Patent ID: 8320587

Claim:
An audio device comprising: an internal sound producer; an earphone jack for establishing a connection with an external sound producer; a detection circuit for detecting a connection between the earphone jack and the external sound producer, and generating a first state signal when the connection is detected and a second state signal when no connection is detected; a volume adjustor preset with first predetermined volume levels suitable for the external sound producer and second predetermined volume levels suitable for the internal sound producer, the volume adjustor generating a first adjustment signal based on the first predetermined volume levels in response to the first state signal, and generating a second adjustment signal based on the second predetermined volume levels in response to the second state signal; and an amplifier electrically connected with the volume adjustor, the internal sound producer, and the earphone jack, the amplifier receiving audio signals, amplifying the audio signals, and adjusting volume of the amplified audio signals according to the adjustment signals, then outputting the adjusted audio signals to the internal sound producer and the earphone jack; wherein each of the first predetermined volume levels and the second predetermined volume levels indicates an adjustable volume range, each of the first predetermined volume levels corresponds to one of the second predetermined volume levels, the first predetermined volume level is lower than the corresponding second predetermined volume level, the amplifier comprises a positive output terminal and a negative output terminal, the internal sound producer is connected with the amplifier via the positive output terminal and the negative output terminal, the adjusted audio signals are output to the internal sound producer via the positive output terminal and the adjusted audio signals output to the internal sound producer via the negative output terminal are in phase when the amplifier receives the first state signal, and the adjusted audio signals output to the internal sound producer via the positive output terminal and the adjusted audio signals output to the internal sound producer via the negative output terminal are out of phase when the amplifier receives the second state signal.