Broadcast Engineer's Reference Book

Gordon AndersonTechnical Training Tandberf Television Ltd

2.7 VBI Data Carriage

 

 

 

The original purpose of the Vertical Blanking Interval (VBI) was to allow early television receivers to have very simple sync recovery circuits. Modern receivers are not affected if extra waveforms are placed in the VBI, so broadcast engineers can now use this precious resource for test, control and data signals (Figure 2.7.1).

In Europe (and other 25 Hz regions) a popular text and data distribution system called teletext has used spare capacity in the VBI (Figure 2.7.2). Variants of teletext have been used for broadcasting Internet, private data and control signals. Several advanced forms of teletext have been designed but have not been widely used for a ...