Abstract: A servomechanism for pump capacity control includes an adjustable throttle of the "nozzle-gate" type formed with two operating slots communicating through two fixed throttles with duct, a source of supply feeding the duct, an input signal converter whose movable element is connected to the gate of the nozzle-gate throttle and a four-slot, five-line distributor whose control spaces are in communication through two fixed throttles with the duct of the source of supply, two operating slots being formed in the adjustable throttle, whereas its operating spaces communicate with the corresponding spaces of an actuating hydraulic cylinder. The latter is connected to the control element and, by a mechanical position feedback, to the gate. The mechanical position feedback is constituted by a bar which is linked to the movable element of the hydraulic cylinder and has a slanted surface. The slanted surface interacts with a spring-loaded pusher, whose springs act on the gate.