而1980年的撤销管理规定引起了铁路业20多年的重建和巩固，其间，只有7家一级铁路公司幸存下来。
Deregulation in 1980 led to more than 20 years of restructuring and consolidation. Only seven Class I railways survived.
铁路信号自控系统是一级供电负荷，要求有两路高质量的供电电源。
The railway signal auto-control system is a level of power supply load, which requires two lines of high quality power supply.
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