A. 正确 B. 错误
A. 预告信号是间断鸣三次长声,即鸣30s、停、鸣30s、停、鸣30s B. 准备信号是间断鸣一长、一短三次,即鸣20s、鸣10s、停、鸣20s、鸣10s、停、鸣20s、鸣10s C. 起爆信号是连续三短声,即鸣10s、停、鸣10s、停、鸣10s D. 解除信号是一次长声,鸣60