Mobile communication terminal system

A mobile communication terminal system includes a serial interface port, a multimedia output/input module, a multimedia processor, a frequency-signal output/input module, and a baseband processor. The serial interface port is coupled to a computer system via a serial interface. The multimedia output/input module provides a first input signal. The multimedia processor processes the first input signal to generate a first serial interface signal. The frequency-signal output/input module provides a second input signal. The baseband processor processes the second input signal to generate a second serial interface signal to the multimedia processor. The multimedia processor selectively establishes one of a communication connection between the multimedia processor and the serial interface port and a communication connection between the baseband processor and the serial interface port to correspondingly output one of the first serial interface signal and the second serial interface signal to the computer system via the serial interface port.