煤矿立井井筒的信号传输，由于其传输环境特殊，一直没有很好地解决。
The problems of the signal transmission in a shaft have not been solved because the transmission environment is very bad.
信号工要确保井筒内无人，才能发送升降信号。
Signal worker can't send hoisting signal until be ensure that no worker is in it.
信号工要确保井筒内无人，才能发送升降信号。
Signal worker can't send hoisting signal until be ensure that no worker is in it.
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