Transmission system with improved tone detection
US5982874A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jan 23, 1997 |
| Grant date | Nov 9, 1999 |
| Priority date | — |
| Expiry date | Jan 23, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04Q1/453
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
In a transmission system a pair of signalling tone signals is transmitted by a transmitter (2) to a receiver (6) via a transmission channel (4). In the terminal (6) a tone detector is used to detect the presence of the pair of signalling tone signals. In order to improve the reliability of the tone detector in the case of differing strength of both tone signals, the decision on the presence of the pair of signalling tone signals is based on a combined strength measure which is determined by an adder (23). The combined strength measure is compared with a reference level TH.sub.2. In a further embodiment, also a check on the level of the individual tone signals is done with comparators (11) and (9), in order to specify the maximum strength difference tolerated.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.