地铁信号系统，是保证列车高效、安全运行的核心部件。
Metro signal system is core component to ensure trains efficient and safe operation.
这对于地铁乘客来说尤为重要，这些人在地下时经常没有手机信号。
This is especially important for subway riders who frequently lose cell service while underground.
这对于地铁乘客来说尤为重要，这些人在地下时经常没有手机信号。
This is especially important for subway riders who frequently lose cell service while underground.
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