telegraph signal

• 电报信号

telegraph signal的用法和样例：

例句

1. He was already an expert on the telegraph before he came up with a gadget that sent telegraph signals between unmanned stations.
   他发明的这种装置，用于在无人看管的两站之间传输电报信号，在此项发明前，爱迪生就已经是位电报专家了。