While a general-purpose interface circuit and another general-purpose interface circuit are provided so as to transmit/receive data between a host appliance and a device appliance, when the general-purpose interface of the device appliance happens to hang up, a control section transmits a reset signal via a dedicated interface circuit. When a dedicated interface circuit provided on the side of the device appliance receives this reset signal and then outputs this received reset signal to the general-purpose interface circuit, the general-purpose interface circuit is reinitiated.