Electronic loaded/nonloaded telephone loop identification circuit
US4224483A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1979 |
| Grant date | Sep 23, 1980 |
| Priority date | — |
| Expiry date | Mar 12, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04B3/26
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
An electronic loop identification circuit identifies loaded and nonloaded customer telephone loops. The loops can then be segregated to allow separate balance networks to be used for hybrid circuits which connect the customer loops to a digital switching office. Separate balance networks for loaded and nonloaded loops improve singing margin on those loops. An impedance measuring circuit (214) measures the real part of the impedance of a connected loop which is compared to a reference signal. If the real part of the loop impedance is greater than the reference signal, a loaded loop is identified; and, if the real part of the loop impedance is less than the reference signal, a nonloaded loop is identified. The circuit includes a self-calibrating arrangement which connects a reference impedance (209) to the impedance measuring circuit so that a capacitor (304) held reference signal can be set before each loop identification operation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.