Telegraphy – Systems – Printing
Patent
1979-06-22
1983-04-05
Cangialosi, Sal
Telegraphy
Systems
Printing
179 15R, H04L 900
Patent
active
043792057
ABSTRACT:
A speech scrambling system using discrete prolate spheroidal sequence coefficients (PC). The problem is to provide high fidelity and high security in a scrambling system while limiting the bandwidth of the scrambled signal to the bandwidth of the original speech signal. The disclosed system uses PC to solve this problem. The analog speech signal is digitally sampled (100), converted to PC (203, 204, 205), scrambled (208, 209), and converted to scrambled samples (211, 212, 213). The scrambled samples are transmitted using pulse amplitude modulation (102) in the same bandwidth as the original signal. At the receiving end, the inverse steps are performed to recover the original speech. The scrambling is periodically modified (220, 320) to improve security.
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Information Theory and Reliable Communication, Gallager, Wiley and Sons, 1968, pp. 402-404.
"Probate Spheroidal Wave Functions-V", Bell System Technical Journal, vol. 57, No. 5, 1978, pp. 1371-1430, D. Slepian.
The Algebraic Eigenvalve Problem, Clarendon Press, 1965, Wilkinson.
An Analog Scrambling Scheme Which does not Expand Bandwidth; I:Discrete Time, pp. 261, 274, Wegner, IEEE Transactions on Informator Theory, vol. II-25, No. 3, May 1979.
Bell Telephone Laboratories Incorporated
Cangialosi Sal
Phillips S. J.
Popper H. R.
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