Remote testing of metallic loops with a trans hybrid signal
US4870675A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Nov 28, 1988 |
| Grant date | Sep 26, 1989 |
| Priority date | — |
| Expiry date | Nov 28, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/303
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Currently, metallic loops are tested for shorts, opens and grounds by applying a test signal (DC or 20 Hz) directly to the metallic looop. A test signal cannot be applied to any part of the network other than the metallic loop because it will be blocked by the A-to-D converters and the hybrid of the system before it can reach the metallic loop. In this invention, digital signal processing is used to test a metallic loop for shorts, opens, grounds and the presence of loading coils from a remote location. Direct metallic connection to the metallic loop is no longer necessary. Briefly, a test signal, in digital form, is fed into the network at some convenient location remote from the metallic loop that is to be tested. As the signal passes through the A-to-D converter from the digital section of the network to the analog metallic loop, it is converted by the A-to-D converter into an analog signal having a specific frequency and a predetermined amplitude. Defects - opens, shorts and grounds - in the metallic loop cause reflections of the analog test signal. These reflections, as they travel back toward the digital network, are converted by the A-to-D converter into digital form. The re…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.