The radio port then transmits, over a pre established unidirectional virtual circuit, {TAIL ~ the OA&M cell} to {HEAD ~ a radio port manager} 
The radio port then transmits , over a pre established unidirectional virtual circuit , { TAIL ~ the OA&M cell } to { HEAD ~ a radio port manager }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD