An improved client locating and user discovery system is disclosed. The cards of the first series have their own associated MAC address tables for addressing traffic between ports through the interconnection unit. The leak sensor has a through hole having a pair of opposed walls with a predetermined space. Stable bituminous compositions comprising 6 to 25 parts by weight of block copolymer per 100 parts of asphalt are also provided as well as their application as roofing shingles. The transfer coating of the transfer sheet includes a powdered thermoplastic polymer and a film-forming binder. An error is compensated for by allowing coordinates according to the electromagnetic induction formed on the sensor board and varied with the rotation disposition state of the sensor board to correspond to a position of the nib.