The 405-line monochrome analogue television broadcasting system was the first electronic television system to be used in regular broadcasting. It was introduced with the BBC Television Service in 1936, suspended for the duration of World War II, and remained in operation in the UK until 1985, and was also used for some time in Ireland, Hong Kong and New Zealand. Sometimes called the Marconi-EMI system, it was invented in 1934 by Alan Dower Blumlein of the EMI Research Team led by Sir Isaac Shoenberg. The system was the first to use interlacing; the 405 scanning lines were broadcast in two complementary fields, 50 times per second, creating 25 frames per second. Of the 405 lines, 377 were used for the image. A photograph of a sign in grayscale The same photograph in black and white Monochrome comes from the two Greek words mono (μωνο, meaning one), and chroma (χρωμα, meaning surface or the color of the skin). A monochromatic object has a single color. ... Analog television (or analogue television) encodes television and transports the picture and sound information as an analog signal, that is, by varying the amplitude and/or frequencies of the broadcast signal. ... BBC One is the primary television channel of the BBC, and the first in the United Kingdom. ... Combatants Allied powers: China France Great Britain Soviet Union United States and others Axis powers: Germany Italy Japan and others Commanders Chiang Kai-shek Charles de Gaulle Winston Churchill Joseph Stalin Franklin Roosevelt Adolf Hitler Benito Mussolini Hideki Tōjō Casualties Military dead: 17,000,000 Civilian dead: 33,000... Alan Dower Blumlein was an electronics engineer who made a great many inventions in telecommunications, sound recording, stereo, television and radar. ... The EMI Group (LSE: EMI) is a British music company comprising of the major record company EMI Music which operates several labels, based in Brook Green in London, England, and EMI Music Publishing, based on Charing Cross Road, London. ... Sir Isaac Shoenberg Sir Isaac Shoenberg (March 1, 1880 - January 25, 1963) was an electronic engineer born in Russia who was best known for his role in history of televesion. ... Interlacing is a method of displaying images on a raster-scanned display device, such as a cathode ray tube (CRT). ...

Though articles at the time of its introduction referred to the 405-line system as "high definition", that is in relation to the crude mechanical television systems that preceded it; it should not be confused with modern-day HDTV. Projection screen in a home theater, displaying a high-definition television image. ...

History

The system was used by the BBC from their Alexandra Palace site beginning in November 1936, at first time-sharing broadcasts with the 240-line Baird System; however, after three months of trials (in January 1937) the Baird system was abandoned in favour of exclusive broadcasting with the 405-line Marconi-EMI system on VHF. This became the standard for all British TV broadcasts until the 1960s. The British Broadcasting Corporation,which is usually known as the BBC, is the largest broadcasting corporation in the world in terms of audience numbers, employing 26,000 staff in the United Kingdom alone and with a budget of more than GB£4 billion. ... Alexandra Palace from the south Alexandra Palace was built in an area spanning Wood Green and Muswell Hill, North London, England in 1873 as a public entertainment centre and North London counterpart of The Crystal Palace. ... See also: 1935 in television, other events of 1936, 1937 in television and the list of years in television. Events July 7 - NBCs first attempt at actual programming is a 30-minute variety show featuring speeches, dance ensembles, monologues, vocal numbers, and film clips. ... Bust of John Logie Baird in Helensburgh. ... Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. ... The 1960s decade refers to the years from January 1, 1960 to December 31, 1969, inclusive. ...

In 1954 the BBC lost its monopoly of the British Television market, and the following year the commercial network ITV, comprising a consortium of regional companies, was launched. Some ITV companies, notably Lew Grade's ATV, proposed broadcasting in colour using a 405-line variation on the NTSC system, but the BBC persuaded the Government that colour should await the introduction of a higher-definition system. The British Broadcasting Corporation,which is usually known as the BBC, is the largest broadcasting corporation in the world in terms of audience numbers, employing 26,000 staff in the United Kingdom alone and with a budget of more than GB£4 billion. ... Commercial broadcasting - Wikipedia /**/ @import /skins-1. ... It has been suggested that Channel 3 (UK) be merged into this article or section. ... Lew Grade, Baron Grade (birth name Louis Winogradsky) (December 25, 1906 - December 13, 1998) was an influential showbusiness impresario and television company executive in the United Kingdom. ... This article or section does not adequately cite its references or sources. ... The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ...

The phasing out of the 405-line system (UK)

In 1964 the BBC launched its BBC Two service on UHF using only a 625-line (576i) system, which older sets could not receive. PAL colour was introduced in 1967. In November 1969 BBC One and ITV also started broadcasting on 625-line on UHF in colour. As their programming was now entirely produced using the new standard, the 405-line broadcasts served only as a rebroadcast in monochrome for people who did not have the newer receivers. 1964 (MCMLXIV) was a leap year starting on Wednesday (the link is to a full 1964 calendar). ... The British Broadcasting Corporation,which is usually known as the BBC, is the largest broadcasting corporation in the world in terms of audience numbers, employing 26,000 staff in the United Kingdom alone and with a budget of more than GB£4 billion. ... This article does not cite any references or sources. ... This article is about the radio frequency. ... 576i is the shorthand name for a video mode. ... Television encoding systems by nation. ... BBC One is the primary television channel of the BBC, and the first in the United Kingdom. ... It has been suggested that Channel 3 (UK) be merged into this article or section. ...

One reason for the long switchover period is the difficulty in matching the coverage level of the new UHF 625 line service with the very high level of geographic coverage achieved with the 405 line VHF service.

The last 405-line transmissions were seen on January 3, 1985, in Scotland, having been shut down one day earlier in the rest of the UK. This left only the UHF PAL system in operation in the UK. The frequencies used by the 405-line system were initially left empty, but were later sold off, used now for other purposes including DAB and Trunked PMR Commercial two way radio systems. January 3 is the 3rd day of the year in the Gregorian calendar. ... Year 1985 (MCMLXXXV) was a common year starting on Tuesday (link displays 1985 Gregorian calendar). ... Motto (Latin) No one provokes me with impunity Cha togar mfhearg gun dioladh (Scottish Gaelic) Wha daur meddle wi me?(Scots)1 Anthem (Multiple unofficial anthems) Scotlands location in Europe Capital Edinburgh Largest city Glasgow Official languages English, Gaelic and Scots1 Government Constitutional monarchy  -  Monarch Queen Elizabeth II... Official DAB logo, found on compliant devices Digital Audio Broadcasting (DAB), also known as Eureka 147, is a technology for broadcasting of audio using digital radio transmission. ...

The phasing out of the 405-line system (Ireland)

Ireland's use of the 405-line system began only in 1961, with the launch of Telefís Éireann, but extended solely to two transmitters and five relays of them, serving the east and north of the country where many people had sets for receiving broadcasts from Wales or Northern Ireland. Telefís Éireann (later to become RTÉ One) was also simulcast on 625-line from the summer of 1962 onwards, two years before the BBC had any 625 channels. Radio Telefís Éireann (RTÉ; Irish for Radio [and] Television of Ireland) is the Public Service Broadcaster of the Republic of Ireland. ... RTÉ One is the Republic of Irelands oldest and most popular television channel, operated by Irish state broadcaster Radio Telefís Éireann. ...

• The last 405 line relays, in County Donegal were turned off in 1982, with the main transmitters having been disabled in 1978 to free up frequency for RTÉ Two; with the relays being fed with standards converters from the local 625-line transmitter.
• For the last five years of RTÉ 405-line programming relays a simple orthicon converter, essentially a 405-line camera pointed at a 625-line monitor, was used as the more expensive system converters that RTÉ previously used had broken down.

RTÉ Two (known from 1988 to 2004 as Network 2 or RTÉ Network Two or N2) is Irelands fifth-oldest television channel, operated by Irish state broadcaster Radio Telefís Éireann. ...

The phasing out of the 405-line system elsewhere

Many British colonies used the 405-line system until they became independent. After that, many newly independent countries from the British Empire still used this system, until they switched to other TV broadcast systems, generally PAL-B/G/I and NTSC-M.

405-line video recordings

A few 405-line videotapes still survive. However, the majority of surviving 405-line programmes are in the form of black and white film telerecordings, usually with optical soundtracks. Bottom view of VHS videotape cassette with magnetic tape exposed Videotape is a means of recording images and sound onto magnetic tape as opposed to movie film. ... Telerecording (known as kinescoping in the USA) is the British name for a process pioneered during the 1940s for the storing of electronically-shot television programmes on film, which was used for the preservation, re-broadcasting and sale of television programmes before the use of commercial broadcast-quality videotape became...

System A

405-line is system A in the CCIR assignment of broadcast systems. The audio uses Amplitude Modulation rather than the Frequency Modulation in use on modern analogue systems. In addition, the system was broadcast in an aspect ratio of 5:4 until 3rd April 1950 when it changed to the more common 4:3 format.^[1] The ITU Radiocommunication Sector (ITU-R) is a standards body subcommittee of the International Telecommunication Union (ITU) relating to radio communication. ... There are several broadcast television systems in use in the world today. ... Amplitude modulation (AM) is a technique used in electronic communication, most commonly for transmitting information via a radio carrier wave. ... Frequency modulation (FM) is a form of modulation that represents information as variations in the instantaneous frequency of a carrier wave. ... The aspect ratio of a two-dimensional shape is the ratio of its longer dimension to its shorter dimension. ... Year 1950 (MCML) was a common year starting on Sunday (link will display the full calendar) of the Gregorian calendar. ...

All System A transmitters used vestigial sideband transmission, with the single exception of Alexandra Palace in London, which closed down in 1957 when it was replaced by Crystal Palace.

Why 50 fields per second

Since the mid-1930s it has been standard practice to use a field frequency equal to the AC mains electric supply frequency (or a submultiple therof) 50 Hz in most countries (60 Hz in others) because studio lighting generally uses alternating current lamps and if these were not synchronised with the field frequency, an unwelcome strobe effect could appear on TV pictures. Secondly the smoothing (filtering) of power supply circuits in early TV receivers was rather poor and ripple superimposed on the DC could cause visual interference. If the picture was locked to the mains frequency, this interference would at least be static on the screen and thus less obtrusive.

Why 405 lines

Because an interlaced system requires accurate positioning of scanning lines it is important to make sure that the horizontal and vertical timebases are in a precise ratio. This is accomplished by passing the one through a series of electronic divider circuits to produce the other. Each division is by a prime number. Therefore there has to be a straightforward mathematical relationship between the line and field frequencies, the latter being derived by dividing down from the former. Technology constraints of the 1930s meant that this division process could only be done using small integers, preferably no greater than 7, for good stability. The number of lines was odd because of 2:1 interlace. The 405 line system used a vertical frequency of 50 Hz (Standard AC mains supply frequency in Britain) and a horizontal one of 10,125Hz (50 × 405 ÷ 2) In mathematics, a prime number (or a prime) is a natural number that has exactly two (distinct) natural number divisors, which are 1 and the prime number itself. ... Hz or hz may mean: Herero language (ISO 639 alpha-2, hz) Hertz, unit of frequency This is a disambiguation page — a list of articles associated with the same title. ...

• 2 × 3 × 3 × 5 Gives 90
• 2 × 2 × 2 × 2 × 2 × 3 Gives 96
• 2 × 2 × 3 × 3 × 5 Gives 180
• 2 × 2 × 2 × 2 × 3 × 5 Gives 240 (Used for the experimental Baird transmissions in England)
• 3 × 3 × 3 × 3 × 3 Gives 243
• 7 × 7 × 7 Gives 343 (Early North American system also used in Poland before WW2)
• 3 × 5 × 5 × 5 Gives 375
• 3 × 3 × 3 × 3 × 5 Gives 405 (Used in Britain Ireland and Hong Kong before 1985)
• 2 × 2 × 2 × 5 × 11 Gives 440
• 3 × 3 × 7 × 7 Gives 441 (Used by RCA in North America America before the 525 standard was adopted and widely used before WW2 in Continental Europe with different frame rates )
• 2 × 3 × 3 × 5 × 5 Gives 450
• 5 × 7 × 13 Gives 455 (Used in France before WW2)
• 3 × 5 × 5 × 7 Gives 525 (A compromise between the RCA and Philco systems Still used today In America and parts of Asia)
• 3 × 3 × 3 × 3 × 7 produces 567 (used for a while after WW2 in the Netherlands)
• 5 × 11 × 11 Gives 605 (Used by Philco in North America before the 525 standard was adopted)
• 5 × 5 × 5 × 5 gives 625 (Still used today in most parts of the world)
• 3 × 3 × 7 × 13 Gives 819 (Used in France in the 1950’s)

405 compared with later standards

Bandwidth

When used with vestigial sideband filtering the total bandwidth of a 405-line TV channel is 5 MHz, significantly less than the 8 MHz required by the 625-line system I, which replaced it in Britain. Systems in other countries used anything between six and fourteen megahertz of bandwidth per channel.

Coverage

The use of VHF frequencies combined with the narrow vision bandwidth (AM signals are less affected by noise as bandwidth is reduced) meant that 405-line signals could be received well even under marginal conditions and consequently it was possible to cover virtually all of the country with a relatively small number of transmitting stations.

Susceptibility to impulse interference

The use of AM (rather than FM) for sound and the use of positive (rather than negative) video modulation made 405-line signals very susceptible to impulse interference, such as that generated by the ignition systems of vehicles. Such interference manifested itself as a loud popping on sound and large bright spots on the picture which viewers found a lot more noticeable than the dark spots encountered when such interference is encountered on a signal using negative video modulation.

Whistle due to lineoutput transformer magnetostriction

The 405-line system produced a noticeable 10,125 Hz whistle in many sets, equal to the number of lines per second. This high-pitched whistle is caused by magnetostriction in the line-timebase transformer, that is, the transformer used to power the beam 10,125 times from left to right and back again changes dimensions in tune with that frequency.^[2][3] This is a common effect of sets that use a cathode ray tube, and while all CRT-based television systems produce such a noise, the higher number of lines per second in later standards produce frequencies (PAL's 15,625 Hz and NTSC's 15,734 Hz) that are at the upper end of the audible spectrum, and which not all people are able to hear; more modern sets also tend to be less susceptible to this effect. Magnetostriction is a property of ferromagnetic materials that causes them to change their shape when subjected to a magnetic field. ... Cathode ray tube employing electromagnetic focus and deflection Cutaway rendering of a color CRT Electron guns Electron beams Focusing coils Deflection coils Anode connection Mask for separating beams for red, green, and blue part of displayed image Phosphor layer with red, green, and blue zones Close-up of the phosphor... Hearing is the following: Hearing is the sense by which sound is perceived. ...

Interlace/timing issues

The lack of equalising pulses in the vertical blanking period of the 405-line system often resulted in imperfect interlacing, which manifested itself as increased flicker and poor resolution when the two fields per frame failed to line up correctly.

Experimental colour transmissions

During the late 1950s amd early-mid 1960's some experimental colour broadcasts were made in the UK using the 405-line system using NTSC colour encoding. The subcarrier frequency was 2.6578125 MHz (525/2 times line frequency) with an "I" signal bandwidth of 500 kHz and a "Q" signal bandwidth of 300 kHz. Tests with PAL SECAM and other NTSC subcarrier frequencies were also attempted [#. The references in this article would be clearer with a different and/or consistent style of citation, footnoting or external linking. ... Television encoding systems by nation. ... SECAM, also written SÉCAM (Séquentiel couleur à mémoire, French for Sequential Color with Memory), is an analog color television system first used in France. ...

Some of these broadcasts were on UHF (also an experimental technology at the time), while others were carried over the regular VHF network outside of normal broadcasting hours. Ultra high frequency (UHF) designates a range (band) of electromagnetic waves whose frequency is between 300 MHz and 3. ... Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. ...

Notes and References

1. ^ Pawley, Edward. BBC Engineering 1922 - 1972, ISBN 0-563-12127-0, p 366.
2. ^ Television Repair and Restoration. Retrieved on 2007-04-03.
3. ^ 405 Alive - Welcome. Retrieved on 2007-04-03.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ...

See also

• Broadcast television system
• Television systems before 1940

There are several broadcast television systems in use in the world today. ... A number of experimental and broadcast pre World War II systems were tested. ...

External links

• 405 Alive - Welcome. Retrieved on 2007-04-03.
• Irish TV - Over forty years of Irish TV History. Retrieved on 2007-04-03.
• The UK 405-Line Television Network. Retrieved on 2007-04-03.
• 405 Line Colour TV. Retrieved on 2007-04-03.
• World Analogue Television Standards and Waveforms - Line Standards. Retrieved on 2007-04-03.

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 93rd day of the year (94th in leap years) in the Gregorian calendar. ...