radio distress frequencies

例句：

1. 1. The distress signalwas received by the rescue team.
   求救信号被救援队接收到了。
2. 2. They usedto broadcast distress signals duringemergencies.
   他们在紧急情况下曾经广播求救信号。
3. 3. The distressfrequency is set at148.5MHz.
   求救频率设定在148.5 MHz。