Top teletext - main characteristics of the top teletext

“Teletext” is the technical name given to the well known service for the transmission of information visualized on a tv screen as text pages and simple graphics. In Italy it has a trade name that varies according to the provider who distributes it, for instance "Televideo" for RAI, "Mediavideo" for Mediaset, "La7video" for La7, and so on.

The teletext is made up of a group of pages, each identified with a 3 figure number, composed of a group of alphanumeric and graphic characters on a matrix of 24 lines and 40 columns. The pages are transmitted cyclically, continually, one after the other, in particular fragments of the television signal, more precisely in the moment in which the electronic paintbrush that drafts the image on the screen is interrupted in the passage from one image to another, in the so-called vertical blanking interval. The pages can be added, modified or removed from the teletext cycle based on the editorial requirements of the broadcaster. Also the criteria for associating the pages to their contents can be different from one broadcaster to another. Normally the pages are grouped in magazines composed (up to a maximum) of 100 pages with a homogeneous content: For example pages 100 to 199 make up the magazine number 1 and can contain the news, those from 200 to 299 make up the magazine number 2 and are reserved for sport, and so on.

With the standard teletext the user must select a page by consecutively inputting on the remote control the three figures that make up the number of the page desired. In order to pass on to the successive page a key for incrementing the page number by 1 is available so that, if actually present, the successive page is acquired immediately by the tv set and shown on the screen. If this page is not present in the cycle the television set waits for it indefinitely. This occurs because the television does not know that the immediately successive page in the cycle is not present.

In the case of “TOP” teletext (Table of Pages) the situation is rather different. The TOP teletext is a particular improvement of the standard teletext service that results in an easier consultation of the pages present in the teletext cycle, and to avoid unnecessary waiting for pages not transmitted at that moment. The choice of the teletext pages takes place through particular coloured function keys present on the remote control of the teletext decoder. Moreover, the TOP allows a fast overview of the teletext information available and therefore becomes an effective guide for the user.

The introduction of such procedure requires relatively low investments to the transmitting station; moreover it involves only a minimum burden of work for the editorial staff that takes care of the teletext service.