A channel pointer extractor extracts channel pointer value inserted in a SDH signal based on the pointer position information contained in the channel information, each time the channel information is detected by a channel information detector. The method includes inputting user data into a user identification reader of the remote control system, and in response to inputting user data, requesting updating a remote user list stored by the remote control system with a central user list stored by the central control system using a wireless communicator of the remote control system and a wireless communicator of the central control system. In addition, an ultrasonic carrier signal has at least one sideband which represents the pre-encoded audio signal. The power-saving mode setting means receives the network information stored on the network information memory.