Digital tone detector using concatenated detection intervals
US3990006A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 8, 1975 |
| Grant date | Nov 2, 1976 |
| Priority date | — |
| Expiry date | Jan 8, 1995 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/448
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Known tone detectors are adversely affected by various signaling tone distorting sources, including noise as well as talk-off due to tone-like speech, e.g., due to averaging of speech frequencies over a detection interval. As a result, improper tone detection often occurs. This problem is mitigated by dividing a detection interval into a plurality of detection sub-intervals which are then concatenated for tone detection. Detection of the desired tone in at least a predetermined number of concatenated sub-intervals is interpreted as the presence of a valid tone. Conversely, absence of detection of the desired tone in at least a second predetermined number of concatenated sub-intervals is interpreted as the absence of a valid tone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.