Multiple-frequency signal classification through use of a second-order statistic

  • US Patent No. 9179202
  • Issued: November 03, 2015
  • Status: Active

A multi-frequency (also known as multiple-frequency) signal, such as a dual-tone signal, can be a repeating signal that indicates a character designated on a keypad. The signal can be processed such that the character is identifiable. This processing can include using first and second-order statistics of the signal to determine an estimated average frequency of the signal. A table can be accessed that lists individual characters of the keypad and specific average frequency values can be associated with the individual characters. The specific average frequency value that is closest to the estimated average frequency can be identified and the character associated with this closest specific average frequency value can be appointed as the character indicated by the signal. Thus, the multi-frequency signal can be classified as communicating the appointed character.

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