Typically, the upstream or ATU C modem transmits data to the downstream or ATU R {HEAD ~ modem} over {TAIL ~ a first set} of subchannels, which are usually the higher frequency subchannels, and receives data from the downstream or ATU R modem over a second, usually smaller, set of subchannels, commonly the lower frequency subchannels 
over
Typically , the upstream or ATU C modem transmits data to the downstream or ATU R { HEAD ~ modem } over { TAIL ~ a first set } of subchannels , which are usually the higher frequency subchannels , and receives data from the downstream or ATU R modem over a second , usually smaller , set of subchannels , commonly the lower frequency subchannels
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH