Subscriber line interface circuit with complex impedance
US4558185A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Dec 1, 1982 |
| Grant date | Dec 10, 1985 |
| Priority date | — |
| Expiry date | Dec 1, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B1/586
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
For the purpose of realizing a line circuit, especially a two-wire four-wire conversion circuit of a telephone exchange in the form of LSI and providing the conversion circuit with an impedance which is suitable to a side tone characteristic of the telephone set, in a line circuit composed of a hybrid circuit wherein the four-wire input line is connected to the two-wire subscriber line via a buffer amplifier and a terminating impedance and in addition the four-wire output line is connected to the output of a subtractor which subtracts an input signal of the four-wire input line passed through a filter circuit from a signal fed from the two-wire subscriber line, the terminating impedance is formed by a resistor component and in addition a feedback circuit having such a transfer characteristic that the impedance of the line circuit seen from the two-wire subscriber line side will become a specified complex impedance is installed between a line which couples the two-wire subscriber line to the subtractor and an input of the buffer amplifier.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.