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早在70年代,在欧洲的法国,瑞典、德国等国家,发展了一种基于在立体声调频节目的副载波上,发送数字信息的广播方式,简称为“RDS”(Radio Dalo System)的数据广播系统。这是一种继声音广播,电视广播之后的又一种广播形式。它传送的信号不是声音,也不是电视图像,它是把需要传送的信息数据化后,调制到调频节目的副载波上,和调频节目一起传送出去。它首先应用于节目跟踪和全球寻呼等方面。几乎是同时,美国率先推出图文电视广播业务。图文电视是将数字化了的信息加载在电视节目的“场逆程”行扫描线上。它对正程电视节目的传送毫无影响。
As early as the 1970s, in Europe, France, Sweden, Germany and other countries, the development of a based on the FM stereo sub-carrier on the way to send digital information broadcast, referred to as “RDS” (Radio Dalo System) data broadcast system. This is another form of broadcasting following sound broadcasting and television broadcasting. It transmits the signal is not sound, nor is it a television image, it is the need to send the information data, the modulation to FM subcarrier, and FM programs sent together. It first used in program tracking and global paging and so on. Almost simultaneously, the United States took the lead in introducing the teletext broadcasting business. Teletext loads digitized information on the “field reversal” line of the television program. It has no effect on the delivery of regular TV programs.