PURPOSE:To set a DC component to ''0'', to increase the width of a detecting window and the minimum inversion interval and to reduce the maximum inversion interval by replacing 8-bit data in a binary data string divided in each 8 bits by a 12-bit code and NRZI-modulating the 12-bit code. CONSTITUTION:An input data string is divided in each 8 bits and converted into 12-bit codes in accordance with a conversion table by an 8/12 bit conversion part 3 and the 12-bit codes are modulated and outputted by/from an NRZI (non- return-to-zero change on1) conversion part 2. The 12-bit code is selected when the difference between the ''high'' period and ''low'' period of a signal of the code itself is ''0'', i.e., the total digital value is ''0''. The sum of codes setting the minimum inversion interval to 2T/3 and the maximum inversion interval to 2T is 440 codes. These code words are satisfied with the conditions of the minimum inversion interval and the maximum inversion interval even at the connection parts of the code words. A data word consisting of 8 bits requires 256 or more code words.
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