transmitting data communication signals of the user with {HEAD ~ the second highest priority} at regular intervals to form the synchronization signal when a normal clock pulse generated synchronization signal and data communication signals of {TAIL ~ the highest ranking user} are not received 
transmitting data communication signals of the user with { HEAD ~ the second highest priority } at regular intervals to form the synchronization signal when a normal clock pulse generated synchronization signal and data communication signals of { TAIL ~ the highest ranking user } are not received
OTH OTH OTH OTH OTH OTH OTH OTH HEAD 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 TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH