NAPLPS (NorthAmericanPresentationLevelProtocolSyntax) is a graphics language for use originally with videotex and teletext services. NAPLPS was developed from the Telidon system developed in Canada, with a small number of additions from AT&T Corporation. The basics of NAPLPS were later used as the basis for several other microcomputer-based graphics systems.
The Canadian Communications Research Centre (CRC), based in Ottawa, had been working on various graphics systems since the late 1960s, much of it led by Herb Bown.[1] Through the 1970s they turned their attention to building out a system of "picture description instructions", which encoded graphics commands as a text stream.
Graphics were encoded as a series of instructions (graphics primitives) each represented by a single ASCII character. Graphic coordinates were encoded in multiple 6-bit strings of XY coordinate data, flagged to place them in the printable ASCII range so that they could be transmitted with conventional text transmission techniques. ASCII SI/SO characters were used to differentiate the text from graphic portions of a transmitted "page". These instructions were decoded by separate programs to produce graphics output, on a plotter for instance. Other work produced a fully interactive version. In 1975, the CRC gave a contract to Norpak to develop an interactive graphics terminal that could decode the instructions and display them on a color display.
During this period, a number of companies were developing the first teletext systems, notably the BBC's Ceefax system. Ceefax encoded character data into the lines in the vertical blanking interval of normal television signals where they could not be seen on-screen, and then used a buffer and decoder in the user's television to convert these into "pages" of text on the display. The Independent Broadcasting Authority quickly introduced their own ORACLE system, and the two organizations subsequently agreed to use a single standard, the "Broadcast Teletext Specification". This later became World System Teletext.
At about the same time, other organizations were developing videotex systems, similar to teletext except they used modems to transmit their data instead of television signals. This was potentially slower and used up a telephone line, but had the major advantage of allowing the user to transmit data back to the sender. The UK's General Post Office developed a system using the Ceefax/ORACLE standard, launching it as Prestel, while France prepared the first steps for its ultimately very successful Minitel system, using a rival display standard called Antiope.
By 1977, the Norpak system was running, and from this work the CRC decided to create their own teletext/videotext system. Unlike the systems being rolled out in Europe, the CRC decided from the start that the system should be able to run on any combination of communications links. For instance, it could use the vertical blanking interval to send data to the user, and a modem to return selections to the servers. It could be used in a one-way or two-way system.[1]
In teletext mode, character codes were sent to users' televisions by encoding them as dot patterns in the vertical blanking interval of the video signal. Various technical "tweaks" and details of the NTSC signals used by North American televisions allowed the downstream videotex channel to increase to 600 bit/s, about twice that used in the European systems. In videotext mode, Bell 202 modems were typical, offering a 1,200 bit/s download rate. A set top box attached to the TV decoded these signals back into text and graphics pages, which the user could select among.
The system was publicly launched as Telidon on August 15, 1978. Compared to the European standards, the CRC system was faster, bi-directional, and offered real graphics as opposed to simple character graphics. The downside of the system was that it required much more advanced decoders, typically featuring Zilog Z80 or Motorola 6809 processors with RGB and/or RF output. The Innovation, Science and Economic Development Canada (then Department of Communications) launched a four-year plan to fund public roll-outs of the technology in an effort to spur the development of a commercial Telidon system.[1]
AT&T Corporation was so impressed by Telidon that they decided to join the project.[citation needed] They added a number of useful extensions, notably the ability to define original graphics commands (macro) and character sets (DRCS). They also tabled algorithms for proportionally spaced text, which greatly improved the quality of the displayed pages. A joint CSA/ANSI working group (X3L2.1) revised the specifications, which were submitted for standardization. In 1983, they became CSA T500 and ANSI X3.110, or NAPLPS.[2] The data encoding system was also standardized as the NABTS (North American Broadcast Teletext Specification) protocol.
Business models for Telidon services were poorly developed. Unlike the UK, where teletext was supported by one of only two large companies whose whole revenue model was based on a read-only medium (television), in North America Telidon was being offered by companies who worked on a subscriber basis.
One-way systems
Telidon-based teletext was tested in a few North American trials in the early 1980s —CBC IRIS, TVOntario, MTS-sponsored Project IDA, to name a few.
NAPLPS was also part of the NABTS teletext standard, for the encoding and display of teletext pages.
In the late 1980s and early 1990s, affiliates of the regional sports network group SportsChannel ran a service called Sports Plus Network, which ran sports news and scores while SportsChannel was not otherwise on the air. The screens, which frequently featured team logos or likenesses of players in addition to text, were drawn entirely with NAPLPS graphics and resembled the loading of Prodigy pages over a modem, though slightly faster.
Two-way systems
Various two-way systems using NAPLPS appeared in North America in the early 1980s. The biggest North American examples were Knight Ridder's Viewtron (based in Miami) and the Los Angeles Times'Gateway service (based in Orange County). Both used the Sceptre NAPLPS terminal from AT&T. The Sceptre contained a slow modem that connected over the consumer's telephone line to host computers. The Sceptre was expensive whether purchased or rented. Despite huge investments by their parent companies, neither Viewtron nor Gateway lasted into the second half of the decade. Another system, Keyfax, was developed by Keycom Electronic Publishing, a joint venture of Honeywell, Centel (since acquired by Sprint) and Field Enterprises, then-owner of the Chicago Sun-Times newspaper. Keyfax had originally been a WST teletext service, broadcast overnights on Field's Chicago television station WFLD-32[3] and through the VBI of both WFLD and national superstation WTBS; the decision was made to convert Keyfax into a subscription service, using a proprietary NAPLPS terminal device in a last-ditch effort to save the service. It did not work and Keyfax had ceased operations by the end of 1986.[4]
Other early-1980s NAPLPS technology was deployed in Canada, both as a way for rural Canadians to get news and weather information and as the platform for touchscreen information kiosks. In Vancouver these were featured at Expo 86. The kiosks became ubiquitous in Toronto under the name Teleguide, and were deployed in many shopping centres and at major tourist attractions. The latter city was the North American nexus of NAPLPS and the home of Norpak, the most successful of NAPLPS-oriented developers. Norpak created and sold hardware and software for NAPLPS development and display. TVOntario also developed NAPLPS content creation software.
London, Ontario - based Cableshare used NAPLPS as the basis of touch-screen information kiosks for shopping malls, the flagship of which was deployed at Toronto's Eaton Centre. The system relied on an 8085-based microcomputer which drove several NAPLPS terminals fitted with touch screens, all communicating via Datapac to a back end database. The system offered news, weather and sports information along with shopping mall guides and coupons. Cableshare also developed and sold a leading NAPLPS page creation utility called the "Picture Painter."
In the late 1980s, Tribune Media Services (TMS) and the Associated Press operated a cable television channel called AP News Plus that provided NAPLPS-based news screens to cable television subscribers in many U.S. cities. The news pages were created and edited by TMS staffers working on an Atex editing system in Orlando, Florida, and sent by satellite to NAPLPS decoder devices located at the local cable television companies. Among the firms providing technology to TMS and the Associated Press for the AP News Plus channel was Minneapolis-based Electronic Publishers Inc. (1985–1988).
In 1981, two amateur radio operators (VE3FTT and VE3GQW) received special permission from the Canadian Department of Communications to carry out on-air experiments using NAPLPS syntax which was technically not legal at the time because it was a "coded transmission". Following their report on the success of the tests, the DOC then permitted general use of NAPLPS on amateur radioteletype. This was reported in the ARRL Radio Handbook for several years following.
Between 1988 and 1994, Bell Canada offered a dial-up Telidon service called Alex,[5] similar in spirit to the French Minitel, with the telephone directory its principal information offering.
Decline
NAPLPS lived on into the early 1990s as the graphical basis for the Prodigy online service. Some bulletin boards were able to serve NAPLPS content to callers on their 1200 and 2400 bit/s modems. But the technology's chief advantage in an era of slow telecommunication - its ability to encode complex graphics in terse object commands - became moot as data communication speeds increased and raster graphics compression became popular.
Legacy
In the 1980s, the Graphical Kernel System (GKS) library, based on a 1970s specification with a similar basic geometry and command structure to NAPLPS, was widely implemented on microcomputers, and became the basis of Digital Research's GSX graphics system used in their GEMGUI. GKS was later extended into a 3D version, and additions to this resulted in PHIGS (Programmer's Hierarchical Interactive Graphics System), a competitor to OpenGL.
Closed captioning (CC) and subtitling are both processes of displaying text on a television, video screen, or other visual display to provide additional or interpretive information. Both are typically used as a transcription of the audio portion of a program as it occurs, sometimes including descriptions of non-speech elements. Other uses have included providing a textual alternative language translation of a presentation's primary audio language that is usually burned-in to the video and unselectable.
Telidon was a videotex/teletext service developed by the Canadian Communications Research Centre (CRC) during the late 1970s and supported by commercial enterprises led by Infomart in the early 1980s. The CRC referred to Telidon as a "second generation" system, offering improved performance, 2D colour graphics, multilingual support and a number of different interactivity options supported on various hardware. With additional features added by AT&T Corporation, and 16 other contributors in North America and supported by the Federal Government, Telidon was redefined as a protocol and became the NAPLPS standard.
Videotex was one of the earliest implementations of an end-user information system. From the late 1970s to early 2010s, it was used to deliver information to a user in computer-like format, typically to be displayed on a television or a dumb terminal.
Ceefax was the world's first teletext information service and a forerunner to the current BBC Red Button service. Ceefax was started by the BBC in 1974 and ended, after 38 years of broadcasting, at 23:32:19 BST on 23 October 2012, in line with the digital switchover being completed in Northern Ireland.
The Minitel was a videotex online service accessible through telephone lines, and was the world's most successful online service prior to the World Wide Web. It was invented in Cesson-Sévigné, near Rennes in Brittany, France.
Prodigy Communications Corporation was an online service from 1984 to 2001 that offered its subscribers access to a broad range of networked services. It was one of the major internet service providers of the 1990s.
The term telesoftware was coined by W.J.G. Overington who invented the concept in 1974; it literally means “software at a distance” and it often refers to the transmission of programs for a microprocessor or home computer via broadcast teletext, though the use of teletext was just a convenient way to implement the invention, which had been invented as a theoretical broadcasting concept previously. The concept being of producing local interactivity without the need for a return information link to a central computer. The invention arose as spin-off from research on function generators for a hybrid computer system for use in simulation of heat transfer in food preservation, and thus from outside of the broadcasting research establishments.
Prestel, the brand name for the UK Post Office Telecommunications's Viewdata technology, was an interactive videotex system developed during the late 1970s and commercially launched in 1979. It achieved a maximum of 90,000 subscribers in the UK and was eventually sold by BT in 1994.
Antiope was a French teletext standard in the 1980s. It also formed the basis for the display standard used in the French videotex service Minitel.
NABTS, the North American Broadcast Teletext Specification, is a protocol used for encoding NAPLPS-encoded teletext pages, as well as other types of digital data, within the vertical blanking interval (VBI) of an analog video signal. It is standardized under standard EIA-516, and has a rate of 15.6 kbit/s per line of video. It was adopted into the international standard CCIR 653 of 1986 as CCIR Teletext System C.
Teletext, or broadcast teletext, is a standard for displaying text and rudimentary graphics on suitably equipped television sets. Teletext sends data in the broadcast signal, hidden in the invisible vertical blanking interval area at the top and bottom of the screen. The teletext decoder in the television buffers this information as a series of "pages", each given a number. The user can display chosen pages using their remote control. In broad terms, it can be considered as Videotex, a system for the delivery of information to a user in a computer-like format, typically displayed on a television or a dumb terminal, but that designation is usually reserved for systems that provide bi-directional communication, such as Prestel or Minitel.
Electra was a teletext service in the United States that was in operation from 1982 up until 1993, when it was shut down due to a lack of funding, and discontinuation of teletext-capable television sets by the only US television manufacturer offering teletext capability at the time, Zenith. It was owned, operated and maintained by Cincinnati-based Taft Broadcasting and Tulsa, Oklahoma-based Satellite Syndicated Systems (SSS), later known as Tempo Enterprises, in cooperation with cable/satellite TV station Superstation WTBS, who carried Electra's data on their vertical blanking interval. SSS's own TV network, the Satellite Program Network, carried the service before it was shut down in 1989. The service was also available to C-band satellite dish users via the Galaxy 1 and Satcom 3R satellites.
Genesis Storytime was a cable TV channel founded in 1983 in Canada by Art Doerksen and Greg Stetski and distributed to several cable TV systems throughout the USA. Its mascot is named Robbie Rainbow.
World System Teletext (WST) is the name of a standard for encoding and displaying teletext information, which is used as the standard for teletext throughout Europe today. It was adopted into the international standard CCIR 653 of 1986 as CCIR Teletext System B.
Norpak Corporation was a company headquartered in Kanata, Ontario, Canada, that specialized in the development of systems for television-based data transmission. In 2010, it was acquired by Ross Video Ltd. of Iroquois and Ottawa, Ontario.
The AT&T Sceptre was a graphical terminal launched by AT&T in October 1983, used for the two largest deployments of videotex in the United States: Knight Ridder's Viewtron service in Florida, and the Los Angeles Times' Gateway service in Southern California. The Sceptre was the basic bit of home kit needed for the services, to paint NAPLPS-standard geometrically-specified pages to the screen.
This article covers technical details of the character encoding system defined by ETS 300 706, a standard for World System Teletext, and used for the Viewdata and Teletext variants of Videotex in Europe.
JTES, the Japanese Teletext Specification, is a protocol used for encoding teletext pages, as well as other types of digital data, within the vertical blanking interval (VBI) of an analog video signal in Japan. It was adopted into the international standard CCIR 653 of 1986 as CCIR Teletext System D.
NBC Teletext was a teletext service provided by the NBC, based on the NABTS standard.
References
1 2 3 Cynthia Boyko, "Telidon", Friends of the CRC, 14 October 1997
This page is based on this Wikipedia article Text is available under the CC BY-SA 4.0 license; additional terms may apply. Images, videos and audio are available under their respective licenses.
