An audio, video, and navigation system implemented in a single unit comprising: a battery voltage detection circuit configured to detect an output voltage of a main battery to generate one of first and second control signals, each having a different voltage level according to the output voltage; a peripheral circuit unit configured to provide at least one of audio, video, and navigation services to a user; a central controller, including an integrated microcomputer configured to control a CAN network and an application processor configured to perform at least one of the music, the radio, the digital multimedia broadcasting and the navigation functions, and configured to generate an accident occurrence message when an airbag inflation signal is received; a normal power circuit configured to output power of the main battery to the central controller and the peripheral circuit unit if the battery voltage detection circuit detects a voltage of a power output terminal of the main battery and the detected voltage is within a normal output voltage range; and an e-call power controller configured to output power of a back-up battery to the central controller in response to the second control signal, wherein the central controller provides an emergency voice call with an emergency rescue center which receives the accident occurrence message, wherein the normal power circuit supplies the power of the main battery to the central controller and the peripheral circuit unit when the output voltage is within a normal output voltage range, while the e-call power controller supplies the power of the BUB to the central controller when the output voltage is out of the normal output voltage range. a battery voltage detection circuit configured to detect an output voltage of a main battery to generate one of first and second control signals, each having a different voltage level according to the output voltage; a peripheral circuit unit configured to provide at least one of audio, video, and navigation services to a user; a central controller, including an integrated microcomputer configured to control a CAN network and an application processor configured to perform at least one of the music, the radio, the digital multimedia broadcasting and the navigation functions, and configured to generate an accident occurrence message when an airbag inflation signal is received; a normal power circuit configured to output power of the main battery to the central controller and the peripheral circuit unit if the battery voltage detection circuit detects a voltage of a power output terminal of the main battery and the detected voltage is within a normal output voltage range; and an e-call power controller configured to output power of a back-up battery to the central controller in response to the second control signal, wherein the central controller provides an emergency voice call with an emergency rescue center which receives the accident occurrence message, wherein the normal power circuit supplies the power of the main battery to the central controller and the peripheral circuit unit when the output voltage is within a normal output voltage range, while the e-call power controller supplies the power of the BUB to the central controller when the output voltage is out of the normal output voltage range.