Active impedance line feed circuit with improved ground fault protection
US4571460A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1984 |
| Grant date | Feb 18, 1986 |
| Priority date | — |
| Expiry date | Mar 12, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/005
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A typical active impedance line feed circuit includes tip and ring amplifiers being controlled to exhibit a.c. impedance and d.c. resistance characteristics for the purpose of supplying energizing current for tip and ring leads of a two wire communication line. Protection from excessive heat generation in an instant of a ground fault on the communication line is provided by a d.c. amplifier having an input resistively connected to the tip and ring leads and an output connected via a resistive unidirectional current path to an input of the ring amplifier. A ground fault occurrence causes the resistive unidirectional current path to become conductive and reduces the current flow in the ring lead by causing the output voltage of the ring amplifier to vary in the direction of ground potential. The output of the d.c. amplifier is also useful for improving circuit tolerance of longitudinal interference.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.