论文部分内容阅读
一、电通信与光通信 不论市内通信或是长途通信,长期以来都曾使用电的信号,相应地所有通信系统都利用电的传输和电的交换,组成电通信网。以电话通信来说,模拟话音信号经过脉码调制变成数字信号,电通信网就成为数字化的电通信网,它不仅用于实现电话通信,还可以用于数据通信和视频通信,包括可视电话和可视会议等等。
I. Electrical and Optical Communication Whether in the city or long-distance communications, the signals of electricity have long been used. Correspondingly, all communication systems make use of the transmission and exchange of electricity to form an electric communication network. In telephony, an analog voice signal is converted into a digital signal by pulse code modulation and the electrical communications network becomes a digitized electrical communications network that is used not only for telephony but also for data communications and video communications, including visual Telephone and video conferencing and more.