Book excerpt: Telecommunications Engineer's Reference Book maintains a balance between developments and established technology in telecommunications. This book consists of four parts. Part 1 introduces mathematical techniques that are required for the analysis of telecommunication systems. The physical environment of telecommunications and basic principles such as the teletraffic theory, electromagnetic waves, optics and vision, ionosphere and troposphere, and signals and noise are described in Part 2. Part 3 covers the political and regulatory environment of the telecommunications industry, telecommunication standards, open system interconnect reference model, multiple access techniques, and network management. The last part deliberates telecommunication applications that includes synchronous digital hierarchy, asynchronous transfer mode, integrated services digital network, switching systems, centrex, and call management. This publication is intended for practicing engineers, and as a supplementary text for undergraduate courses in telecommunications.