adj.信号的；预示的；告知的
动词signal的过去式和过去分词.
In digital signal technique, a signal that uses a positive(or negative) excursion and ground as the two binary signal states. 在数字信号技术中，用正(或负)向电压与地两个电平来表示二进制“1”和“0”的一种信号
A police car drew alongside and signalled to me to stop. 一辆警车开到我身边示意我停下来。
The defeat signalled the end of the war. 那一次失败标志着战争的结束。
Heavy footsteps signalled the teacher's approach. 沉重的脚步声显示教师已经走近了。
