Light-curtain area security system

An area-security system consisting of radiation-transmitting and receiving elements arranged in an area to be secured and producing a report if the radiation is influenced within the secured area, characterized by the fact that along one side of the secured area a transmitting/receiving strip is arranged which is subdivided into transmitting regions and receiving regions, each transmitting region consisting of plural transmitting elements arranged alongside of each other and combined in at least two transmitting groups wherein each transmitting group includes at least one transmitting element of each transmitting region;

• each receiving region consisting of plural receiving elements which are arranged alongside of each other and are combined in at least two groups of receiving elements arrayed with an intervening transmitting group;
• a multi-channel evaluation means coupled to evaluate the output signals of the respective receiving elements;
• and a control circuit connected for alternating excitation of the respective transmitting groups, said control circuit also having a synchronizing connection to said evaluation means for coordinating the evaluation (a) of first-group receiving-element responses to reflections from first-group transmitting-element transmissions and (b) of second-group receiving-element responses to reflections from second-group transmitting-element transmissions, the transmitting and receiving elements having such relatively wide responses within the secured area that, for a sufficiently large reflector in said area, plural first-group receiving elements are responsive to reflections of plural first-group transmitting-element transmissions, to the exclusion of second-group transmitting-element transmissions, and plural second-group receiving elements are similarly responsive to reflections of plural second-group transmitting-element transmissions.