An apparatus control system in which a controller (3) and a plurality of terminal devices (6-n) are connected via the respective communication control units (1) to a common communication path (5). Each terminal device is provided with a picture constituent information keep section (61, ..., or n1) for keeping information related to picture constituent elements for each display picture unit. The controller includes a picture data keeping section (31) for keeping display element information such as characters, basic pictures of a plurality of kinds, and an image generating software module so as to produce, based on the information related to picure constituent elements, a picture to be displayed by use of display element information. As a result, even when a new terminal is connected to the system, a display picture can be displayed for a control of the new terminal without requir­ing the controller to achieve a modification associted with the new terminal.