A company has deployed a U1900 series unified gateway as the voice system (see the following figure). Extensions on the U1960 call extensions on the U1911 through the outgoing call prefix 9. Test…

Question

Options

• ANo number change rule (delete the first digit 9 in the called number) is configured for prefix 9 on
• BIntra-office call prefix 6 is not added on the U1911.
• CThe prefix for calling extensions under the U1960 is not added on the U1911.
• DThe PSTN access parameter for intra-office call prefix 6 on the U1911 is set to No.

• A
  16% (10)
• B
  75% (47)
• C
  3% (2)
• D
  6% (4)

Explanation

Option B is correct because when two U1900 gateways are interconnected, each gateway must have the appropriate intra-office call prefix configured to handle incoming calls from the other gateway. Since A and B (on U1960) cannot reach C (on U1911), the U1911 is missing prefix 6, which means it cannot properly accept and route intra-office calls arriving from the U1960 - the calls arrive but have nowhere to go on the U1911 side.

Option A is wrong because if the number-change rule (stripping the leading 9) were missing on U1960, the malformed number would be sent to U1911 but C can still successfully call both A and B, confirming the U1960 outgoing configuration is intact. Option C is wrong because it would prevent C from calling A or B, yet that direction works perfectly - so the prefix for reaching U1960 extensions clearly exists on U1911 already. Option D is wrong because the PSTN access parameter on prefix 6 governs public telephone network access, not internal gateway-to-gateway routing, and the fault here is purely an intra-office routing issue.

Memory tip: Think "both sides must know each other" - when calls work in one direction only (C → A/B works, A/B → C fails), the problem is always a missing prefix on the receiving gateway (U1911), not on the sending one. If the sending side (U1960) were misconfigured, calls would fail in both directions.

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