Telephone line interface circuit with virtual impedance
US6647114B1 · kind B1 · utility
Assignee
Inventor
Key dates
| Filing date | May 14, 1999 |
| Grant date | Nov 11, 2003 |
| Priority date | — |
| Expiry date | May 14, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/76
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Using a telephone line interface circuit with negative feedback, it is possible to control the current through the circuit so that the ratio of the voltage applied across the circuit to the current is the desired value of impedance. Voltage feedback from the line controls the current through the circuit, thereby reflecting a “virtual” impedance to the telephone line. By adequately filtering the voltage feedback, the reflected impedance to the line can be adjusted to any desired impedance function, without using the actual values of the impedance. The circuit is thus ideally suited for applications in which the impedance values need to be varied depending upon the characteristics of the telephone system.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.