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