Background communication using shadow of audio signal
US6891809B1 · kind B1 · utility
20Cited by
4References
5Claims
0Family size
Assignee
Inventors
Key dates
| Filing date | Nov 5, 1999 |
| Grant date | May 10, 2005 |
| Priority date | — |
| Expiry date | Nov 5, 2019 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04M3/568
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Data is transferred by delaying an audio signal less than fifty milliseconds to produce a shadow signal and combining the shadow signal with the audio signal. The shadow represents the data to be transferred A telephone constructed in accordance with the invention has at least two, separate machine states, each of which includes operating in half duplex mode and two, separate machine states, each of which includes operating in full duplex mode. The state is selected based upon one or more shadows detected at the line input of the telephone.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.