running disparity (RD)

In some transmission processes, the difference between the transmitted 0-bit values and the 1-bit values plays an important role, since inequality results in a DC component that negatively affects the coding and thus the transmission properties.

If the coding is characterized by a disparity between the number of logical zeros and the number of logical ones, this is referred to as running disparity ( RD). The disparity of logical states is determined between the beginning of a data sequence and a point in time during data transmission. If the number of logical 0-levels corresponds to the number of logical 1-levels, i.e. there is no difference between the two values, then there is no running disparity (RD). The RD value is 0. If the RD value is greater than zero, then more 1- level signals are transmitted, and if it is less than zero, then more 0-level signals are transmitted.

The running disparity signal can also be used for error detection.