| 6980657 |
Communications system using chaotic synchronized circuits |
| Dec-27-2005 |
A chaotic communication system employs transmitting and receiving chaotic oscillating circuits. In an embodiment of the invention employing a Chua circuit as the basic chaotic circuit, the transmitter... |
| 6683958 |
Apparatus and method for embedding and extracting information in analog signals using distributed signal features and replica modulation |
| Jan-27-2004 |
Apparatus and methods are provided for embedding or embedding digital data into an analog host or cover signal. A distributed signal feature of the cover signal in a particular domain (time, frequency... |
| 6427012 |
Apparatus and method for embedding and extracting information in analog signals using replica modulation |
| Jul-30-2002 |
Apparatus and methods are provided for embedding or encoding auxiliary signals into an analog host or cover signal. A replica of the cover signal or a portion of the cover signal in a particular domain... |
| 6389138 |
Method and apparatus for generating a complex scrambling code sequence |
| May-14-2002 |
A complex spreading and/or scrambling code sequence generation system uses a first complex code sequence having at least two components and a second complex code sequence having at least two components.... |
| 6363325 |
Automotive emergency awareness system |
| Mar-26-2002 |
A vehicular emergency awareness system and method is provided. A vehicle is provided with an onboard computer system adapted to receive and process signals generated at an external source. Under predetermined... |
| 6249583 |
On-line signal processing method |
| Jun-19-2001 |
A method for encryption and decryption of analog signal, wherein encryption and decryption are performed in analog domain. The transmitter creating digital representations with unique behavior; producing... |
| 6229897 |
Apparatus and method of secured analog voice communication |
| May-8-2001 |
An apparatus and method for improved security in wire or wireless communication systems includes scrambling the audio signal, combining a masking signal with the scrambled audio signal, and then transmitting... |
| 5864625 |
Methods and apparatus for secure optical communications links |
| Jan-26-1999 |
Methods and apparatus for providing a secure optical communications link are disclosed. Communications information is encrypted with a security key. An optical beam is then modulated with both the security... |
| 5790591 |
Spread spectrum transmitter and communications system using multiple spreading codes |
| Aug-4-1998 |
A spread spectrum transmitter for generating a plurality of spread spectrum codes comprises a shift register having a plurality of stages, with a plurality of tap sets connected to selected ones of said... |
| 5642397 |
Paging system which combines a paging signal with a standard broadcast baseband signal |
| Jun-24-1997 |
An electronic paging system and method for transmitting paging signals over a broadcast network, such as a standard pre-existing commercial radio broadcast system, adds paging signals to a normal radio... |
| 5471531 |
Method and apparatus for low cost audio scrambling and descrambling |
| Nov-28-1995 |
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 scrambled... |
| 5379345 |
Method and apparatus for the processing of encoded data in conjunction with an audio broadcast |
| Jan-3-1995 |
A method and apparatus for the identification and verification of audio transmission segments, such as may be broadcast by a radio station, consists of the generation of a data stream corresponding in... |
| 5305384 |
Apparatus, system and method for transmitting secure signals over narrow spaced channels |
| Apr-19-1994 |
An encryption/decryption device, system and method for providing secure communication over a communication channel. The encryption device includes a radio interface unit connected to a conventional radio,... |
| 5268926 |
Method and apparatus for the simultaneous transmission of separate data signals |
| Dec-7-1993 |
A method of simultaneously transmitting first and second data signals by the technique of spectrum spreading by direct sequence, comprises using the first data signal to modulate a spreading code produced... |
| 5258996 |
Spread spectrum apparatus |
| Nov-2-1993 |
For use in a spread spectrum communication system there is provided in an embodiment of the invention a spread spectrum transmitter which uses a voltage controlled oscillator (VCO) for generating a carrier... |
| 5228055 |
Spread spectrum communication device |
| Jul-13-1993 |
On the transmitter side of a spread spectrum communication device according to the present invention, transmission date are converted into a plurality of parallel data sets by a serial-parallel convertor... |
| 4972479 |
Method and apparatus for providing privacy/security in a communication system |
| Nov-20-1990 |
Apparatus and methods are disclosed for providing privacy on communications systems which include radio links, such as cellular telephone, marine radiotelephone, IMTS, and RDSS systems, in a manner which... |
| 4908860 |
System for the secret transmission of audio signals and television receiver for receiving such signals |
| Mar-13-1990 |
Encoding is realized by means of a first low-pass input filter (21), a first modulator (20), a second low-pass filter (19), a second modulator (18) whose modulating signal has a frequency which is pseudo-random... |
| 4841571 |
Privacy signal transmission system |
| Jun-20-1989 |
A privacy signal transmission system having a transmitter portion and a receiver portion. The transmitter portion digitizes an analog message signal and enciphers the digitized signal into a privacy signal... |
| 4799257 |
Wireless transmission system for PM modulation signal |
| Jan-17-1989 |
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 terminal,... |
| 4658436 |
Disguised transmission system and method |
| Apr-14-1987 |
Data signals are transmitted at a variable information rate with variable power so the transmitted information rate and transmitted power level increase and decrease together to simulate high frequency... |
| 4653069 |
Spread spectrum correlation receiver |
| Mar-24-1987 |
A spread spectrum communication system having a correlation receiver for decoding an information signal transmitted on a pseudo-noise (PN) carrier. The receiver synchronizes to the transmitted signal by... |
| 4652838 |
Phase randomization to reduce detectability of phase or frequency-modulated digital signals |
| Mar-24-1987 |
A communications system for conveying information angle-modulated onto a carrier includes a modulator which angle-modulates the data onto the carrier and which also randomly changes the phase of the carrier.... |
| 4652699 |
Voice scrambler using frequency-inversion and band-splitting technique |
| Mar-24-1987 |
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 and... |
| 4538281 |
Adaptive acquisition of multiple access codes |
| Aug-27-1985 |
An adaptive acquisition technique is disclosed for enabling the initial acquisition of a received coded signal in a direct sequence spread spectrum system using multiple access codes for code division... |
| 4516078 |
Variable frequency passband circuit |
| May-7-1985 |
A variable frequency passband circuit comprising two passband filters and three mixers (front, intermediate and output mixers) connected in a cascade fashion disposed in a signal path. Two VCOs inject... |
| 4411017 |
Secure mobile telephone system |
| Oct-18-1983 |
A communications system including a central station and a plurality of remote stations, for example, a mobile telephone system, is disclosed in which communications channel establishing signalling transmissions... |
| 4410911 |
Multiple signal transmission method and system, particularly for television |
| Oct-18-1983 |
A method and system for scrambling a plurality of input signals for secure transmission thereof, as well as various methods and systems for television transmission, are disclosed. The disclosed scrambling... |
| 4398216 |
Multiple signal transmission method and system, particularly for television |
| Aug-9-1983 |
A method and system for scrambling a plurality of input signals for secure transmission thereof, as well as various methods and systems for television transmission, are disclosed. The disclosed scrambling... |
| 4365110 |
Multiple-destinational cryptosystem for broadcast networks |
| Dec-21-1982 |
A method of protecting communications through encryption is disclosed which is particularly useful for multiplexed communications. On the transmit side, each message is multiplied by an enciphering key... |
| 4358857 |
Communication system |
| Nov-9-1982 |
1. In combination, a first source for producing a first signal representative of intelligence to be transmitted from one point to another, second source for producing a binary carrier signal having a first... |
| 4245346 |
Communication system |
| Jan-13-1981 |
1. In combination: a signal source for producing a signal having characteristic variations representative of intelligence, a first code source for producing a first code signal having apparently random... |
| 4206462 |
Secure communication and ranging system |
| Jun-3-1980 |
15. In a secure communication system a transmitter comprising first means to modulate a carrier wave with a sub-carrier wave and a desired signal, a code generator synchronized to said sub-carrier wave,... |
| 4052565 |
Walsh function signal scrambler |
| Oct-4-1977 |
A digital speech scrambler system allowing for the transmission of scrambled speech over a narrow bandwidth by sequency limiting the analog speech in a low-pass sequency filter and thereafter multiplying... |
| 3970791 |
Voice controlled disappearing audio delay line |
| Jul-20-1976 |
A delay line which disappears under voice control is comprised of a pluray of shift registers delays the incoming voice signal to permit transmission of the voice scrambler preamble. The delay is removed... |
