<p>Each band-pass unit of a second transmitting/receiving apparatus includes a band-pass means and a receiving quality detection means. The respective band-pass means have different passbands. The receiving quality detection means detects receiving quality information of a signal that has passed through the band-pass means. A receiving quality control means generates a receiving quality control signal based on the receiving quality information. The receiving quality control signal is a signal which becomes a basis for controlling the electric energy level of a signal transmitted by a first transmitting/receiving apparatus. The first transmitting/receiving apparatus adjusts the level of the signal transmitted in each passband.</p>
