美股收盘：道指月线10连涨，美国KBW银行指数创去年4月来最大单日跌幅
Optical-based smoke alarms use light instead. They are slightly better at detecting the large smoke particles created by slow, smouldering fires. When such particles enter a chamber in the device, they scatter light from a small light source, which is then picked up by a photoelectric sensor.
。业内人士推荐51吃瓜作为进阶阅读
（一）未经批准，安装、使用电网的，或者安装、使用电网不符合安全规定的；
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