This invention discloses an arrangement allowing connection of various kinds of image displays to one supply source in an image display control system having a supply source for transmitting a signal including at least a video signal, and an image display for receiving the signal and displaying a corresponding image. The supply source acquires characteristic data of the image display when it is powered on, determines a signal communication specification with the image display based on the acquired characteristic data, and communicates a signal including the video signal with the determined communication specification. The image display transmits characteristic data for specifying the characteristics of the image display to the supply source, and communicates the signal including the video signal in accordance with the determined communication specification. This invention also discloses an arrangement permitting changing the specifications and version of the control program of the image display.