Back in 1970, as a young trainee broadcast engineer, I found myself working in the telecine department at a regional studio. We still operated dual standard standard at the time, switching between 405 and 625 line as required, though both were still monochrome. One day, we had some American engineers visiting, who were quite complementary about the resolution of our 625 images. They were very shocked to be informed that, at the time of their visit, we were actually operating 405-line...! 405-line was much better than people give it credit for, but by the time we were preparing for 625-line, other improvements had been made to the transmission system, most notably FM audio replacing AM, and negative picture modulation of the vision carrier. Both these gave a huge improvement in both interference rejection and fringe reception, and were at least as valuable as the improved resolution.

We didn't have electricity in our house in Southern England until 1967, when I was 7 years old. Soon afterwards my Dad rented our first TV set. I remember the times before the TV, all of us sitting around the kitchen table, Dad reading the newspaper, Mum and Nan knitting and us kids playing cards or board games like snakes and ladders or Ludo. On Sundays we were lucky enough to have a roast dinner and afterwards we all sat around the kitchen table talking to each other... Then the TV arrived and the conversation stopped dead. Everybody's chair was turned to face the TV. We had 3 TV channels then, BBC 1 and ITV were broadcast on 405 lines, whereas the newer BBC2 channel was 625 lines. Our TV had a switch on the side to select 405 and 625 lines. Of course it was my job to operate this and change the channels. A little bit older now and many years have past but I can still remember that very first television.

I remember when I were a kid growing up in the early 70's, a lot of houses had 2 lots of VHF aerials on the rooftops ; one aimed towards Pontop Pike (BBC) & Burnhope (Tyne Tees) & the other towards Holme Moss (BBC) & Emley Moor (Yorkshire). In the mid-80's, I remember going on a day out to Lincoln & spotting 3 UHF aerials on a house rooftop. The bloke who lived there told me how, prior to 1974, he could pick up Anglia from Belmont, ATV from Waltham & Yorkshire from Emley Moor. Absolutely amazing

I remember our TV with the two channel dials! One was for 405 and the other for 625. A blast from the past. Thanks Adam

405 lines on a typical 12 inch set of the 50s looked fine, but once larger sets became available the picture was noticeably 'liney'. The dual standard TVs of the 1960s were notoriously unreliable, but the 625 picture was a big improvement. You can still see the occasional band I and band III VHF aerials on rooftops, unused for around 40 years.

At the beginning of the 70s I worked for a TV shop as a delivery and installation driver, a lot of our customers still had only 405 line sets with 2 aerials a X, and an H, many were venturing into the new colour sets (the rich ones) where they had to have a new toastrack aerial fitted which was also required for BBC 2 which if I remember was always on 625 lines

Thanks for this really interesting & excellently put together video. As a retired electronics engineer who started off in the 405 - line only days, on domestic television, so seeing in the evolution to 625-line UHF monochrome & then colour TV gradually being taken up by the general public, it was fascinating to re-live part of it. Shortly after the introduction of colour, I moved into the broadcast engineering sector, where I remain almost until retirement. And still the technology marches on, with most people being totally unaware of the constantly evolving electronics behind it all.

Just for the joke, "high def" in France was imposed in 1948, with a 819 standard. This is due to the fact that the 441 lines system was an inherited from the German system, during the occupation (The occupation TV for German troops was supposed to be destroyed during the retreat, but let intact and fully functionnal). The "low def" 441 system was stopped brutally due to a fire of the transmitter in 1956, and the very small number of tv sets (less than 500) : offering a vouncher to buy an "high-def" system was cheaper for the state than rebuild the transmitter. The 819 "K" system was developed by Henri de France , was to wide on frequency to add a colour system. And funnily, this is the same engineer who created the SECAM colour system, on the CCITT standard 625 lines "BG" system.

My grandparents kept their old monochrome 405-line TV until just before the shutdown. I remember watching it in the 80s, not bothered by the lack of colour or less definition. A lot of older houses in the place I grew up had the old aerials for a long time as well. EMI's system really lasted.

The geographical coverage of the 405 line VHF transmitters was phenomenal - many viewers could receive pictures from two or even three ITV companies. For example ATV/ABC Midlands could be seen as far south as parts of Surrey from the Membury transmitter and as far north as Liverpool from the Lichfield transmitter. UHF 625 line coverage was much patchier at the start - many people had to resort to installing masthead amplifiers to get a strong enough signal - particularly for an adequate colour picture.

Fabulous documentary! It must have been amazing to see 405 line TV in the UK years before decent quality TV programming occurred anywhere else! regards for Canada!

I remember the introduction of 625 line TV. It really seemed a quantum leap in viewing quality. Also after the introduction of colour the US programs like The Rowan & Martín Laugh In were still 525 lines with black bands top and bottom. The standards conversion equipment used by the BBC was big and expensive, Worth a video maybe? Thanks for the nostalga. Subscribed!

I was a television engineer in 1985 when the 405 system was switched off and had managed to find an old Murphy dual standard black and white set that I got working and watched the shut down on 405. The set was on its last legs but having managed to unsolder the system switch that would give so much trouble as the set aged and were often soldered up by engineers to be permanently on 625 and replacing a couple of capacitors it actually gave a reasonable picture. I think I had to rejuvenate the crt, something that used to give a few months life to a well used t.v. I don't recall what happened to the old Murphy but I no doubt it's been consigned to landfill.

I grew up with 405 lines tv and the black and white pictures it showed were very acceptable with a good contrast between light and dark and the definition was sharp especially when viewed on the screen sizes of the day. Also using a comparatively small number of transmitters almost all of the UK's population could receive the service.

Thank you very much. I was working at MTV Finland as a senior video maintenance engineer and was always wondered that your 405 line system. We admired the BBC picture quality which was the very best of all the countries.

I remember it being so much easier to get a good 405-line picture than a 625 one, but that's mainly because coverage was so much better on VHF. Also, on-screen noise due to a weak signal tended to result more in lack of contrast rather than snow, so you could turn up the contrast to make it a bit more watchable. Obviously, 625 lines was better, as long as you had a good aerial in a reasonable reception area, but 405 wasn't at all bad, and it didn't really look a lot different on smaller screens. Of course, they did experiment with colour on 405 lines in the 1950s (using a version of NTSC adapted for positive modulation) - no idea what that looked like.

The vision modulation on a 405 line set was the opposite way round to that of a 625 set which gave quite a different 'feel' and contrast to the picture, particularly in weak signal areas. Typically a 405 line set with no signal had a dark screen - the signal created the light parts of the picture. (The same was true for the French 819 line system.) With a 625 line set the screen without a signal was typically white and the introduction of the signal created the dark parts of the picture. The positive modulation on 405 also tended to create very noticeable interference problems if unsuppressed electrical devices were used nearby, or if cars without a good condenser passed nearby.

I vaguely remember watching the 405 line transmissions in the early 80s as a kid. We had a sony b&w portable tv that received both 405 & 625. When watching tv up in the bedroom I found that the 405 reception was pretty much perfect on a crappy pull out aerial compared to the 625 b&w picture. Though it noticeably had lower resolution and lines, it was overall clearer. I remember being disappointed when 405 was switched off as the portable then only received the snowy 625 uhf picture. The colour tv downstairs was fine - having a proper rooftop aerial.

My first TV was an old 405 line monster with a glass panel in front of the tube. And a dead spider in there. It had frame linearity problems, which seemed to be very common on this vintage of equipment. When I got a Thorn 1500 mono 625 TV, it seemed such a leap of technology. Thankfully I never had dual standard TV, they were unreliable with all those big switches in there.

During the 1950s, before BBC Divis (Northern Ireland) was opened in 1955 people the only signal possible in central Eire was to receive BBC TV from Northern England. A teenager (BATV fan) in 1960 I was surprised by the number of Band 1 aerials I saw on houses in Port Laoise, Abbeyleix and further south. Reception was usually not possible till after dark and the 3-element aerials were at roof level. I remember looking at several single channel 12" sets at a repair shop in Abbeyleix (1959) that had been recovered as people installed tall masts and switched to ground wave reception from Divis about +100 miles distant. I also vividly remember hearing NYC taxis breaking though on my uncle's 405 TV (41.5 mHz sound curtesy of the high MUF 1960 sun spot cycle).

Brilliant documentary, as ever ❤ The standard to which you create them is so high 🎉

I remember the TV of my childhood having a 405 / 625 line switch.

The bulk of if not almost ALL tv sets manufactured and sold in the UK until the JAPANESE imports, were some of the worst electrical items that we Brits were subjected to. Unreliable, overheating and overbearing let alone as we would have said; over here... absolute and utter garbage. The first time I bought a JAPANESE tv set I realized there were those who were capable of making something that WORKED, WAS RELIABLE and worth every penny...

Thank you for covering 405 line television, one of my favourite topics. I'm currently restoring a 1937 HMV 900 and this is inspiring me to get on with it (it is a very big job!). Cheers

Great video thank you for making it! The info is very much appreciated to a ludite on this topic like myself.

Amazing video! As a collector and restorer of our lovely vintage televisions, and one of 12 owners of one of the rarest pre war TVs in the UK, it’s exciting to see someone shedding some light on our entrance into “high definition” television!

Something to bear in mind about 405 lines is that the surviving programmes from that era are not always indicative of the transmitted picture quality. Surviving programmes are usually telerecordings (kinescopes for our American friends) and these are often of considerably lesser quality than the original video feed, Telerecordings in which the line structure is visible are usually the result of the telerecording operators placing the camera too close to the monitor.

I had an old 405 line TV given to me as an 11 year old back in 1981 and it gave good pictures, BBC1 and ATV (Central after 1982) only but I never watched BBC2 anyway! It lasted until 405 closed down in January 1985 and I shed a tear that day.

Well memories! I was a sound engineer at HTV Wales (now ITV Wales) during that period. I was on the news crew covering the shutdown at the St Hilary transmitter outside Cardiff. We did an interview with the cheif transmitter engineer, got some pictures of the old equipment and then took the executive decision that we needed to see the 'big switch' thrown and the monitors go blank. Se we cued the engineer to switch it off. Several hours early. When we got back to base the switchboard had blown up with complaints! Bonus facts. The predecessor to HTV was TWW. the scene at 6:13 was from the studio that I spent my first years at; Pontcanna in Cardiff. Also the coming of stereo sound. We were the generation who trained up for its launch, we got a pay rise for the extra complexity.

Who remembers the big H shaped TV antennas used for 405 TV''s.m

Great video. In Ireland, most of the 405 line transmitters were switched off by 1978, to make frequency space for Ireland's second channel, RTE 2. The last place in Ireland to turn off 405 line transmissions was in County Donegal. I think this was due to poor signals of 625 line signals up there until a new transmitter at Holywell Hill (very close to the Northern Ireland border, which in turn make RTE 1 and RTE 2 accessible to people who lived in Derry / Londonderry city and county) was built in 1981. This spelled the end of 405 line transmissions in 1982. Even though we had 625 line television about 2 years before Britain, Ireland didn't have full time colour broadcasts until 1976, with Studio 1 of RTE Television Centre in Dublin being the last studio to get colour equipment.

One thing that should be an added advantage of the 625 line system vs. 405 line is the audio. 405 line was used an amplitude modulated sound carrier in the mid 1930’s frequency modulation was in it’s infancy still was an R&D project at RCA in the United States. By the time 625 was introduced in the mid 1960’s FM television audio was the standard and brought sound with better frequency response not well heard with the quality of speakers used TV sets, and better dynamic range over AM sound used in 405 line television.

any plans for history of irish tv (both northern ireland & republic of ireland)?

There was an amusing newspaper advert that appeared in 1964 with little explanation at first. All it said was the mathematical equation 'pi times 625 = 1964'. It was eventually revealed to be an advert for Pye televisions ready for BBC2's 625 line service if you use the usual approximation of pi as 22/7.

I noted last year, while visiting various areas of the UK there are quite a number of Band 1 and Band 3 VHF TV antennas still in situ, when you think although the 405 line system lasted as explained until early 1985, it was running simultaneously with the UHF system for several years, I can't think there can have been many VHF TV antennas installed after say the mid 1970s? This meaning those remaining antennas must have in situ around 50 year now, certainly a tribute to qualify and some excellent aerial riggers using quality gear!

I don't know if this would merit a whole video but the BBC, as far as I know, was the first in the world to broadcast digital audio to the public. From what I've heard they had been using NICAM encoded audio in their backfeeds to transmitters and decided that they could just as easily broadcast it to the public so everyone could enjoy digital stereo audio. This happened right around when American television networks were finally beginning to broadcast _stereo_ FM audio.

France had broadcast at 819 lines in black and white from 49 to 83...

One thing I remember growing up with a 405 line telly. It didn't work when the vacuum cleaner was being used. Don't know whether this would happened with a 625 line one! Our telly was 19inch. Remember when my friend got the first 26 inch screen colour telly in the area. You did need HD for such a large screen!

I was living in the Crystal Palace area during the time when 405 lines was transmitted from the BBC tower up there. As a result I remember well the RF interference that would come through audio equipment loud and clear (not good). Playing your electric guitar through an amp would ensure you were accompanied (quite loudly) by whatever was currently on BBC1. You could get some relief from this by wiring an RF choke into your guitar lead (but nothing completely remedied it). I remember a rehearsal room in Sydenham where they had tried to build a faraday cage around the room with chicken wire to minimise the effect this had on an entire band transmitting BBC1. I can also remember this problem affecting some hifi equipment (the cheaper stuff, I recall). And clearly remember Eddie Waring's voice blasting over the PA during an open air gig (Mahavishnu Orchestra, Yes & Lindisfarne) at Crystal Palace Bowl one Saturday afternoon. It was an absolute relief when this all came to halt on that fateful day in 1985 when 405 ceased. Good riddance!

Back in 1985 when 405 line transmissions ceased, I arranged with the IBA as it was then for a friend to have the redundant 625 to 405 line standards converter from the Mendelsham transmiiter in Suffolk. It was several 7ft equipment bays of electronics including a lot of diode matrix modules. An interesting day out. I can't remember now what happened to it in the end, but I still have a note from the IBA about it.

Very early television is so interesting, thank you! BTW, David McCallum the famous actor (who sadly just passed on, RIP) said in an interview that his father placed an order for a TV before WW2 started and it was delivered unexpectantly in 1945 at their door! I love the way earlier TV is different in each region. I was in London 10 years ago and learned that they have some TVs with coin boxes on them to watch them. I was watching a program about people on UK public assistance who would rig the coin box, lol.

Mm in Oct 2016 I was pleased to attend, in Ally Pally, celebrations re the 80th anniv of the 1st hd UK TV transmissions, from 1936 and of course then on 405. There, with a live b+w BBC 2 feed of a concert on HD, they had a computer converter. Turn the dial and one then had the feed reduced to 625 (with reduced res). Turn it again and now BBC2 was displayed on 405, which of course it never originally had! Then turn again and now simulated Baird appeared, with its flicker!! Wonderful..!!

You've got to love an AMTV documentary!

From what I know 405 was better than VHS at displaying a test card typically type C. The image also was more solid . The lines were obvious if thinking about them. They seemed to disappear if the programme was interesting. I constructed an exact frequency single element aerial for London ITV. It received at 60 miles distance. I often used 405 as my preference due to the better program choice. Hannington that had the mystery alien interruption was 42 mikes away on 625 lines. It required an 18 element aerial for inferior reception. 405 was a practical system. The. Sony TV 9-90 was about £120 if I remember circa £1500 now. 100% reliable over 15 years. 625 often looked washed out in black and white. Perhaps 405 had better contrast. The Sony showed this.

Looking back now the pictures look quite fuzzy, but at the time we didn't really see that, not did we miss colour - black and white tv was all we were used to and it was 'the best' as far as we kids were concerned. Of course, when colour came out it was magical. I remember seeing my first colour tv programme - Dad's Army - and being immediately amazed by the coloured titles. One thing I do remember about 405 lines is that my father made his own tv antenna (aerial) - it was an 'H', made out of bamboo canes and copper wire, and was inside the roofspace. When 625 lines came along everyone had to buy a new aerial - a metal thing shaped like a trumpet. Another thing I remember is that my grandparents had Rediffusion, which was a cabled radio and tv service - something I hear nothing about now.

Something i just realised: Colour tv has always existed we just havent had the right cameras until the 70s when it started

I’m surprised that it took the UK so long to dump the 405 system.

Wow! This is amazing! I really love analogue TV and B/W TV and all these fab documentaries are very interesting to me, Keep up the great work Adam!

I once had a dual standard television, it was fascinating to switch between 405 and 625 lines and note the difference in quality!

I remember being very sensitive to the 10.125 kHz line whistle.

I saw you on chris's channel just wanted to say hi🎉

Nice video Adam. Rhodesia also had 405 line long before South Africa turned tv on in 1976. The original vhf transmitter (converted to pal )channels were still in use untill quite recently. Im not sure if this is still the case with digital migrations. 😊I transferred some films shot in the 60s of the studios in Harare. Very interesting

I still remember it & colour tele appearing. Match of the day.. "for those of you with black & white sets, Leeds are in the yellow shirts" 😁

liked 405 line TV it was good got half a dozen of them still running perfectly i use a standard converter to run them and just to say I'm a collector📺📺 thank again other great video😊

A very interesting video, thank you.

Interesting piece of history. I'd just add that 625-Line and the switch to UHF were just coincidentally combined. Plenty of countries broadcast 625 Line and PAL on VHF. Ireland for example had PAL I on both UHF and VHF (Band III in later years but originally on Band I too) until well into the 1990s. The current DVB-T system only uses UHF. Australia used VHF/UHF with PAL B/G and now uses DVB-T on both VHF and UHF.

2:35 a very young Petula Clark.

I love the big triodes at 5:42. I have one, made by STC. Sadly, low emission when I tested it.

Love that in the background near the end of the clip is the old ITN news theme. Happy memories of hearing that with the early evening ITN bulletin on my nans Sobell b&w set in the 60s

A nice documentary. Thanks for uploading.

This was really good to watch. TV history is fascinating. ✌️❤️🙂

I remember living near to Ringway ( Manchester ) Airport as a kid. Every time an aircraft flew over our house the 405 line single was affected and the picture went "wavy". Never had the same issue with 625 lines.

Yet another amazing documentary as always!

What an excellent job you have done Adam!

405 lines refers to the broadcast definition, but a typical TV of the day would probably only resolve 150-200 lines. Even with 625 line transmissions, you would be lucky to actually get 300 lines on your set. I remember watching 405 lines in the 1960s and it looked all right then. When we bought our first TV in 1971 ( instead of renting) it was UHF only.

It's surprising how the quality of TV programmes is inversely proportional to the quality of the technology by which to view them!

I remember being disappointed with the first dual-standard 405/625 tvs. They produced a picture that was inferior to our single standard 405 line tvs. Dual-standard sets were introduced in the UK before the advent of modern comb filters etc So to reduce the patterning and interference from the colour subcarrier and to simplify the mechanics of system switching, manufacturers chose to limit the vision bandwidth. This compromised the video resolution of both 405 and 625 pictures. While we got less noticeable lines with 625, particularly on larger sets, the pictures were not as sharp as our single standard 405 sets. The move to 625 only Tvs, coupled with finer shadow masks etc, allowed later 625 colour sets to demonstrate better resolution of 625 over 405.

Very interesting, thank you. Bizarre to think that what we call High Definition channels are still limited and buried way down the list on freeview - legacy systems are still sticking around!

Really good TV history, Thanks Adam

Hi, your videos are the best!

It seems incredible now, that Alan Blumlein and his brilliant team at EMI saw 405 lines as a "stopgap", until something better could be developed!

405 is before my time but I remember the old UHF well and even have some videos of the old signal before digital

I recall the London area in the 405 Line era only need one transmitter to cover the whole region with the coming of 625 a lot of relay stations had to built as the UHF transmitter did cover the whole region with a strong signal. Likewise in the Midlands during the 405 line days there where three transmitters to cover the region with the coming of 625 many relays had to be built plus two further main transmitters.

Was there ever a "set top box" way of accessing 625 broadcasts on a 405 TV to enable people to watch BBC2 without changing their set? I'm guessing not, but it wouldn't surprise me if a company had found a way to keep existing TVs as usable as possible rather than just throwing them away. After all, TVs were a lot more expensive and less disposable than TVs are these days.

It's argued that the Sony KV1800 although PAL compatible was really a NTSC set. It had fabulous colour. If right it had a 90 degree defection tube. Delay line model KV 1810 was less impressive. Lucy an archive lady from the BBC told me NTSC recordings on big.reals were very high definition. Ruined when NTSC to PAL converted. She did the Doctor Who 405 line transfers. A beautiful lady with a technical mind and Saab convertible. I upgraded a Garrard 401 for her. She was a friend of the lady who wrote the Dr Who music. I have some 78 BBC programme records if the my boss kept them form Lucy. The Clitherow Kid recorded on Tottenham Court road was one. About 20 introductions per side looking like an LP. Lucy archived these things also. The 401 had two pick up arms. We had a group of new Sony 405 video recorders in boxes with monitors for Lucy. Some idiot threw them away! I think that they were 1964 imported by Debenhams.

Experimental colour transmissions were made by the ITA on 405 line from the Croydon transmitter circ.1964

HD is just a buzzword. I got a mint condition color TV set from 1979 a few months ago and abandoned my 42" 1080p TV for it. I use HDMI to RCA and RCA to RF converters to feed it and the quality is amazing. Vibrant colors, no noise, just a nice sharp picture.

Use to love looking around on vhf 405 years ago watching regional services as some times different programs would be showed to your local service

I would consider that 240 line Baird system to be almost unwatchable. In North America, the 525 line NTSC standard was set in 1941, but 441 lines had been commonly used before then. After WW2, there were some changes such as FM audio instead of AM and also rearrangement of some of the channels. Other than that, the system remained the same, even with the introduction of colour. The NTSC colour system was fully compatible with B&W. In Canada, those living close to the U.S. border could receive American TV and TV broadcasts here started in 1952. Colour arrived in time for Canada's centennial in 1967.

I remember, as a child, our very modern large screen TV that had a lever (think old railway signal), that would swith it from the VHF 405 lines to UHF 625. It was a dramatic change, especially when viewing the Olympics that were being broadcast by satellite, which virtually impossible on 405.

not forgetting the 405 line whistle

1.54.........Baird system.I think the date here was 1937 not 1957.

0:53 I hear "Rhythm Is A Dancer".

405 line tv signals had a much longer reach. I remember my dad struggling to get a decent picture on our temperamental set only to discover it was in Welsh!

I don't know if it is true, but I believe to have read somewhere that for the latter part of the 405 transmissions, the signal was produced by aiming a 405 camera on a "normal" PAL TV.

So the 625-line system was the Ultra-HD of it's age. I wonder how 4K video will be compared to 256K video by our grandchildren.

8:06 Pronounced Televish-Airon. UTV is also a Northern Irish station, not an Irish station.

The one thing I wish I could see what it looked like on 405 line television is the first Harlech (HTV) logo, because I read that somehow there was no moiré effect on 405 line tv, and I wish I knew what that look like. But I don't think it can be replicated in a digital video. :(

I think you have over estimated the Baird mechanical timebase it was only ever 30 line, he did develop a electrical timebase system but it was never taken up by the BBC and they chose EMI's

I had a Sony TV9-90 dual standard TV. Often used as props in TV dramas. London ITV was possible in Oxford. 405 was my main choice due to content. Picture quality was very good. The lines were fascinating. I understand 405 was a disguise for secret radar production. BBC were obliged to do it Alan Blumlein beintg a key name. 405 colour was a BBC invention circa 1960 in NTSC. RCA adopted some of the BBC improvements. BBC were told to adopt PAL. Apparently 405 with spot modulation was good up to 18 inches. A typical size then.

Pleaseeee do SED TVs next

Nice documentary.

Did I hear "The Baird 240 line system was closed down in January 1957?" Methinks it was twenty years earlier.! Also why are references to 240 lines accompanied with visuals of Baird's earlier 30 line efforts? In actual fact 240 line non-interlaced pictures achieved a definition comparable to 405 line interlaced pictures

IMO, the 625/405 difference wasn't great (576i vs. 3xxi): the main reason IMO for it looking better was that in most cases, the 405 sets were pretty old, and not displaying the pictures at their best - soot-and-sawdust, line pairing, and many other reasons. I suspect the main reason for its demise was that everyone else (in western Europe, anyway) _was_ using 625 (apart from the French with their 819!), so 405 was a purely UK system. (And the shortcomings of NTSC colour - which they did try on 405! - were worse at VHF. The rest of EU had 625 on both VHF and UHF.)

This is a really nice Documentary, In the states, we had NTSC, And unlike 405, VHF Stations can handle Color, without needed to use Strictly UHF.

HI ADAM PLEASE COULD YOU DO THE HISTORY OF REDIFFUSION TV COMPANY

I really like that I'm enjoying this in 1080p, so it's possible to see the progression of lines across the decades.

Never underestimate the power of David Sarnoff’s RCA (30 Rock used to be the RCA headquarters.) He tended to squat on new technologies like TV Color and resolution, and FM radio until the corp had everything ready and the affiliates wouldn’t be harmed and bail on him. That way the more nimble wouldn’t take market share.

Did the introduction of 625 in 1964 also herald a move from most televisions sold in the uk containing 17inch tubes to containing 19inch tubes?

I think that the real meaning of "high definition" is simply "higher definition than you are currently using". But we've now reached the stage where the resolution available is so high that it is actually pointless except on very large screens viewed at close quarters.