Pump 1 delivers fluid through starting valve 2 and directional valve 3 to power cylinders 4 and 5 with pistons linked to slides 6 and 7. Slides 6 and 7 are linked together by gear racks 8 and 9, and pinion 10, meshing with both racks. Linked to the axle of pinion 10 is rod 11 which, upon unequal feed of the slides, turns lever 12. This shifts the spool of valve 3 so that a greater amount of fluid is delivered to the cylinder whose piston is linked to the slide that lags behind, and a lesser amount to the other cylinder, thereby equalizing the rates of feed of the slides.
$4203$CHP,Dr$