·2,447,543篇论文数据，部分数据来源于NoteExpress
自己动手制作一套联络信号装置，既可解决前后呼应问题，又利于文明操作。
To do a set of connection signal apparatus by self can solve the question echoing each other in front and behind, and benefit civilized operation.
youdao
应用推荐
模块上移
模块下移
不移动