Movement of the shaft and vent follower continues until the pressure between {TAIL ~ the two cells} is equalized and the vent follower is once again in {HEAD ~ direct relation} to the vent 
Movement of the shaft and vent follower continues until the pressure between { TAIL ~ the two cells } is equalized and the vent follower is once again in { HEAD ~ direct relation } to the vent
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 OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH