We report on a class of high-rate dc-free codes, called multimode codes, where each source word can be represented by a codeword taken from a selection set of codeword alternatives. Conventional multimode codes are analyzed using a simple mathematical model. The criterion used to select the "best" codeword from the selection set available has a significant bearing on the performance. Various selection criteria are introduced and their effect on the performance of multimode codes is examined.

Traditional schemes for encoding and decoding runlength-constrained sequences using the enumeration principle require two sets of weighting coefficients. A new enumeration is presented requiring only one set of coefficients.