Cisco 400-051 Exam

How many signaling bits are there in each T1 time slot using channel associated signaling with Super Frame?

  • A. 1
  • B. 2
  • C. 4
  • D. 8
  • E. 12
Answer: Option B.

Each T1 CAS has 24 channels that can transmit 8 bits per channel each. This gives us a total of 192 bits. The T1 has one additional bit for framing, bringing the total to 193 bits. Two types of line coding can be used on a T1 CAS. The first type of line coding is called Super Frame (SF). This is an older and less – efficient type of framing. Super Frame bundles 12 of these 193 – bit frames together for transport. It then uses the even – numbered frames as signaling bits. The T1 CAS signaling then looks at every sixth frame for signaling information. This comes out to be 2 bits that are referred to as the A and B bits, which reside in frames 6 and 12.

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