 Currently, progressive displays dominate the HDTV market.In the 1970s, computers and home video game systems began using TV sets as display devices.At that point, a 480-line NTSC signal was well beyond the graphics abilities of low cost computers, so these systems used a simplified video signal that made each video field scan directly on top of the previous one, rather than each line between two lines of the previous field, along with relatively low horizontal pixel counts.