The valve can only be switched while {TAIL ~ energy} is being transmitted from {HEAD ~ the service device} 
The valve can only be switched while { TAIL ~ energy } is being transmitted from { HEAD ~ the service device }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD