In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary and moving parts of the image. When displaying a natively interlaced signal, however, overall spatial resolution is degraded by simple line doubling—artifacts such as flickering or "comb" effects in moving parts of the image appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan device such as an LCD Television, digital video projector or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.Video can be transmitted or transported in a variety of ways. Wireless broadcast as an analog or digital signal. Coaxial cable in a closed circuit system can be sent as analog interlaced 1 volt peak to peak with a maximum horizontal line resolution up to 480. Broadcast or studio cameras use a single or dual coaxial cable system using a progressive scan format known as SDI serial digital interface and HD-SDI for High Definition video. The distances of transmission are somewhat limited depending on the manufacturer the format may be proprietary. SDI has a negligible lag and is uncompressed. There are initiatives to use the SDI standards in closed circuit surveillance systems, for Higher Definition images, over longer distances on coax or twisted pair cable. Due to the nature of the higher bandwidth needed, the distance the signal can be effectively sent is a half to a third of what the older interlaced analog systems supported.
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