To discriminate whether a cable in conformity with a conventional standard or a cable in conformity with a new standard is connected.An HPD signal line (902) has, on an expanded HDMI sink apparatus (402) side circuit, a pull-up resistor (911) between the HPD signal line (902) and a voltage supply and a pull-down resistor (913) between the HPD signal line (902) and the ground, and a reserved line (903) has, on the expanded HDMI sink apparatus (402) side circuit, a pull-down resistor (914) between the reserved line (903) and a ground, and within a new HDMI cable (901), a pull-up resistor (912) between the reserved line (903) and a voltage supply of an expanded HDMI source apparatus (401). The expanded HDMI sink apparatus compares a voltage at a test point (19) on the reserved line (903) on the expanded HDMI sink apparatus (402) side with a reference voltage by using a voltage comparator (916). A CPU of the expanded HDMI sink apparatus (402) determines, when an output from the voltage comparator (916) is High, a normal state where the new HDMI cable (901) is inserted, and when an output from the voltage comparator (916) is Low, determines a state where a conventional HDMI cable (931) is erroneously inserted.