The two main justifications for adding chips to passports are that they improve security at border crossings and speed up immigration procedures.

有两个主要说辞支持在护照中加入芯片：提高边境口岸的安全性与加快入境手续办理。

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All trains at main border crossings are now inspected.

所有越境列车现在都要检查。

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The zero-crossings of the AC voltage and digital frequency synthesizer are used in solving the two main problems in frequency hopping system-synchronization and fast frequency synthesizing.

利用电力系统三相交流电压过零点和高速数字频率合成器解决了跳频系统中同步和快速频率合成的两个关键问题。

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Roads: One of the two main crossings over the Severn between Wales and England has reopened.

BBC: Snow latest across the UK