signal用作及物动词时,可接名词、代词或that/wh从句作宾语。signal还可接双宾语,常以带或不带疑问词的动词不定式作直接宾语,其间接宾语可以由介词to引出, to可以省略。不用于被动结构。

用作不及物动词
▲S+～(+A)
She is signaling.她正在发送信号。
The submarine signaled for help.潜水艇发出求救的信号。
用作及物动词
▲S+～+n./pron.
She signaled the advance.她发出信号前进。
A bell signals the end of a school period.铃声标志着学校里一节课的结束。
▲S+～+that-clause
She signaled that he was about to turn left.她打信号灯表示他就要转到左面去了。
▲S+～+wh-clause
They signaled which way one is going to turn?他们打信号示意走哪一条路。
用作双宾动词
▲S+～+pron./n.+to n./pron
He signaled a message to his brother.他用信号向他哥哥发信息。
▲S+～+(to) n./pron.+to-v
He signaled the waiter to bring the menu.他做手势要侍者拿菜单来。
The conductor signaled the orchestra to rise.指挥打手势让乐队起立。
Jim signaled his helplessness to Mary to leave the party.吉姆无法从宴会脱身时,他向玛丽使了个眼色,表示无可奈何。
▲S+～+(to) n./pron.+wh-to-v
Tom signaled his friend which way to go.汤姆示意他的朋友走哪条路。

signal还可用作形容词,意思是“明显的,(非常)显著的,非凡的”。例如:
This is a signal failure.这是明显的失败。
People speak of Mark Twain as a signal humorous writer.人们称马克·吐温为杰出的幽默作家。

［同义词］ n.  indication, sign v.  gesture, motion

Signals are made with flags or lamps.用旗或灯传递信号。
We live too far from the city to get a strong television signal.我们住的地方离城里太远,不能收到清晰的电视图像。