Which of the following statements are CORRECT about the narrowband trunk? (Multiple Choice)

Question

Options

• AThe ATO is a type of narrowband trunk.
• BThe SS7 can be configured at the user side or at the network side.
• CThe PRA uses the 30B+D structure.
• DThe R2 refers to CNo.1.

• A
  76% (13)
• B
  6% (1)
• D
  18% (3)

Explanation

A is correct because ATO (Analog Trunk Office) is a classic example of a narrowband trunk, operating over analog telephone lines - the category of trunks that carries voice using traditional, low-bandwidth signaling methods.

C is correct because PRA (Primary Rate Access), the ISDN Primary Rate Interface used in Europe and many countries, uses the 30B+D structure: 30 Bearer channels for voice/data plus 1 D-channel for signaling, all over a single E1 link.

B is wrong because SS7 (Signaling System No. 7) is strictly a network-side signaling protocol used between carrier network nodes (e.g., SSPs, STPs, SCPs). User-side signaling uses protocols like DSS1/Q.931, not SS7.

D is wrong because R2 (MFC-R2) is an ITU-T channel-associated signaling standard widely used internationally - it is not the same as China No.1 (CNo.1), which is a separate signaling system specific to the Chinese PSTN.

Memory tip: Think "Analog Trunk Office = narrowband" and PRA = 30B+D (Europe uses E1 with 30 channels). For the distractors, remember SS7 never touches the user side, and R2 ≠ CNo.1 - different regions, different protocols.

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