A control system for a plurality of mechanical units, namely robots and/or external axes. A manually-operated control, such as a joy-stick or key panel, is adapted to move at least one of the mechanical units or part thereof. The control system includes an indicator adapted to indicate whether the at least one mechanical unit or part thereof that is to be moved is associated with any other mechanical unit(s) or part(s) thereof and consequently indicate that movement of the at least one mechanical unit or part thereof will also result in the movement of the indicated associated mechanical unit(s) or part(s) thereof.