短語詞組短語tpt propagation delay time 傳播延時propagation time delay 傳播時間延遲英語Propagation Delay Time HIGH -to-LOW Level 傳播延遲高到低Propagation Delay Time LOW -to-HIGH Level 傳播延遲低到高Propagation time -delay of ground-wave 地波傳播時延 返回 propagation delay time