极频自动闭塞 automatic block with coded track circuit: 电码自动闭塞asymmetrical impulse track circuit: 不对称脉冲轨道电路impulse track circuit current: 脉冲轨道电路电流track circuit permissive block: 有轨道电路的容许闭塞audible frequency track circuit: 音频电路下载手机词典可随时随地查词查翻译