Abstract: A device used as a switching device between a telephone and a fax machine, especially for providing a general fax machine with a function of telephone connection including a calling circuit, a calling-detector circuit, a tone-detector circuit, a telephone-hold circuit and a telephone sounding circuit. Once a caller dials a fax number, the calling circuit and the tone-detector circuit start to detect the input signal. If the input signal is telephone-input, then the telephone-hold circuit holds the circut and a switch is triggered to make a telephone connection. Further, the telephone sounding circuit drives the buzzer of the telephone. Then the telephone switching is completed.