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【多选题】
以下说法正确的是 ()。A.
列车在升弓前必须先操作降弓按3秒
B.
受的正常工作压力为490KPa，最小工作压力为343Kpa
C.
升弓是通过升弓电磁阀得电，推动连杆，使受锁钩动作，从而打开锁钩，通过弹簧力，使受升弓
D.
由于升弓是靠电，所以升弓前先按降弓按钮，给油缸充气并推动活塞杆动作，让油缸内部的活塞杆有足够行程，当受在升弓时，推压活塞杆，从而形成一定缓冲，对受形成保护
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