With her free hand, she reached for the other phone and dialed 911.

她一边和女儿通话，另一只手抓起另一部电话，立即拨打了911。

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IntroductionIn the communication systems, echo and noise will seriously affect speech communication quality, such as IP telephone, videophone and hand-free digital cell phone systems etc.

引言在通信系统中，例如IP电话、可视电话及免提数字蜂窝电话系统中，回声和噪声会严重影响通信质量。

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NHTSA's study will assess hands-free, semi-hands free and hand-held mobile phone use and assess the risk and distraction associated with each, the administration said.

WSJ: Just Ahead: Cars That Tweet, Buy Tickets

"Although it is legal to use a hands-free set at the moment, the research shows that actually, in terms of distraction, there is very little difference between a hand-held mobile phone and a hands-free one, " he said.

BBC: Mary Bowers

"There's conflicting evidence" on whether hands-free cell phone conversations would be as unsafe as those by hand-helds, Harsha said, adding that more "definitive research" is needed.

CNN: Call for car-phone ban likely to meet busy signal in states