movable point frog 可动心轨辙叉 ; 可动辙岔

movable point crossing 移动车叉道

frog movable point 可动辙岔

movable-point frog 可动心轨辙叉

Movable Point Frogs 可动心轨

crossing with movable point 可动心轨辙叉

movable point-movable area relationship 动点动面关系

movable pivot point 活动枢轴点

movable end-point system 可动端点系统