A.2B.4C.6D.12
A.開(kāi)斷主電路B.輔助電路轉(zhuǎn)換C.控制電路轉(zhuǎn)換D.機(jī)車(chē)方向、工況轉(zhuǎn)換
A.電氣B.電器C.常開(kāi)D.常閉