If a device non-compatible with CEC is contained in an input path when a display apparatus is HDMI-connected hierarchically to a plurality of external devices, an external device which has transmitted <Active Source> is selected as an operation object device. First and second communication sessions are established. The relief valve includes a movable plunger. The Metamodel innovatively goes beyond the existing art and harnesses the IDL parsing ability of the IDLJ and generates an XML output for the parsed contents. The body portion of the SIP response message includes a number of service specific information parameters, such as a collected address, primary and alternate routing addresses, an alternate routing condition, manipulated digits and recording instructions.