About R2 signaling, which of the following is true? (Select two Answers)

Question

Options

• AR2 signaling is belong to common channel signaling
• BR2 signaling contains line signaling and interregister signalling
• Cinterregister signalling of R2 signaling is belong to signaling in band
• Dline signaling of R2 signalline are used to transfer number, user class, priority and billing,

• A
  21% (9)
• B
  70% (30)
• D
  9% (4)

Explanation

B and C are correct because R2 signaling is composed of two distinct parts: line signaling, which handles call supervision states (seizure, answer, clear), and interregister signaling, which uses Multi-Frequency (MF) tones transmitted in-band - meaning within the same voice frequency band (300–3400 Hz) as the speech path.

A is wrong because R2 is channel-associated signaling (CAS), not common channel signaling (CCS). In CAS, signaling is tied to each individual voice channel; CCS (like SS7) uses a separate dedicated channel to carry signaling for many circuits simultaneously.

D is wrong because it misattributes responsibilities - line signaling handles supervisory functions only (on-hook, off-hook, seizure, release). It is interregister signaling (the MF tones) that carries number digits, caller category, priority, and billing information.

Memory tip: Think of R2 as a two-layer system - the Line layer is like a light switch (on/off supervision), while the Interregister layer is like a phone keypad (tones carrying numbers and caller info, sent in-band through the voice path). R2 ≠ SS7, so it's never "common channel."

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