Labels:bulletin board | earth | sky OCR: Other attributes For further study subscr Digital riber Layer functions info 64 kbit/s infr 64 with digital kbit/s access network digitat anal circuit oque. circuit switch access Laver functions Signalling handling pue exchange *ontro functions CCIIT-S9S1 FIGURE 1/Q.522 Type I exchange connection subscriber infa logue control exchangc
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