天为一个周期的巡回检查和维护，控制电梯运行质量。

Inspection and maintenance shall be conducted once every five days to control the performance of elevator operation.

youdao

天为一个周期的巡回检查和维护，控制电梯运行质量。

Inspection and maintenance shall be conducted once every five days to control the performance of elevator operation.

youdao