Line codes for digital subscriber lines (ISDN basic access)

The attributes of the several line codes considered for a North American standard for ISDN basic access are compared. Impairments that affect line code performance are examined, and their performance characteristics are discussed. An intuitive explanation of why the code performs as it does is attempted in each case. Some variations of the codes that were considered and that were intended to improve their performance are also discussed. The codes considered are bi-phase, modified duobinary, alternate mark inversion, 3B2T, 2B1Q and 4B3T.>