continuing {TAIL ~ the synchronous scanning} of frequency channels according to {HEAD ~ a synchronous scan list} when no response to the scanning is received 
continuing { TAIL ~ the synchronous scanning } of frequency channels according to { HEAD ~ a synchronous scan list } when no response to the scanning is received
OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH