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The video voltage units are called IRE units because they were standardized by the IRE (Now IEEE). The original setup spec for black and white was looser, and tended toward zero, but the NTSC color spec set it at 7.5 IRE. However, it was not stated in IRE units in 1953, but rather as percent of RF modulation, so the IRE scale may have come later but some time before the IRE and AIEE merged to become the IEEE (1963).
I think setup was ill-advised because it resulted in objectionable variations in black level when it was not carefully maintained. Specifying zero setup as Europe did would have served the industry much better, IMO.
[Edit - oh yes, thanks for the link!]
Last edited by old_tv_nut; 06-20-2013 at 10:30 PM.
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