但目前的煤矿通信系统却非常落后，仅能在作业面外进行相对简单的有线通信。

However, the coal-mining communications are still so outdated that only wire telephone can be used far from the working place.

youdao

但目前的煤矿通信系统却非常落后，仅能在作业面外进行相对简单的有线通信。

However, the coal-mining communications are still so outdated that only wire telephone can be used far from the working place.

youdao