middle marker beacon

例句：

1. 1. The middle marker beacon is a crucial navigational tool for ships in the harbor.
   港口中的船只使用中间标记灯塔作为重要的导航工具。
2. 2. The beacon was used to guide ships safely into the harbor.
   灯塔被用来引导船只安全地进入港口。
3. 3. The lighthouse at the entrance of the harbor is a symbol of safety and guidance for all who visit.
   港口入口处的灯塔是所有访问者安全和指引的象征。