The invention 2 further comprising control means for accurately setting, conveniently adjusting and immediately releasing the fluid pressure applied to said piston, said means comprising {HEAD ~ a fluid pressure control device} attached to {TAIL ~ the trenching apparatus} for regulating the fluid pressure in said piston chamber and a release value attached to the trencher for relieving the fluid pressure in said piston chamber 
attached to
The invention 2 further comprising control means for accurately setting , conveniently adjusting and immediately releasing the fluid pressure applied to said piston , said means comprising { HEAD ~ a fluid pressure control device } attached to { TAIL ~ the trenching apparatus } for regulating the fluid pressure in said piston chamber and a release value attached to the trencher for relieving the fluid pressure in said piston chamber
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