This paper introduces a way of simple place signal communication. The way is proved to be effective by practice. It has the high practical value at present condition of the PLC USES.

本文介绍了一种简易位信号通讯方式，通过实际应用效果理想，它在目前PLC应用现状下有较高的实用价值。

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This was our signal to enable communication to take place.

这是我们的信号，允许通讯开始发生。

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First of all, every commuter rail system has full time maintenance crews, and they always have plenty of work: changing lightbulbs in the tube, fixing a signal that got bumped, replacing an on-track communication cable that was vibrated out of place and smashed, etc.

FORBES: Why Does BART Need To Do Nightly Maintenance?