Audio warning device for use with a line current protection circuit in a PCMCIA-architecture modem card
US5783999A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 29, 1996 |
| Grant date | Jul 21, 1998 |
| Priority date | — |
| Expiry date | May 29, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M11/06
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A novel line-current protection circuit that is useable with a PCMCIA modem card is disclosed. The protection circuit is adapted to detect when an excessive voltage is present across the tip and the ring leads of a telephone subscriber loop by sensing the amount of line-current being supplied to line interface circuitry disposed on the PCMCIA modem card. The protection circuit includes a current sensing circuit portion that is placed in series with the tip lead and which detects when the line current exceeds a predetermined maximum amount. In the event the line current exceeds the maximum amount, the current sensing circuit asserts an excessive line current signal which is being monitored by a digital processor. The digital processor responds by causing a relay circuit to be opened, thereby causing the PCMCIA modem to be in an "on-hook" state. In the presence of the excessive line current signal the digital processor also causes an audible signal to be emitted, thereby alerting the user to the existence of the fault condition. When the magnitude of the line-current does not exceed the predetermined maximum amount, the excessive line current signal is not asserted and the digital pr…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.