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Data compression method and apparatus

  • US 3,914,586 A
  • Filed: 10/25/1973
  • Issued: 10/21/1975
  • Est. Priority Date: 10/25/1973
  • Status: Expired due to Term
First Claim
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1. Apparatus for encoding successive identical groups of bits of binary data comprising:

  • clocking means for forming a plurality of bit cells of uniform time durations and for defining the leading edge and midpoint of each bit cell, and bit pair encoder means responsive to the first of said successive groups of binary data and to said clocking means and comprising parallel in serial out shift register means for storing said groups of bits and gate means for detecting the binary character of adjacent uncoded bits shifted through said register means, said gate means responding to those bits of one binary characterization in said first group of bits by producing first control pulses at the midpoint of only those of the corresponding bit cells which immediately follow a bit cell in which no pulse occurs and which are immediately followed by a bit cell containing a bit of said one binary characterization, said gate means further responding to those of said bits of the other binary characterization in said first group of bits by producing second control pulses at the leading edge of only those of the corresponding bit cells which immediately follow a bit cell in which no pulse occurs and which are immediately followed by a bit cell containing a bit of said other binary characterization, detector means for detecting the number of said successive groups of bits, signal generating means responsive to the number of said successive groups, and to the state of the last bit of said first group of bits by producing third control pulses, said third control pulses consisting of five pulses, the first pulse occurring at the trailing edge of the bit cell corresponding to the last bit of said first group of bits, the second pulse occurring at least two bit cells displaced from said first pulse and occurring at the midpoint or leading edge of a bit cell depending upon whether the state of the last bit of said first group of bits is said one or said other binary characterization respectively, the third pulse displaced from said second pulse by 1 1/2 bit cells, the fourth pulse displaced from said third pulse by 1 1/2 bit cells, and the fifth pulse displaced from said fourth pulse by an amount which exceeds 1 1/2 bit cells by a multiple of 1/2 bit cells for each group of bits following said first group of bits, output state controller means for providing a bistable output signal containing transitions between separately identifiable states in response to either of said first, second or third control pulses.

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