Line interface battery feed arrangements with PTC resistors
US6507654B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 21, 1998 |
| Grant date | Jan 14, 2003 |
| Priority date | — |
| Expiry date | Dec 21, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/745
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone line interface circuit is disclosed that functions with use of PTC resistors so that temperature increases within the battery feed resistors is minimized. Utilizing current and voltage feedback loops within the line interface circuit, the PTC resistors are implemented without significantly reducing the performance of the overall circuit that would normally be caused by the PTC resistors' inherent impedance inaccuracies. In normal operation, the feedback loops adjust the current and voltage on the telephone line to the desired level without regard for the impedance values of the PTC resistors. In the case that a high voltage is applied to a telephone line, the significant increase in current flow into the line interface circuit causes the battery feed resistors to heat up, and therefore the PTC resistors, that are physically local to the feed resistors, to heat up and significantly increase in impedance.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.