One of {HEAD ~ the further chambers} contains {TAIL ~ a first electro magnetic control valve} fed by a D.C. voltage, and operable to control an orifice through which the first chamber communicates with atmosphere 
One of { HEAD ~ the further chambers } contains { TAIL ~ a first electro magnetic control valve } fed by a D.C. voltage , and operable to control an orifice through which the first chamber communicates with atmosphere
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL 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 OTH OTH