The transmitter comprises: a detection part for detecting an identifier (CI-ID) for identifying a band use to be received; an identifier setting part for previously setting the identifier (CI-ID) for identifying the expected band use; and a control part for monitoring the detection part and identifier setting part in each minimum unit of a line, wherein the control part periodically monitors the identifier for identifying the band use to be received in the previously defined band, and when the identifier is different from the identifier for identifying the expected band use, the identifier for identifying the expected band use is re-established as the identifier for identifying the band use to be received.