Circuit and method for loopback test and on-hook transmission integrated in a telephone subscriber line interface circuit
US5659570A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 30, 1995 |
| Grant date | Aug 19, 1997 |
| Priority date | — |
| Expiry date | Jan 30, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/005
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A method and circuit for loopback testing a telephone subscriber line interface circuit (SLIC) includes current sources connected to each of tip and ring circuits from which switch-hook is detected in the SLIC. A loopback test of the SLIC is conducted when the telephone is on-hook and is successful when the current from the current sources simulates a switch-hook detection, The current sources may also be used during on-hook transmission. A ground key detect circuit in the SLIC may be used to verify a successful loopback test by using current from the current sources in the ground key detect circuit to check for a grounded ring circuit in the SLIC.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.