AX4A Non-Technical Page

Real-Time Data Receivers

Introduction

This summary is not aimed at an audience with technical expertise, but attempts to provide an understanding of the basic principles involved with Datacasting.

About Broadcasting

Have you ever thought about how, in this modern world with all its different methods of communication, that most of the population can receive television and radio signals without any congestion? This is because it was originally designed as a fine point to multipoint system. This is another way of saying, that it was designed to provide exceptional quality independent of the numbers of end-users/subscribers connected to it.

About Datacasting

During the 1970’s it was found that data could ‘piggy-back’ or ‘be inserted’ onto television transmissions. In a frame of television picture data not all lines were used, with the first 22 lines of each frame being empty. These empty lines are known as the Vertical Blanking Interval or VBI and it was into these ‘empty lines that a new type of data was inserted. The already established world-wide network of television broadcasters made it possible for the introduction of this type of data insertion, which is now known as teletext. This then provided a method of communicating information to all who were correctly connected.

The Vertical Blanking Interval

In the world of television broadcasting the blank lines at the start of each television frame are known as the VBI. During Datacast transmissions other kinds of data are now inserted and it is not limited to teletext. The insertion of data into these blank lines enables the transmission of ‘real-time’ information which is at present the most reliable and cost effective method available anywhere.

How Do You Publish Your Data?

The methods employed when preparing data for ‘publishing’, using datacast, are the same methods and common tools that are used when publishing on Internet. The difference being that once the data is prepared, instead of up-loading it to an Internet server, it is supplied to a television broadcaster who then transmits it by inserting it onto the VBI part of the television signal.