The access controller 160 includes an interface 710, {HEAD ~ a DS0 Handler} 720, a microprocessor unit 730, {TAIL ~ a message processor} 740, and a clock processor 750 
The access controller 160 includes an interface 710 , { HEAD ~ a DS0 Handler } 720 , a microprocessor unit 730 , { TAIL ~ a message processor } 740 , and a clock processor 750
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH