The amplifier has a build-in protection circuit to protect the transistors and speakers in following conditions: * The amplifier is overheated * A DC current is generated in speakers * The battery voltage is too low or too high * The speaker terminals are short circuited When the protector indicator lights up in red, the amplifier shuts down automatically. In this case please: * Take out the disc or tape and turn off the car audio * Check the cause of the malfunction * If the amplifier is overheated, let it cool down