Channels are dynamically distributed using the control signaling. MSK modulated digital common signal is used as air signal, characterized by its fast connecting.

由控制信道来动态分配信道，空中信令采用MSK调制的数字共路信令，具有接续速度快的特点。

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There were 15 minutes between the first air raid alert and the sounding of the all-clear signal.

从第一个空袭警报到警报解除号音其间有15分钟。

《柯林斯英汉双解大词典》

The fighting starts when a signal such as an air horn or whistle blows, and can last anywhere from a few minutes to a few hours.

当用号角或口哨发出信号时，大战就可以开始了，在任何位置都行，能持续几分钟到几个小时。

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Just a simple tuner and antenna will do the job if your local station has a digital over-the-air signal.

ENGADGET: What if your cable provider doesn't have ABC in high-def? HD

There's only one problem: you can't seem to pull in a reliable OTA (over-the-air) signal.

ENGADGET: blogger-avatar

Two-thirds of its 4.5m subscribers receive the channel through a scrambled, over-the-air, analogue signal, not as part of a broader cable or satellite package.

ECONOMIST: A television company in trouble