单项选择题
Voice activity detection （VAD） suppresses the transmission of silence patterns. On average， and assuming that a link carries at least 24 calls， what percentage of total bandwidth could VAD save？（）
A.5 B.15 C.25 D.35 E.45 F.55
多项选择题 Whatarethreefeaturesofvoicetrafficonanetwork？（）
多项选择题 WhenanalogsignalsaredigitizedusingtheG.711codec，voicesamplesareencapsulatedintoprotocoldataunits（PDUs）involvingwhichthreeheaders？（）
单项选择题 WhichstatementistrueaboutthedistributedcallcontrolinaVoIPnetwork？（）
