Abstract: A compatible circuit and method for 4- and 5-pole earphones and a portable device are disclosed. The compatible circuit and method alter the path of audio signals, using switches, according to control signals, so that the 4-pole earphone can be used in a portable device designed primarily for a 5-pole earphone. The apparatus and method include determining the type of earphone, altering the audio signal path according to the type of earphone, and transmitting the audio signal to the earphone.

Abstract: A compatible circuit and method for 4- and 5-pole earphones and a portable device are disclosed. The compatible circuit and method alter the path of audio signals, using switches, according to control signals, so that the 4-pole earphone can be used in a portable device designed primarily for a 5-pole earphone. The apparatus and method include determining the type of earphone, altering the audio signal path according to the type of earphone, and transmitting the audio signal to the earphone.

Abstract: An apparatus for generating a magnetic field in a portable communication terminal for the hearing impaired. The apparatus includes an amplifier for amplifying an electric signal of a voice band from a codec to a predetermined level, a Low Pass Filter (LPF) for removing harmonic components from an output electric signal of the amplifier, and a coil for converting an output electric signal of the LPF into a magnetic signal. Accordingly, the apparatus for generating the magnetic field can be implemented using the Class-D audio amp. Also, the efficiency of the apparatus for generating the magnetic field can be improved, while reducing its size.