You have a Microsoft Teams Phone deployment. You have a PBX that connects to the PSTN by using an E1/T1 Primary Rate interface (PRI). You plan to migrate to Direct Routing by using the existing PSTN…

Question

Options

• Aa physical Session Border Controller (SBC)
• Ban FXO SIP Analog Telephony Adapter (ATA)
• Ca virtual Session Border Controller (SBC)
• Da Session Border Controller (SBC) in Azure

• A
  81% (30)
• B
  5% (2)
• C
  3% (1)
• D
  11% (4)

Explanation

A physical SBC is required here because the existing PBX connects to the PSTN via an E1/T1 PRI - a traditional TDM circuit that requires hardware-level signal conversion into SIP/IP before Direct Routing can handle it; only a physical device can terminate that TDM interface. Option B (FXO ATA) is wrong because FXO adapters handle analog (POTS) lines, not digital PRI circuits. Option C (virtual SBC) is wrong because a software-only SBC has no physical ports to terminate an E1/T1 PRI - you need real hardware for that TDM handoff. Option D (SBC in Azure) is similarly wrong for the same reason: a cloud-hosted SBC cannot physically connect to an on-premises PRI circuit.

Memory tip: Think "PRI = physical wire = physical box." Whenever you see E1/T1 or PRI in a scenario, that's a hardware signal that demands a hardware SBC upstream to bridge the TDM world into the IP/SIP world that Teams Direct Routing expects.

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