Preferably, {HEAD ~ the compressor} includes {TAIL ~ a delivery control mechanism} responsive to pressure in the suction passageway to vary the effective cross sectional area of the suction passageway 
includes
Preferably , { HEAD ~ the compressor } includes { TAIL ~ a delivery control mechanism } responsive to pressure in the suction passageway to vary the effective cross sectional area of the suction passageway
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH