Transformerless line interface circuit
US4322586A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 13, 1980 |
| Grant date | Mar 30, 1982 |
| Priority date | — |
| Expiry date | Nov 13, 2000 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/586
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A line circuit includes a fixed resistance feed consisting of a pair of resistors connected in series with a d.c. power source and tip and ring leads of a communication line. A variable current feed includes a current sink and a current source also connected in series with the d.c. power source and the TIP and RING leads. Energizing current flow in the communication line results as the combination of currents passed by the two feeds. A control circuit determines the currents conducted by the current source and current sink and introduces variations in these currents in accordance with signals for transmission along the communication line. Differences between current flows in the variable current feed and current imbalance conditions on the communication line are accommodated by the fixed resistance feed which also determines the terminating impedance for the communication line.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.