Vertical blanking interval
The vertical blanking interval (VBI) is an interval in a television signal that temporarily suspends transmission of the signal for the electron gun to move back up to the first line of the television screen to trace the next screen field.The vertical blanking interval can be used to carry data, since anything sent during the VBI would naturally not be displayed; various test signals, closed captioning, and other digital data can be sent during this time period.
