Matches 1 - 42 out of 42
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7051203 Data watermarks created by using an uneven sampling period  
Input signals are electronically watermarked using an uneven or non-uniform sampling rate. The uneven or non-uniform sampling may be pseudo-random. The uneven or non-uniform sampling meets the...
6823026 Apparatus and method for baseband detection  
A baseband detector includes a complex differential detector, a constellation point computer, and a phase shift keying (PSK) decoder. The complex differential detector outputs complex values in...
6570988 Simple technique for implementing a cryptographic primitive using elementary register operations  
A technique which implements a primitive for computing, e.g., a checksum. Specifically, this primitive replaces a mod(M) operation with a series of simple elementary register operations. These...
5991416 Scrambling and descrambling circuit for a cordless telephone  
A scrambling and a descrambling circuit for cordless telephone provides a higher security level than current phone scrambling circuitry. The higher security level is accomplished by separating an...
5796838 Method and apparatus for performing frequency spectrum inversion  
An apparatus and method for creating voice privacy by performing frequency spectrum inversion in electronic voice transmission systems includes the steps of digitizing an analog signal and...
5471531 Method and apparatus for low cost audio scrambling and descrambling  
Audio signals are descrambled by double sideband modulating the scrambled audio signal with a modulation carrier having a carrier frequency slightly above the highest audio signal present in the...
5446795 Universal decoder for television signal scramble systems  
A universal decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses...
5235640 Master decoder for television signal scramble systems  
A master decoder for scrambled television signals in which the signals are processed in a circuit by converting them to other frequencies and then removing the scrambling signal. One method uses...
5150401 Retrofittable encryption/decryption apparatus using modified frequency modulation  
A communication system for providing secured communication over a communication channel. The system includes a DES encryption device and a DES decryption device retrofittable into or within a...
5065430 Voice band splitting scrambler  
Disclosed is a voice band splitting scrambler. To simplify the hardware thereof, the apparatus comprises a band splitting unit (11) for splitting an input voice signal into a plurality of band...
5018198 Speech privacy processing method and apparatus therefor  
A speech privacy processing apparatus is disclosed including: a unit for obtaining the number of coefficients commonly included in a set of coefficients obtained by Fourier transformation and...
4984219 Method and apparatus for decoding of frequency inversion based scramblers  
A method and apparatus for decoding of frequency inversion based scramblers is disclosed. A quadrature amplitude modulation detector determines the frequency of the tone used for inverting the...
4949378 Toy helmet for scrambled communications  
A toy helmet that permits the wearer to speak as to generate unintelligible noise so far as bystanders are concerned but which can be understood by another child wearing an identical helmet. Each...
4924512 Method and apparatus for preventing recognition of a telephone dialing signal  
A method and apparatus for preventing recognition by a telephone system of a telephone dialing signal which inverts at least a portion of the telephone dialing signal in response to receiving the...
4817141 Confidential communication system  
The respective feature parameters extracted from a speech signal is converted into the corresponding line spectrum data in a first frequency band obtained by dividing the speech signal frequency...
4802219 Method and apparatus for distorting a speech signal  
Method of distorting a speech signal by rearranging and/or reversing frequency bands in this signal. The speech signal is divided into a plurality of sub-bands by filtering, and the sub-bands are...
4799257 Wireless transmission system for PM modulation signal  
A wireless transmitter for PM (phase modulation) signal with a spectrum scrambler for relocation of input spectrum for privacy purposes is comprised of a differential circuit coupled with an input...
4790009 Scrambler system  
A scrambler system comprises in a transmitter part thereof as oscillator circuit for generating a local oscillation signal, a frequency dividing circuit for obtaining a frequency divided signal by...
4773092 Speech scramblers  
A band scrambler which processes only time domain samples is described. The band scrambler has the effect of dividing the input signal spectrum into N sub-bands. The N sub-bands are permuted such...
4652699 Voice scrambler using frequency-inversion and band-splitting technique  
A spectrum inversion type voice scrambler for secret speech communication comprises a first spectrum inversion section, a second inversion section and an adder for summing the outputs of the first...
4623980 Method of processing electrical signals by means of Fourier transformations  
In order to upgrade input signals for further processing, one or more of the input signals is split up by a decimating technique into spectral component signals which are processed according to the...
4232194 Voice encryption system  
An apparatus and method of voice encryption uses segment swapping. Features of the invention include weighting the input time-function segments by a Hamming or Hanning Window function, before...
4195202 Voice privacy system with amplitude masking  
A voice privacy system enhances the privacy of a transmission by disguising the amplitude characteristics and cadence content of transmitted voice signals. Encoding apparatus first divides a voice...
4188506 Method and installation for masked speech transmission over a telephone channel  
A method and an installation for masked or scrambled speech transmission utilize a time-scrambling unit for dividing the speech band into at least two sub-bands, for delaying the one sub-band with...
4160875 Security system  
A security system for use in homes, hotels, businesses, schools, streets, and other locations requiring a high degree of security but where it is important to insure the privacy of the protected...
4107470 Digital SSB-FDM communication system derived from a complex band-pass digital filter bank and by a filter breakdown process  
An SSB-FDM modulator derived from a complex band-pass digital filter bank and by a filter breakdown process comprises a discrete Fourier transform (DFT) processor capable of giving phase offsets to...
4068094 Method and apparatus for the scrambled transmission of spoken information via a telephony channel  
A method of scrambling and unscrambling speech transmissions by first dividing the speech frequencies into two frequency bands and reversing their order by modulating the speech information, the...
4020285 Voice security method and system  
The specification discloses a voice scrambler technique wherein a voice signal is split into a plurality of discrete frequency sub-bands. A random code generator generates a randomized sequence of...
3995115 Speech privacy system  
The communication of confidential information is generally accomplished by transforming applied message waves into an unintelligible form prior to transmission. Such a transformation may be...
3909534 Voice privacy unit for intercommunication systems  
A system for coding and decoding voice signals in an intercommunication system to prevent unauthorized recognition thereof comprises identical units placed at each station in the system. When a...
3824468 SYSTEM FOR TRANSMITTING INFORMATION IN THE PRESCRIBED FREQUENCY-BAND  
A transmission system in which auxiliary information in the form of a pulse pattern is transmitted with main information without frequency or time separation. Secrecy in the system is increased by...
3777064 VOICE PRIVACY SYSTEM  
A selected bandwidth of speech frequencies is divided into a plurality of b-bands and each sub-band is processed in a "Weaver modulator" type of circuit for filtering, frequency translation, and...
3723878 VOICE PRIVACY DEVICE  
A voice privacy coder system enables transmission of voice communication in privacy by first inverting the communication and then scrambling it directly with a complex code word. In one embodiment,...
3678390 FREQUENCY MODULATION COMMUNICATION SYSTEM  
The frequency modulation communication system modifies the frequency spectrum of transmission signals in transmission and reception so as to allow them to have desired characteristics, equivalently...
3651404 VOICE PRIVACY ADAPTER  
A voice privacy adapter inverts the order of frequencies in a band of frequencies transmitted by radio to prevent unauthorized reception. The adapter includes an input circuit for selecting signals...
3638121 NONPERIODIC ENERGY COMMUNICATION SYSTEM CAPABLE OF OPERATING AT LOW SIGNAL-TO-NOISE RATIOS  
1. An intelligence communication system comprising a transmitter and a receiver, said transmitter comprising means for obtaining a narrow band reference signal, bandwidth expansion means for...
3614780 CRYPTOGRAPHIC COMMUNICATION SYSTEM  
The invention as described comprising in combination, means for producing a signal 9 a frequency proportional to the instantaneous rate of change in distance between a pair of vessels, means for...
3603734 SECRET SIGNALLING SYSTEM  
Secret signalling apparatus comprising a source of a message signal to be transmitted, means for producing a transmitter random signal and a transmitter synchronizing signal from a transcription,...
3530472 CUE SIGNAL COMMUNICATION SYSTEM  
3328526 Speech privacy system  
3029309 Method of operating a secrecy communication system  
3012098 Telephone privacy  
Matches 1 - 42 out of 42