Broadcasting in Britain: New Dimensions in Broadcasting – Colour and Stereophony 

30 December 2022 tbs.pm/76616

 

Cover of Broadcasting in Britain

From ‘Broadcasting in Britain’, published in 1972 by HMSO

Whilst many features of present-day broadcasting were actually or potentially established by 1956, there were some notable restrictions. Colour television existed in America, and had been successfully demonstrated by the BBC using the American techniques, but there was no prospect of a colour service in Britain. There was no entirely satisfactory means of recording television programmes; pictures could be relayed only from Europe, and then only with noticeable loss of quality. Radio was exclusively monophonic, and ‘local’ radio non-existent.

Colour television

In principle, colour television can be achieved quite simply, by sending three signals, similar in form to ‘monochrome’ signals but respectively conveying the ‘red’, ‘green’ and ‘blue’ content of the scene. At the receiver, each signal is made to create a picture in the appropriate colour, and the three pictures are superimposed.

Systems in which the three signals are conveyed simultaneously over three separate circuits have been used in ‘closed circuit’ applications, but early attempts to broadcast colour used the ‘sequential’ technique, in which only a single signal is transmitted. Discs made from segments of red, green and blue filter-material are synchronously rotated in front of a ‘monochrome’ camera and a ‘monochrome’ receiver, persistence of vision merging the rapid succession of red, green and blue pictures presented to the eye.

Unfortunately, for satisfactory results, such a ‘sequential’ system requires three times as many pictures per second as monochrome television, so (like a ‘simultaneous’ system) must either occupy three times as wide a band of radio frequencies, or employ a degraded standard of definition. An equally serious objection to both types of colour system is that they are not ‘compatible’ – that is, they cannot provide a satisfactory black and white picture on existing monochrome receivers.

Nevertheless, a very advanced sequential system was developed during the 1940s by America’s Columbia Broadcasting System (CBS) and in 1950 was actually adopted by the Federal Communications Commission as the official American colour standard.

During the late 1940s, however, American research scientists were examining the characteristics of human colour vision in search of tolerances that could be exploited for colour television, and in 1951 the National Television System Committee (NTSC) proposed an elegant new system which exploited the eye’s tolerance of blurred colouring in an otherwise sharp picture. The transmitted signal occupied no more of the waveband than a monochrome signal, and was also compatible; by means of advanced techniques of modulation, a normal monochrome television signal was augmented by an additional low-definition colouring signal, sharing the same band of frequencies yet contrived to produce very little interference on monochrome receivers. In colour receivers, decoding circuits reconstituted separate red, green and blue signals.

At the same time, the Radio Corporation of America (RCA) introduced a radically new design of cathode-ray tube which enabled three coloured images to be simultaneously displayed on a single screen. The screen was covered with tiny dots of red-emitting, green-emitting and blue-emitting phosphors, in an orderly array. Three electron guns, side by side in the neck of the tube, supplied electron beams bearing the appropriate colour signals, and a perforated sheet of metal (‘shadow-mask’) just behind the screen ensured that each beam could only reach its own colour of phosphor-dots.

With these two inventions, colour television at once became technically feasible. In 1953 the FCC gave its approval to the NTSC system (reversing its previous ruling on the CBS system).

Unfortunately, America’s dedication to commercial broadcasting hampered the establishment of a colour service. With few colour receivers in use, sponsors were unwilling to bear the extra expense of originating programmes in colour; with few of the programmes in colour, the public were unwilling to buy colour receivers. As late as 1961, seven years after the first commercial transmission in colour, only one of the three major networks was transmitting colour at all.

In Britain, the prospect of colour television made it necessary to reconsider the future of the 405-line standard. By simply using the NTSC system in a 405-line version (which had been shown to give excellent results) the two established networks could readily have been converted to colour. To have done this, however, would have committed the country for many more years to a standard which larger screens were already making obsolescent in the late 1950s.

The alternative was to change to the 625-line standard, which had been generally accepted in continental Europe since 1953. The transition, however, would be complicated by the need to keep faith with the owners of 405-line receivers. The existing 405-line services would have to be left in occupation of the valuable v.h.f. bands for perhaps ten years, and the new 625-line transmissions established exclusively on u.h.f. bands (between 470 MHz and 960 MHz) which had been allocated to television but not yet used. It was known that at the very short wavelengths of the u.h.f. bands, hills cast marked shadows, necessitating many more transmitters than are needed at v.h.f., and there was some doubt whether the needs of all European countries could be met without unacceptable interference between the numerous stations that would have to share each channel.

Before informed decisions could be reached, it was necessary first to carry out field trials to find how u.h.f. television signals propagated, and also laboratory tests to find what level of interference between stations could be tolerated. Armed with this data, engineers could then attempt to work out an internationally acceptable allocation of frequencies.

The results proved favourable, and at Stockholm in 1961 a plan was agreed for the European Broadcasting Area, involving thirty-six countries and over 4,000 u.h.f. stations. The plan (which was exclusively for the 625-line standard) provided for Britain to operate sixty-four main stations, each radiating four programmes; to extend the coverage, about 1,000 small ‘relay’ stations were envisaged. Subsequently, the BBC has devised computer programmes, allowing more detailed planning than would otherwise have been practicable for an operation of this magnitude, and as a result the required coverage will in fact be achieved with about fifty main stations and 450 relay stations.

A relay station is sited so that it can receive good signals from a main station, or from another relay station. The signals thus received are passed to ‘transposers’, one for each programme, which shift their frequencies to different channels, for amplification and re-transmission.

Britain’s first implementation of the Stockholm plan came in 1964, with the opening of a second BBC network (BBC 2), transmitted exclusively on 625 lines, u.h.f.

The large number of u.h.f. transmitters has made it essential to provide for unattended operation of both main and relay stations. The station’s performance is automatically monitored and, when a fault is detected, remaining resources are automatically redeployed to maintain the best service possible; usually this merely involves a slight fall in effective radiated power. At the same time, the occurrence of a fault is reported to a manned centre, so that an engineer can be sent to repair it.

 

A tall concrete transmitter tower

The ITA’s transmitter tower at Emley Moor, Yorkshire, 1971: The concrete tower is the first of its kind in the UK. It supports u.h.f. aerials radiating the ITV programme and both BBC programmes on 625 lines (colour), and v.h.f. aerials radiating the ITV programme on 405 lines (monochrome); similar reciprocal arrangements apply at the BBC’s u.h.f. stations. The total height of the structure is 1,080 ft (330 metres)

 

The choice of a colour system

The Stockholm plan largely resolved the ‘standards’ dilemma. Meanwhile, however, a new complication had arisen. In America, practical experience of the NTSC colour system had shown that the form of coding employed made the ‘colouring’ information unduly susceptible to some of the distortions it encountered along its path. Accordingly, France and Germany had each developed a variant of the NTSC system, using methods of coding designed to be more tolerant of distortion.

Once again, extensive field trials and laboratory-tests were necessary; to make the task even more formidable, the French system, ‘Secam’, itself underwent periodic modification in attempts to improve its performance, whilst the German system, PAL, provided for either ‘standard’ or ‘de-luxe’ decoding arrangements in receivers. The BBC played a leading part in the assessments, and over the period 1958-67 submitted 70 documents to the European body that had been set up to study the problem.

As the comparisons proceeded, the PAL system gained ground, but not so markedly as to eliminate what have tactfully been termed ‘considerations of national prestige’, and hopes for a common European colour standard declined. In March 1966, Britain formally announced that, unless some other system were internationally agreed at a forthcoming meeting, she would adopt the PAL system. No agreement was in fact reached, though the PAL system was adopted by a majority of European countries. In Britain, a final complication was the existence of a vociferous lobby for adding colour to the 405-line v.h.f. services; this was being publicly advocated as late as October 1966.

 

OB units line up behind scaffolding holding cameras

Derby Day 171: BBC and ITV have separate technical facilities but share camera gantries

 

After a decade of uncertainty, the situation was finally resolved with remarkable speed. On July 1, 1967, colour was officially launched on BBC2, with the Wimbledon tennis championships, and by December a full colour service had been established on that network. From November 1969, the BBC 1 and ITV networks were radiated in colour on 625 lines, u.h.f., while continuing in monochrome on 405 lines, v.h.f., to maintain the existing services. The BBC and the ITV programme companies rapidly re-equipped their studios and outside-broadcast units, so that colour programmes predominated from the outset.

Inevitably, the change-over period was inconvenient for viewers who wished to take immediate advantage of the new services; between 1964 and 1969, to receive all three networks required three aerials and a dual-standard receiver, capable of tuning over both v.h.f. and u.h.f. bands and of operating at both 405 and 625 lines (with, respectively, a.m. and f.m. sound signals). From 1967 to 1969, with 625 lines and colour on only one network, colour receivers too had to be dual-standard, and were largely used for viewing 405-line monochrome pictures.

Subsequently, as the 625-line service has spread, the advantages of the new regime have taken effect. All three networks are on u.h.f and come from the same transmitting mast, so a single, compact aerial suffices; the receiver needs only a u.h.f. tuner, and need operate only on 625 lines.

 

Cut-away diagram of a recording head

The principle of the four-head videotape recorder

 

Videotape recording

Recording the signal from a television camera on magnetic tape is a great deal more difficult than recording a sound signal; an impracticably high tape speed is required if a conventional form of recorder is to accommodate the rapid oscillations that occur in a television signal, and this speed must be held to an impracticable constancy if the reproduced picture is not to wobble.

Both difficulties were overcome by the ‘Ampex’ company in a recorder of revolutionary design that was introduced on to the American market in 1957 and was first used in Britain by an ITV company, Rediffusion, in the following year. This uses a tape 2 inches (51 mm) wide, running at only 15 inches (38 cm) per second. The recording is laid down as a succession of narrow tracks across the width of the tape by four heads spaced around the rim of a wheel, which spins rapidly in a plane perpendicular to the tape’s length; a guide curls the tape around the rim so that recording is continuous. By this means, a recording speed about a hundred times faster than the tape speed is achieved, and is stabilized by the inertia of the wheel.

The Ampex machine produced negligible loss of picture quality, and eclipsed a recorder of more conventional design that the BBC had developed to the stage of service trials. The specification of the original Ampex recorder has remained the basis of subsequent generations of videotape recorders for broadcast use, though simpler types, in which the recorded tracks lie almost longitudinally, have been evolved for less exacting applications.

Within a few years, videotape recording was used for all studio or outside broadcasts other than the minority whose nature demanded ‘live’ transmission.

 

A man sits at a very large video tape machine

Videotape machine: A high proportion of programmes are pre-recorded on tape and edited before transmission

 

Satellite communication

The possibility of using artificial earth satellites for long-distance radio communication was discussed in some detail in a Wireless World article of October 1945, twelve years before Sputnik I was launched; the author was Arthur C Clarke, now famous as a writer of science fiction.

Television must be transmitted on very short wavelengths, which cannot reach far beyond the horizon, and a satellite overcomes this limitation by providing straight paths between distant points. However, the great distances involved and the small size of the satellite cause the transmission loss to be very great, so that the satellite must amplify the weak signal it receives before returning it to earth.

The first satellite capable of relaying television was ‘Telstar 1’, launched on July 10, 1962, operating in conjunction with earth stations in America, England and France, whose huge ‘dish’ aerials followed it across the sky. The satellite orbited the earth every two and a half hours and even during the most favourable orbits was visible from both sides of the Atlantic for only a few minutes.

Because of the historical significance of ‘Telstar’, and the publicity that the project had received, it was decided to broadcast the first television pictures transmitted by the satellite rather than confine them to an audience of engineers. Thus when the British Post Office’s earth station at Goonhilly, Cornwall, received only very weak signals, the engineers’ sense of dismay was shared by millions of viewers; the French station, however, received good pictures.

Frenzied checking at Goonhilly revealed that the fault lay in an internationally agreed definition, which contained an ambiguity, and had been differently interpreted by the American and British engineers. A component in the Goonhilly aerial was reversed, and highly successful results were obtained the following day.

Satellite communication entered a new phase a year later with the first successful launching of a ‘synchronous’ satellite – that is, one whose orbit was such that it always stayed above the same point on the earth’s surface. This advance (prophesied in Clarke’s 1945 article) made relays continuously available over a wide area. In April 1965 the first commercial satellite was launched by the international body (‘Intelsat’) set up to operate satellite communication for civil use.

Subsequently, the television audience has grown used to seeing events televised ‘live’ from all parts of the world. Such transmissions are very expensive, because each television circuit uses satellite capacity that would otherwise be available for carrying about a thousand telephone circuits; telephony is, of course, the mainstay of satellite communication.

 

A view down into a television studio

Colour television studio equipment: Lights and monitors suspended from the roof leave the floor free of obstruction

 

Standards conversion

With the opening of BBC 2 on 625 lines, conversion between the 625-line and 405-line standards became necessary on a greater scale than hitherto. Subsequently, there has been a further large increase, with all BBC 1 and ITV programmes originated and distributed on 625 lines, but transmitted on both standards.

Equipment existing in the early 1960s, in which a camera operating at one standard was focussed on a picture displayed at the other, inevitably produced significant loss of quality, which would have become unacceptable when 405-line viewers received only converted pictures. The equipment also required the attendance of a skilled operator, which would be unacceptable when, to avoid the expense of separate 405-line and 625-line distribution networks, large numbers of converters were operated at transmitter sites.

To overcome these difficulties, the BBC undertook the development of a new form of standards conversion equipment in which the signal was not displayed as a picture, but was retained as a waveform throughout. As well as ‘prolonging’ the lines of the 625-line picture to occupy the longer line period of the 405-line standard, a converter has to average between neighbouring lines of the 625-line picture. These processes require storage of the picture information, but by arranging for the two standards to scan down the picture together it is sufficient to provide for the storage of only one or two lines of signal.

Such was the urgency of the project that the BBC simultaneously developed two quite independent designs of ‘line-store’ converter. The two designs differed radically in the techniques they employed for averaging, but both employed high-speed electronic switching to route into separate circuits the six hundred or so ‘picture elements’ into which each line was dissected.

Prototype models of both designs were successfully developed and put into service at Television Centre. Subsequently, the design that was cheaper to make was produced commercially, a total of sixty-nine converters eventually being installed within the BBC and ITA distribution networks.

The exchange of programmes with the United States is complicated by the fact that the picture is scanned sixty times a second on the American 525-line standard, as against fifty on European standards. It is thus no longer possible for the two standards to scan down the picture together, and very much more storage must be provided in the converter. Again, the BBC concurrently developed two forms of converter, but this time one was an ‘interim’ version, which was relatively simple but which produced a picture of diminished size framed by a black border. It entered service in 1967, and in the following year was succeeded by a more advanced version, free from this limitation, which enabled British viewers to see live colour pictures relayed by satellite from the Olympic Games in Mexico.

The heart of this ‘field-store’ converter is a bank of fused-silica delay devices – polygonal slabs into which the signal is launched as an ultrasonic wave; after numerous reflections from the faces of the polygon, the wave is converted back to an electrical signal. Each of the various slabs imposes some precisely known delay (up to 3.5 milliseconds in value), and the converter’s logic circuits deduce, for each line of the incoming signal, which slabs should be switched into circuit to make the information emerge just when it will be required to contribute to the output signal. For colour pictures, the conversion process must also include translation of the colour information between the NTSC and PAL systems.

Digital techniques in broadcasting

In 1972 the BBC began to put into service a new system, of its own design, for distributing the sound signal of a 625-line television picture within the picture signal. This is done by fitting a sequence of pulses into the brief gaps that occur between successive scanning lines. By this means, the cost and complication of a separate sound-distribution network is avoided. Moreover, since the pulses are simply a succession of twenty-one ‘Noughts’ or ‘Ones’ within each gap, the sound signal does not lose quality as the distribution path is lengthened; it is merely necessary for the pulses to remain identifiable, which they do over even the longest links. At the transmitter the pulses are removed and reconverted to a sound signal before being broadcast.

This system is significant as the first operational application to broadcasting of the so-called ‘digital’ techniques that are increasingly being used in many branches of communication. By 1972 the BBC was on the point of extending digital-sound techniques to the distribution of stereo radio programmes, whilst both the BBC and the ITA had demonstrated experimental 625-line/405-line standards converters performing the much more formidable task of handling television signals in digital form.

 

A camera on a crane gets very close to a woman halfway up a tall tree

The compactness of a modern colour camera makes for freedom of movement, here illustrated by the use of a ‘crane’ (Wendy Hiller in rehearsal for ‘Peer Gynt’, 1972)

 

Cameras and studios

Britain entered colour television at a very timely stage in the evolution of camera tubes. Early colour cameras had employed three image-orthicon tubes; the characteristics of this type of tube were not well suited to colour work, whilst their large size made for a clumsy camera whose sensitivity was impaired by the long, and consequently inefficient, light paths between the lens and the tubes.

In 1950 RCA introduced the ‘vidicon’, a tube whose target responded to light not, as in other tubes, by emitting electrons, but by becoming more conductive. Because of its small size, cheapness and simplicity of operation, the vidicon has been widely used in closed-circuit and industrial television, but its use for broadcasting has been restricted by limitations of performance, particularly its tendency to smear moving objects.

By replacing the vidicon’s antimony-trisulphide target with one of lead oxide, the Philips company was able to develop the ‘Plumbicon’, which retained the vidicon’s merits while greatly improving its performance. The first Plumbicon tubes appeared in 1957, and in 1964, when the BBC had to make its forward plans for colour cameras, small-scale production had begun, though only experimental Plumbicon cameras existed, and none were in operational service. Moreover, important technical deficiencies of the tube were yet to be overcome, and its future depended entirely upon one manufacturer. Such was the tube’s promise, however, that the BBC made the bold decision to base its plans for colour exclusively on the Plumbicon, and tacitly confirmed this by taking no steps to ensure the development of an image-orthicon camera capable of meeting its requirements. Subsequent events have shown the wisdom of this course, Plumbicons (or similar tubes produced by other manufacturers) having become universal in new designs of colour camera.

The first generation of colour cameras to be installed in Britain included both three-tube and four-tube types. In a three-tube camera, the monochrome (‘luminance’) signal is formed by adding together, in appropriate proportions, the signals from the ‘red’, ‘green’ and ‘blue’ tubes. If the three images are slightly misregistered, the sharpness of the picture suffers, though the colouring may still be acceptable. Registration becomes less critical if a fourth tube is included solely to provide the ‘luminance’ signal.

Colour studios are planned for high productivity, and are in use twenty-four hours a day, scenery and lighting being rigged during the night in readiness for camera rehearsals and recording during the day and evening. The BBC quotes a daily output of thirty minutes’ programme from each studio, with only half a day a week for maintenance.

An essential factor in this achievement is the studio lighting equipment. Rigging time is minimized by providing a very large number of lights, suspended from remotely-controlled hoists closely spread over the ceiling. By this means, light is immediately available at any point in the studio, and the floor is kept clear of obstruction. Each lighting plot is ‘filed’ in computer-type stores, and can be instantly recalled. It has been found that a useful degree of dimming can be used without upsetting the colour of the illumination.

Correct exposure of the colour cameras, which should be accurate to an eighth of a stop, is primarily achieved by control of the incident lighting level (1600 lux), and iris controls are used only for fine adjustments. A scene must be restricted in contrast to a range of only thirty to one, and to enable this condition to be met without requiring completely uniform illumination of the scene, costumes and scenery are restricted to an even narrower range (twenty to one).

Thus, artistic and engineering staff have co-operated to overcome technical limitations by maintaining strict quantitative control over each individual aspect of the operation.

Local radio

With the advent of v.h.f./f.m. broadcasting, local radio became technically feasible. V.h.f. waves grow rapidly weaker beyond the service area, whilst f.m. is more tolerant than a.m. of signals picked up from other stations on the same frequency. It is therefore possible to plan local broadcasting with a considerable degree of frequency-sharing between stations in different parts of the kingdom.

In 1967 the BBC received government approval for an experimental trial of local broadcasting, and eight stations were opened between November 1967 and January 1968. In 1969, approval was given for twelve further stations, and the BBC made plans to increase the total number to about forty, which would have given 90% population coverage. Following the change of government in 1970, however, the BBC’s network was halted at the twenty stations (75% coverage) already authorized, and a Bill was introduced providing for up to sixty commercial stations to be established under the control of an Independent Broadcasting Authority (IBA), which would succeed the Independent Television Authority.

The Bill (which is expected to have become law by the time this is published) provides for each station to have both a v.h.f. and a medium-wave transmitter. A low-power medium-wave transmitter on a shared channel gives satisfactory service during daylight, but after dark there is considerable interference between stations.

The BBC’s local-radio studios are designed to be operated by nontechnical staff. A new form of limiter amplifier brings variations in sound level, occurring during a programme, within the range required by the transmitter. The signal is delayed on its way to the gain-controlling circuit, which can thus be brought into action by the time the signal reaches it. In this way, even a sudden loud sound is accommodated without distortion.

 

A man sits at a complicated but streamlined control desk

Stereo control cubicle in Broadcasting House, London: The studio manager faces away from the observation window, and is thus spared conflict between the visual scene and the stereo illusion he is creating

 

Stereophony

In 1958, stereophonic gramophone records came on the market (using a technique patented in 1933 by one of the designers of the Marconi-EMI television system). At the same time, the BBC began to investigate the ‘studio’ end of stereophonic broadcasting, and to radiate experimental transmissions in which ‘Third Programme’ and ‘Television Sound’ transmitters respectively carried the left-hand and right-hand signals; it was appreciated, however, that a practical service would have to await the development of a ‘multiplex’ system for broadcasting both signals from a single transmitter. Several such systems were then under development, and in 1961 the Federal Communications Commission approved one of them for use in the United States; this was the ‘Zenith-GE Pilot-Tone System’, named after the firms that had jointly developed it.

To be successful, a stereo multiplex system must operate within existing channel allocations, and must also be ‘compatible’ (ie must provide an acceptable service for those with monophonic receivers); the problem is, in fact, rather like that of colour television transmission. Moreover, the pilot-tone system has points in common with colour coding methods, a monophonic signal being augmented by a coded signal conveying the stereophonic information. Unfortunately, however, the ear is in some respects less easily deceived than the eye, and bandwidth saving tricks of the type devised for colour television cannot be used. The stereo signal applied to the transmitter has, in fact, over three times the bandwidth of the monophonic signal, and thus cannot be transmitted on medium waves. On v.h.f., where the use of frequency modulation in any case necessitates wider spacing between channels, the additional bandwidth of the signal can be accommodated. The addition of stereo to a transmission makes very little difference to monophonic reception; stereophonic reception, however, cannot tolerate nearly as weak a signal as monophonic reception without becoming noisy.

The multiplex signal in the pilot-tone system may be thought of as coming from a rapidly operating change-over switch, alternately giving connection to the left-hand and right-hand signals. A monophonic receiver does not follow these rapid alternations, but simply reproduces the average value of the left-hand and right-hand signals, this is the required ‘compatible’ signal. A stereophonic receiver is equipped with a ‘decoder’, which contains a change-over switch operating synchronously with the coding process; thus, one output circuit is always connected at moments when the input is conveying the ‘left-hand’ signal, and the other at moments when it is conveying the ‘right-hand’ signal. The switch is synchronized by the ‘pilot-tone’ after which the system is named.

The BBC began field-trials of the pilot-tone system in 1962, and in 1966 regular broadcasts commenced. These were confined to the ‘serious music’ network, and radiated only from the London area’s v.h.f. transmitter at Wrotham. Spreading stereophony to the rest of the country was delayed by the need to use carefully matched circuits for distributing the ‘left-hand’ and ‘right-hand’ signals or, alternatively to use wide-band circuits for distributing the multiplex signal. The latter method was adopted, using radio links, and the service was extended to parts of the Midlands and the North of England in 1968; this gave a population coverage of about 60%, but little further progress has been made by 1972.

Extension of stereophony to the ‘light music’ network (scheduled for Autumn 1972) has been delayed by the need to provide stereo facilities in the numerous studios contributing to this network.

The prospect from 1972

In its engineering aspects, British broadcasting has reached a point of relative stability, with many former uncertainties resolved. When existing plans have been implemented, people living almost anywhere in the UK will have a choice of three colour television programmes and three stereophonic radio programmes, and many will in addition have a local radio programme; moreover, all technical provision has been made for a fourth television network. Both the 625-line PAL colour standard and the pilot-tone stereo system are highly satisfactory, and likely to remain in use for many years.

Radio broadcasting

In the 1950s, many engineers thought that as soon as a v.h.f. radio service was established, medium-wave broadcasting would rapidly lose importance. In fact, the imminence of commercial radio, which depends upon a mass audience that v.h.f. cannot yet command, has created an urgent new demand for medium-wave channels.

It is too early to say whether the additional realism made possible by ‘quadraphonic’ sound (four-channel stereo), with two speakers in front of the listener and two more behind him, will eventually cause it to supersede two-channel stereo as the norm for high-fidelity reproduction. Nor can it be said which of numerous competing schemes for achieving quadraphony would be used. Any four-channel system adopted for broadcasting, however, would have to be compatible with the existing pilot-tone stereo system.

Another recent development in sound reproduction, stimulated by stereophony, has been a revived interest in headphones. For the solitary listener, headphones can provide high fidelity more cheaply than loudspeakers, avoid disturbance to other people, and reproduce stereo signals with a striking illusion of immersion in the performance, though they cannot, of course, provide quadraphonic reproduction. Headphones incorporating a v.h.f. stereo receiver have been marketed, offering stereophony to listeners ‘on the move’.

Television broadcasting

The possibility of broadcasting from satellites to small communities or even to individual viewers is receiving much study, but its initial application is likely to be in those developing countries where scattered communities cannot economically be served by existing methods of distribution.

Considerable uncertainty exists over the extent to which broadcasting will be affected by two recent innovations which offer alternative sources of television.

The first of these is the extension of the ‘wired’ system by which many people, especially those living in ‘difficult’ areas, receive their programmes. Though traditionally such systems have simply been an alternative means of distributing the normal broadcast programmes, in America there has been an increasing tendency for the operators to originate programmes as well, and since April 1971 the Federal Communications Commission has actually required the operators of all systems with more than 3,500 subscribers to originate programmes on at least one channel. In Britain, on July 1 1972, Greenwich Cablevision Ltd began to distribute locally originated television programmes, free of advertising, in addition to those of the BBC and the ITA. (The viewer pays an inclusive rental for the service, which thus differs radically from ‘subscription television’ systems, in which he pays for individual programmes of ‘premium’ calibre, such as new feature-films. A service of this type was operated by Pay-TV Ltd for a trial period in areas of London and Sheffield from 1966-8, but the company was disbanded after the Postmaster General imposed restrictions on continuation of the service.) The significance of this development lies in the fact that it is feasible, technically if not economically, for a wired system to provide many more channels than can be provided in any one area by broadcasting.

The other innovation is the development of various ‘video cassette’ systems which enable the viewer to reproduce recorded television programmes on a normal receiver. In some systems, the programme material must be bought or hired ready recorded, but others are essentially domestic videotape recorders, permitting the viewer to record programmes ‘off the air’ or even to produce his own material from a television camera. It remains to be seen whether any of these systems will become cheap enough for widespread use.

 

Your comment

Enter it below

A member of the Transdiffusion Broadcasting System
Liverpool, Saturday 28 January 2023