registering {HEAD ~ the clock time} of {TAIL ~ the day} when said change of state occurs at each station; and 
of
registering { HEAD ~ the clock time } of { TAIL ~ the day } when said change of state occurs at each station ; and
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH