the feedback system
in the system. For all these reasons the (deleted:figure) additional time and effort involved in achieving the improved results, compared with the first exercise, will be significant. It would thus appear that the choice lies between a fast, simple, single channel, open-loop system with a high incidence of error and a relatively slow, complex, multi-channel, closed-loop, more costly system that produces a much higher proportion of correct answers. # Communication Structure # A third approach to the problem can, in suitable cases, achieve the accuracy of the feedback system with the speed of the open-loop system by employing feedforward. Its suitability will depend on two factors: the ability to define the information content and the will to invest in developing the system. The ultimate in feedforward communication is probably to be found in the forces. At the Trooping of the Colour it is manifestly impossible for the troops at the back of the massed formations to understand any of the words uttered by the OC parade on the opposite side of Horse Guards. Yet they all move together in the right way