Dual tone multifrequency signal receiver

Details Dual tone multifrequency signal receiver Dual tone multifrequency signal receiver

1978-08-31

1980-06-03

Konick, Bernard

H04M 150

Patent

active

042063230

ABSTRACT:
A system and method for detecting the presence of a tone burst and identifying the frequency signals contained within the tone burst of a dual tone multifrequency system includes an arrangement for applying the tone burst to a plurality of filter circuits that are tuned to respectively different frequencies including those frequency signals of which the tone burst may be comprised. The outputs of the filter circuits are monitored and signals representative of the filter outputs are compared with a first set of reference criteria, at a prescribed interval of time after beginning the monitoring of the outputs of the filter circuits. A history profile for each of the signal outputs of the filter circuits is maintained and in order to accurately identify a valid tone pair, an analysis is made of the level signal outputs of the filter circuits. Specifically, upon the monitored outputs of the filter circuits satisfying the first set of reference criteria and being also identified as those which satisfy a prescribed history profile, there are produced identification codes indicating the frequency signals which correspond to a valid tone burst.

REFERENCES:
patent: 3912869 (1975-10-01), Ullakko
patent: 4016370 (1977-04-01), Laoteppitaks et al.

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