Saturday, August 23, 2014

Iconic TV Function: Why the teletext can not be killed – Business Week

Kathrin Grannemann

Teletext lives – all digital achievements notwithstanding. Why the art relic is still relevant and how evolved the format.

Every day it thousands of people, although he is not only visually but also technically a relic from the early days of television: The teletext. In 1974, the first version of the service of the BBC has been developed, which today is still supported by every television – and apparently still has its raison d’être.

While a preferred sports results to retrieve on the teletext, other information on the current news or the weather. However, as the size of teletext arose over all and how it will evolve in the coming years?

The teletext is Technically a stopgap. The analog TV picture according to Central European radio standard 625 image lines, of which only 576 lines for the transmission of television picture are needed. TV technician for the BBC came up with the idea to use this gap and transmitted over text data.

The first trials started already in 1970, in September 1974 started at the BBC Ceefax the offer, so to speak, the first version of the well known today teletext. In the following years developed stations and TV manufacturers a common specification for teletext and associated decoder which have to this day.

The current teletext standard already exhausted all possibilities, there are no changes or additions possible. A page of teletext comprises a maximum of 24 lines of 40 characters, 22 of which can be used by the editors. Also offered are 96 characters including numbers. A special software plays content created in the blanking interval and delivers them as it were from the TV show. Up to 899 pages current teletext usually have. To provide a better overview, the early nineties the so-called TOP text was introduced, allowing the decoder to creating a table of contents.

The data rate in the standard European PAL format corresponds to a transfer of data from 128 kilobits per second. These, however, are only 15 to 47.5 kilobits per second. For comparison: An ISDN line offers a transmission rate of 64 kilobits per second



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