A signal switching system includes a first connector, a second connector, a switch unit, a first comparator, and a second comparator. The first connector is electronically coupled to a television. The second connector is electronically coupled to a video playback device. The first comparator is electronically coupled between the first connector and the switch; and the second comparator is electronically coupled between the second connector and the switch. The first comparator outputs a control command to the switch unit according to the voltage of the first connector, and the second comparator outputs a control command to the switch unit according to the voltage of the second connector. The switch unit selectively outputs a first signal or a second signal to the first connector or the second connector according to the control commands output from the first comparator and the second comparator.