Method of providing d.c. feed to a telephone line
US5511118A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 21, 1995 |
| Grant date | Apr 23, 1996 |
| Priority date | — |
| Expiry date | Apr 21, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M19/023
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A two-wire telephone line is supplied with d.c. feed from a drive circuit including two amplifiers via which a transmission signal is supplied to the line. Output potentials of the two amplifiers determine a loop current on the line, which is monitored and used to control a supply voltage for the drive circuit, the amplifier output potentials being offset from the supply potentials by headroom voltages to accommodate the transmission signal. The resulting current limiting voltage control acts iteratively to converge the supply voltage and a target voltage which is inversely dependent on an amount by which the loop current exceeds a predetermined value, the rate of convergence being fast for high loop currents for rapid response and slow for small differences to provide stable operation. The headroom voltages can be increased to nearly the supply voltage to reverse the polarity of the d.c. feed while maintaining current limiting.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.