Patent ID: 6987430

Claim:
A power line communication system for allowing communication between a plurality of communication devices by using an indoor power line, comprising: an indoor power line; a communication channel that is branched off from the indoor power line and connectable to a communication device for performing communication by using the indoor power line; a power supply channel that is branched off from the indoor power line and connectable to electrical equipment that requires electric power; an impedance matching circuit provided on the power supply channel, for setting an impedance of the indoor power line to a predetermined value; and a filter circuit provided on the power supply channel, for reducing noise occurring from the electrical equipment when the equipment is connected to the power supply channel, wherein the power supply channel includes two power supply lines, and the impedance matching circuit includes: a matching impedance element provided between the two power supply lines, for setting the impedance of the indoor power line to a predetermined value when the electrical equipment is not connected to the power supply channel; a high-pass filter element provided between the two power supply lines, being connected in series to the matching impedance element, for interrupting a frequency component of electric power carried by the indoor power line; and a variation-suppressing impedance element provided on at least either one of the power supply lines at a position closer to the electrical equipment than the matching impedance element and the high-pass filter element are, for suppressing variations in the impedance of the indoor power line resulting from connection of the electrical equipment to the power supply channel.