To switch two wired transmission lines for connecting pieces of communication apparatus without any omission of user signals by a simple procedure without depending on a special control cell for generating an increase in traffic volume.

At transmission and reception sides, a data frame including time information is used for the first wired transmission line for transmission/reception (procedures ST301, ST302). In the process, the reception side transmits a reproduction start instruction 303 to the transmission side. The transmission side reproduces the data frame for broadcasting to the first and second wired transmission lines (procedure ST304), and sends a confirmation response 305 to the reception side. As a result, the reception side receives the data frame having time information that is later than a predetermined time from the second wired transmission line (procedure ST306). The transmission side receives a reproduction end instruction 307 and transmits the data frame to the second wired transmission line (procedure ST309).