Patent ID: 8138910

Claim:
An uninterruptible power supply unit comprising: a power supply circuit that generates a predetermined alternating current power from an alternating current power supplied to a power receiving terminal or from a backup power and supplies the generated power to one or more power supply terminals; a plurality of modem means each installed corresponding to the power receiving terminal and each of the one or more power supply terminals in a one-to-one manner, and transmitting or receiving a power line communication (PLC) signal; a plurality of low-pass filter circuits each coupled to a power line between each of the modem means and the power supply circuit, and eliminating the PLC signal; and a control means that makes at least one of the other modem means transmit a PLC signal, based on a PLC signal received by one of the modem means, wherein each of the modem means demodulates a received PLC signal into communication data, and modulates demodulated communication data into a PLC signal and transmits the modulated PLC signal; and the control means transmits communication data demodulated by the modem means to the modem means other than the modem means that has demodulated the communication data.