As the boom position detecting means there may be used a detector which detects the angle of the boom 3, but in this embodiment there is used {HEAD ~ a stroke meter} 71 which detects {TAIL ~ the length} of the cylinder 50 shown in FIG 7 and which is attached to the cylinder 50 
detects
As the boom position detecting means there may be used a detector which detects the angle of the boom 3 , but in this embodiment there is used { HEAD ~ a stroke meter } 71 which detects { TAIL ~ the length } of the cylinder 50 shown in FIG 7 and which is attached to the cylinder 50
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