The switch opens a solenoid valve which vents the hydraulic pumps which move {HEAD ~ the tracks} of {TAIL ~ the trencher} in the forward direction 
of
The switch opens a solenoid valve which vents the hydraulic pumps which move { HEAD ~ the tracks } of { TAIL ~ the trencher } in the forward direction
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH