A frame-shaped cover for covering resilient holding pieces is mounted at an opening edge of a fitting, and clearances Cb for permitting displacements of the cover in forward and backward directions intersecting a mounting direction of a base with respect to the fitting are defined between the outer surfaces of front and rear walls ) of the fitting and the cover. Services are handed over between the access point devices responsively to the wireless terminal device moving. The data center selects the user ID of a viewer whose viewing time of the video program is longer than a predetermined time from the received viewing information, and distributes advertisement information corresponding to the video program, together with a reception acknowledgment added thereto, to a mail address corresponding to the selected user ID. Each supplier”s offers can also be changed to reflect each supplier”s capacity utilization.