Telephone line interface circuit with voltage switching
US5323461A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 2, 1992 |
| Grant date | Jun 21, 1994 |
| Priority date | — |
| Expiry date | Apr 2, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH02M3/33569
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
A two-wire telephone line interface circuit comprises a driver circuit for supplying direct current on the line, a controlled voltage generator, a sensing circuit for monitoring the line current, a control circuit for controlling an output voltage of the voltage generator, and a switching circuit. The control circuit controls the switching circuit to supply, as a supply voltage for the driver circuit, a battery voltage in an on-hook state of the line or the controlled output voltage of the voltage generator in an off-hook state of the line, this output voltage being controlled to provide off-hook current limiting. The control circuit also controls the switching circuit to selectively supply the controlled output voltage of the voltage generator as a signalling voltage to at least one wire of the line for high voltage signalling, e.g. ringing, on the line. Desirable forms of the switching circuit are described.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.