DC-FREE CODES

An encoder that encodes a communication signal including a precoder that precodes portions of the communication signal. The portions comprise M bits, where M is greater than. A buffer buffers said portions. A DC tracking device that modulates a flip signal based on a comparison of a DC value of one of the portions of the communication signal and an average DC value of N previous bits of the communication signal where N is greater than M. A flip device that selectively flips said portions based on said flip signal.