locomotive units backward electropneumatic valve

例句：

1. 1. The locomotivesare the backbone of the railway system.
   机车是铁路系统的骨干。
2. 2. The engineers were tasked withretrofitting the locomotives for efficiency.
   工程师们被指派为改造机车以提高效率。
3. 3. The backwardelectropneumatic valve was agame-changer in the industry.
   反向电气动阀门在行业中是一个革命性的改变。