The time window is determined by {TAIL ~ a window timer} which is preset with a number corresponding to {HEAD ~ the opening time} of the window 
The time window is determined by { TAIL ~ a window timer } which is preset with a number corresponding to { HEAD ~ the opening time } of the window
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH