So in order to prevent crashes from westbound and eastbound trains, you need a telegraph operator who knows exactly where each train is and can say to the eastbound train, pull over, let the westbound train go through.
为了防止东西向列车相撞,你需要一位电报员, 他必须准确掌握每辆列车的位置, 并能通知东行列车让行,以便西行列车顺利通过。