Refers to the polarity of the black portion of the picture signal with respect to the white portion of the picture signal.

For example, in a “black negative” picture, the potential corresponding to the black areas of the picture is negative with respect to the potential corresponding to the white areas of the picture; in a “black positive” picture, the potential corresponding to the black areas of the picture is positive.

The signal as observed at the broadcasters’ master control rooms and telephone company television operating centers is “black negative.”