这个系统使用起来十分简单：把一个能够发射无线电的信号灯放在家里，把信息发射器绕在你的脚踝上。
The system works simply: you keep a radio beacon in your home and a transmitter around your ankle.
如果没有电，人们需要借助微弱的烛光来摸索前行，路上的汽车由于没有交通信号灯的指示将会迟疑不前，食物也会在没有电的冰箱里腐烂。
When there is a power failure, people grope about in flickering candlelight; cars hesitate in the streets because there are no traffic lights to guide them, and food spoils in silent refrigerators.
如果没有电，人们需要借助微弱的烛光来摸索前行，路上的汽车由于没有交通信号灯的指示将会迟疑不前，食物也会在没有电的冰箱里腐烂。
When there is a power failure, people grope about in flickering candlelight; cars hesitate in the streets because there are no traffic lights to guide them, and food spoils in silent refrigerators.
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