Abstract: A regulator for regulating the output of an output shaft is discosed, the regulator comprising a number of chambers to and from which working medium can be fed and discharged in dependence upon control means to effect axial movement of the output shaft via pressure transmitting elements.In accordance with the invention, the regulator comprises a number of series-connected units, the units providing fixedly spaced walls to define separated chambers through which the output shaft effectively extends, each chamber having at least one pressure transmitting element therein which is connected directly or indirectly to said output shaft. With such an arrangement the or each pressure transmitting element, when activated, exerts either individually or in unison an axial force on the output shaft substantially corresponding to the sum of the forces exerted on the active pressure transmitting elements.