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Kỹ thuật truyền số liệu 2

Tham khảo tài liệu 'kỹ thuật truyền số liệu 2', giáo dục - đào tạo, cao đẳng - đại học phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 2 i Basic Concepts Í Í -L í Í î II vriy Before examining the specifics of how data are transmitted from one device to another it is important to understand the relationship between he communicating devices. Five general concepts provide the basis for this relationship El Line configuration. B Topology. Transmission mode. Si Categories of networks. E3 Internetworks. 2.1 LINE CONFIGURATION Line configuration refers to the way two or more communication devices attach to a link. A link is the physical communication pathway that transfers data from one device to another. For the purposes of visualization it is simplest to imagine any link as a line drawn between two points. For communication to occur two devices must be connected in some way to the same link at the same time. There are two possible line configurations point-to-point and multipoint sec Figure 2.1 . I. I lie co 111 i gil ral i 11 .let incs the al I acl 11 ncnl ol communication devices to a link. Point-io-Point A point-to-point line configuration provides a dedicated link between two devices. The entire capacity of the channel is reserved for transmission between those two devices. Most point-to-point line configurations use an actual length of wire or cable to connect the two ends but other options such as microwave or satellite links are also possible see Figure 2.2 . When you change television channels by infrared remote control you are establishing a point-to-point line configuration between the remote control and the television s control system. 22 Cl A PTER 2 BA SIC C0NCEP1S Figure 2.1 Two categories of line configuration Figure 2.2 Point-to-point line configuration Multipoint A multipoint also called multidrop line configuration is one in which more than Iwoispecific devices share a single link see Figure 2.3 . In a multipoint environment the capacity of the channel is shared either spatially or temporally. If several devices can use the link simultaneously it is a .spatially .shared line .