Subscriber circuit with built-in polarity switching circuit
US5943419A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 13, 1997 |
| Grant date | Aug 24, 1999 |
| Priority date | — |
| Expiry date | Aug 13, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M1/738
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
The subscriber circuit has a balanced amplifier and a built-in call-current polarity changing circuit. Moreover, the output stage circuits of the direct feed-back and offset cancel circuits of the subscriber circuit have the same configuration. By switching the input voltage supplied to the direct feed-back and offset cancel circuits by a switch, the signals fed back to the inputs of the balanced amplifier are switched. Thus, the polarity of the loop current can be inverted. Furthermore, it is possible to switch the loop current without adopting an extra circuit, and the part of the circuit in which the switches are not required to withstand pressure can be constructed with CMOS thereby allowing minimization of the circuit size.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.