s. Propagation for satel- lite communications. Summary of radio wave propagation. Refer- 19 Digital modulation ences. Introduction. Digital transmission. Digital modulation of a carrier. Pulse code modulation. Differential pulse code modulation. Delta 28 Digital transmission modulation. Coding programme quality sound. Coding video sig- Design principles. Transmission error performance. Line codes. nals. Acknowledgements. References. Clock extraction. Frame alignment. References. 20 Frequency division multiplexing FDM principles. History. FDM hierarchy. Frequency translation. Carriers. Pilots. Noise contributions. Measurement of noise con- Part 4 - Communications tributions. Overload. Hypothetical reference system. Companding. applications Through connections. Trnasmultiplexers. Repeatered cable line equipment. References. 29 Telephone networks Introduction. Network architecture. Network standards. Trans- 21 Time division multiplexing mission. Integrated digital networks. Network services. Numbering General definition. Digital time division multiplex structure. The and charging. Routing. Dimensioning. References. digital hierarchy levels. The T carrier framing and coding formats. The CEPT PCM-30 framing format. T1 and PCM-30 alarms and error conditions. Coding schemes. Examples of digital network 30 Transmission planning services. Introduction. Purpose of a transmission plan. Typical service groups. End to end requirements. Meeting end to end requirements. 22 Telecommunication standards Key influence on end to end performance. Summary of interactions. Example transmission plan. Future network trends. References. The growth of telecommunication standards. The standards making process. International standards organisations. European standards. USA standards organisations. Canadian standards organisations. 31 Principles of switching systems Japanese standards organisations. Australian standards organisa- Introduction. Structure of telephone systems. Teletraffic. Analogue tions. New Zealand standards organisations. Bi