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[Door opens, footsteps]

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[Creak!] [THUD!]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[vaccum cleaner noise]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[TV static noise]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[Steam hisses]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[sewing machine rattles]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]
[*Whoop!*]

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[Jazzy music: 'The Russians Are Coming' - Val Bennett]

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Of all the machines in the home, the television is probably the most mysterious

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The very idea of a machine taking something out of the air and converting it to recognisable pictures

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would probably seem quite absurd if it hadn't actually already been invented.

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And all that's inside these machines is a mass of equally mysterious bits and pieces,

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none of which appear to do anything at all.

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There are basically two things inside a telly:

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the circuit boards that process the signal being picked up by the aerial,

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and the picture tube, or cathode ray tube, that actually creates the picture you're looking at now.

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We'll be looking at both in detail later on, but surprisingly the idea of television

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started long before the days of electronics and cathode ray tubes .

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While an electric telegraph cable was being laid across the Atlantic in the 1870s

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it was noticed that the resistance readings were varying according to the light falling on the instrument.

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[thunder]  Man: Oh no. Rain...
Man2: Quick, close the door.

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Man: Now look at this, look at that!  ...how did that happen?
Man2: I say! The needle's moved.

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Tim: The reason was this resistor, made of an element called selenium.

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If we cover it up, you should be able to see the resistance change.

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Not very spectacular, but this chance observation out in the middle of the Atlantic,

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was really the first tangible evidence that light could interact with electricity.

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This discovery, coming at almost the same time as Bell's discovery of the telephone

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led to a rash of speculation that communicating in vision as well as sound would soon be possible,

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but no one could make it work.

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One of the reasons was the inadequacy of the selenium itself,

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it actually reacts quite slowly to a change in light.

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much too slowly to be any use for television.

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After the initial failures, more theoretical proposals for television appeared

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in the early 1900s, incorporating the newly invented cathode ray tube.

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But it wasn't until the 1920s, when powerful valve amplifiers

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and fast reacting light sensitive materials had been perfected

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that the technology to make television possible had really arrived.

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A Russian physicist Vladimir Zworikin who had emigrated to America

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patented an all-electronic system in 1923.

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Zworikin: But I was keeping after my boss all the time, for permission to work with television

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so finally after several years I was given the permission to do it.

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Now was the work I was looking for long time.

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So I put my, all my efforts in this thing; I work days and nights practically,

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and, er, after about year or so assembled, all a system,

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including the cathode ray pickup tube, which I called iconoscope,

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and cathode ray receiving tube, which I called kinescope, from greek words.

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Tim: Needing more money for research, Zworikin arranged

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to show his pictures to an executive from Westinghouse where he was working.

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Zworikin: He wasn't very impressed.

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So finally he ask me a few question, mostly how long did I work with this system, and so on,

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and departed, saying few words to the director of the laboratory.

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Later on I found out, what he said was "Put this guy to work on something more useful".

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Tim: So Zworikin's system was delayed, which left the field open for a young Scottish inventor.

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John Logie Baird was one of the least academic early experimenters.

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In his youth, he worked as a mechanic, while also embarking on entrepreneurial schemes.

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Man: Actually, I was wondering about the undersocks, do you have any on the go at the moment?
Baird: Aye, aye, the undersocks, aye.

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Baird: That's a wee sideline of mine.

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Tim: He also attempted to make articifial diamonds, using the facilities of the powerstation where he worked.

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Baird: This will make me famous...

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...create diamonds.

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[chugging noise]

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[BANG!]

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Tim: Dogged by ill health, he then moved to a warmer climate: Trinidad.

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Here he made attempts to start up a jam making factory, but was defeated by the local bees.

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People: Argh, Owww, arrgh!

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Baird: I think everything's ready isn't it?
Man: I've got the high-voltage...

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Tim: Back in Britain, he then started his experiments for 'seeing with wireless'

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attracting a group of enthusiastic amateurs around him.

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By 1924 he had a crude mechanical system transmitting silhouettes.

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"Oh, look!" "There it is!" "Ooh, super!" "Spiffing!"

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Tim: His main contribution to the history of television

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was really his flair for publicity, exciting the public's imagination.

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[Woman warbles away on television set]

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[Applause]
Man: Marvellous!

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Tim: He also gave sets to very important people.

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Journalists: Morning Mr Baird, just one there, thank you thank you...
Baird: Mr MacDonald, here's your televisor.

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Finally, in 1936, the BBC arranged trials of Baird's television

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BBC man: Good morning Mr Baird, we are the BBC of course, we will be with you in a moment.

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In competiton was EMI's all-electronic system, similar to Zworikin's.

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[BBC mens footsteps]

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Tim: Baird's cameras were cumbersome and immovable.
[Singing]  Camera tech: You're moving too much!

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[Plane flying around]
Tim: In contrast the EMI cameras were compact and completely portable.

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[Plane noise getting rapidly louder!]

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So Baird lost the competition.

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But undeterred, he continued improving his system,

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and in 1946 showed a giant colour picture.
[people on television set making sighing noises]

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But a week later, he died, aged 58.

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Tim: Since then all television has been based on the EMI electronic system.
[Whistle blows and marching music]

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Woman: This is direct television from the studios at Alexandra Palace.

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[Rousing nationalistic music]
Woman: Now you are going to see and hear someone you know well.

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[music]
Adele Dixon): # A mighty maze of mystic magic rays,

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# Is all about us in the blue.

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# And in sight and sound they trace,

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# Living pictures out of space,

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# To bring a new wonder to you.

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# There's joy in store,

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# The world is at your door,

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# It's here for everyone to view.

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# Conjured up in sound and sight

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# By the magic rays of light,

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# That bring Tele-vision to you. #

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[Music fades]

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Tim: The heart of any telly is the picture tube itself

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erm, if you look inside, you can see there isn't much inside really.

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In fact there's nothing at all, it is normally a vacuum when it is working

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We usually think of electricity flowing in wires, but under the vacuum inside the tube

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electricity is actually flowing from the neck to the screen,

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as a sort of invisible beam a stream of electrons..

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The inside of the screen is coated with chemicals called phosphors,

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and it is actually these phosphors that you are watching at this moment glowing behind your screen.

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The television tube needs a high voltage between the neck and the screen to make the electrons flow.

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You can see this wire going to the screen does rather look like the spark plug lead of a car,

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which also has a high voltage.

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The device which creates the high voltage in television does have other uses.

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[Rex's footsteps]
Rex: I made this plasma lamp entirely out of old television components.

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the main components being the line output transformer,

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and transistors, which supply the television with a high voltage.

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It's quite a fun thing.  They're sold in some of the large department stores

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for an amazing amount of money - approaching £2000, some of the bigger ones.

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Erm, this one was a total cost of, I suppose £7 or £8.

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[Didgeridoo music]

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This is the national museum of film, photography and television in Bradford.

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And this part is all about how television works.

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I helped design it with the curators a few years ago.

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In this first display you can see the spot of light

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caused by the electrons hitting the phosphors on the back of the screen.

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If I hold a magnet over the screen, the spot moves,

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because the beam of electrons is attracted by magnetism.

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And with a electromagnet strapped round the neck of the tube,

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the magnetic field can be very accurately controlled,

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so that the spot can be moved precisely anywhere on the screen.

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And of course if I move the spot into this patch where we scraped

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the phosphors off, the spot will disappear.

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Also, by adjusting the instensity of the electron beam,

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the brightness of the spot can be varied.

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In a television the spot is made to scan the screen line by line,

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The image is formed by varying the intensity of the spot as it scans.

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This model uses ink marks on string to represent the variations in intensity

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of the scanning spot. So you can see how the picture builds up.

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So if we increase the scanning speed, the illusion of a complete picture

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starts to appear.

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The sharpness of the picture depends on the number of lines,

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todays sets have 625, the original EMI system had 405 and Baird's had only 240.

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Gerald Wells, who runs the West Dulwich radio museum, has collected some of the first domestic television sets.

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His earliest set doesn't look like a television at all.

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Gerald: It's a model 900, and it's probably the first television in the country of its type

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and it was bought out in time for television, originally it was dual standard and switched

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for 240 line, and 405 lines so you could watch with the Marconi-EMI system or the Baird system.

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Tim: It doesn't look like a television.
Gerald: No, it doesn't, because in those days the early

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cathode ray tubes were so long in the neck, the only way you could

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mount them was vertically, with a mirror in the lid

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and reverse the scanning coils so the picture was the right way round,

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and you actually watched it in a mirror.

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You can watch it in that position for sitting position,

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or you could turn it up like that and watch it in the standing position.

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Or you could close it down altogether, and it would just look quite inoffensive sort of cabinet.

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As nobody could afford that model, at £100 a go,

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Marconi-EMI bought out the 707 and the 705, which was a 5" and 7" set

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respectively, which would sell for 29 guineas and 31 guineas.

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They maintained that even if a television system failed,

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and they had a sort of idea that it might be shut down, somehow or other,

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that at least you had a good quality radio for your money.

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Although then you started getting screens larger again,

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you started off with screens at 9", no 12" then went down to 5" and 7"

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and gradually they crept up to 9", with this model, erm, erm, the 709.

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Which was quite a fine receiver, this one's working a bit,

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and also a first class radio, this came out at about £60

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and was currently in the shops up till the outbreak of war.

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Tim: Which is the earliest example of a post-war set?

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Gerald: Well, I'd say it was this 9" Pye here.

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Pye's didn't do anything astounding before the war with television,

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they made a few that weren't particularly brilliant, and then

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after the war, with the experience they gained from radar and

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the money they'd made out of the war, they ploughed back into the company.

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They produced this thing, it was an absolute work of art.

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Tim: It looks much more compact.

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Gerald: It's very compact, beautifully designed, easy to work;

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had a little panel on the front where you could get at the

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line-hold and frame-hold controls to adjust it,

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gave a high definition picture, mirror backed tube.

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and all the technology that we'd learnt during the war came out in this, it was brilliant.

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Tim: And this portable here, what date was this?
Gerald: Well it's not exactly portable, lets see.

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Little 9" Bush which came out in 1950.

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A lovely little bit of engineering, also slightly out of adjustment,

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and erm they made use of a jelly mould, the bakelite, lovely substance.

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It matched their the 1890 radio they bought out at the same time,

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It was small, it was compact, it didn't have a large mains transformer in it,

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it was miniture valves, and modern plastics again.  This was alot said:

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You couldn't kill yourself on one of these, well you could if you were actually stupid,

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but these sets were absolutely lethal, in fact before the war,

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the main insulating materials was paper, tar, wax and varnish.

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A first man to be killed by a television was a friend of mine,

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and that happened at Newton Le Willows in the 50s.

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On a set I'd actually taken up there, that one of that model.

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So, erm, it really brought home to me very definitely how dangerous these sets were.

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Tim: So this was...
Gerald: No second chance ever.

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Tim: So this was a big improvement?
Gerald: One touch of that and you're in the service department in the sky, hmm, you've had it.

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Gerald: But these, if you did catch hold of a high voltage, the resistance of the skin,

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the moisture in the body, would collapse the voltage.

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Gerald: So apart from a very nasty burn,
Tim: hmm,

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Gerald: Sometimes you weren't even really aware that you'd burnt yourself until you came to wash your hands in Ajax.

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And then you knew all about it. But it certainly didn't kill.

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Tim: The pictures on these old televisions now have to be converted

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from today's 625 lines, to the old 405 line standard.

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This convertor is a bulky machine and Gerald's now got such a large

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collection of televisions and radios that the only place he could find for it was next to his bed.

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Tim: Colour television uses three different colour phosphors, red, green and blue,

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with a fine metal mesh behind.

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This mesh has a grid like pattern of tiny holes ,or lozenge shapes.

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This is a mesh we've taken out of a telly, and if I hold a torch behind it, you can see the holes clearly.

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Inside the tube there are three electron guns, and three separate streams of electrons.

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[Beep!]

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[Beep!]

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[Beep!]

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The mesh, or mask blocks the electrons and only lets them through the holes.

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So each beam hits the screen in slightly different places.

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[Beep!]

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[Beep!]

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Inside the screen, the three coloured phosphors are laid in fine strips,

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here shown greatly enlarged.

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When the mask is in place, each electron gun,

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here shown by holes in white card, only reaches one colour of phosphor.

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Now look closely at an actual television: You can see

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the gridlike pattern over the whole screen, created by the mesh.

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And if you look even closer, through a magnifying glass, you can see

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the three coloured phosphors.  As the picture changes, you can see any colour

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can be created by just varying the relative intensity of the three phosphors.

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Even white is obtained by mixing the three.

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[whirring noise]

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[clang clang]

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Rex: We made this wind powered clock at the Liverpool Garden festival a couple of years ago.

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The windpower generator on top merely charges this battery, the battery

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powers the electronics, and the electronics supply an impulse to this windscreen wiper motor,

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which actually drives the clock movement round, every 30 seconds.

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Now when I developed that clock unit, I did the electronics indoors in the workshop,

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and it worked perfectly, and I left it on test for about a fortnight. 

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I bought it out here, installed it in the clock,

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had second thoughts that I'd connected it wrong, so I reconnected it,

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and this time I connected it backwards, and blew the whole lot up,

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every transistor and every chip, and had to start from square one again.

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And as a friend said, it's easy to make something which is foolproof,

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but it is very difficult to make it idiotproof.

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You could soon connect something backwards, and you can't see that you've done anything wrong.

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You know, but when you, when you actually err go to connect it up, 

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you get a big bang, a puff of smoke and all your work is gone.

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You've wasted a fortnight.

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Tim: I think it's because electronic components don't move, or give any indication

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of what they're there for, that it's so easy to make mistakes like Rex's.

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The electronics in a television, which process the broadcast signal,

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and power the loudspeaker and tube itself are very complicated.

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But they're not quite as baffling as they first appear.

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One thing which makes electronics less intimidating to me,

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is that all the circuits are made up of a relatively small number of different types of component.

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I can show you quite a lot of these just with a lightbulb and a battery.

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A resistor just acts like a restriction, and makes the light dimmer. 

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so twice the resistence makes it dimmer still. 

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A diode lets the electricity flow one way...

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...but not the other. 

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A capacitor stores electricity only letting the current flow until it is fully charged.

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It can then release its stored electricity again, when connected straight to the bulb.

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A transistor often acts as a sort of switch.

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The tiny amount of electricity from a battery made of a potato,

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can switch the main battery and power the headlight.

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In fact over 90% of the components on this board, are like the ones I've just shown you.

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The integrated circuits, are just, really just a lot of components all sandwiched together, mostly transistors.

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I do admit that when you start joining everything together, the circuits very quickly become very complicated.

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The other thing that helps to reduce my intimidation about electronics,

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is that you often don't need precise knowledge of a circuit to mend a fault.

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Rex: When a repair man repairs your telly,

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some of the faults are blatantly obvious as soon as he takes the back off:

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components are either burnt out, or been smoking and you can

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actually smell the pungent smell from some of the components actually burning.

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Other faults are fairly obvious like erm, dry joints on the solder.

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That's when the solder hasn't flowed properly onto the component on the circuit board. 

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Although the circuit looks really complicated,

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it can be rather likened to a road map of the British Isles.

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And if you were travelling between London and Brighton, for instance,

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you're not really worried about what the roads are doing around Glasgow and Edinburgh.

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And the same really applies to a TV set.

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Like reading a map, you can soon find the area that you are interested in,

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without detailed knowledge of the circuit boards.

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You can then narrow the fault down to a few suspect components. 

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Tim: We've managed to get a picture out of most of these old scrap tellies. 

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From the outside they don't look very different from modern tellies, 

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but inside things have changed quite radically in the last 15 years. 

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For a start, the old telivisions needed an elaborate set of adjustments.

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There were so many knobs that they were rarely set up accurately.

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Most of these adjustments have now become obsolete,

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simply by ingenious refinement of the tube design. 

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The older sets also used much more power, and generated much more heat

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and heat is not very good for electronics.

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Finally instead of the individual valves and transistors, modern sets use integrated circuits. 

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A modern set has less than half the number of components of a 15 year old one. 

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It looks as if there is almost nothing inside in comparison. 

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All this has made tellies much cheaper and simpler to build, and it's also made them more reliable.

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I think they are the only machine in this series that's actually become more reliable in recent years.

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I think that it's quite wonderful that someting that so recently was 

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stretching the limits of modern technology, can now be achieved so easily. 

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The days when people rented their tellies because they were so expensive 

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and they needed mending so often, are really gone forever.

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And all these old elaborate tellies, none of which are 

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working properly anyway, are not really worth mending

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But instead of just throwing them away, we decided to give them 

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a rather more dramatic end, particularly as it's the end of the series. 

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[Explosion and breaking glass]

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[roaring flames and shattering glass]

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[screeching of burning components]

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[Jazzy music: 'Take 5' - Dave Brubeck]

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[more explosions and louder shattering glass]
[Jazzy music: 'Take 5' - Dave Brubeck]

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[Jazzy music: 'Take 5' - Dave Brubeck]