However, this purely visual system was useless in bad weather, and, by the 1930s, radio communication was coming into use for ATC.
然而，这种纯粹的视觉系统在恶劣天气下毫无用处，到了20世纪30年代，无线电通信开始用于空中交通管制。
The main functions, construction and system bus in the building visual talk back communication system were analyzed.
分析了楼宇可视对讲通信系统的主要功能、结构和系统总线。
As the most advanced cabling system in the world, providing the highest level of networking, it can realize voice, data and visual communication effortlessly.
国际最先进布线系统，最高布线配置级别，可实现语音、资料与视频通讯的理想传送。
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