DOCUMENT RESUME ED 082 512 EM 011 485 TITLE Technology of Cable Television. INSTITUTION Cable Television Information Center, Washington, D.C. SPONS AGENCY Ford Foundation, New York, N.Y.; John and Mary R. Markle Foundation, New York, N.Y. PUB DATE 73 NOTE 33p. AVAILABLE FROM Cable Television Information Center, The Urban Institute, 2100 M Street, N.W., Washington, D.C. 20037 EDRS PRICE MF-$0.65 HC Not Available from EDRS. DESCRIPTORS *Cable Television; *Community Antennas; Community Change; Community Leaders; *Community Planning; Community Programs; *Decision Making; Local Issues; Social Change; *Technological Advancement; Telecommunication; Television ABSTRACT The technology of cable television (CATV) is one area in which local community officials need to develop knowledge so that their decisions about the structure of CATV within the community will be informed. Thus, this paper is designed to familiarize local decision makers with the technological aspects of cable communications, to isolate specific questions which local officials must consider as they plan for CATV in their communities, and to note and explain options available to franchising authorities in dealing with those questions. Section One of the report describes cable technology past, present and future; the second section considers issues involved in systems design technical performance standard, and the implementation of future technology. (Author/SR) 5 Cable Television Information Center Technology of Cable Television the urban institute "PERMISSION TO REPRODUCE THIS COPYRIGHTED MATERIAL BY MICRO. FICHE ONLY HAS BEEN GRANTED BY CebleTeletk-sioIn(crwmi,9AnIty TO ERIC AND ORGANIZATIONS OPERAT NO UNDER AGREEMENTS WITH THE NA TIONAL INSTITUTE OF EDUCATION. FURTHER REPRODUCTION OUTSIDE THE ERIC SYSTEM REQUIRES PERMIS SION OF THE COPYRIGHT OWNER." Copyright © 1973 by Cable Television Informa- tion Center, The Urban Institute. All rights reserved. No part of this document may be used or reproduced in any manner whatsoever without written permission except in the case of brief quotations embodied in critical articles and reviews. For information address: Cable Television Information Center, 2100 M Street, N.W., Washington,D.C. 20037. Att: Information Group. TECHNOLOGY OF CABLE TELEVISION U.S. DEPARTMENT OF HEALTH, EDUCATION & WELFARE NATIONAL INSTITUTE OF EDUCATION THIS DOCUMENT HAS BEEN REPRO DUCED EXACTLY AS RECEIVED FROM THE PERSON OR ORGANIZATION ORIGIN. ATING IT. POINTS OF VIEW OR OPINIONS STATED DO NOT NECESSARILY REPRE SENT OFFICIAL NATIONAL INSTITUTE OF EDUCATION POSITION OR POLICY. CABLE TELEVISION INFORMATION CENTER The Urban Institute 2100 M Street, N.W., Washington, D.C. 20037 PREFACE This document was prepared by the Cable Television Information Center under grants from the Ford Foundation and the John and Mary R. Markle Foundation to The Urban Institute. The primary function of the center's publications program is to provide policy makers in local and state governments with the information and analytical tools required to arrive at optimum policies and procedures for the development -of cable television in the public interest. ACKNOWLEDGMENTS The center is indebted to The MITRE Corporation, McLean, Virginia. CONTENTS INTRODUCTION 7 I. TECHNOLOGY OF CABLE TELEVISION 7 A.Traditional CATV Systems 7 B. Modern Cable TelevisionI 11 C. Broadband Communications Cable's Future 14 II.MAJOR ISSUES FOR FRANCHISING AUTHORITIES 19 A. Design Decisions 19 B. Technical Standards 29 C. Role in the Evolution of Cable Technology 32 III. CONCLUSION 33 7 INTRODUCTION The second and third goals are treated in Section II. The issues involved in system design, technical performance standards, and the implementation Cable television's entrance into a community of future technology are examined from the per- poses special problems for local officials. spective of the local public official faced with deci- Although it is an opportunity to determine how sions. the community wants to regulate a new service a new medium of communication itis an TECHNOLOGY OF opportunity often overlooked. Taking full advan- tage of the opportunity usually requires a basic CABLE TELEVISION educational effort so that decisions can be made on the basis of a working knowledge of how cable This chapter explains how traditional commun- television operates, how local citizens can make ity antenna TV (CATV) systems work, discusses use of it, and what decisions local authorities can the technical characteristics of modern cable tele- take responsibility for making. vision, and, examines problems and prospects for The technology of cable television is one area broadband cable .communications -4-- the in which local officials need to develop the know- advanced systems that exist now only in pro- ledge on which to base their decisions. It is impor- totype. tant that local decision makers understalnd cable television technology for several reasons. First, A. Traditional CATV Systems because a cable television system's technical design importantly influences its social and enter- Cable television began by providing a service tainment usefulness, systems should be planned which extended the range of broadcast television with thorough consideration of local demog- stations, or, differently put, brought broadcast TV raphic, social, and political characteristics and the to those who could not otherwise receive it. service demands which these characteristics may Broadcast television service is most attractive make on that system. Second, since there must economically when the area it covers (a radius be reliable delivery of high quality television sign- of roughly 35 miles around the transmitter) is heav- alsif cable is to perform adequately any of its ily populated. The reason is that broadcast televi- existing or projected functions, franchising sion station revenur ;s derived almost entirely authorities should establish technical standards from advertisers, ,,t:hu pay for "time" on an against which the performance Of a system can amount-per-viewer basis. The more viewers a TV be measured. Third, because cable technology station reaches, the more it can charge for audi- will continue to grow in sophistication, local offi- ence time. cials will want to develop regulations that will per- However, the ability to saturate an area, while mit their community to accommodate changes in implortantitO the station owner and advertiser, that technology. poses certain disadvantages. Once a television sta- This publication has three goals: tion begins to broadcast, the same assigned fre- To familiarize local decision makers with the quency, or channel number, cannot be used by any other broadcaster within 200 miles; the two technological aspects of cable communications; To isolate specific questions which local offi- signals will interfere with one another. Further, a local station broadcasting on a VHF cials must consideras theyplan for cable television (broadcast channels 2-13) channel adjacent to the in their communities; and . channel of another station within 100 miles will To note and explain, where applicable, options available to franchising authorities in dealing with interfere with the distant signal. The 12 VHF chan- nels are not all adjacent to one another. But inter- those questions. ference problems among those that are, limit the Section 1 of this report describes cable number of VHF broadcast television stations a technologythe first goal of this paper. The basic viewer can receive to seven.' Table 1 illustrates components of a cable television system are this problem in Baltimore and Washington. explained both in the historical context of how In practice, the economics of broadcast televi- most systems were built before governments and sion usually, limit the number of stations even citizens were aware of cable's potential impor- further. Small cities and towns simply do not have tance, and how systems are being planned today. 'Any of two TV channels are considered adjacent when their Discussion is also directed to the role of cable video carriers are 6 MHz apart. Channels 4-5 and 6-7 are the communications in the future. only non-adjacent channels. 8 enough viewers to support more than one or two Hence, the number of stations that can be carried stations. Itis this economic limit which has is limited by the number of cables one can afford retarded the development of UHF television to lay not by any fundamental restvictions as once thought to be the key to diversity and local- in broadcasting. ism in television service because of the number Finally, since the cable protects signals it carries of channels. from ocAside interference, it potentially can CATV systems grew in towns whose citizens deriver i1 !1;;,ter quality signals than those received received either poor reception or no signals at off-thcx. all. These systems typically provided one to five A CA,TV system consists of three components: broadcast TV signals to subscribers, and thus were A headend, or control center not radically different from broadcast television A distribution system a network of cables service. which delivEr signals to subscribers' homes However, cable TV systems do use coaxial cable A subscriber terminal in this case, merely as a medium for delivering television signals, with the subscriber's television set. characteristics different from broadcast TV. A single cable can carry as ,many as 40 television HEADEND signals that do not interfere with each other from one point to another. Further, because signals car- The headend includes an electronic control ried by cable'Veak" only slightly from the inside center (sec.. Figure 1), which may or may not be of the cable, q.re frequencies used in one cable housed near e 100 to 500 foot tower with a sensitive can be used again in another cable next to it. antenna mouir:ed on it for each broadcast televi- Table 1. TV Channel Allocations (VHF) CHANNEL BALTIMORE WASHINGTON OTHER 2 WMAR-TV Harrisonburg, Va. 3 and Philadelphia, Pa. 4 WRC-TV 5 WTTG Richmond, Va. and 6 Philadelphia, Pa. 7 WMAL-TV Richmond, Va. and Lancaster, Pa. 9 s WTOP-TV Altoona and Phila- 10 delphia, Pa. 11_..WBAL-TV Richmond, Va., 12 ), Wilmington, Del. and Lynchburg, Va.