Or they use low-power transmitters heard only on school grounds .

或者他们使用只在学校场地上听得到的低功率发射机。

He thought about his early days in radio , working around high-powered transmitters .

他回想起早年做无线电工作时，守在高能量发射机旁工作的那些日子。

The last of the big television stations still broadcasting in analogue will turn off their transmitters and begin digital transmissions only .

最后一批仍以模拟方式进行广播的大电视台，将关闭它们的发射机，开始只传送数字信号。

Only a few countries can carry out dazzle attacks , but dozens of countries can jam satellite signals using ground-based transmitters to overwhelm their signals .

只有少数几个国家能进行强光攻击，但却有很多国家能利用陆基发射机淹没卫星信号，来干扰这些信号。

Most nations will hope that signals from global positioning system ( gps ) satellites and ground-based differential gps transmitters will be usable shortly after a nuclear explosion , as well as traditional communications channels which must be protected .

多数国家希望来自全球定位系统（globalpositioningsystemgps）卫星以及差分gps地基发射机的信号在核爆过后不久既能恢复接收，对于那些必须保护的传统通信信道来说也是如此。