Patent ID: 8229513

Claim:
An IT terminal having a built-in audio equipment including a common jack interface to which a plural kinds of audio equipment can be connected, an input/output selector circuit to be connected to the jack interface and an audio CODEC to be connected to the input/output selector circuit, comprising: a conversion circuit connected in a LEFT signal path and a RIGHT signal path between the jack interface and the input/output selector circuit for converting an impedance of an audio equipment plug to be connected to the jack interface into a corresponding voltage, and outputting V-LEFT voltage corresponding to the impedance of a LEFT channel of the audio equipment and V-RIGHT voltage corresponding to the impedance of a RIGHT channel of the audio equipment; comparator circuits for comparing the V-LEFT voltage of the conversion circuit with a reference voltage and comparing the V-RIGHT voltage of the conversion circuit with the reference voltage; and a CPU connected to a controller of the audio CODEC and performs processing in response to the kind of audio equipment identified based on outputs from the comparator circuits, wherein the CPU identifies the audio equipment as a headphone upon the V-LEFT voltage being lower than the reference voltage and the V-RIGHT voltage is lower than the reference voltage, the CPU identifies the audio equipment as a stereo microphone upon the V-LEFT voltage being higher than the reference voltage and the V-RIGHT voltage is higher than the reference voltage, and the CPU identifies the audio equipment as an earphone microphone upon the V-LEFT voltage being higher than the reference voltage and the V-RIGHT voltage being lower than the reference voltage.