Digital tone decoder and method of decoding tones using linear p

Details Digital tone decoder and method of decoding tones using linear p Digital tone decoder and method of decoding tones using linear p

1984-11-09

1987-08-25

Krass, Errol A.

Multiplex communications

Wide area network

Packet switching

375 94, 381 34, 364576, 379386, G06G 719, H04M 300

Patent

active

046897607

ABSTRACT:
An all digital feature based pattern recognition tone detection system distinguishes one or more tones from speech or other background noise and provides extremely reliable, low cost DTMF tone detection. The system includes a digital signal processing system which uses a modified PARCOR signal analysis technique to efficiently calculate inverse filter coefficients defining in functional form a smoothed LPC spectrum from a received frame of digital pulse code data. A Fourier transform provides high resolution evaluation of the LPC data at frequencies of interest to permit evaluation of the spectral response in accordance with known features of an expected tone signal.

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patent: 4563681 (1986-07-01), Godard
Boddie, J. R., Sachs, N. and Tow, Jr., "Digital Sound Processor: Receiver for Touch-Tone Service," The Bell System Technical Journal, vol. 60, No. 7 (Sep. 1981), pp. 1573-1583.
Mitel, "An Introduction to Mitel DTMF Receivers," application note MSAN-106 (Nov. 1981), pp. 3-3 to 3-9.
Markel and Gray, "Linear Prediction of Speech," Springer-Verlag, (Berlin, Heidelberg, New York 1976), pp. 1-17, 31-35.
V. LeRoux and C. Gueguen, "A Fixed-Point Computation of Partial Correlation Coefficients," IEEE Trans. ASSP-25, p. 257, 1977.

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