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Data telecommunications system and method for transmitting compressed data

  • US 5,027,376 A
  • Filed: 05/31/1988
  • Issued: 06/25/1991
  • Est. Priority Date: 10/30/1985
  • Status: Expired due to Term
First Claim
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1. Apparatus for transmitting data in a compressed form between an initiating unit of data terminal equipment and a receiving unit of data terminal equipment connected over communications lines, one of said units having a compressing modem connected between said unit and telephone lines, and the other of said units having a decompressing modem connected between said other unit and telephone lines, said apparatus comprising:

  • (a) means for fetching a next data character from a data stream to be sent over communication lines;

    (b) means for transmitting a compressed character code assigned to said next data character to the decompressing modem;

    (c) means for incrementing a relative frequency counter for said next data character;

    (d) means for comparing said relative frequency counter for said next data character to a relative frequency counter of a next more frequently occurring character;

    (e) means for determining whether the relative frequency of said next data character is greater than the relative frequency of said next more frequently occurring character, and, if so, means for exchanging the compressed character codes assigned to said next data character and to said next more frequently occurring character;

    (f) means for repeating the operations of means (d) through (e) until the relative frequency of said next data character is less than the relative frequency of said next more frequently occurring character or said next data character is the most frequent character; and

    (g) means for repeating the operations of means (a) through (f) for next data characters and for transmitting said compressed character codes to said decompressing modem.

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