Modem loop current detect system to detect an off-hook condition in an extension telephone
US6134321A · kind A · utility
8Cited by
7References
8Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Jun 16, 1998 |
| Grant date | Oct 17, 2000 |
| Priority date | — |
| Expiry date | Jun 16, 2018 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S379/902
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone line monitoring circuit uses an optoisolator to convert the telephone line current to a voltage which is applied to the input of an AID converter. The A/D values are coarse values representing telephone line current. The A/D is sampled at a predetermined interval to identify changes introduced by the telephone company central office, and to take those changes into account when deciding if an extension telephone has gone off-hook. When a customer causes an extension telephone to go off-hook, the line current divides between the extension telephone and the IRD modem, and such change is detected.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.