PURPOSE: To simply identify an erroneous wiring state in an external electronic apparatus by displaying an alarm sound and picture using a voice synthesizing part and letter generator at the time of erroneous wiring of external signal.

CONSTITUTION: When an external audio (A)/video (V) signal is not matched or applied due to erroneous connection wiring, the state of a video and audio signal outputted from an A/V switching part 1 are detected with a signal detecting part 7 controlled with the output P2 from an A/N control logic 6, and an erroneous wiring signal is outputted and applied to the terminal P1 of an audio switching part 4. The erroneous wiring detecting signal is also applied to the output P1 of a remote control regulating part 8, the output P3 of the regulating part 8 is applied to the terminal P2 of the audio switching part 4 through the voice synthesizing part 9, thereafter the output P3 is applied to a speaker SP through a voice signal processing part 5 and amplifier AMP to generate an alarm sound. Also, a CRT drive 3 is controlled with the output P2 of the regulating part 8 through a letter generator 10, and the letter 'erroneous wiring' is generated on the screen of the CRT.