Line 13 of Beijing Metro is the first ground line of Beijing urban rail transit.

摘要北京地铁13号线是北京城市轨道交通的第一条地面线路.

Could I somehow create a flat signal that kept one speaker line high relative to the ground line?

我能以某种方式创造一个平坦的信号，保持一个扬声器线高相对地面线？

Note that the signal ground line should also be connected in the system.

当然,系统的信号接地线也应该连接.