A user programmable control mechanism is coupled to the drug pump and is effective to selectively control {HEAD ~ movement} of {TAIL ~ the valves} between the open and closed positions 
A user programmable control mechanism is coupled to the drug pump and is effective to selectively control { HEAD ~ movement } of { TAIL ~ the valves } between the open and closed positions
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH