Secure voice data transmission system
US5091941A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 31, 1990 |
| Grant date | Feb 25, 1992 |
| Priority date | — |
| Expiry date | Oct 31, 2010 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K1/006
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
In the secure radio transmission system of the present invention the sign bit for each byte of audio digital data is scrambled to generate a scrambled sign bit. By altering the sign bit, the resultant sound is significantly affected regardless of the amplitude range of the source audio. A key is stored in each authorized radio transmitter/receiver telephone. The key is used to select the bits of the digital voice data to be transmitted which are used to scramble the sign bit. The selected bits of the voice data are then used to scramble the sign bit and the voice data with the scrambled sign bit are transmitted to the receiving device. The receiving device executes the reverse process wherein the receiving device selects predetermined bits of the received voice data according to the key stored in the receiving device and scrambles the scrambled sign bit using the same algorithm in accordance with the data bits selected. This process generates the unscrambled sign bit and unscrambled voice data is generated at the output of the receiving device.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.