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Claim 1

APPARATUS FOR RECOGNIZING AN ARTICLE BEARING MARKINGS IN THE FORM OF LONG PERSISTENT LUMINESCENT MATERIAL, SAID APPARATUS COMPRISING: MEANS FOR IRRADIATING THE LUMINESCENT MATERIAL ON SAID ARTICLE, DETECTOR MEANS TO RECEIVE RADIATION FROM SAID LUMINESCENT MATERIAL ON SAID ARTICLE, AND MEANS TO CONTROL SAID IRRADIATING MEANS IN A MANNER OPERABLE TO ESTABLISH PREDETERMINED TIME PERIODS OF IRRADIATION OF SAID LUMINESCENT MATERIAL SEPARATED BY TIME PERIODS OF NON-IRRADIATION OF SAID MATERIAL IN ORDER TO ENABLE SAID DETECTOR MEANS TO RESPOND TO THE RADIATION FROM THE LONG PERSISTENT LUMINESCENT MATERIAL DURING THE TIME PERIODS OF NON-IRRADIATION, SAID CONTROL MEANS CAUSING SAID IRRADIATING MEANS TO BE ALTERNATELY ENERGIZED AND DE-ENERGIZED FOR APPROPRIATE TIME PERIODS AND FURTHER CAUSING SAID DETECTOR MEANS TO RESPOND TO RADIATION FROM SAID LONG PERSISTENT LUMINESCENT MATERIAL DURING SAID TIME PERIODS OF DE-ENERGIZATION AND IN THE ABSENCE OF ANY ADDITIONAL IRRADIATING SOURCE, SAID DETECTOR MEANS BEING POSITIONED IN OPTICAL RELATION TO THE ARTICLE AND BEING OPERABLE TO PROVIDE A DISTINCTIVE OUTPUT IN RESPONSE TO THE EMISSION FROM SAID LONG PERSISTENT LUMINESCENT MATERIAL BORNE BY THE ARTICLE WHILE THE IRRADIATING MEANS IS DE-ENERGIZED.