Method and apparatus for looping around a digital transmission line at a channel unit
US4688209A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 27, 1984 |
| Grant date | Aug 18, 1987 |
| Priority date | — |
| Expiry date | Nov 27, 2004 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/244
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Method and apparatus for looping around a digital transmission line (150) at a predetermined channel unit (172) to test the line from either end of the line. Each channel unit in the line is responsive to a first and a second received control code to perform one of two operations. When the first and second received control codes are both first predetermined control codes from one end of the line, the data channel assumes a state to pass the second received first control code and any subsequently received control codes to the next channel unit. However, when the first and second received control codes are first and second predetermined control codes from the one end of the line, respectively, the data channel unit connects the transmit path from the one line end to the receive path back to the one line end, thus looping back to the digital transmission line. To loop around a line at a predetermined channel unit, a maintenance circuit (152) at one line end applies an individual first predetermined control code for the predetermined channel unit and each of the intermediate channel units followed by the application of a second predetermined control code for the predetermined channel u…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.