Patent ID: 8258940

Claim:
A power line communications system, comprising: slave apparatuses to be individually connected to a plurality of electric power line wirings; a master apparatus connected to one of a plurality of electric power line wirings; and couplers each connected between the master apparatus and the others of the plurality of electric power line wirings; the master apparatus including: a communicator for performing power line communications with the slave apparatuses via the electric power lines; a power supply terminal device connected to the one electric power line wiring; a communication connector provided between the communicator and the power supply terminal device; and a coupler connecting terminal device connected to each of the couplers via a signal line, wherein the communication connector has: a first capacitor connected to the power supply terminal device for cutting off a frequency component of commercial power supply and transmitting a frequency component for use in the power line communications, and a first transformer connected between the first capacitor and the communicator, and the coupler connecting terminal device is connected between the first capacitor and the first transformer, wherein: each coupler includes: a slave apparatus connecting terminal device connected to a corresponding slave apparatus via one of the other electric power line wirings:, a plurality of signal line connecting terminal devices connected to the master apparatus or another coupler via a corresponding signal line; and a communication connector connected between the slave apparatus connecting terminal device and each of the signal line connecting terminal devices, wherein the communication connector has: a second capacitor connected to the slave apparatus connecting terminal device for cutting off the frequency component of commercial power supply and transmitting the frequency component for use in the power line communications, and a second transformer connected between the second capacitor and each of the signal line connecting terminal devices, each coupler includes: an overcurrent protection element for protecting the coupler from an overcurrent; and a notifier for notifying an operator that the coupler is kept in an overcurrent protection state by the overcurrent protection element.