An input/output device inputting and outputting information to an external device includes a control section for communicating with an external controller. Electric equipment for communicating with the input/output device includes an input/output assignment storing section for storing which port of an input circuit an input from the external device is assigned to, and which port of an output circuit an output is assigned to. The electric equipment also includes an electric-equipment-side input/output control section for operating a function of the electric equipment based on information from the control section, or transmitting, to the control section, the information indicating which port of the output circuit an output of the electric equipment is output to. The electric equipment, using the external controller, stores the information related to the assignment in the input/output assignment storing section, or alters the information related to the assignment stored in the input/output assignment storing section.