A display device includes a signal receiving unit, an image display unit, a communicating unit, a position designating unit, and an information transmitting unit. The signal receiving unit receives a video signal by a differential signal through a plurality of channels from an external apparatus via a transmission path. The image display unit processes the vide signal received in the signal receiving unit to display an image. The communicating unit performs a bi-directional communication by using a predetermined line which constitutes the transmission path. The position designating unit designates a position on a display screen of the image display unit. The information transmitting unit transmits, by the communicating unit, coordinate information on the position designated by the position designating unit to the external apparatus.