Some phone companies in the us already offer call-blocking service, allowing the user to block calls from Numbers that are proving a nuisance.

美国的一些电话公司已经提供呼叫限制服务，它能使用户阻挡来自骚扰者的电话。

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Unplug the phone and use a white-noise machine, or a fan or an air conditioner, to block out background noise.

把电话线拔掉，使用一个能产生白噪声的机器，或是打开电风扇、空调，以阻断背景噪音。

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If you get a message from somebody you don't want to chat with from your phone, just reply with the word BLOCK.

如果你收到一条短消息而这个人你又不想与他交谈，只需要回复一个BLOCK单词就行了。

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One phone-sized device can block cell phone signals in a 20 foot radius.

CNN: Mobiles used in high-tech terror

Representative Henry Waxman (D-Calif.) is tapping Wu for advice on legislation that would make it illegal for phone companies to block access to the Internet on mobile devices.

FORBES: Magazine Article

Allow prison governors to block mobile phone signals, to prevent inmates from carrying out illegal activities while inside.

BBC: Bill-by-bill: Guide to MPs' private members' bills