Abstract: In a pneumatic-hydraulic system for driving a hydraulic actuator, a single pneumatic-hydraulic converter includes a cylinder casing with inlet and outlet ports and a plunger reciprocably disposed within the casing to form a hydraulic chamber in open communication with the inlet and outlet ports and a pneumatic chamber for connection to a pneumatic pressure source, the hydraulic chamber having a displacement capacity filled with a predetermined amount of hydraulic fluid necessary for producing at least one reciprocating motion of the actuator.