The ship radioed a call for help.

那用无线电发出求救信。

The ship radioed for help.

发出无线电求救信。

Suddenly a steamer hove in sight. The captain immediately gave an order to send out a signal for rescue.

"突然一轮驶入视线,立刻命令发出求救的信。"

The submarine signaled for help.

潜水艇发出求救的信。