<Tr> <Th> Original network </Th> <Td> NBC </Td> </Tr> <Tr> <Th> Picture format </Th> <Td> 480i (4: 3 SDTV) (1975--2005) 1080i (16: 9 HDTV) (2005--present) </Td> </Tr> <Tr> <Th> Audio format </Th> <Td> Mono (1975 - 1985) Stereo (1985 - 1989) Stereo Surround (1989 - 1994) Dolby Surround (1994 - 1997) Dolby Digital (1997 - present) </Td> </Tr> <Tr> <Th> Original release </Th> <Td> October 11, 1975--present </Td> </Tr>

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