Mobile apparatus capable of automatic detection and communication of voice and digital data

A cellular phone comprising:

• an earphone jack having a first terminal for receiving a first signal, a second terminal for transmitting a second signal, and a third terminal for providing a third signal;
• a processor comprising:
• a communication module for serial transmission and reception of a digital data signal;
• a voice module for processing a voice signal;
• an analog-to-digital module for converting the first signal into a voltage value;
• and
• an input-output module for receiving the third signal and providing a selection signal;
• wherein the input-output module detects the third signal periodically and sets the selection signal according to the voltage value, and the analog-to-digital module is enabled to convert the first signal into the voltage value when the third signal is detected at a predetermined state;
• and
• a selection unit, responsive to the selection signal, for selectively establishing a first path between the first and the second terminals of the earphone jack and the communication module or a second path between the first and the second terminals of the earphone jack and the voice module to pass the first and the second signals.