US3909534A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Voice privacy unit for intercommunication systems
Assignee: Boeing Co
•
Filing: 1973-11-12
•
Granted: 1975-09-30
•
Expires: 1993-11-12
Abstract
Abstract 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 user at one station desires to communicate with a user at another station, the closure of his microphone press-totalk switch energizes circuitry within his unit so that two lowfrequency tones are transmitted therefrom. A predetermined time after the initiation of these two tones, the phase of one of the tones is reversed. Identical detectors within each unit develop a synchronizing pulse from the phase reversal which enables a pseudo-random frequency generator. In the transmitting unit, the set of pseudo-random frequencies comprising the output of the pseudo-random frequency generator is mixed with voice signals to provide a coded transmission signal. An identical pseudo-random frequency generator in each receiving unit also develops an identical set of pseudo-random frequencies in response to the synchronizing pulse which is used to decode the transmission signal. The transmitted voice signals are garbled and cannot be recognized by unauthorized parties.
Inventors
- 👤 Henrie L Majeau
- 👤 Roland O Barnes
- 👤 Robert G Hove
- 👤 Jr Abraham L Angell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 09:55
CPC Classifications
H; H04; H04K; H04K1/00; H04K1/02
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
198 words
An apparatus for coding audio signals which are present in a unit of an intercommunication system to prevent unauthorized voice recognition thereof, comprising: a. means for providing a coding signal when the audio signals are to be coded; b. a first frequency generator means for producing, in response to said coding signal, a first signal having a frequency f1 and a second signal having a frequency f2; c. a control means which is coupled to said first frequency generator means for causing a shift in the relative phasing of said first and said second signals to occur at a predetermined time after production of said coding signal; d. detecting means having said first and said second signals coupled thereto and including a phase detecting means responsive to said shift in the relative phasing of said first and said second signals for providing a synchronizing signal; e. a second frequency generator means capable of providing an output signal whose frequency fc varies in a pseudo-random sequence; f. means starting said second frequency generator means at a predetermined point in said pseudo-random sequence in response to said synchronizing signal; and, g. means mixing said output signal with the audio signals.
Claim 2
Independent Claim
198 words
An apparatus for coding audio signals which are present in a unit of an intercommunication system to prevent unauthorized voice recognition thereof, comprising: a. means for providing a coding signal when the audio signals are to be coded; b. a first frequency generator means for producing, in response to said coding signal, a first signal having a frequency f1 and a second signal having a frequency f2; c. a control means which is coupled to said first frequency generator means for causing a shift in the relative phasing of said first and said second signals to occur at a predetermined time after production of said coding signal; d. detecting means having said first and said second signals coupled thereto and including a phase detecting means responsive to said shift in the relative phasing of said first and said second signals for providing a synchronizing signal; e. a second frequency generator means capable of providing an output signal whose frequency fc varies in a pseudo-random sequence; f. means starting said second frequency generator means at a predetermined point in said pseudo-random sequence in response to said synchronizing signal; and, g. means mixing said output signal with the audio signals.
Claim 3
Dependent Claim
51 words
An apparatus as recited in claim 1, wherein said phase-shifting means comprises a phase inverter which is operable to invert the phase of said first signal in response to a control signal, and timing means operable to provide said control signal at a predetermined time after production of said coding signal.
Claim 4
Dependent Claim
44 words
An apparatus as recited in claim 1, wherein the frequencies f1 and f2 are in the audio range so as to aid in masking the audio signals, wherein f1 2f2, and further including means summing said first and second signals with the audio signalS.
Claim 5
Independent Claim
233 words
An apparatus for coding or decoding audio signals which are present in a unit of an intercommunication system to prevent unauthorized voice recognition thereof, comprising: a. means for providing a coding signal when the audio signals are to be coded; b. first frequency generator means for producing, in response to said coding signal, a first signal having a frequency f1; c. a control means which is coupled to said first frequency generator means for causing a modulation of said first signal to occur at a predetermined time after production of said coding signal; d. means summing said first signal with the audio signals; e. detecting means having the output of said summing means coupled thereto, said detecting means being responsive to said modulation for providing a synchronizing signal; f. a second frequency generator means capable of providing an output signal whose frequency fc varies in a pseudo-random sequence; g. means starting said second frequency generator means at a predetermined point in said pseudo-random sequence in response to said synchronizing signal; h. means mixing said output signal with the audio signals; i. circuit means coupled to the unit which is placed in first or second states corresponding to the operation of the unit in transmit or receive modes; and, j. means responsive to said first and second states of said circuit means for enabling and disabling said first generator means and said control means.
Claim 6
Independent Claim
233 words
An apparatus for coding or decoding audio signals which are present in a unit of an intercommunication system to prevent unauthorized voice recognition thereof, comprising: a. means for providing a coding signal when the audio signals are to be coded; b. first frequency generator means for producing, in response to said coding signal, a first signal having a frequency f1; c. a control means which is coupled to said first frequency generator means for causing a modulation of said first signal to occur at a predetermined time after production of said coding signal; d. means summing said first signal with the audio signals; e. detecting means having the output of said summing means coupled thereto, said detecting means being responsive to said modulation for providing a synchronizing signal; f. a second frequency generator means capable of providing an output signal whose frequency fc varies in a pseudo-random sequence; g. means starting said second frequency generator means at a predetermined point in said pseudo-random sequence in response to said synchronizing signal; h. means mixing said output signal with the audio signals; i. circuit means coupled to the unit which is placed in first or second states corresponding to the operation of the unit in transmit or receive modes; and, j. means responsive to said first and second states of said circuit means for enabling and disabling said first generator means and said control means.
Claim 7
Dependent Claim
44 words
An apparatus as recited in claim 4, wherein said detecting means includes means extracting said first signal from the signals present at the output of said summing means, and means responsive to a modulation of said extracted first signal for providing said synchronizing signal.
Claim 8
Dependent Claim
116 words
An apparatus as recited in claim 5, wherein said first frequency generator means produces, in response to actuation of the unit, a second signal having a frequency f2, and further including means summing said second signal with said first signal and said audio signals, and wherein said detecting means further includes means extracting said second signal, wherein said modulation is a shift in the relative phasing of said first and second signals, and wherein said control means comprises a phase inverter operable to invert the phase of said first signal in response to a control signal, and a timing means operable to provide said control signal at a predetermined time after production of said coding signal.
Claim 9
Dependent Claim
40 words
The apparatus as recited in claim 6, wherein said detecting means further includes synchronizing detecting means providing said synchronizing signal at the next change in state of said extracted second signal after the phase inversion of said extracted first signal.
Claim 10
Dependent Claim
73 words
The apparatus as recited in claim 6, further including decoding means having coupled thereto the signals appearing on the output of said summing means and one of said extracted first or second signals and operative to provide an inhibit signal if said extracted signal is not included in said signals on said output for a predetermined duty cycle thereof, and means responsive to said inhibit signal to block operation of said detecting means.
Claim 11
Dependent Claim
26 words
The apparatus as recited in claim 8, further comprising means blanking the signals on the output of said summing means in response to said inhibit signal.
Claim 12
Dependent Claim
56 words
The apparatus as recited in claim 4, further comprising carrier detection means which is enabled when said circuit means is in said second state to provide a carrier output signal only when a predetermined set of frequencies is present in the audio signals, and means responsive to said carrier output signal for inhibiting said detecting means.
Claim 13
Independent Claim
331 words
A system for providing coded communication between transmitting and receiving locations, comprising: a. at the transmitting location, a source of voice signals, a first switching means which is actuated by a user desiring to transmit said voice Signals, timing means producing a timing signal at a predetermined time after the actuation of said first switching means, a frequency generator for producing, in response to said timing signal, first and second signals having frequencies within the audio range of frequencies, means adding said first and said second signals to said voice signals, signal transmission means, means coupling the output of said adding means to said signal transmission means, means modulating said first signal, a first pseudorandom frequency generator providing an output whose frequency varies in a pseudorandom sequence, detecting means coupled to said first and said second signals for providing a synchronizing signal in response to said modulation, mixing means for modulating the output of said first pseudorandom frequency generator with the output of said adding means, and second switch means responsive to said synchronizing signal for starting said first pseudorandom frequency generator at a particular point in said pseudorandom sequence and enabling said mixing means; b. at the receiving location, a receiving means for detecting the output of said signal transmission means and removing audio signals therefrom, filter means for extracting components from said audio signals which correspond to the frequencies of said first and said second signals, a second detecting means for providing a second synchronizing signal in response to said modulation, a second pseudorandom frequency generator providing an output whose frequency varies in a pseudorandom sequence identical to the pseudorandom sequence of said first pseudorandom frequency generator, second mixing means for modulating the output of said second pseudorandom frequency generator with said audio signals, means starting said second pseudorandom frequency generator and enabling said mixing means in response to said second synchronizing signal, and means converting the signals at the output of said second mixing means into audible frequencies.
Claim 14
Independent Claim
331 words
A system for providing coded communication between transmitting and receiving locations, comprising: a. at the transmitting location, a source of voice signals, a first switching means which is actuated by a user desiring to transmit said voice Signals, timing means producing a timing signal at a predetermined time after the actuation of said first switching means, a frequency generator for producing, in response to said timing signal, first and second signals having frequencies within the audio range of frequencies, means adding said first and said second signals to said voice signals, signal transmission means, means coupling the output of said adding means to said signal transmission means, means modulating said first signal, a first pseudorandom frequency generator providing an output whose frequency varies in a pseudorandom sequence, detecting means coupled to said first and said second signals for providing a synchronizing signal in response to said modulation, mixing means for modulating the output of said first pseudorandom frequency generator with the output of said adding means, and second switch means responsive to said synchronizing signal for starting said first pseudorandom frequency generator at a particular point in said pseudorandom sequence and enabling said mixing means; b. at the receiving location, a receiving means for detecting the output of said signal transmission means and removing audio signals therefrom, filter means for extracting components from said audio signals which correspond to the frequencies of said first and said second signals, a second detecting means for providing a second synchronizing signal in response to said modulation, a second pseudorandom frequency generator providing an output whose frequency varies in a pseudorandom sequence identical to the pseudorandom sequence of said first pseudorandom frequency generator, second mixing means for modulating the output of said second pseudorandom frequency generator with said audio signals, means starting said second pseudorandom frequency generator and enabling said mixing means in response to said second synchronizing signal, and means converting the signals at the output of said second mixing means into audible frequencies.
Claim 15
Dependent Claim
85 words
A system as recited in claim 11, wherein said filter means at said receiving location is connected between the output of said second mixing means and the input of said signal converting means, and further including means connected to said filter means for blocking the output thereof from the input of said signal converting means if the frequency components of said audio signals which correspond to the frequency of said second signal do not have a minimum duty cycle with respect to said audio signals.
Claim 16
Dependent Claim
27 words
A system as recited in claim 12, further including means blocking the operation of said second detecting means in response to the operation of said blocking means.
Claim 17
Dependent Claim
69 words
A system as recited in claim 11, further comprising a carrier detection means located at said receiving location, said carrier detection means including a high-pass filter having said audio signals coupled thereto, and a detector comparator which is connected to the output of said high-pass filter for enabling said second detecting means if a predetermined frequency spectrum is absent from said audio signals for a predetermined period of time.
Claim 18
Dependent Claim
37 words
A system as recited in claim 11, further comprising means for providing alternative, uncoded voice transmission, said means including third switching means at said transmitting location for coupling said voice signals directly to said signal transmission means.
References Cited (Backward Citations)
US3435141A
Cited
US3659046A
Cited
US3624297A
Cited
US3681708A
Cited
US3696207A
Cited
US3694757A
Cited
US3723878A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |