US5278907A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Analog scrambling with continuous synchronization
Assignee: Transcrypt International Inc
•
Filing: 1993-03-01
•
Granted: 1994-01-11
•
Expires: 2013-03-01
Abstract
Abstract A device and method for scrambling and de-scrambling audio and voice communications including radio, cellular telephone, and conventional telephone communication. The audio communication can be scrambled using, for example, time varying pseudo-random spectral modification. Continuous data containing synchronization information is transmitted with the scrambled signal to eliminate time lags that occur with synchronization bursts and without detrimentally affecting audio quality.
Inventors
- 👤 Kenneth L. Snyder
- 👤 Ronald B. Kabler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 08:54
CPC Classifications
H; H04; H04K; H04K1/00; H04K1/04
Claims Analysis
Total Claims: 49
Claim 1
Independent Claim
73 words
A method of transmitting communications which are scrambled comprising: scrambling an audio signal that is used to modulate a transmission RF carrier; generating a continuous synchronization signal correlated to the scrambling of the audio signal; combining the synchronization signal with the audio signal; and so that the synchronization signal can be continuously transmitted with the audio signal to allow immediate initialization synchronization and continuous synchronization as long as the audio signal is transmitted.
Claim 2
Independent Claim
73 words
A method of transmitting communications which are scrambled comprising: scrambling an audio signal that is used to modulate a transmission RF carrier; generating a continuous synchronization signal correlated to the scrambling of the audio signal; combining the synchronization signal with the audio signal; and so that the synchronization signal can be continuously transmitted with the audio signal to allow immediate initialization synchronization and continuous synchronization as long as the audio signal is transmitted.
Claim 3
Dependent Claim
16 words
The method of claim 1 wherein the transmission RF carrier is used in conventional telephone communications.
Claim 4
Dependent Claim
15 words
The method of claim 1 wherein the transmission RF carrier is used in radio communications.
Claim 5
Dependent Claim
16 words
The method of claim 1 wherein the transmission RF carrier is used in cellular telephone communications.
Claim 6
Dependent Claim
15 words
The method of claim 1 wherein the scrambling comprises spectral modification of the audio signal.
Claim 7
Dependent Claim
14 words
The method of claim 1 wherein the audio signal is band-passed prior to scrambling.
Claim 8
Dependent Claim
18 words
The method of claim 6 wherein the band passing removes control information utilized by some audio transmission systems.
Claim 9
Dependent Claim
24 words
The method of claim 5 wherein the scrambling comprises frequency inversion which utilizes a switching means which is switched according to a pseudo-random sequence.
Claim 10
Dependent Claim
21 words
The method of claim 1 wherein generation of the synchronization signal comprises generating data correlated to scrambling of the audio signal.
Claim 11
Dependent Claim
16 words
The method of claim 9 wherein the data is modulated to a data RF carrier frequency.
Claim 12
Dependent Claim
19 words
The method of claim 10 wherein the data RF carrier frequency is sub-audible in comparison to the audio signal.
Claim 13
Dependent Claim
20 words
The method of claim 9 wherein the data is put into a continuous data stream and made up of segments.
Claim 14
Dependent Claim
19 words
The method of claim 12 wherein the segments include a preamble, a synchronization code, and an error correction code.
Claim 15
Dependent Claim
27 words
The method of claim 10 further comprising combining the scrambled audio signal and the PSK modulated data RF carrier into a combined radio frequency band for transmission.
Claim 16
Dependent Claim
18 words
The method of claim 14 wherein the combined radio frequency band is modulated on the transmission RF carrier.
Claim 17
Dependent Claim
18 words
The method of claim 14 wherein the modulated synchronization signal comprises a sub-band of the scrambled audio signal.
Claim 18
Dependent Claim
18 words
The method of claim 14 further comprising filtering the combined scrambled audio and modulated signal prior to transmission.
Claim 19
Dependent Claim
45 words
The method of claim 1 further comprising decoding a transmitted signal by separating the sub-band from the radio frequency band containing the scrambled audio signal and the modulated synchronization signal, recovering the audio signal from the scrambled audio signal, and recovering data from the sub-band.
Claim 20
Dependent Claim
25 words
The method of claim 18 wherein the recovered data from the sub-band is utilized to synchronize the recovery of the audio from the scrambled audio.
Claim 21
Dependent Claim
14 words
The method of claim 19 wherein the recovered audio is output to a receiver.
Claim 22
Dependent Claim
90 words
An audio communication system comprising: at least one transmitter including an encoder; at least one receiver including a decoder; the encoder comprising an audio band scrambler; a sub-band generator which produces a frequency band which carries synchronization information on a continuous basis, and a combiner to combine the audible and sub-bands for transmission output; the decoder comprising a separator to separate the audio and sub-bands, a synchronization information recovery device to recover the synchronization information, and an audio recovery device which utilizes the synchronization information to recover the audio communication.
Claim 23
Dependent Claim
90 words
An audio communication system comprising: at least one transmitter including an encoder; at least one receiver including a decoder; the encoder comprising an audio band scrambler; a sub-band generator which produces a frequency band which carries synchronization information on a continuous basis, and a combiner to combine the audible and sub-bands for transmission output; the decoder comprising a separator to separate the audio and sub-bands, a synchronization information recovery device to recover the synchronization information, and an audio recovery device which utilizes the synchronization information to recover the audio communication.
Claim 24
Dependent Claim
15 words
The system of claim 21 wherein the transmitter and receiver are combined in a transceiver.
Claim 25
Dependent Claim
24 words
The system of claim 21 wherein the audio band scrambler includes a device to scramble an analog audio signal using time-varying, pseudo-random spectral modification.
Claim 26
Dependent Claim
32 words
The system of claim 23 wherein the audio band scrambler includes a frequency inverter device and a control device which generates a switching signal to operate the inverter in a pseudo-random fashion.
Claim 27
Dependent Claim
25 words
The system of claim 24 further comprising a microprocessor which includes an encryption algorithm to instruct the control device regarding generation of the switching signal.
Claim 28
Dependent Claim
14 words
The system of claim 21 wherein the sub-band is narrower than the audio band.
Claim 29
Dependent Claim
14 words
The system of claim 26 wherein the sub-band is in-band with the audio band.
Claim 30
Dependent Claim
11 words
The system of claim 26 wherein the sub-band is effectively sub-audible.
Claim 31
Dependent Claim
11 words
The system of claim 26 wherein the sub-band is effectively super-audible.
Claim 32
Dependent Claim
24 words
The system of claim 26 wherein the sub-band carries synchronization information by modulating data on a data carrier in a relatively narrow frequency band.
Claim 33
Dependent Claim
12 words
The system of claim 21 wherein the combiner comprises a summer device.
Claim 34
Dependent Claim
16 words
The system of claim 21 wherein the separator comprises frequency filters which pass selected frequency bands.
Claim 35
Dependent Claim
19 words
The system of claim 21 wherein the synchronization information recovery device includes a limiter and a data recovery decoder.
Claim 36
Dependent Claim
31 words
The system of claim 21 wherein the audio recovery device includes an inverter, a frequency generator which issues a switching signal to the inverter, and a microprocessor including a decryption algorithm.
Claim 37
Independent Claim
34 words
A method of audio communication comprising: scrambling an audio signal that is used to modulate a radio frequency signal; combining with the audio signal data modulated to a frequency sub-band within the audio signal.
Claim 38
Independent Claim
34 words
A method of audio communication comprising: scrambling an audio signal that is used to modulate a radio frequency signal; combining with the audio signal data modulated to a frequency sub-band within the audio signal.
Claim 39
Dependent Claim
17 words
The method of claim 35 wherein the scrambling comprises analog scrambling using time varying pseudo-random spectral modification.
Claim 40
Dependent Claim
22 words
The method of claim 36 wherein the audio signal is generally of a band that includes a portion of the audible spectrum.
Claim 41
Dependent Claim
11 words
The method of claim 35 wherein the data includes synchronization information.
Claim 42
Dependent Claim
12 words
The method of claim 38 wherein the data includes error correction information.
Claim 43
Dependent Claim
11 words
The method of claim 38 wherein the data includes identification information.
Claim 44
Dependent Claim
21 words
The method of claim 35 wherein the frequency sub-band containing the data is a relatively low frequency within the audio band.
Claim 45
Dependent Claim
28 words
The method of claim 35 wherein the frequency sub-band containing the data is a relatively low frequency immediately below the audio band and is effectively a sub-audible band.
Claim 46
Dependent Claim
22 words
The method of claim 35 wherein the frequency sub-band containing the data is a relatively high frequency band within the audio band.
Claim 47
Dependent Claim
27 words
The method of claim 35 wherein the frequency sub-band containing the data is a relatively high frequency immediately above the audio band and is effectively super audible.
Claim 48
Dependent Claim
21 words
The method of claim 35 wherein the frequency band containing the data is a relatively narrow band within the audio signal.
Claim 49
Dependent Claim
16 words
The method of claim 35 wherein the data is modulated in the sub-band by PSK signalling.
References Cited (Backward Citations)
US5220584A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-01-10 | 1997-07-12 | 1998-01-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-01-10 | 2001-07-12 | 2002-01-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-01-10 | 2005-07-12 | 2006-01-11 | $7700.00 | Window Closed / Lapsed |