Apparatus and method for audible signaling tone recognition
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United States of America Patent
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May 10, 1994
Grant Date -
N/A
app pub date -
Mar 31, 1992
filing date -
Mar 31, 1992
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
A method and apparatus for detecting dual-tone, multi-frequency (DTMF) digits and call progress tones by determining the amplitudes of preselected frequencies in a signal over a predetermined time period, and determining a candidate tone by selecting two of the preselected frequencies with the highest amplitudes and comparing the two selected frequencies to known DTMF and call progress tone frequencies. The amplitudes of the two selected frequencies are then tested against predefined thresholds corresponding to a candidate tone having the two selected frequencies. The candidate tone in the current time period is tested against candidate tones in previous time periods for consistency. If the candidate tone is a DTMF digit and passed all of the tests, then the DTMF digit is returned. If the candidate tone is a call progress tone, the pattern of the candidate tone over a plurality of predetermined time periods is recorded and tested against known patterns of the candidate tone. If the candidate tone meets all of the above tests, the call progress tone is returned.
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