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Mechanical Television at the BBC

After more than three years of self-supported broadcasts from the Baird Company's premises at Long Acre, in 1932 the BBC reluctantly decided to take on television broadcasting on its own using Baird's 30-line system.

The Baird Company was to design and build the new equipment which the BBC would lease for the duration of the 30-line television production time frame. Facilities were granted in the newly constructed Broadcasting House in Studio BB, in the sub-basement of the building. Originally intended for Henry Hall's Dance Band, the studio was a double-height room boasting a 19 foot ceiling and a small balcony, in total measuring 29 feet by 18 feet with a small, 90 square foot adjacent listening room that would serve as a small but usable control room.  This would be the home of all 30-line broadcasts until February 1934 when the facilities were moved to a larger studio in another BBC building just down the road at 16 Portland Place. 


Eustace Robb was recruited from the gramophone department to be the first television producer and proved to be the perfect man for the job, introducing new production techniques and pushing the limits of 30-line technology. One of the first improvements he made was to replace the brand new studio's carpet with a linoleum black-and-white checkerboard pattern to help create contrast and the illusion of depth on the screen, much to the irritation of the management.


Mannequin parade fashion show in 1932. The devices on stands are photocells, acting as studio lights. The window to the control room is behind the left mannequin.

The Baird Company also agreed to transfer three of its engineers to the BBC to help with the infant medium. Tony Bridgewater, Douglas Birkinshaw, and Desmond Campbell (whose initials notably spell BBC) made the move to the new building. Although improvements and tweaks had been made to the 30-line system since its launch, the format itself had to remain the same as it was in Long Acre to keep compatibility with the Televisors already on the market.

The sound and vision signals were broadcast on two different wavelengths, since at this time it was not possible to combine the two into one radio channel. Vision went out on 261.6 meters (1146 kHz) via the London National transmitter, and sound on 398.9 meters (751.5 kHz) through Midland Regional.  This meant that two radios were needed, to receive picture and sound but it was assumed that those who were able to buy or build a Televisor would also have access to a separate receiver. The half-hour long programs were made live Monday through Friday (except for a day off on Wednesday) at 11pm after the ordinary radio broadcasts had finished.


V.C. Clinton-Baddeley and Josephine Baker. The object on the pedestal in front of Josephine is the BBC's "bomb" microphone.

Although the late hour was a drawback for many "lookers-in", there was one unintended benefit of broadcasting at this time. Medium wave broadcasts propagate very well at night, when the effects of the sun on the atmosphere are minimal. This, coupled with the fact that most other radio stations had already signed off for the evening meant that reception was possible over huge distances. Letters from viewers were received from across the continent, and as far as Iceland and North Africa.


The Equipment

The Projector-Scanner

At this time, it was more practical to use the Flying-Spot method of televising over the Flood Light method. This required a light spot projector-scanner, simply called the Projector, to act as the primary "camera" for the studio. It was responsible for throwing the light beam in the form of a raster out into the darkened studio, and was required to be able to focus all the way from a "long shot," where the whole person was visible, to a tight close up of the head and neck. This was a massive machine nestled into the comparatively tiny window in the sound-proof wall between the studio and control room. John Logie Baird himself remarked to a reporter before the inaugural program at the BBC that the thing looked like a machine gun.

The scanner was specially designed by Baird company engineer extraordinaire J.C. Wilson for the limitations of Studio BB.5 Inside was an 8" diameter by 5.75" wide mirror drum and a 10 amp Ziess carbon arc lamp mounted underneath it on a running shoe. The lamp slid forwards and backwards on this shoe to facilitate focusing. Directly in front of the shoe was a disc with four small nickel diaphragms mounted on it, each one holding a square aperture to give the projected light beam it's size and spot shape. Only one aperture was used at a time- the others were spares in case the heat from the arc lamp burned the diaphragm. The light shining through the aperture passed through a fixed lens before being reflected onto the mirror drum by a small mirror in the front of the projector (see diagram.) The entire apparatus rested on a set of tube steel rails and could be slid from side to side as well as panned within the 5 ft x 20 in window.  Thus, it could follow the action of the performer. This new feature compared to the previous "staring eye" at Long Acre was probably the single most important improvement in 30-line television's development.

The Projector-Scanner (with side cover removed) and its panning platform and rails in Studio BB.

The internal components of the scanner (left) and the overall layout diagram of the system (above).




To reduce gyroscopic forces on the motor and drum during quick panning movements which could destabilize the picture, the small mirror in the nose could be rocked sideways over a small angle to follow the performer. This accounted for the width of the mirror drum. For close ups, a field lens was swung in by the operator between the drum and the nose of the projector to reduce the size of the scanned area. Without it, the performer would have to squeeze his or her head inside the projector housing to fill the picture!


The nose of the projector also contained a pair of metal jaws, called the gate, that defined the shape of the scanning area; these could also be adjusted vertically as a whole to allow for tilting, but it is unclear if this was done dynamically "on the air" or pre-set during a show's preparation. The projector-scanner had a few other bells and whistles, including a pair of color filters that could be inserted separately or together to make the light less bothersome during certain acts, like musicians playing a stringed instrument, where beat interference from the beam could cause a distraction. These filters reduced much of the visible light, but allowed most of the near-infrared light to which the phototubes were most sensitive, to pass.


Caption Scanner

Operating in conjunction with the projector was the Caption Scanner, a conventional Nipkow disc-based flying spot scanner fixed in position to scan a small area 2 1/4" wide by 4 3/4" tall.  In truth, this machine didn't come into use until after the move to 16 Portland Place,   but due to it's importance to the quality of the transmissions, I am mentioning it here. In front of the scanner was a plywood board where a paper caption would be placed, and a pair of photocells facing it to pick up the reflected light. Later on the plywood was replaced by a 12-sided wooden drum holding multiple captions that could be rotated, ready to bring in the desired caption when needed. 



Both scanners were driven with synchronous motors, locking them to the local power grid's AC frequency, and ensuring that they would remain in perfect step. By locking them together in this way, the currents from the photocells from both scanners could be mixed, creating some artistic effects. For example, a doorway could be drawn on a caption card, then mixed in with a dancer in the studio to give the effect of the performer dancing in a large room.


Television control room at Portland Place in 1935. Projector "camera" operator is on the far right, followed by the vision engineer, and the sound engineer on the left. The caption scanner is in the foreground. 

John Swift best describes the atmosphere of these pioneering transmissions in his 1950 book, Adventure in Vision- the first 25 years of Television" (page 57):

"For eighteen months broadcasts were made from Studio BB. They were intensely exciting months. They saw a remarkable procession of notabilities representing the theatre, film, sport, industry and the professions in programmes under the guidance of the first television director, Eustace Robb, who left the gramophone department for the adventure of television. Ballet was attempted on the spacious (for those days) black-and-white checkered floor that became the most familiar setting on the screen."

Examples of captions used during programs. The two on the left announce the name of the artist.

"Of nine out of ten of these early 'subjects for television' it can be said, however, that they regarded it as great fun-- adventure. Everybody who agreed to appear and anything that could appear went down the lift-shaft into the [basement] studio. Boxers and ju-jitsu wrestlers, mannequins and news-vendors, art treasures and model railways. Animals-- wild, tame and pet- were brought by their owners or guardians to be put through their paces by this happy family of pioneers who exulted on surprise items." Birds, reptiles and a monkey made their small screen debuts in the basement studio amid the flickering lights.

On one occasion, Sammy (also credited as Sally) the performing sea lion arrived at the BBC main entrance by car after a local show for her television performance, prompting an internal memo stating: "For Your Information: Performing animals will, in future, only be admitted to the BBC by the goods entrance."


Broadcasting on 30-lines continued until September of 1935, well after higher definition non-mechanical systems had been built and tested. However, it was not until 1936 when the so-called High Definition electronic television service using cathode ray tubes was finally put on the air, leaving the country with nothing to watch for almost a year.

The new high definition service was undoubtedly better than the mechanical method, so much so that the old "spinning disc" television developed a stigma   of poor quality, not only in picture clarity but also in the performances. This is unfortunate, given the effort put into these programs (especially compared to the United States, where television on mechanical systems were by rule restricted to experimental, non-commercial transmissions only). However, several short snippets of the vision signal as broadcast from the BBC were preserved by amateurs who recorded them onto metal audio discs using simple "novelty" home recording equipment. Although highly degraded by time and the recording process, the recordings give a hint at what was being seen back in the day. They are discussed in detail on Don McLean's website, All in all, these scratchy recordings, a small handful of staged off-screen photos, and some written descriptions and articles are all that remain of one of the first "official" broadcast television systems.



1.   Bridgewater, T. H.  Just a Few Lines... The Birth and Infant Years of BBC Television British Vintage Wireless Society, 1992 p. 4

2.   Ibid., 10

3.   Ibid., 16

4.   "The BBC 'First Night'", Television, September 1932, p. 243, quoted in John Logie Baird: A Life Edinburgh: NMS Publishing, 2002. ISBN 1-901663-         76-0

5.   Ibid. 1, 6

6.   McLean, D. F. Restoring Baird's Image, IEE, ISBN 0 85296 795 0, September 2000 p. 185

7.   Birkinshaw, D.C. "The B.B.C.'s New Television Studio, An Official And Exclusive Description", Television, April 1934, p. 142

8.   Wilson, J.C. "The Design of Television Transmission Equipment" Journal of the Television Society, Vol. 1, p.257

9.   Robb, Eustace. "Putting Vision on the Radio Programmes", Television, June 1934 p. 280.

10. Bridgewater, T. H. Interview by Bruce Norman in 1984, included on the CD The Dawn of Television Remembered, disc 2, by Don McLean, 2005.             0048-4a-THBridgewater.mp3, 8:05.

11. Norman, Bruce. Here's Looking At You: The Story of British Television 1908-1939, British Broadcasting Corporation and the Royal Television                   Society, 1984 p. 83

12. Ibid. 6, 270

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