Digital tone decoder and method of decoding tones using linear prediction coding
US4689760A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 9, 1984 |
| Grant date | Aug 25, 1987 |
| Priority date | — |
| Expiry date | Nov 9, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/4575
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.