短语词组短语Crossing Off A Concern 删去一个问题crossing detection is off 隧道检测是关闭;穿越检测已关闭;交叉检测是关闭digit -crossing off test 划字测试zero crossing time pick -off 零点交叉时间选域zero -crossing current switching-on-off 零电流投切 返回 crossing off