TAILIEUCHUNG - Signaling System No.7 Protocol Architecture And Sevices part 12

Access and Transmission Facilities Connections to PSTN switches can be divided into two basic categories: lines and trunks. Individual telephone lines connect subscribers to the Central Office (CO) by wire pairs | Access and Transmission Facilities Connections to PSTN switches can be divided into two basic categories lines and trunks. Individual telephone lines connect subscribers to the Central Office CO by wire pairs while trunks are used to interconnect PSTN switches. Trunks also provide access to corporate phone environments which often use a Private Branch eXchange PBX or in the case of some very large businesses their own digital switch. Figure 5-4 illustrates a number of common interfaces to the Central Office. Figure 5-4. End Office Facility Interfaces Lines Lines are used to connect the subscriber to the CO providing the subscriber access into the PSTN. The following sections describe the facilities used for lines and the access signaling between the subscriber and the CO. The Local Loop Analog Line Signaling Dialing Ringing and Answer Voice Encoding ISDN BRI The Local Loop The local loop consists of a pair of copper wires extending from the CO to a residence or business that connects to the phone fax modem or other telephony device. The wire pair consists of a tip wire and a ring wire. The terms tip and ring are vestiges of the manual switchboards that were used a number of years ago they refer to the tip and ring of the actual switchboard plug operators used to connect calls. The local loop allows a subscriber to access the PSTN through its connection to the CO. The local loop terminates on the Main Distribution Frame MDF at the CO or on a remote line concentrator. Remote line concentrators also referred to as Subscriber Line Multiplexers or Subscriber Line Concentrators extend the line interface from the CO toward the subscribers thereby reducing the amount of wire pairs back to the CO and converting the signal from analog to digital closer to the subscriber access point. In some cases remote switching centers are used instead of remote concentrators. Remote switching centers provide local switching between subtending lines without using the resources of the CO.

• Kỹ thuật lập trình
• thủ thuật lập trình
• ngôn ngữ lập trình
• tài liệu lập trình
• hướng dẫn lập trình
• kĩ năng lập trình
• mẹo lập trình
• kỹ thuật lập trình
• kỹ năng lập trình
• bí quyết lập trình
• phương pháp lập trình
• tư liệu lập trình
• kĩ thuật lập trình
• AutoIT