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單項(xiàng)選擇題

Which statement is true about the capabilities of a voice gateway router?()

A.voice gateways with analog interfaces need a gatekeeper to convert analog signals into digital format before voice is encapsulated into IP packets
B.voice gateways need a gatekeeper to interconnect the VoIP networks the PSTN network
C.voice gateways with Cisco Unified CallManager Express (CME) can permanently act as a call agent for IP phones
D.voice gateways equipped with a DSP module can take the role of the call agent during WAN failure.

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