1. Apparatus for encoding a binary data stream into a modified Miller Code data stream comprising: first means responsive to said binary stream and a control signal indicating whether the bits of said binary stream are to be coded according to a conventional Miller Code or a modified version thereof to detect successive pairs of successive binary "0" bits in said binary stream and to detect the number of binary "1" bits in said binary stream disposed between each bit of each of said pairs of "0" bits; second means coupled to said first means responsive to said binary stream and the output signal of said first means to produce said control signal; and third means coupled to said first and second means responsive to said binary stream, the output signal of said first means and said control signal to produce said modified Miller Code data stream including a transition period of two bit periods for every pair of binary "1" bits disposed between each bit of each of said pairs of "0" bits, said transition period extending from the transition at the end of the first bit of an associated one of said pairs of "0" bits.