nowledgement 56/17 inefficient and proprietary networks they have developed. This is working, which will ultimately be under the same networking followed by a new network switching infrastructure called (see banner AAN, all working to the goal 'the network is the product'. Chapter 41) Asynchronous Transport Mode (ATM), which caters for the growing demand of higher switching connectivity and packet mode of both LAN, voice, video and image. Also included is the arrival of management architectures based on OSI standard and with Acknowledgement the ability to separate/partition services and function from this single management architecture. Acknowledgement to Steve Gerrard, Marketing Manager for local The changes within the network during 1990s and early next and wide area integration, with Newbridge Networks, who practi- century will see an ever demanding role for WAN and LAN net- cally wrote the LAN section. This page intentionally left blank Video transmission Pat Hawker Formerly IBA Engineering Division (Sections 57.1-57.2) J R Fox MA (Cantab) MSc PhD MIEE CEng MSCTE BT Laboratories (Section 57.3) DG Morrison BT Laboratories (Section 57.4) Ian Corbett BSc CEng MIEE BT Laboratories (Section 57.5) Contents Principles of video transmission 57/3 57.2 Television transmission 57/3 Cable distribution systems 57/17 57.4 Digital video coding 57/23 57.5 Videophony and videoconferencing 57/29 57.6 References 57/34 This page intentionally left blank Principles of video transmission 57/3 57.1 Principles of video transmission links and networks designed to carry a flexible mixture of televi- sion, telephony and data services. The European standard ISDN The development of electronic television in the mid 1930s, for the levels are: 64kbit/s, 2048kbit/s, 8448kbit/s, 34.368Mbit/s and first time, presented communications engineers with the need to 139.264Mbit/s. The last two of these levels are of particular interest handle signals having a base bandwidth measured in MHz rather in television broadcasting, and are usually referred t