Method and structure for detecting a customer premises equipment alerting signal
US5862212A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 29, 1996 |
| Grant date | Jan 19, 1999 |
| Priority date | — |
| Expiry date | Aug 29, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/46
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A method and device for detecting a customer premises equipment alerting signal (CAS) tone in a telephone system which has both caller identification and call waiting. The present invention distinguishes between valid CAS tones transmitted by the telephone company central office and invalid CAS tones which are caused by music or a human voice. The present invention samples detected tone during a plurality of sample periods. The change of frequency, as well as the direction of frequency change, between successive sample periods is calculated. The number of transitions in the direction of frequency change are counted and used to determine whether the detected tone corresponds to a valid CAS tone or an invalid CAS tone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.