Abstract: A video device includes a signal generating circuit configured for generating video signals; an internal resistor connected to the output port of the signal generating circuit and matching with an external resistor of an external device; a detecting circuit connected to two ends of the internal resistor through two input ports thereof, and configured for detecting voltages of the two ends of the internal resistor and outputting a voltage difference therebetween; a controlling circuit connected to the output port of the detecting circuit, and configured for determining whether or not the external device is connected to the video device according to the voltage deference, and outputting a controlling signal to the signal generating circuit; an auxiliary detecting circuit connected to the output port of the controlling circuit, and configured for generating an auxiliary detecting signal transmitted to the internal resistor.