DTA - Viewdata

An Overview of Videotex
What is Videotex?

Videotex is a system which allows an exchange of information between a user and a computer. The user and computer are connected via the telephone system, and the information is displayed on a modified TV screen or monitor.

Under the umbrella title 'videotex', there are two major classifications; 'Teletext' and 'Viewdata'. Practically everybody has seen, if not used, teletext. It is transmitted, along with the picture, on both BBC and IBA television channels and displayed on a modified television. The BBC version of the system is called 'CEEFAX' and the IBA system 'ORACLE'.

The main difference between 'teletext' and 'viewdata' systems is that, whilst teletext simply transmits information to you, viewdata is `interactive', i.e. the user can not only view the screens of information but can create screens and access them in the way that best suits them.

The pioneer work on videotex began in the UK around 1970. The concept of viewdata was proposed by Sam Fedida working at the Post Office's Research Centre at Martlesham Heath in Suffolk, and a feasibility study into a national viewdata system, which was eventually to become Prestel, initiated.

At the same time, the BBC and IBA were experimenting with their own, non-interactive, videotex, for which pilot trials were carried out in 1974 and a full commercial system introduced in 1976.

Prestel, British Telecom's viewdata service, was introduced in 1979, and has grown rapidly to a state where there are currently over 40,000 Prestel terminals in use - the world's largest viewdata system.

The rapid growth in the use of viewdata systems owes much to their many attractive features, not the least of which are the low cost of both the equipment and the software, their ease of use by even the most inexperienced operators, the use of colour and graphics, and the interactive nature of the systems.

Along with the growth of BT's Prestel system, many private videotex systems have been developed, of which DTA Videotex represents the state of the art.

The main advantage of a privately-run viewdata system, over a public system such as Prestel, lies in the fact that total control of the system is available to you or your company.

DTA Videotex allows you full control over the registration of users, full monitoring and analysis of access to the system, and the ability to create purpose-designed data-entry systems and page ordering - tailoring the system precisely to your requirements. In addition, DTA Videotex is highly cost-effective for large volumes of traffic.

How do Viewdata Systems Work?

There are essentially two components in a viewdata system, the `host computer', and the `terminal'.

The host computer holds the `database' i.e. all the information that the system holds, and communicates with the terminal through the telephone system. There is no limit to the distance between the host computer and the terminal, provided a telephone link is available.

The terminal can be a modified television set, a monitor, or a computer, and will be connected to the telephone system via a modem (a modem is simply a device which translates information for transmission over the telephone system, this may well be built into the terminal).

In addition, you will need some way of entering information into the system or selecting the information you wish to view. In the case of a computer, this will simply be the computer keyboard, in the case of other terminals it may vary between a full "QWERTY" keyboard, and a simple keypad.

In order to select information from the system, the only keys that are needed are the ten numbered keys, 0-9, the # (`Hash') key, and the * (`star') key.

The connection between keyboard (or keypad), and terminal will vary from system to system. On many systems a direct physical link, via a cable, will be required, whilst on other systems the connection may be remote (infra-red).

Selecting the information you require couldn't be easier. Often it is simply a matter of keying in a single-digit number from a list of options displayed on the screen. In the most complex cases it is still only a matter of keying in the number corresponding to the `page' of information you wish to view.

The host computer holds all the individual `pages' of information in a large `database' in its memory. When you key in your page selection the page number is transmitted down the telephone lines from your terminal to the host computer. The host computer then searches through its database to the correct page and transmits that page to your terminal.

In addition, you may transmit information to the host computer which it will then add to its database, thus forming new pages which can be transmitted back to a terminal on request.

No level of computing experience or expertise is needed to use a videotex system. Anybody who can press a key can take full advantage of all the many advanced features of the DTA Videotex system.

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