Describes several telegraph systems, in many countries, that predate electrical telegraphs.
Describes several telegraph systems, in many countries, that predate electrical telegraphs.
文中讲述了在电话之前许多国家的几种电报系统。
Describes several telegraph systems, in many countries, that predate electrical telegraphs.
文中讲述了在电话之前许多国家的几种电报系统。