He was on this big undergroundcommunication west coast tour.
他对这个大的地下通信西海岸之旅。
2
The practice proved that the filter could realize system identifying and noise removing and achieve the effect of improving quality and increasing distance of undergroundcommunication.
实践证明该滤波器较好地实现了系统识别和噪声消除，能够达到改善井下通信质量、增加井下通信距离的效果。
3
There's been no communication with the miners since an underground explosion, and there are concerns about the threat of poisonous gases.