Speech circuit for subscriber telephone apparatus
US5710811A · kind A · utility
1Cited by
0References
10Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Apr 10, 1996 |
| Grant date | Jan 20, 1998 |
| Priority date | — |
| Expiry date | Apr 10, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/76
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The speech circuit matches the impedance of the telephone line by synthesizing a complex impedance using a positive feedback loop which has a single resistor (11), and cancels out the side tone using a subtractor (20') which extracts from the signal (Va) coming from the line a signal (Vb) correlated to the signal to be transmitted. In order to achieve cancellation of the side tone unaffected by the noise produced in the impedance synthesizing circuits, the signal (Vb) is derived by processing the signal present in the resistor (11) at the output of the feedback loop.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.