A number of existing audio systems are designed to play back the signals from the auxiliary audio source using receivers. Radio and television (TV) receivers are the most widely available entertainment devices in the world. Stereo receivers are generally adapted to receive a radio frequency signal, derive from it a stereo composite signal and decode the stereo composite signal into left and right channel audio frequency signals. An FM/AM stereo receiver has an FM stereo receiving system for receiving an FM stereo broadcasting signal and an AM stereo receiving system for receiving an AM stereo broadcasting signal. In an AM stereo receiver an amplitude modulation (AM) sum signal L+R and a phase modulation (PM) difference signal L-R are transmitted from a transmitter. The letter L stands for the left channel stereo signal and the letter R designates the right channel stereo signal. In the case of an FM stereo RF signal the stereo composite signal generally comprises a sum of channels signal in the audio frequency range of approximately 30 to 15 kilohertz, which is required for monaural compatability, and a difference of channels signal comprising a set of side bands of a suppressed 38 kilohertz subcarrier, the side bands extending from 23 to 53 kilohertz, a frequency range above the audio frequency range. FM stereo receivers are designed so as to receive FM mono or stereo and include means for decoding the transmitted composite stereo signal into left and right audio signals. Commercial AM and FM broadcast bands include a plurality of evenly spaced channels. A particular broadcast station is allocated a unique channel to conduct broadcasting within an assigned frequency range.

A receiver may have both analog and digital receiving circuits, and be capable of receiving both types of broadcasts. Digital audio broadcasting has many advantages over analog broadcasting, especially for mobile receivers. Transmission of an audio signal in digital form from a transmitter to a receiver is known as such and it is going be become more common as digital television and broadcasting systems replace older systems based on analog frequency modulation. Generally, communications of digital audio signals between home appliances such as digital audio systems are performed in accordance with a protocol of DAI format. Digital audio broadcasting employs orthogonal frequency division multiplexing (OFDM) together with powerful error-correcting functions to transmit digital data at high speed with high reliability. A broadcasting receiver selects any one of a plurality of broadcasting waves received through a terrestrial wave antenna by a digital tuner, selects any one of a plurality of channels included in the selected broadcasting wave by demultiplex processing, extracts a digital signal on the selected channel, and decodes the extracted digital signal, to output a video/audio signal. In the DAI format, PCM (pulse code modulation) audio signals and control signals are transmitted after being modulated by bi-phase mark modulation. The transmission signal in the DAI format is restored to original PCM audio data in other digital audio appliances in accordance with DAI format, and after operations of the above digital signal processing, the PCM audio data is then converted into analog signals by a D/A converter.

A broadcasting receiver that receives both digital broadcasting and analog broadcasting comprises a digital tuner, a digital demodulator, an error correcting circuit (FEC), a demultiplexer, an audio decoder, a video decoder, and so on in a digital broadcasting video generator, and comprises an analog tuner, an analog demodulator, an analog-to-digital (A/D) conversion circuit, and so on in an analog broadcasting video generator. Most receivers also include means for automatically switching into the stereo decode mode when a stereo signal is being received. A DAB receiver includes an automatic frequency control (AFC) circuit that keeps the receiver tuned to the center frequency of the broadcast signal. An FM radio receiver generally comprises a front end including a tuner, intermediate frequency amplifier/detector, stereo demodulating stage and audio stage. An AM stereo receiver includes an antenna circuit, an RF amplifier stage and an intermediate frequency amplifier stage. An AM stereo receivers typically include light emitting diodes (LEDs) for indicating when the receiver is tuned to a station and when the receiver is tuned to a stereo signal. In a stereo receiver for receiving a compatible AM stereo broadcast signal, a stereo corrector is used to restore the original left and right signals. As audio, visual, and audio/visual application have become more sophisticated, receivers are now characterized as having multiple possible input signals, whether these input signals be audio, visual, or some combinations.