The process that led to the opening of the world’s first regularly scheduled high-definition television service by the BBC in 1936 was a long and complex one, employing not one but two almost incompatible systems, brought together by uniquely British compromise. In these two articles, Richard Elen tells the story of how high-definition television came to London.

Part 1: Baird and the BBC

“Gentlemen, you have now invented the biggest time-waster of all time. Use it well.”
– Isaac Shoenberg, head of the Marconi-EMI TV development team

Baird with the innards of a 30-line mechanical Televisor receiver
(from "Television Comes To London", BBC, 1936)

John Logie Baird is rightfully regarded as the father of television, but the experimental “low definition” transmissions on medium wave that the BBC, after continuing lobbying of the Postmaster General, Sir William Mitchell-Thompson, by the Baird company, began, from September 30, 1929, to transmit on 2LO from Baird’s studio facility at Savoy Hill were hardly representative of the shape of things to come.

The single broadcast wavelength was not able to carry both sound and picture, and as a result the test transmissions had to alternate between sound and vision until the following year, and were carried on outside normal broadcasting hours. And most important of all, the pictures, by modern standards, were terrible.

The first photo of a television image ever published:
a screen shot from Baird's Televisor in 1926.

Baird’s television system at the time consisted of a mass of whirring discs at both the transmission and the reception end of the system. The transmission mechanism was almost completely counter-intuitive.

With the “flying spot” method used initially, a rotating disc with 30 holes punched in it had a powerful lamp behind it. As the disc rotated, a spot of light scanned the object in the studio while banks of photocells registered the changes in reflected light intensity, and these changes were amplitude modulated on to a medium wave carrier.

The “lighting” of the object could be changed somewhat by varying the sensitivity of the photocells, but the basic picture was created from no more than 30 vertical, slightly curved lines, at a rate of 25 frames per second. Shadowy heads and shoulders were the best that could be managed.

Viewed on a Baird “Televisor”, of which several thousand had been sold over the previous few years while Baird was transmitting experimentally from his own premises, the tiny, flickering picture, effectively 4 in high by 2 in wide, was seen through a lens looking at a modulated neon lamp through another spinning disc, rotating in sync (you hoped) with the wheel in the studio.

Synchronisation was a difficult trick to manage, and there were even crude videodiscs produced which could help you get your machine up to speed before the beginning of transmissions. If your receiver drifted out of sync, the picture dissolved into meaningless dots and lines. Such was the experimental “low definition” service from the BBC.

There were some notable firsts, however, including a performance of Pirandello’s play, “The Man with a Flower in His Mouth” – the first play to be performed on television in Britain, on July 14, 1930, and produced with the assistance of the BBC’s Programme Branch.

The set of Pirandello's play, "The Man with the Flower In His Mouth",
the first play performed on British television, in 1930. Note the chequered
"fade board" on the left - see text. (BBC)

The area that could be illuminated by the flying spot and reproduced with 30 lines was so small that only one actor could appear on “stage” at a time, with a special “fade board” of chequered squares slid in front of the photocells when it was necessary for a new actor to appear. And if any movements were too sudden, the system was all too likely to lose sync.

The BBC Control Board was not particularly pleased with the results. On July 22, 1930, they decided to suspend programming involvement and continue solely with engineering support, the minimum they were obliged to give Baird under their orders from the PMG.

Technical advances

The Baird Company found a method of using the flying spot scanner to broadcast movie film, and as a result developed the earliest “telecine” apparatus, which worked with some success.

A new scanning system based on a rotating drum with 30 angled mirrors was brought into use, with some initial difficulties including the mirrors flying off and causing considerable consternation, if not damage, and the photocells improved to the point where they could be mounted on movable stands and angled and positioned carefully, to be used as the equivalent of spotlights.

The first outside broadcast followed, and then the Derby was televised live in June 1931 and with higher quality the following year. Noel Ashbridge, who had replaced P.P. Eckersley as the BBC’s Chief Engineer, advised Lord Reith to take television seriously, and on August 22, 1932, basement studio BB in the newly completed Broadcasting House was opened, and the BBC began a regular television service, albeit still experimental and still low-definition. Vision was transmitted on 261.3 metres and sound on 398.9 metres, medium wave.

In 1934 the studio moved from Broadcasting House up the street to a specially converted studio at 16, Portland Place.

The Baird 30-line studio at 16, Portland Place, around 1934. Note the forerunner of the "Wooden Mickey" caption carousel in the foreground. L to R: Tony Bridgewater (sound), John Bliss (vision) and Desmond Campbell at the flying spot "camera".

In addition to the main flying spot system there was a second scanner in the control room that was pointed at caption cards about the size of postcards, such as the one shown below. The two “cameras” could also be mixed, and used for primitive matting of an actor in the main studio with scenery on a caption card.

Recreation of a BBC Caption Card from the 30-line service (R. Elen).
The card is visible on the carousel in the photo above.

Transmissions were now broadcast from the transmitter at Brookmans Park. Receiver technology improved, with the development of mirror-drum-based receivers, but the 30-line video was still flickery and indistinct, particularly after having travelled the phone lines to Brookmans Park from central London.

The Second System

But meanwhile, something else was happening. Television had been hampered by the fact that the ideas that went into it were some way ahead of the technical capability to implement them.

The rotating disc method had been patented by Nipkow in 1884, but it was not until the twenties that Baird was able to get it beyond the shadowy images stage, while in 1908 A A Campbell Swinton had written to the journal Nature indicating how “distant electric vision” could be transmitted and received by means of the cathode ray tube.

Again, the realisation of this all-electronic method of creating and decoding a television signal required the development of valves and improvements in the sensitivity of photoelectric materials – but these were to come.

Vladimir Zworykin, working for RCA in the USA, and J D McGee at EMI, evidently developed the first cathode ray “camera” tubes independently. EMI had already made progress with CRTs for use in television receivers – including receiving 150-line mechanically generated signals – and ultimately with the help of all-round genius Alan Dower Blumlein, McGee and W F Tedham, initially secretly, managed to transmit a picture all-electronically across the laboratory in 1932.

Making an EMI "Emitron" camera tube.
The light-sensitive mosaic can be seen inside the tube
(BBC - "Television Comes To London")

Their camera used a light-sensitive mosaic that was discharged pixel by pixel as an electron beam scanned it, the discharge current intensity being proportional to the light falling on the dot.

At the other end, a CRT’s electron beam scanned a phosphorescent screen in sync with the transmission end, and lit up phosphor dots in the screen when they corresponded to illuminated dots in the camera mosaic.

By the end of November, EMI had shown the BBC a 5 inch-square CRT receiver capable of receiving 150-line mechanically generated transmissions via VHF over a distance of two miles. EMI wanted the BBC to begin transmissions with their system the following year, but to avoid political problems and because the EMI system was at that time only capable of telecine operation, Sir John Reith at the BBC preferred to keep the Corporation’s research with EMI under wraps.

Luckily, the head of the EMI television team, Isaac Shoenberg, did not give up, and when Zworykin published information on his “iconoscope” in 1933, the team was able to read between the lines enough to know that their “Emitron” was virtually identical.

Knowing they were on the right course, EMI brought additional resources to bear, working not only on cameras but on higher vacuums and on improving the performance of receiving-end CRTs, developing screens larger than 7in and a true black-and-white display rather than the black-and-green previously demonstrated.

Baird knew by now that there was competition in the wings, and tried to smear EMI by claiming that theirs was an American-controlled invention, although Shoenberg had turned down an offer from RCA, feeling that EMI were in front of the Americans technologically and that they had little, if anything, to learn from them.

EMI showed a 120-line all-electronic system to the BBC and the GPO, who regarded it as superior to Baird’s latest effort, which was now also offering 120 line images, telecine and a CRT-based electronic receiver. Baird increased the number of lines to 180 and began to use VHF for additional bandwidth, as EMI were already doing.

Initial electronic transmission demonstrations to EMI management in early 1934 were disappointing. Their mechanical transmission system was now up to 180 lines and the electronic images, initially, were vastly inferior.

But by April, they had significantly better results. EMI built a vision mixer with six channels – two telecine and four Emitron cameras – and were able to run a camera outside the Hayes factory by the local canal as well as cameras in the studio and for telecine to show the system off to the BBC when they came to visit, on 18 April 1934.

Early Emitron cameras like this one did not have viewfinders
(BBC - "Television Comes To London")

The BBC’s Engineer In Charge of Television, Douglas Birkinshaw, quoted in Bruce Norman’s impressively-researched (if not always 100% accurate) work on early British television, Here’s Looking At You, noted: “No whizzing discs, no mirror drums: silence, lightness, portability. It showed the way things were going. It was quite easy to see, even then, that the Baird system couldn’t eventually lead anywhere…”

He felt that it was inevitable that TV would have to provide outside broadcasts, and with the Baird system’s heavy, fixed equipment, this didn’t seem possible.

Following his success in the telecine field, Baird borrowed an idea from his licensees in Germany, where they had developed a system of using a film camera to shoot studio images, the film going instantly into baths of developer, fixer and then water, and while underwater was scanned by a flying spot scanner.

The British implementation of the system – called the “Intermediate Film Technique” – worked, some of the time, but it had problems with underwater air-bubbles interfering with the sound, and also with the fact that it needed lethal cyanide developer to get the processing time down to “almost instantaneous” – in fact it took just under a minute.

Baird, obliged to begin to consider electronic transmission technologies, somewhat half-heartedly struck up a relationship with American Philo T. Farnsworth, whose system, although it had major flaws that Baird might have been able to sort out, did produce electronic pictures.

High-Definition Considered

In the middle of 1934, the government set up the Television Committee, under the chairmanship of the Postmaster General Sir William Mitchell-Thompson, now Lord Selsdon, including BBC, government and GPO representatives.

Its job was to evaluate the possibility of replacing the existing low-definition service with a high-definition successor, and which system to use to do so.

Baird was by now offering a gamut of technologies including 30-line flying spot, Intermediate Film at 180 lines and telecine at 240 lines, 25 frames per second, all using mechanical scanning. There was also the Farnsworth all-electronic option if they could iron out its problems. EMI, now working with Marconi to provide them with transmission capability, were officially offering 240-line mechanically scanned telecine and little else – as their electronic system was still in its infancy.

Shoenberg decided to take the plunge and committed the Marconi-EMI team to delivering 405 lines, 50 frames – and, giving up drum scanning, to all-electronic signal generation. It was an incredible leap of faith.

The Selsdon Report

The Selsdon Report was issued on January 31, 1935, and Lord Selsdon announced that there would be two systems of television for the London High-Definition TV service: Baird and EMI, chosen from half a dozen contenders. High-definition was defined as a minimum of 240 lines, 25 frames – the limit of the Baird system. The two systems would run side by side for six months, alternating programmes.

After the event, it became evident that there had been political motives behind this complex and expensive compromise – protecting the government and the Post Office from criticism that would have resulted from excluding Baird, who was, of course, the pioneer television broadcaster.

It also seems that they saw bankruptcy of the Baird company, already in financial difficulties, as likely and didn’t want to that to be blamed on their excluding Baird either.

On September 11, 1935, the BBC closed down its low-definition service, which certainly was a blow to Baird, and orphaned the several thousand medium wave mechanical Televisors already in the marketplace.

High-definition TV was coming to London – and the BBC had just eighteen months to do it. Gerald Cock, formerly the BBC’s Outside Broadcast Director, was appointed Director, Television Service.

To Part II - "Magic Rays of Light"