广西医科大学：《计算机网络 Computer Networking》课程教学资源（PPT课件讲稿）CHAPTER 9 COMMUNICATIONS CIRCUITS

CHAPTER 9 COMMUNICATIONS 1934 CIRCUITS 1 The first section 计算机网络 2 Exercises 3 Online lect Department of Computer Networking Application

Department of Computer Networking Application CHAPTER 9 COMMUNICATIONS CIRCUITS 1 The first section 2 Exercises 3 Online lecture

Chapter 9 Communications Circuits 9.1 INTRODUCTION 9.2 COMMUNICATIONS CIRCUITS The physical connection between two or more points used for the purpose of communicating is called a line or circuit A link is a segment of a circuit between two points a node is a functional unit that connects two transmission links or lines www.gxmu.edu.cn

Chapter 9 Communications Circuits 9.1 INTRODUCTION 9.2 COMMUNICATIONS CIRCUITS The physical connection between two or more points used for the purpose of communicating is called a line or circuit. A link is a segment of a circuit between two points. A node is a functional unit that connects two transmission links or lines. www.gxmu.edu.cn

Chapter 9 Communications Circuits Node Server PC Nodes Figure 9-1 Links are segments of a circuit Nodes connect links or lines or may be an end point on a link www.gxmu.edu.cn

Figure 9-1 Links are segments of a circuit. Nodes connect links or lines or may be an end point on a link. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits 9.2 COMMUNICATIONS CIRCUITS a channel is a subdivision of a circuit and is a one way path for communicating. a data circuit is sometimes divided into two channel: data channel and control channel The data channel is called the forward channeland the control channel is the reverse channel www.gxmu.edu.cn

9.2 COMMUNICATIONS CIRCUITS A channel is a subdivision of a circuit and is a one way path for communicating. A data circuit is sometimes divided into two channel:data channel and control channel. The data channel is called the forward channel,and the control channel is the reverse channel. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits 9.3 THE ENVIRONMENTIN WHICH CIRCUITS OPERATE LAN WAN 9.4 TYPES OF CIRCUITS 9.4.1 Point-to-Point circuit a point-to-point circuit connects two and only two nodes. www.gxmu.edu.cn

9.3 THE ENVIRONMENT IN WHICH CIRCUITS OPERATE LAN WAN 9.4 TYPES OF CIRCUITS 9.4.1 Point-to-Point Circuit A point-to-point circuit connects two and only two nodes. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits Circuit A Point-to-Point Circuit A C Circuit Host B D Multipoint(Multidrop) circuit Figure 9-2 Types of circuits with nodes A, B, C, D, and the host computer. www.gxmu.edu.cn

Figure 9-2 Types of circuits with nodes A, B, C, D, and the host computer. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits 9.4.2 Multipoint Circuits A circuit that connects more than two points is called a multipoint circuit or multi-drop circuit. 9.4.3 Tw0-wire and Four-wire Circuits Four-wire circuits are preferable to two wire circuit for data transmission because they can carry communications in both directions simultaneously without employing any special multiplexing techniques www.gxmu.edu.cn

9.4.2 Multipoint Circuits A circuit that connects more than two points is called a multipoint circuit or multi-drop circuit. 9.4.3 Two-wire and Four-wire Circuits Four-wire circuits are preferable to two wire circuit for data transmission because they can carry communications in both directions simultaneously without employing any special multiplexing techniques. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits 9.4.4 Analog Circuits A modem converts a signal from digital to analog mode for transmission on an analog circuit, and back to digital mode at the receiving end 9.4.5 Digital circuits A DSU/CSU provides the signal timing and shaping interface between a dte and a digital circuit www.gxmu.edu.cn

9.4.4 Analog Circuits A modem converts a signal from digital to analog mode for transmission on an analog circuit, and back to digital mode at the receiving end. 9.4.5 Digital Circuits A DSU/CSU provides the signal timing and shaping interface between a DTE and a digital circuit. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits An amplifier takes the input signal and produces an exact replica(including noise and distortion) at a higher level on the output Analog signal Leaving Source Source Amplified signal After Transmission, Showing Still Distorted Attenuation and Distortion Amplifier Figure 9-3 Amplification of an analog signal www.gxmu.edu.cn

Figure 9-3 Amplification of an analog signal. An amplifier takes the input signal and produces an exact replica (including noise and distortion) at a higher level on the output. www.gxmu.edu.cn Chapter 9 Communications Circuits

Chapter 9 Communications Circuits a repeater regenerates the input signal so that its output is clean and free of distortion and noise. Digital Signal Leaving source Source After Transmission Showing Attenuation Regenerated and Distortion Signal repeater Figure 9-4 Regeneration of a digital signal www.gxmu.edu.cn

Figure 9-4 Regeneration of a digital signal. A repeater regenerates the input signal so that its output is clean and free of distortion and noise. www.gxmu.edu.cn Chapter 9 Communications Circuits