What is the function of the AJB bits on DS1 using Extended Super Frame (ESF)?

Question

Options

• AIt is used for signaling on-hook and off-hook status.
• BIt carries CRC information for error detection.
• CIt is used for a control and performance information.
• DIt is used for a frame's synchronization and alignment.

• A
  75% (12)
• B
  6% (1)
• C
  13% (2)
• D
  6% (1)

Explanation

DS1 frame synchronization[edit source | edit] See also: Synchronization in telecommunications Frame synchronization is necessary to identify the timeslots within each 24-channel frame. Synchronization takes place by allocating a framing, or 193rd, bit. This results in 8 kbit/s of framing data, for each DS1. Because this 8-kbit/s channel is used by the transmitting equipment as overhead, only 1.536 Mbit/s is actually passed on to the user. Two types of framing schemes are Super Frame (SF) and Extended Super Frame (ESF). A Super Frame consists of twelve consecutive 193-bit frames, whereas an Extended Super Frame consists of twenty-four consecutive 193-bit frames of data. Due to the unique bit sequences exchanged, the framing schemes are not compatible with each other. These two types of framing (SF, and ESF) use their 8 kbit/s framing channel in different

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