie around the entry area.

Abstract: A light curtain system for sensing the intrusion of objects into detection planes which define a protected zone. A plurality of light curtain segments are provided with each segment including spaced-apart transmitter and receiver heads. The transmitter and receiver heads are each connected in series by flexible cables which form a part of a control circuit. The series-connected segments permit the detection planes to be aligned in predetermined angular orientations as required by the particular application.