A system for moving a member such as a robotics arm, includes a motor (1) for moving the member, a position indicating encoder (5) for producing an indication related to the position of the member, valves (7, 8) which in a first condition enable the motor to move the member in a first direction, in a second condition enable the motor to move the member in the opposite direction, and in a third condition disable the motor from moving the member, and a computer (6) for controlling the valves in positioning the member. The valves are effectively on/off valves.