{HEAD ~ Discharge valve} 12 can be moved by an adjustment mechanism 15 in such a way that either of the apertures 13 or 14 is positioned in {TAIL ~ the flow passageway} to the outlet of exhaust line 11 
{ HEAD ~ Discharge valve } 12 can be moved by an adjustment mechanism 15 in such a way that either of the apertures 13 or 14 is positioned in { TAIL ~ the flow passageway } to the outlet of exhaust line 11
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH