The present invention provides a technique for determining which nodes are to provide various functions on traffic along a particular communication path. Example treatments include thermal treatments using particulate or powderized materials to form a coating. The mailing identifier and the content can be associated with the recipient identifier. The ordinary communication nodes enter their sleep state in accordance with the sleep-transition command signal from the particular communication node, without individually determining the necessity to make a transition to the sleep state. The CPU corrects the detected detection patterns based on the detected quantity of reflection light.