基于pstn网的远程分布式智能传感器阵列（中英文）本科毕设论文.docVIP

外文翻译 毕业设计题目：基于PSTN网的远程分布式智能传感器阵列 学生：黄淮滨 1002311 指导老师：刘大茂、魏云龙 原文1： The Public Telecommunications Network By far the largest circuit-switched network is the public telecommunications network－the telephone network. This is actually a collection of national network interconnected to form an international service. Although originally designed and implemented to service analog telephone subscribers, it handles substantial data traffic via modem, and is gradually being converted to a digital network. The public telecommunications network, as with any communications network, can be described using four generic architectural components. 稴tations: generally denoted as subscribers, these are the devices that attach to the network. 稩nterfaces: the interface between the stations and the network, referred to in the phone system as the local loop. 種odes: the switching centers in the network. 稬inks: the branches between nodes, referred to as trunks. Most of the subscribers on the network are telephones. The telephone contains a transmitter and receiver for converting back and forth between analog voice and analog electrical signals. With the introduction of the digital data system, some subscribers that transmit digital signals have been incorporated into the network. The local loop is a pair of wires, generally twisted pair, that connects a subscriber to one of the nodes in the network. The local loop generally covers a distance of a few kilometers to a few tens of kilometers at most. A two-wire connection is inherently half-duplex; that is, it can carry voice in one direction at a time only. Similarly, it can carry digital signals in one direction at a time only. For full-duplex DDS connections, two twisted pair links are generally used. Each subscriber connects via local loop to a switching center, known as an end office, Typically, an end office will support many thousands of subscribers in a localized area. There are over 19000 end offices in the United States, so