The preceding section treated control systems from the standpoint of the kind of hardware used, analog or digital, the amount of automatic operation provided was a secon-

dary consideration In this regard it should be noted that the presence of a digital computer implies no special level of automation For example, many digital systems have been installed which perform only the control functions of a set of analog feedback controllers with the added benefit of automatic data logging

To avoid hardware implications, we will take the functional approach and use the degree of automation to define the extent to which the operator is removed from the immediate closed loop