Abscissa and ordinate is the distance between the projection and the origin of the axis, and whose sign is given by the location on the projection relative to the origin (before: negative; after: positive). Usually these are the horizontal and vertical coordinates of a point in a two-dimensional rectangular Cartesian coordinate system. The terms can also refer to the horizontal and vertical axes respectively (typically "x"-axis and "y"–axis) of a two-dimensional graph. An ordered pair consists of two terms—the abscissa (horizontal, usually "x") and the ordinate (vertical, usually "y")—which define the location of a point in two-dimensional rectangular space. Though the word "abscissa"
Paired disparity code negative level (negative disparity) is paired with some other codeword that averages to a positive level (positive disparity). In a system that uses a paired disparity code, the transmitter must keep track of the running DC buildup the running disparity and always pick the codeword that pushes the DC level back towards zero. The receiver is designed so that either codeword of the pair decodes to the same data bits. Most line codes use either a paired disparity code or a constant-weight code. The simplest paired disparity code is alternate mark inversion signal. Other paired disparity codes include 8B10B, ,