Patent ID: 7047555

Claim:
An in-building CATV system connected to a lead-in wire from an external bi-directional CATV system for transmitting a downward signal inputted from said lead-in wire to plural in-building terminals via in-building transmission lines, transmitting an in-building upward signal inputted to said terminals via an up-converter for frequency-converting an upward signal outputted from a terminal device, with a frequency lower than that of said downward signal to an in-building upward signal with a frequency higher than that of said downward signal, and frequency-convert said in-building upward signal to an upward signal with an original frequency outputted from said terminal device by a down-converter provided between said transmission line and said lead-in wire to transmit said upward signal to said lead-in wire, wherein the in-building CATV system comprises: a reference signal generating means for generating a reference signal with a constant frequency different from that of any of various transmission signals flowing upward and downward in said transmission line, and a reference signal transmission means for transmitting said reference signal generated by said reference signal generating means to said transmission line, and said up-converter at the terminal side and said down-converter at said lead-in wire side can frequency-convert said upward signal and said in-building upward signal, respectively using said reference signal with the constant frequency, wherein said reference signal generating means and said reference signal transmission means are provided in said down-converter.