listed directory number display-attendant（列出目录号码显示–话务员） long line circuit（长线路用户） meet-me paging-attendant（会聚式呼叫–话务员） ..
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Protection against motor over - load usually adopt thermal relay, but protection against line over - load usually adopt long delay over- current release of circuit- breaker.
电动机过载保护通常采用继电器，而配电线路过载保护多采用断路器的长延时过电流脱扣器来完成。
The detecting circuit of power line touching of the suspension system of DC long-distance reserve power supply of PHS Cell Station was designed by the characteristic of gaseous discharge tube.
利用气体放电管的特性，实现了小灵通基站后备直流远供电源悬浮系统动力线碰触的检测；电路结构简单，实用性强。
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