Appendix
Data transmission over TV and radio channels - more popularly known as teletext and RDS - is an increasingly important aspect of modern broadcasting technology. This book bridges the gap between established television and radio practice and the computer technology that is used in these new systems.
The background to the development of teletext is described together with the data signal format and coding methods used. The various units that are required to implement a complete system are described. Further chapters deal with such topics as subtitle preparation and recording, the networking of teletext data signals and regional requirements, teletext decoders and re-transmission of decoded teletext signals as a video signal, and the transmission of data using the MAC packet format. The special measuring techniques that are required to maintain broadcast networks and to test decoders for both teletext reception and data distribution are described.
RDS (Radio Data Systems is a recent development that allows digital data to be combined with a VHF radio signal. The background is described together with the necessary techniques for both coding and decoding the data signal. Various applications are detailed including the use of RDS to provide a local traffic information service by interrupting networked radio programmes.
Both the authors are directly involved through their company, VG Electronics, in the design, manufacture and marketing of equipment for broadcast data systems, and this technical over-view is the definitive book on the subject. It provides vital and up-to-date information for engineers, managers, and systems and service planners in broadcast, cable and satellite services.
It is now some 20 years since the progress of semiconductor technology, stimulated by the computer industry, first made it realistic to contemplate the addition of data processing devices to a product as sensitive to cost as the television receiver. An enormous potential market was seen, built on the existing mass TV set market. Another spur for rapid development was the spirit of competition between the UK broadcasters – the BBC and the IBA. This period quickly led the broadcasters to give separate ‘over-air’ public demonstrations of their technically different systems in 1973. Then, working with industry and government in a joint technical committee under BREMA’s chairmanship, a unified specification, soon dubbed ‘The Teletext Spec’, was agreed and published in 1974. Separate BREMA/Post Office talks led to the adoption of the same display standard for ‘Viewdata’ (later ‘Prestel’).
It had been evident to the members of the joint committee – of whom one was Peter Mothersole – that teletext would have wider applications than the broadcasting of textual information and subtitles. Provision was therefore made so that later extensions could be introduced without making earlier teletext equipments obsolete. This ‘backward compatibility’ has proved invaluable in allowing new applications to be grafted onto the specification as needed. An example is the 1990 extension to provide for the automatic control of videocassette recorders.
The extended UK teletext system is now known internationally as CCIR Teletext System B or World System Teletext (WST). It has now been adopted by most of the countries which operate a teletext service. This book is therefore of immediate value in many countries throughout the world. It describes in some detail, in a readable, non-mathematical style, the systems and techniques needed to provide a comprehensive data broadcasting service. The direct approach to the applications described arises from the authors’ first-hand experience over many years. The book should whercfore be of use to newcomers to the topic who are anxious to get on-air as quickly and efficiently as possible; to those wishing to widen their experience; and to students whose privilege it may be in the future to build on what is described here, to achieve yet better things.
George McKenzie
Formerly Head of the Automation and Control Section, IBA,
Crawley Court
Teletext and the Radio Data System provide digital communication channels that are combined with the normal television and VHF radio signals. The origination and transmission of these digital signals introduce new equipment and techniques for their implementation in broadcasting systems. This book is intended to bridge the gap between established television and radio practice and the computer technology that is used in these new systems for practising engineers and students.
We gratefully acknowledge the use of material published by the BBC, the IBA, the IRT and the EBU and for the assistance given by Mr B. J. Rogers and our colleagues at VG Electronics Limited.
P.L.M.
N.W.W.
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First published 1990
First published as a paperback edition 1992
© Butterworth-Heinemann 1990
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British Library Cataloguing in Publication Data Mothersole,
Peter L. (Peter Leonard)
Broadcast data systems: teletext and RDS
1. Teletext systems
I. Title II. White, Norman W.
621.388
ISBN 0 240 51354 1
Library of Congress Cataloguing in Publication Data
Mothersole, Peter L.
Broadcast data systems: Teletext and RDS/
Peter L. Mothersole. Norman W. White
p. cm.
Includes bibliographical references
ISBN 0 240 51354 1
1. Teletext systems. I. White, Norman W.
II. Title
TK5105. M84 1990 384. 3' 52 - dc20
90 - 33586
Printed and bound in Great Britain by Hartnolls Ltd, Bodmin, Cornwall
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