Such a hole is likely used as an undergroundantenna able to recharge the batteries of submarines in the Pacific and Indian Ocean through ELF broadcasts.
这种黑洞很可能用作地下天线能够充电电池潜艇在太平洋和印度洋，通过极低频广播。
2
One of the museum exhibits is this underground magnet antenna from the Bita cryptographic hardware.
博物馆的展馆之一是来自于 Bita 加密硬件的地下磁铁天线。
3
Introduced some new type underground mobile communication system, such as leakage communication system, distributed antenna communication and region mobile communication, etc.