A communication system and method for transmitting information in the form of binary digital data to be transmitted is encoded into two separate two level sequences S1 and S2 such that the first occurrence of a logic "1" is encoded into the same level in both sequences and each subsequent occurrence...http://www.google.es/patents/US4791407?utm_source=gb-gplus-sharePatente US4791407 - Alternate mark/space inversion line code
