The following summary of the Television Comittee's report appeared in the February
1935 edition of Television and Shortwave World Magazine. Being a comittee report,
theres lots of text I'm afraid :-(
Note : The report is often referred to as the "Selsdon Report".
The Report of the Television Committee was presented by the Postmaster General to Parliament on Thursday, January 31ist. The Committee consisted of THE RIGHT HON. THE LORD SELSDON K.B.E. (Chairman), SIR JOHN CADMAN, G.C.M.G., D.Sc. (Vice-Chairman). COL. A. S. ANGWIN, D.S.O., M.C., B.Sc., Assistant Engineer-in-Chief, General Post Office. NOEL ASHBRIDGE, B.Sc., Chief Engineer, British Broadcasting Corporation. 0. F. BROWN, M.A., B.Sc., Department of Scientific and Industrial Research. VICE-ADMIRAL SIR CHARLES CARPENDALE, C.B., Controller, British Broadcasting Corporation. F. W. PHILLIPS, Assistant Secretary, General Post Office. Secretary : J. VARLEY ROBERTS, M.C., of the General Post Office. Its appointment had been announced in the House of Commons on March 33th, 1934, with the following terms of reference : "To consider the development of Television and to advise the Postmaster General on the relative merits of the several systems and on the conditions under which any public service of Television should be provided."
The Committee examined thirty-eight witnesses ; consulted with members of
various Departments of the Government; received numerous written statements
regarding television from various sources; received much formal evidence containing
secrets of commercial value, which evidence will not be published ; inspected
all the different television systems belonging to firms who were prepared
to provide demonstrations, the most distinctive being those of the Baird,
Cossor, Marconi-E.M.I. and the Scophony Companies; other organisations which
gave evidence were Ferranti, General Electric, Plew Television, the B.B.C.,
the Newspaper Proprietors' Association, the Radio Manufacturers' Association,
the Television Society, whilst a number of other interests—this journal among
them—presented written evidence. In America, the delegation visited and inspected
many of the chief centres of television experimental research, as well as
the plant and laboratories of the principal Broadcasting, Telephone and Telegraph
Authorities. They had also the advantage of consultation in Washington with
the Federal Communications Commission. In Germany, the delegation inspected
the experimental installations belonging to the Reichspost and also of those
of several private firms in Berlin.
In these pages, which the reader will understand we have added to TELEVISION AND SHORT-WAVE WORLD at the very last moment possible, we reproduce the greater part of the Report and the reader can be confident that we have not omitted anything of moment ; we shall take an opportunity in our next issue of commenting on the Report and explaining any point that may need such treatment.
The Advisory Committee already announced comprises Lord Selsdon (Chairman) ; Sir Frank Smith, Secretary of the Department of Scientific and Industrial Research (Chairman of Technical Sub-Committee) ; Colonel Angwin, Assistant En- gineer-in-Chief of the Post Office ; Mr. Noel Ashbridge, Chief Engineer of the B.B.C. ; Vice-Admiral Sir Charles Carpendale, Controller of the B.B.C. ; and Mr. F. W. Phillips, Assistant Secretary of the Post Office. The Secretary will be Mr. J. Varley Roberts of the Post Office. The Committee's task is to advise the Postmaster General on points arising in connection with the initiation and development of the broadcast television service.
The Advisory Committee will get to work immediately so as to lose no time in giving effect to the leading recommendations made in the report.
The Committee's principal conclusions and recommendations are summarised below :—
|(1)||No low definition system of television should be adopted for a regular public service.|
|(2)||High definition television has reached such a standard of development as to justify the first steps being taken towards the early establishment of a public television service of this type.|
|(3)||In view of the close relationship between sound and tele- vision broadcasting, the Authority which is responsible for the former—at present the B.B.C.—should also be entrusted with the latter.|
|(4)||The Postmaster General should forthwith appoint an Advisory Committee to plan and guide the initiation and early development of the television service.|
|Ultra-short Wave Transmitting Stations.|
|(5)||Technically, it is desirable that the ultra-short wave transmitting stations should be situated at elevated points and that the masts should be as high as practicable.|
|(6)||It is probable that at least 50 per cent. of the population could be served by 10 ultra-short wave transmitting stations in suitable locations.|
|(7)||It is desirable in the general interest that a comprehensive Television Patent Pool should eventually be formed.|
|(8)||A start should be made by the establishment of a service in London with two television systems operating alternately from one transmitting station.|
|(9)||Baird Television, Limited, and Marconi-E.M.I. Television Company, Limited, should be given an opportunity to supply subject to conditions, the necessary apparatus for the operation of their respective systems at the London station.|
|(10)||In the light of the experience obtained with the first station, the Advisory Committee should proceed with the plan- ning of additional stations—incorporating any improvements which come to light in the meantime—until a network of stations is gradually built up.|
|(11)||The aim should be to take advantage, as far as possible, of all improvements in the art of television, and at the same time to work towards the ultimate attainment of a national standardised system of transmission.|
|(12)||The cost of providing and maintaining the London station up to the end of 1936 will, it is estimated, be £180,000.|
|(13)||Revenue should not be raised by the sale of transmitter time for direct advertisements, but the permission given in the B.B.C.'s existing Licence to accept certain types of "sponsored programmes" should be applied also to the television service.|
|(14)||Revenue should not be raised by an increase in the 10s. fee for the general broadcast listener's licence.|
|(15)||There should not be any separate licence for television reception at the start of the service, but the question should be reviewed later in the light of experience.|
|(16)||No retailer's licence should be imposed on the sale of each television set, but arrangements should be made with the trade for the furnishing of periodical returns of the total number of such sets sold in each town or district.|
|(17)||The cost of the television service—during the first experimental period at least—should be borne by the revenue from the existing 10s. licence fee.|
As far back as the autumn of 1929 the B.B.C. gave the Baird Company facilities for experimental transmissions of television from a broadcasting station. During the next two or three years a large number of experimental transmissions were carried out by the Baird Company independently, as well as in liaison with the B.B.C.
Improvements were gradually made in the system, and in August, 1932, the Corporation arranged with Baird Television Limited for public experimental transmissions from their London Station (Brookmans Park) of television on a wavelength of 261 metres, and of the accompanying sound on a wavelength of 398 metres from the Midland Regional transmitter (Daventry). The Corporation agreed to provide special programme material and also staff for operating the television apparatus, which was installed in Broadcasting House by the Baird Company on a loan basis. These transmissions, the experimental nature of which was emphasised in a notice issued to the Press, have continued up to the present time, although their frequency has been reduced since 31st March, 1934, to two half-hour periods a week which are extended to three-quarters of an hour when circumstances permit.
In the case of these transmissions the size of the elements (elementary areas) composing the picture is such as to admit of transmission being effected in a series of thirty lines per picture and each picture is repeated 12½ times per second.
Any pictures built up with a structure of the order of thirty lines are, however, comparatively coarse in texture. Little detail can be given, and generally speaking the pictures are only fitted for the presentation of "close-ups"—e.g., the head and shoulders of a speaker—and the quality of reproduction leaves much to be desired. Moreover, any frequency of the order of 12½ pictures per second gives rise to a large amount of "flicker."
Whilst low definition television has been the path along which the infant steps of the art have naturally tended and, while this form of television doubtless still affords scientific interest to wireless experimenters, and may even possess some entertainment value for a limited number of others, we are satisfied that a service of this type would fail to secure the sustained interest of the public generally. We do not, therefore, favour the adoption of any low definition system of television for a regular public service. We refer later to the question of the temporary continuance of the present low definition transmissions pending the institution of a public television service of a more satisfactory type.
With a view to extending the application of television to a wider field and thereby increasing its utility and entertainment value, much attention has been given in recent years to the problem of obtaining better definition and reduced "flicker" in the received pictures.
The degree of definition it is essential to obtain is necessarily a matter of opinion, but the evidence received and our own observations lead us to the conclusion that it should be not less than 240 lines per picture, with a minimum picture frequency of 25 per second. The standard which has been used extensively for experimental work is 180 lines, but we should prefer the figure of 240 and we do not exclude the possible use of an even higher order of definition and a frequency of 50 pictures per second.
To attain such degrees of definition and picture frequency, very high modulation frequencies are required, which in practice can only be handled by radio transmitters working on ultra-short waves the effective range of which is much more restricted than the range of the medium waves used for ordinary sound broadcasting.
For the reception of high definition pictures the cathode ray tube is now usually employed. The cathode ray tube receiver involves no moving parts, and the picture is presented as a fluorescence at the end of the tube. A stream of electrons (particles of negative electricity) is projected along the tube, and impinges on a coating of fluorescent material at the end of the tube, the impact of the electrons on the fluorescent material causing illumination. The amount of illumination can be controlled by varying the flow of electrons, and the point of impact can be changed by deflecting the jet by means of electric or magnetic forces. The jet is modulated or controlled in amount by the received signal, and suitable electrical circuits are provided to move the point of impact in exact synchronism with the transmitter.
The size of the picture produced naturally depends upon the size of the cathode ray tube. At present the most usual size gives a picture of about 8 in. by 6 in., although good results have been seen with larger tubes. The apparent size can, of course, be increased by viewing the tube through a suitable fixed magnifying device, though with a corresponding loss of definition. Experimentat work is proceeding with a view to the projection of pictures on a screen of much larger dimensions, but this is still in an early stage of development. We are informed that the price to the public of a receiving set capable of producing a picture of about the first-mentioned size, with the accompanying sound, would probably at first be considerable, and various estimates have been given ranging from £50 to £80 ; but it is reasonable to assume that, if and when receivers were made on a larger scale under competitive conditions, this price would be substantially reduced.
Most of the high definition television systems follow in broad outline the methods of transmission and reception referred to above, with some variations in technique. We are impressed with the quality of the results obtained by certain of these systems, and whilst much undoubtedly remains to be done in order to render the results satisfactory in all respects, we feel that a standard has now been reached which justifies the first steps being taken towards the early establishment of a public television service of the high definition type in this country.
As regards the existing low definition broadcasts, these no doubt possess, as we have said, a certain value to those interested in television as an art, and possibly, but to a very minor extent, to those interested in it only as an entertainment. We feel that it would be undesirable to deprive these pioneer lookers of their present facilities until at least a proportion of them have the opportunity of receiving a high definition service. On the other hand, the maintenance of these low definition broadcasts involves not only some expense, but also possibly considerable practical difficulties. We can only, therefore, recommend—
|(1)||that the existing low definition broadcasts be maintained, if practicable, for the present; and|
|(2)||that the selection of the moment for their discontinuance be left for consideration by the Advisory Committee.|
with the observation that, if practicable so to maintain these broadcasts, they might reasonably be discontinued, as soon as the first station of a high definition service is working.
In our opinion there will be little, if any, scope for television broadcasts unaccompanied by sound. Television is, however, a natural adjunct to sound broadcasting and its use will make it possible for the eye as well as the ear of the listener to be reached Associated with sound it will greatly enhance the interest of certain of the existing types of broadcast and will also render practicable the production of other types in which interest is more dependent upon sight than upon sound. We are of the opinion that there are two factors which for a number of years will tend to prevent a television service being made use of to the same extent as present day sound broadcasting—
|(1)||The difficulties of wireless communication on ultra-short wavelengths, particularly in hilly districts, may seriously limit the extent to which the country can be effectively covered.|
|(2)||Some time is likely to elapse before the price of an efficient television receiver will be comparable with that of the average type of receiver now in use for sound broadcasting.|
Nevertheless, the time may come when a sound broadcasting service entirely unaccompanied by television will be almost as rare as the silent cinema film is today. We think, however, that in general sound will always be the more important factor in broadcasting. Consequently the promotion of television must not be allowed to prevent the continued development of sound broadcasting.
No doubt the evolution of television will gradually demonstrate the possibility of its application for many purposes other than those of entertainment and illustrative information.
These are obvious, were such deemed desirable. We can conceive, moreover, its potential application—as distinct from existing practice in picture transmission— to public telegraphic and telephonic services to the transmission of lists of prices, or of facsimile signatures or documents, and to its use by the police and the forces of the Crown, or as an aid to navigation.
Holding the view which we do of the close relationship which must exist between sound and television broadcasting, we cannot do otherwise than conclude that the Authority which is responsible for the former—at present the B.B.C.—should also be entrusted with the latter. We therefore recommend accordingly; and we have received an assurance that the Corporation is prepared fully to accept this additional responsibility and to enter whole-heartedly into the development of television in conformity with the best interests of the licence-paying public. In discharging this task the accumulated experience of the Corporation as regards sound broadcasting cannot fail to prove of great value. Presumably a separate licence will be required from the Postmaster General specifically authorising the Corporation to undertake the broadcasting of television.
We have, of course, considered the possible alternative of letting private enterprise nurture the infant service until it is seen whether if grows sufficiently lusty to deserve adoption by a public authority. This would involve the granting of licences for the transmission of sound and vision to several different firms who are pioneering in this experimental field. We should regret this course, not only because it would involve a departure from the principle of having only a single authority broadcasting a public sound service on the air, and because the subsequent process of "adoption" (which we believe would be inevitable) would be rendered costly owing to the growth of vested interests, but also because we foresee serious practical difficulties as regards the grant of licences to the existing pioneers as well as possibly to a constant succession of fresh applicants. It is, therefore, our considered conclusion that the conduct of a broadcast television service should from the outset be entrusted to a single organisation, and we are satisfied that it would be in the public interest that the responsibility should be laid on the B.B.C.
Whilst we think that the B.B.C. should exercise control of the actual operation of the television service to the same extent and subject to the same broad principles as in the case of sound broadcasting, we recommend that the initiation and early development of this service should be plan- ned and guided by an Advisory Committee appointed by the Postmaster General, on which the Post Office, the Department of Scientific and Industrial Research and the B.B.C. should be represented, together with such other members as may be considered desirable. We recommend that this Com- mittee should be appointed forthwith, for a period of, say, five years. The Committee should advise on the following :—
|(a)||The performance specification for the two sets of apparatus mentioned, later including acceptance tests, and the selection of the location of the first transmitting station.|
|(b)||The number of stations to be built subsequently, and the choice of districts in which they should be located.|
|(c)||The minimum number of programme hours to be transmitted from each station.|
|(d)||The establishment of the essential technical data governing all television transmissions, such as the number of lines per picture, the number of pictures transmitted per second, and the nature of the synchronising signals.|
|(e)||The potentialities of new systems.|
|(f)||Proposals by the B.B.C. with regard to the exact site of each station, and the general lines on which the stations should be designed.|
|(g)||All patent difficulties of a serious nature arising from the operation of the service in relation to both transmission and reception.|
|(h)||Any problem in connexion with the television service which may from time to time be referred to it by His Majesty's Government or the B.B.C.|
Normally the Committee would not concern itself with detailed financial allocations, or with business negotiations between suppliers of apparatus and the B.B.C. It is further considered that the Committee should not deal with the compilation of programmes, the detailed construction of stations, or their day-to-day operation, unless specifically invited to do so.
It will be clear from the foregoing that the Committee would be composed of both technical and non-technical members, and it is anticipated that a part of the Committee's work would best be carried out by a technical sub-committee.
Such experimental work as may be necessary for the establishment of stations and the operation of the service would be carried out by the B.B.C. in the usual course of its functions, but this would not, of course, preclude the enlistment of the co-operation of Government Departments or other organisations in technical researches.
As previously mentioned, the transmission of high definition television is practicable only with ultra-short waves, and a wide band of frequencies is necessary. Fortunately, there should be no difficulty, at present at all events, in assigning suitable wavelengths in the spectrum—between 3 and 10 metres—for public television in this country, although in allocating such wavelengths regard must, of course, be paid to the claims of other services. The recent experimental work has been conducted upon wavelengths around 7 metres.
Technically, it is desirable that the transmitting stations should be situated at elevated points, and that the masts should be as high as practicable, consistent with any restrictions which may be deemed necessary by the Government. The mast at present in use in Berlin is about 430 feet high, and the question of employing masts of greater height is under discussion in Germany. Quality of reception varies, of course, with the location of the receiving station and the nature of its surroundings. It may be observed that reception of these ultra-short waves does not seem to be materially affected by atmospherics. The most frequent sources of interference appear at present to arise from some types of electro-therapeutic apparatus, and from the ignition systems of motor cars ; but we understand that it is possible to prevent or reduce certain types of such interference by simple remedial devices.
Present experience both here and abroad seems to indicate that these ultra-short waves cannot be relied upon to be effective for a broadcast service much beyond what is commonly called "optical range." Generally speaking, it is at present assumed that the area capable of being effectively covered by ultra-short wave stations of about 10 kilowatts capacity will not exceed a radius of approximately 25 miles over moderately undulating country. In more hilly districts this may be considerably reduced, and indeed in certain areas an entirely reliable service may be impracticable. It is clear, therefore, that unless and until the effective range be increased, a large number of transmitting stations would be required to provide a service covering most of the country, though we think that with 10 stations, probably at least 50 per cent. of the population could be covered from suitable locations.
We nevertheless envisage the ultimate establishment of a general television service in this country, and in this connection we contemplate the possibility of television broadcasts being relayed by land line or by wireless from one or more transmitting stations to sub-stations in different parts of the country. We should observe that recent developments in cable technique render it possible for the first time to transmit, over considerable distances, frequencies such as are required for high definition television.
While the establishment of such a service should be, in our opinion, the aim, we do not feel that we can advise you to proceed at once to approve the construction, at great expense, of a network of stations, intended to cover most of the country. The total number of stations required for such a purpose is as yet unknown to anyone; and the total cost is accordingly purely speculative. Moreover, television will be a constantly developing art, and new discoveries and improvements will certainly involve continued modifications of methods—at least during its early years. A general service will only be reached step by step ; but the steps should be as frequent as possible and in our opinion the first step should be taken now.
We have been furnished with a great deal of information—much of it of a confidential character—concerning various systems of television. Continuous progress is being made in the art; and even during the few months of our investigations, research has brought a number of new and important discoveries.
The task of choosing a television system or a public service in this country is one of great difficulty. The system of transmission governs in a varying degree the type of set required for reception ; and it is obviously desirable to guard against any monopolistic control of the manufacture of receiving sets.
At the same time it is clear from the evidence put before us that those inventors and concerns, who have in the past devoted so much time and money to research and experiment in the development of television, are looking—quite fairly—to recoup themselves and to gather the fruits of their labours by deriving revenue from the sale of receiving apparatus to the public, whether in sets or in parts, and whether by way of royalties paid by the manufacturers or by manufacturing themselves. It is right that this should be so, and that the growth of a new and important branch of industry, capable of providing employment for a large number of workers, should in every way be fostered and encouraged to develop freely and fully.
The ideal solution, if it were feasible, would be that, as a preliminary to the establishment of a public service, a Patent Pool should be formed into which all television patents should be placed, the operating authority being free to select from this Pool whatever patents it desired to use for transmission, and manufacturers being free to use any of the patents required for receiving sets on payment of a reasonable royalty to the Pool.
We have come to the conclusion that a start could best be made with a service of high definition television by the establishment of such a service in London
SERVICE IN LONDON.
It seems probable that the London area can be covered by one transmitting station and that two systems of television can be operated from that station. On this assumption we suggest that a start be made in such a manner as to provide an extended trial of two systems, under strictly comparable conditions, by installing them side by side at a station in London where they should be used alternately—and not simultaneously—for a public service.
There are two systems of high definition television—owned by Baird Television Limited and Marconi-E.M.I. Television Company Limited respectively—which are in a relatively advanced stage of development, and have indeed been operated experimentally over wireless channels for some time past with satisfactory results. We recommend that the Baird Company be given an opportunity to supply the necessary apparatus for the operation of its system at the London station, and that the Marconi-E.M.I. Company be given a similar opportunity in respect of apparatus for the operation of its system also at that station .... Transmissions from both sets of apparatus should be capable of reception by the same type of receiver without complicated or expensive adjustment. The definition should not be inferior to a standard of 240 lines and 25 pictures per second.
It is scarcely within our province to make detailed recommendations on the subject of television programmes. To what extent those programmes should consist of direct transmissions of studio or outdoor scenes, or televised reproductions of films, must be determined largely by experience, technical progress and public support, as well as by financial considerations. No doubt the televising of sporting and other public events will have a wide appeal, and will add considerably to the attractiveness of the service. We regard such transmissions as a desirable part of a public television service, and it is essential that the B.B.C. should have complete freedom for the televising of such scenes, with appropriate sound accompaniment, at any time of the day.
With regard to the duration of television programmes, we do not consider that it will be necessary at the outset to provide programmes for many hours a day. An hour's transmission in the morning or afternoon which will give facilities for trade demonstrations and, say, two hours in the evening, will probably suffice. As regards the future, the B.B.C. and the Advisory Committee will doubtless be guided by experience and by financial considerations.
We estimate that the cost of providing the London station, including all running and maintenance expenses, programme costs and amortization charges (calculated on the basis of a comparatively rapid obsolescence), for the period up to 31st December, 1936, will be £180,000. We have carefully considered the question of providing the necessary funds. Roughly speaking, the means suggested to us for so doing may be classified under two heads :—
|(a)||Selling time for advertisements, and|
Advertisements may take two forms : they may be either (i) direct advertisements for which time is bought by the advertiser such as, for instance, a dress show by Messrs. Blank ; or (ii) the acceptance, as a gift, of programmes provided by an advertiser and coupled with the intimation of his name, in accordance with a standard formula, such as, for instance, "This programme comes to you through the generosity of Messrs. Dot & Dash," the latter system being usually known as that of "sponsored programmes." As regards direct advertisements, this proposal has been frequently examined in past years. In relation to sound broadcasting it was discussed and rejected by the Sykes Committee on Broadcasting in 1923. We do not differ from that Committee's view and accordingly do not recommend this course. As regards "sponsored programmes," for which the Broadcasting authority neither makes nor receives payment, the Sykes Committee saw no objection to their admission ; and they are now specifically allowed under the B.B.C.'s Licence, although the Corporation has, in fact, only admitted them on rare occasions. We see no reason why the provision concerning sponsored programmes in the existing Licence should not be applied also to the television service ; and we think it would be legitimate, especially during the experimental period of the service, were the Corporation to take advantage of the permission to accept such programmes. In attempting to provide funds from licence revenue there appear to be four possible courses :—
|(1)||The raising of the fee for the general broadcast listener's licence.|
|(2)||The issue of a special television looker's licence.|
|(3)||The imposition of a licence upon retailers.|
|(4)||The retention of the existing listener's licence at l0s. and the contribution from that licence revenue of the necessary funds during the experimental period.|
We are left with the conclusion that, during the first experimental period at least, the cost must be borne by the revenue from the existing 10s. licence fee^ ... We suggest that the best course would be for a reasonable share of the amount to be borne by each of the two parties—the Corporation and the Treasury. The existing programmes represent amazingly good value for one-third of a penny per day and the general body of listeners may not unreasonably be asked to help, at no extra cost to themselves, in a national experiment which, if successful, will ultimately enhance programme values for a large part of their members. We feel that the development of British Television, in addition to being of evident importance from the point of view of science and entertainment, and of potential importance from the angles of national defence, commerce and communications, will also directly assist British industries.
WIRELESS EXCHANGES (RADIO RELAYS).
We have considered the question, which has been raised in evidence, of the relaying of public television broadcast programmes by Wireless Exchanges. We see no reason why such a practice, if technically feasible, should not be allowed under the same conditions as are applicable in the case of sound broadcast programmes.
PRIVATE EXPERIMENTS AND RESEARCH.
We hope that encouragement will continue to be given to all useful forms of experiment and research in television by firms or private persons. It is true that much experimental work can be done by transmission from one room to another by wire without recourse to a radio link. In certain cases, however, the use of such a link is necessary ; and we trust that . . . adequate facilities for experimental work will continue to be given.
The following month, the magazine published their comments on the report :-
SINCE the publication of the Television Committee's Report we have been at pains to ascertain the opinions of many well-known authorities on the various recommendations. These we had hoped to publish fully, but in several cases there are politic reasons why personal views should not be given in detail; we are able, however, to give a general outline of what may be described as an average opinion.
Commendation of the report is general and the only criticism that can be considered in any way adverse is upon the somewhat high scanning frequency recommended. Many people point out that the desirability, or otherwise, of this high scanning frequency can rationally be argued from two points of view. In favour of it are the facts that it is immediately possible, and that it provides a standard which will dispose once and for all of any suggestions of lack of entertainment value in television.
On the other hand such a high scanning frequency as 240 lines places some very difficult obstacles in the way of those who have pinned their faith to mechanical systems; there are several of these at the present time which with a slightly lower frequency are giving wonderful promise of simple methods of reception. Most of these were calculated to go to 180 lines and the additional 60 lines will mean a considerable revision of ideas. We do not for a moment imagine that this extra handicap will rule mechanical systems out, but it is likely to have the effect of retarding development in this direction.
It can, of course, be contended that nothing but the best possible is good enough, and as a 240-line standard is possible with cathode-rays, any system which cannot reach this standard is not worth while. There is, howewer, another aspect of this matter. At the present time it seems that larger pictures are more likely to be obtained by mechanical methods than by cathode-rays and this everyone will admit is desirable. Within the past twelve months remarkable developments have been made in light modulation and it will be unfortunate if this progress is retarded. The whole point is that it would be desirable to give both systems equal chances of development, for either has advantages that are not present in the other —in other words, definition at this stage should not be regarded as the only criterion of the value of a system. Some of the mechanical systems are now simple and at the same time remarkably efficient, and it would be a pity therefore if consideration is not given to their special features. Those who have made comparisons of 180- and 240-line pictures will be aware that there is not a great deal of difference in the quality, whereas the production of the latter increases the difficulties very considerably.
The figure of 240 lines is, of course, only a recommendation, and the final decision will rest with the Advisory Committee to which we understand strong representations are being made on the matter.
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