Telidon | The Canadian Encyclopedia



Telidon, a combination of the Greek words meaning "to know at a distance," was a waypoint en route to the Internet and was an early demonstration of how technology can provide on-demand access to information.


Telidon, a combination of the Greek words meaning "to know at a distance," was a waypoint en route to the Internet and was an early demonstration of how technology can provide on-demand access to information. It was developed by researchers in the federal Department of COMMUNICATIONS in Ottawa in the mid-1970s, combining aspects of television, the TELEPHONE and the computer to produce a new medium of communication and information processing. From television came the ability to display letters and images on a screen; from the telephone, the ability to communicate over a distance; and from the computer, the ability to manipulate, store and retrieve information quickly and inexpensively. The federal government hoped that this combination of capabilities into a new medium of communication would stimulate the development of high-technology industries and help Canada take a position of leadership in the developing field of information technology. Following the successful launch of various trials, the project came to a halt in the mid-1980s following the federal government's decision to cut off funding due to its limited commercial success.

There were 3 major ways to implement Telidon systems: videotex, teletext and as stand-alone systems; and there were significant differences in the capabilities of the resultant systems.


Videotex systems allow the user to receive information from and send information back to a computer located in a different place. These systems may use telephone lines, coaxial cable, optical fibre, laser or radio-communication links to connect the user to the computer. The 2-way capability enables users to exchange messages and perform such interactive tasks as information retrieval, banking and shopping.

Teletext systems are not interactive in the same way as videotex systems. The information is broadcast in the unused portion of a regular television signal called the "vertical blanking interval" and is decoded by a device attached to the television set. Teletext is a one-way system that neither requires nor permits communication from the user back to the central computer. The information to be displayed is simply cycled again and again. Most teletext systems display a menu or index page on the screen when the decoder is first turned on. The user decides which topic is of interest and enters the number on a keypad attached to the unit. When the page the user wants comes around, the "frame grabber" on top of the TV set "grabs" it, stores it in its memory, decodes and displays it on the screen until the user requests the next frame. A major limitation is the amount of information - the number of "pages" or "frames" - that can be kept cycling around.


Stand-alone systems differ from videotex and teletext systems mostly in the way they connect the computer with the user. Because these units may have everything combined into a single box, they are sometimes called "electronic slide projectors." They can be programmed to run a fixed cycle, or may be connected to keypads or other kinds of input devices that allow the user to select the desired pages or to use various "action pages" that have a wide range of response possibilities.

The Telidon Coding System

In addition to the hardware items already mentioned - the television set, the telecommunications link, and the computer - a decoder was required to accept the coded instruction from the computer and generate an electronic signal that creates the display on the screen. The heart of any Telidon system was the Picture Description Instruction - the special code that instructed the decoder what to draw on the display screen. The coding scheme, known as the North American Presentation Level Protocol Syntax (NAPLPS), came to be the North American standard. It uses a system whereby different kinds of geometric shapes - lines, points, arcs, polygons - are specified in concise form. In this "alpha-geometric method," images may be created and manipulated with comparative ease; only a small amount of information is required to specify an image; and the quality of the final image is dependent mainly on the ability of the display device to resolve fine detail.

Service Development

Initially, it was believed that videotex and teletext systems would find consumer acceptance in Canada and the US. However, this has not proven to be the case and eventually the applications of Telidon/NAPLPS focused on business or educational purposes, including Marketfax - a stock market information service; Grassroots, an agricultural information service; and TABS, an information system for pilots. In Canada, Infomart of Toronto, among many others, was prominent in attempting to develop videotex services. While Infomart achieved some success with services such as Grassroots, they did not achieve success in penetrating the consumer market and have now turned their attention to other aspects of electronic publishing. Despite the difficulties experienced with videotex start-ups, many companies still remained interested in this topic. This included such well-known companies as IBM, Sears, AT & T and J.C. Penney, all of whom were rumoured to be planning the introduction of videotex services or products at one point. Among them also was BELL CANADA, which hoped to emulate the success of the French Minitel service.

Industry Development

When Telidon was first announced in 1978, videotex activity in Europe was already gaining momentum and predictions about videotex services becoming almost a necessity in every home within a few years were rampant. France and the UK were particularly active and were marketing their brands. In Canada, the Canadian Videotex Consultative Committee (CVCC) was established to advise the government on actions to be taken. Canada, in fact, had developed a small videotex industry which was capable of responding to the demand for videotex products and services in Canada and is capable of supplying a small export market. While this industry faces increasing competition from abroad, there was hope that it would strengthen its position if videotex and teletext services showed strong development in Canada.

In the spring of 1985, federal funding for the project came to an end, having reached a total of $69 million dollars over the six previous years. Widespread adoption of the technology, the lifeblood of any invention, had failed to materialize in spite of an estimated investment of $200 million from industry. While there were a few fringe efforts to keep the technology alive, it was widely recognized that the project had run its course but not without having provided Canadians with a glimpse into the future of the way information is exchanged.

The inventors of Telidon received several awards for the important contribution they made to the development of information technology in Canada. Herb Bown received the Order of Canada and the gold medal for engineering excellence from the Association of Professional Engineers of Ontario. The Touche Ross New Perspectives Award was awarded to Herb Bown and Doug O'Brien.


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