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