A counter counts a first time duration commencing from {HEAD ~ the last transition} to inspiration and whereby if the first time duration elapses before a transition to expiration is detected, the controller initiates the supply of {TAIL ~ a given expiratory pressure} 
A counter counts a first time duration commencing from { HEAD ~ the last transition } to inspiration and whereby if the first time duration elapses before a transition to expiration is detected , the controller initiates the supply of { TAIL ~ a given expiratory pressure }
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL