JET discharges have plasma currents up to 6MA and Toroidal Fields up to 4T. The plasma parameters during discharges are determined by the action of a number of distinct systems. These systems can be divided into 3 groups; the Toroidal and Poloidal Field systems, the Fuelling Systems and the Additional Heating systems. The systems can either be programmed to follow pre-determined waveforms or they can be feedback controlled to achieve certain values of specific plasma parameters, as measured with JET diagnostics. This paper reviews the feedback control of plasma parameters using the three main digital control systems; the Plasma Position and Current Control system, the Density Feedback System and the Real Time Central Control system. It is planned to integrate these systems using the new ATM technology in the Real Time Data Network