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从电话发明到现在已经一百多年了，电信网技术经历了无数次重要演进，从人工交换到自动交换，从模拟通信到数字通信，从电路交换到分组交换，从固定通信到移动通信，从窄带通信到宽带通信等，使电信网的业务能力大大提高，成本不断下降，其中一些重要技术的发明和应用，使电信
From the invention of the phone to the present one hundred years ago, the telecom network technology has experienced numerous important evolutions, from manual exchange to automatic exchange, from analog communication to digital communication, from circuit switching to packet switching, from fixed communication to mobile communication, From narrowband communications to broadband communications, the operational capabilities of telecommunications networks have been greatly enhanced and costs have been declining. The invention and application of some of these important technologies have enabled telecommunications