When {HEAD ~ the member} is in {TAIL ~ its upper position}, the ring is in the path of the air stream emitted by the fan to produce a stream of bubbles 
is in
When { HEAD ~ the member } is in { TAIL ~ its upper position } , the ring is in the path of the air stream emitted by the fan to produce a stream of bubbles
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL 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 OTH