Theysend pings once per second, to signal their location.

他们每秒发送一次 ping，以表明他们的位置。

In London, an inmate here signaling his precise location to a drone operator.

在伦敦，这里的一名囚犯向无人机操作员发出他的精确位置信号。

They sent pings once per second to signal their location and can transmit data from as deep as 20,000 feet for up to 30 days, when their batteries then run out.

他们每秒发送一次 ping 信号来表明他们的位置，并且可以从深达 20,000 英尺的地方传输数据长达 30 天，直到他们的电池耗尽。