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Multifrequency tone detection by zero-interval analysis

Multifrequency tone detection by zero-interval analysis

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An algorithm is presented which enables a microprocessor to analyse the zero intervals of the multifrequency signals from a pushbutton telephone. A model has shown that, with a 100 kHz clock, the component frequencies of any signal can be predicted to within ±1% from a 30 ms sample, but the speech immunity requires improvement.

References

    1. 1)
      • `‘Technical features of pushbutton telephone sets’. CCITT Fifth Plenary Assembly 1972 (Green Book)', , Vol. VI–1 Recommendation Q23.
http://iet.metastore.ingenta.com/content/journals/10.1049/el_19770003
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