Active impedance line feed circuit
US4764956A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 1, 1987 |
| Grant date | Aug 16, 1988 |
| Priority date | — |
| Expiry date | Jul 1, 2007 |
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 in response to signals at tip and ring voltage taps by control circuit to exhibit a.c. impedance and d.c. resistance characteristics for the purpose of supplying energizing current via tip and ring terminals for tip and ring leads of a two wire communication line. In one example of the active impedance line feed circuit, improved operational tolerance of longitudinal interference and of a ground fault condition is provided by a d.c. amplifier being responsive to voltages at the tip and ring terminals. The circuit is characterized in that an inverting input of the d.c. amplifier is connected via resistors to the tip and ring voltage taps. In operation, the d.c. amplifier provides complete cancellation of all common mode signals at the tip and ring voltage taps and a compensation circuit is also connected between the tip and ring voltage taps and is responsive to the output of the control circuit for compensating for non-symmetrical current, the non-symmetrical current being introduced between the tip and ring voltage taps by normal operation of the control circuit, thereby, a threshold of …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.