Recovery of DTMF tones in the presence of periodic interference and obstruction

  • US Patent No. 9055145
  • Issued: June 09, 2015
  • Status: Active

While a dual tone multi-frequency (DTMF) signal can be easily processed if cleanly obtained, difficulties can arise if the DTMF signal is not cleanly obtained. In one example, part of the signal can be cleanly obtained, but part of the signal can be obstructed. In order to determine the content of the DTMF signal the parts that are cleanly obtained can be compared with known DTMF signals, such as DTMF signals that correspond with buttons on a telephone keypad. A classification of a closest matching known DTMF signal can be identified and that classification can be assigned to the partially obtained DTMF signal. Thus, without clearly obtaining the whole DTMF signal a content of the DTMF signal can be ascertained.

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