Initial development and technologies Videotex

1 initial development , technologies

1.1 united kingdom
1.2 france
1.3 canada
1.4 japan

initial development , technologies
united kingdom

the first attempts @ general-purpose videotex service created in united kingdom in late 1960s. in 1970 bbc had brainstorming session in decided start researching ways send closed captioning information audience. teledata research continued bbc became interested in using system delivering sort of information, not closed captioning. in 1972, concept first made public under new name ceefax. meanwhile, general post office (soon become british telecom) had been researching similar concept since late 1960s, known viewdata. unlike ceefax one-way service carried in existing tv signal, viewdata two-way system using telephones. since post office owned telephones, considered excellent way drive more customers use phones. not outdone bbc, announced service, under name prestel. itv joined fray ceefax-clone known oracle.

in 1974 services agreed standard displaying information. display simple 40×24 grid of text, graphics characters constructing simple graphics, revised , finalised in 1976. standard did not define delivery system, both viewdata-like , teledata-like services @ least share tv-side hardware (which @ point in time quite expensive). standard introduced new term covered such services, teletext. ceefax first started operation in 1977 limited 30 pages, followed oracle , prestel in 1979.

by 1981 prestel international available in 9 countries, , number of countries, including sweden, netherlands, finland , west germany developing own national systems closely based on prestel. general telephone , electronics (gte) acquired exclusive agency system north america.

france

development of french teletext-like system began in 1973. simple 2-way videotex system called tictac demonstrated in mid-1970s. in uk, led on work develop common display standard videotex , teletext, called antiope, finalised in 1977. antiope had similar capabilities uk system displaying alphanumeric text , chunky mosaic character-based block graphics. difference while in uk standard control codes automatically occupied 1 character position on screen, antiope allowed non spacing control codes. allowed antiope more flexibility in use of colours in mosaic block graphics, , in presenting accents , diacritics of french language.

meanwhile, spurred on 1978 nora/minc report, french government determined catch on perceived falling behind in computer , communications facilities. in 1980 began field trials issuing antiope-based terminals free on 250,000 telephone subscribers in ille-et-vilaine region, french ccett research centre based, use telephone directories. trial success, , in 1982 minitel rolled out nationwide.

canada

since 1970 researchers @ communications research centre (crc) in ottawa had been working on set of picture description instructions , encoded graphics commands text stream. graphics encoded series of instructions (graphics primitives) each represented single ascii character. graphic coordinates encoded in multiple 6 bit strings of xy coordinate data, flagged place them in printable ascii range transmitted conventional text transmission techniques. ascii si/so characters used differentiate text graphic portions of transmitted page . in 1975, crc gave contract norpak develop interactive graphics terminal decode instructions , display them on colour display, , running 1977.

against background of developments in europe, crc able persuade canadian government develop system fully-fledged service. in august 1978 canadian department of communications publicly launched telidon, second generation videotex/teletext service, , committed four-year development plan encourage rollout. compared european systems, telidon offered real graphics, opposed block-mosaic character graphics. downside required more advanced decoders, typically featuring zilog z80 or motorola 6809 processors.

japan

research in japan shaped demands of large number of kanji characters used in japanese script. 1970s technology, ability generate of many characters on demand in end-user s terminal seen prohibitive. instead, development focussed on methods send pages user terminals pre-rendered, using coding strategies similar facsimile machines. led videotex system called captain ( character , pattern telephone access information network ), created ntt in 1978, went full trials 1979 1981. system lent naturally photographic images, albeit @ moderate resolution. however, pages typically took 2 or 3 times longer load, compared european systems. nhk developed experimental teletext system along similar lines, called cibs ( character information broadcasting station ). based on 388×200 pixel resolution, first announced in 1976, , began trials in late 1978. (nhk s ultimate production teletext system launched in 1983).