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Publication of BE510089ApublicationCriticalpatent/BE510089A/xx
H04N5/14—Picture signal circuitry for video frequency region
H04N5/16—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level
H04N5/165—Circuitry for reinsertion of DC and slowly varying components of signal; Circuitry for preservation of black or white level to maintain the black level constant