munications 1.3.1 End-Users, Nodes, and Connectivities 1.3.2 Telephone Numbering and Routing 1.3.3 The Use of Tandem Switches in a Local Area Connectivity 1.3.4 Introduction to the Busy Hour and Grade of Service 1.3.5 Simplex, Half-Duplex, and Full Duplex 1.3.6 One-Way and Two-Way Circuits 1.3.7 Network Topologies 1.3.8 Variations in Traffic Flow Quality of Service Standardization in Telecommunications The Organization of the PSTN in the United States 1.6.1 Points of Presence Review Exercises References Chapter 2 Signals Convey Intelligence Chapter Objective Signals in Everyday Life Basic Concepts of Electricity for Communications 2.3.1 Early Sources of Electrical Current 2.3.2 The Electrical Telegraph: An Early Form of Long-Distance Communications 2.3.3 What Is Frequency? Electrical Signals 2.4.1 Introduction to Transmission CONTENTS 2.4.2 Modulation 2.4.3 Binary Digital Signals Introduction to Transporting Electrical Signals 2.5.1 Wire Pair 2.5.2 Coaxial Cable Transmission 2.5.3 Fiber-Optic Cable 2.5.4 Radio Transmission Review Exercises References Chapter 3 Quality of Service and Telecommunication Impairments 3.1 Objective Quality of Service: Voice, Data, and Image 3.2.1 Signal-to-Noise Ratio 3.2.2 Voice Transmission 3.2.3 Data Circuits 3.2.4 Video (Television) 3.3 The Three Basic Impairments and How They Affect the End-User 3.3.1 Amplitude Distortion 3.3.2 Phase Distortion 3.3.3 Noise Level 3.4.1 Typical Levels 3.5 Echo and Singing Review Exercises References Chapter 4 Transmission and Switching: Cornerstones of a Network Transmission and Switching Defined Traffic Intensity Defines the Size of Switches and the Capacity of Transmission Links 4.2.1 Traffic Studies 4.2.2 Discussion of the Erlang and Poisson Traffic Formulas 4.2.3 Waiting Systems (Queueing) 4.2.4 Dimensioning and Efficiency 4.2.5 Quantifying Data Traffic Introduction to Switching 4.3.1 Basic Switching Requirements 4.3.2 Concentration and Expansion 4.3.3 The Essential Functions of a Local Switch 4.3.4 Introductory Switching Concepts 4.3.5 Early Au