Method of and means for scrambling and descrambling speech at audio frequencies
US4086435A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 17, 1976 |
| Grant date | Apr 25, 1978 |
| Priority date | — |
| Expiry date | Sep 17, 1996 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04K1/00
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
Processing an input audio-frequency analog signal, for example, speech, which is to be passed through a communication channel, includes performing an n-level digitizing of the input signal, transforming the levels of the digitized signal to other levels using a pre-selected n-bit transformation code, and converting the transformed digitized signal into analog form that is scrambled with respect to the input signal for transmission through the communication channel. At the receiving end of the channel, an n-level digitizing of the transmitted signal is performed, followed by an inverse transformation of the levels of the digitized signal using the inverse of the pre-selected transformation code used on the digitized input signal. The inversely transformed signal is then converted into an analog signal which is representative of the input signal. The communication channel can be an acoustic medium, a telephone line, or a CB radio link. The signal processing means can be realized using microprocessors with fixed or variable programming to change the pre-selected transformation code, or tape or card readers to which a tape or card is applied for the purpose of establishing the pre-sele…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.