Method and apparatus for DTMF detection
US5818929A · kind A · utility
55Cited by
7References
17Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Dec 13, 1994 |
| Grant date | Oct 6, 1998 |
| Priority date | — |
| Expiry date | Dec 13, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/505
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The total energy of a signal that has entered from a telephone line is detected before the signal is applied to an AGC circuit. After the signal is applied to the AGC circuit, the energy of a DTMF signal, which comprises one frequency from four high group frequencies and one frequency from four low group frequencies, is detected through a band-elimination filter having a short energy-propagation delay time with respect to pass-band frequencies. By detecting the DTMF signal based upon the detected energies, detection of the DTMF signal can be performed in a short period of time and erroneous detection can be suppressed.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.