Line interface unit retrofit circuit
US5347576A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Aug 15, 1991 |
| Grant date | Sep 13, 1994 |
| Priority date | — |
| Expiry date | Aug 15, 2011 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q11/04
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A retrofit circuit for communication one of three conditions from a line interface unit (LIU) to a receiver unit (RU), using only one external connection between the LIU and the RU. The LIU has a detection circuit and two resistors. The RU has a voltage comparator. The detection circuit outputs a first input signal in response to a signal having ESF and no yellow alarm, a second input signal in response to a signal having ESF and yellow alarm, a third input signal in response to a signal having SF with no yellow alarm, and a fourth input signal in response to a signal having SF with yellow alarm. The resistors output to the external connection a first voltage level in response to the first and third input signals, a second voltage level in response to the second and third input signals, and a third voltage level in response to the second and fourth input signals. The voltage comparator outputs a first output signal and a third output signal in response to detecting the first voltage level at the external connection, a second output signal and a third output signal in response to detecting the second voltage level at the external connection, and a second output signal and a fourth o…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.