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1·Before driving away, re-check the trailer coupling.

把车开走前，请再检查一下拖车的挂钩。《柯林斯英汉双解大词典》

2·Physically simulated truck and trailer coupling (option).

物理模拟卡车和拖车耦合(选项)。

3·The coupling heads are used for connecting the tow-line Compressed air Braking system of tractor and a trailer.

气制动接头用作牵引车与挂车之间的气路连接，可适用各类气制动车辆与挂车的连接气路。