A data network storing data relating to work done by vendors for clients is described. A light transmitting surface of each of the sapphire single crystal plates is formed in such a manner as to be offset from the c-plane of the sapphire single crystal plate. Dynamic measurement of ozone concentration with time whilst ultraviolet irradiation is pulsed enables each gas concentration to be calculated without requiring input gases to be scrubbed. The material swiftly reaches the terminal ends of the extrusion parts, and heat welds them together. The processing of the incoming signal may be performed on a mircroprocessor in a housing detachably attached to a telephone, and may be based on a parameter value of a kitchen appliance having a timer, or a state change of a doorbell.