V-chip technology works much like closed captioning and uses the vertical blanking interval in the television signal.
12.
This happens during the blanking interval.
13.
Image data on the bus is interleaved with signals for horizontal and vertical blanking intervals ( porches ).
14.
It consists of a waveform inserted into the non-picture Vertical Blanking Interval ( VBI ) of an analogue video signal.
15.
The video parameters defined by the standard include horizontal blanking ( retrace ) and vertical blanking intervals, horizontal / vertical sync polarity.
16.
In the United States, part of the blanking interval was set aside to carry program identification information, schedules and emergency broadcast functions.
17.
In television, in particular, the vertical blanking interval is long to accommodate the slow equipment available at the time the standard was set.
18.
Early teletext applications also used vertical blanking interval lines 14 18 and 20, but teletext over NTSC was never widely adopted by viewers.
19.
There was also a version that encrypted the audio using a digital audio stream in the horizontal blanking interval like the VCII system.
20.
In teletext mode, character codes were sent to users'televisions by encoding them as dot patterns in the vertical blanking interval of the video signal.
