Hazard prevention for telephone line interface circuits
US5666406A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 10, 1994 |
| Grant date | Sep 9, 1997 |
| Priority date | — |
| Expiry date | Feb 10, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/02
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A telephone line interface circuit comprises a controlled voltage generator for selectively generating a ringing voltage waveform for a telephone line or a supply voltage for a drive circuit for the telephone line, and a switching circuit interconnecting an output of the controlled voltage generator, the drive circuit, and the telephone line accordingly. In order to avoid creating a potentially hazardous condition on the telephone line, an interlock is provided between enabling of the controlled voltage generator and switching of the switching circuit, and software and hardware monitoring functions monitor operation of the control software and the controlled voltage generator and disable the controlled voltage generator in response to fault conditions or unusual behavior.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.