US1480217A - Method and means for signaling - Google Patents

Method and means for signaling Download PDF

Info

Publication number
US1480217A
US1480217A US530528A US53052822A US1480217A US 1480217 A US1480217 A US 1480217A US 530528 A US530528 A US 530528A US 53052822 A US53052822 A US 53052822A US 1480217 A US1480217 A US 1480217A
Authority
US
United States
Prior art keywords
currents
confusion
frequency
signal
waves
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US530528A
Inventor
Mills John
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Western Electric Co Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Western Electric Co Inc filed Critical Western Electric Co Inc
Priority to US530528A priority Critical patent/US1480217A/en
Application granted granted Critical
Publication of US1480217A publication Critical patent/US1480217A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04KSECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00Secret communication
    • H04K1/02Secret communication by adding a second signal to make the desired signal unintelligible

Description

Jan. 8 1924. 1,480,217
- J. MILLS v METHOD AND MEANS FOR SIGNALING Original Filed Dec. 29, 1916 2 Sheets-Sheet 1 lwvehbr: i/0/7/7 /V///s.
ky my Jan; 8 1924.
J. MlLLS METHOD AND MEANS FOR SIGNALING 2 Sheets-Sheet 2 Original Filed Dec. 29, 1916 Patented Jan. 8, 1924. I
UNITED. STATES PATENT OFFICE.
JOHN MILLS, OE WYOMING, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.
METHOD AND MEANS FOR SIGNALING.
Substitute for application Serial No. 139,541, filed December 29. 1916. This application filed January 20,
1922. Serial No. 580,528.
to either wire or wireless telephone commu-.
nication in which it is desirable to prevent an intelligible interception of the signal transmitted.
The present application is a substitute for applicants copending application Serlal No. 139,541 filed December 29, 1916.
An object of. the invention is to send the signal in such a form that it will be unin-' telligible when received by ordinary appa ratus and to clarify the signal at the proper receiving station by specially provided means.
This is accomplishedby superposing, on
the outgoing talkor signal currents, a complex noise formed by. currents of several frequencies lying\ in the most important part of the voice frequency range. To"
clarify the signal at the proper receiving station, the invention provides for thesuperposition upon the incoming talk and its combined noise of a complex noise simllar to the noise originally superimposed but ex actlv opposite in the phase of all itscomponents. The noise is thus suppressed from the signal which may be recelved free from confusion.
Another object of the invention is to provide a source of noise or confusion currents suitable for maskingthe signal currents to be .transmitted. This is accomplished by impulsively exciting an oscillatlon network having several degrees of freedo m i. e., several periods of free vibration, w1th1n the 5 voice frequency range. Thls network when iinpulsed serves as a source of currents of various audio-frequencies correspondlng to the periods of free vibration of the network. Another object of the invention. is to maintain the confusion currents generated at the receiving station in phase opposition to the confusion currents arriving at the receiving station from the sending station. To this end the invention provides an oscillation network at each station for supplying the confusion currents and both net? works are energized by the same source of current and hence each network responds in a like manner to variations in the character of the supplied current. Interposed between the source and the network at the receiving station is provided a. phase adjusts .and these two currents will always be main- In carrying tained in phase opposition.
out the invention various novel combinations of apparatus and methods have been utilized. v
For example 'there has been provided a receiving station in which receivedwaves are successively utilized to produce waves of other frequencies. Interposed between the various stages of frequency changing means are one or more means serving for amplification, selection of one or more components of the resultant waves, and mi directional conduction. The thermionic type of repeater conveniently serves both as an amplifier and as a unidirectional conduc-' tor. The purpose of the unidirectionally conducting means is toprevent backward reaction through the. circuit.
The principles of the invention are ob-v viously, applicable in numerous modified forms of systems.
Forfurther particulars of the invention reference may be made to the drawings, in which Fig. 1 shows diagrammatically: an embodiment of the invention; and Fig 2 illustrates a modification.
To aid in reading the drawings, the thermionic repeaters have been provided with an auxiliary reference letter to indicate the function the audion performs, i. e.,; A:amplifier, Gzgenerator Pzcurrent limiting device.
In Fig. 1 the sending station X and the receiving station Y are in radio communication although these stations may be connected by a wire line if desired. At the sending station X, the generator 4 is adapted I to supply control oscillations of a frequency near the limit of audibility, for instance, a
frequency of thirt cycles which is adj acent' than 30 cycles for example cycles. In
such a case a mechanical generator might be I preferred to the generator 4 on account of the technical difliculties to be surmounted in making vacuum tube generators of such low ,frequencies as 5 cycles per second. The
generator 4, which may be of any suitable type is adapted to energize the line 3 through the two current paths 5 and 6, the former being coupledto the generator 4 by means of the coil 7 and the latter by means of the coil 8. The current path 6 comprises a current limiting device 9. The input circuit of the current limiting device 9 is tuned.
by means of condenser 51 to the frequency of the control oscillations supplied by generator 4. The current limiting device 9 comprises a vacuum tube 10.of the audion type having a resistance 11 in its output circuit. When the' current in the output circuit reaches a certain high value, the voltage drop across resistance 11 becomes large enough to prevent further increase in the current, which accordingly has, a flat top or complex wave form. Coupled with the current limiting device 9 are one or more amplifiers '12 of well known type, by means of which amplified currents having a com lex or flat top wave form maybe suppli to the oscillation network or sectional loaded artificial line 13. I This network may be made in any desired number of sections, the number here-shown being four. An electromotive impulse supplied by the amplifier 12 to the oscillation network 13 will set up in this network a number of free oscillatlons equal to the number of sections of the networkand the frequencies ofwhich are deter-. mined by the constants of the circuit.
For the purposes of this invention, the inductance and capacity elements in each section of the network 13 are chosen to give four frequencies which extend throughout the voice frequency range, that is, frequencies of 100 to 2000. By way of example it may be'cited that ifthe resistance, inducthe tance and capacity of each section have values: R=negligible as compared to L202 henry, C 0.128 m. f., then the four frequencies supplied .by this network will have the Values f :780, f :l170, f =1620,'
71-:1960. The currents delivered by the network 13 will hereafter be'known as noise currents orconfusion currents as they are.
- by means of condenser 55 to the frequency of the control oscillations supplied by generator 4. The amplifier 17 in the current path 5 and the various audion elements shown in the current path 6 are unilaterally conductive, whereby energy is delivered from'the generator 4 to the line 3, but one of these current paths is prevented from sending current through the other of these paths. transmitted is transferred to the line 3 by means of the conventional transmitter circuit 19. It will be observed that the network 131is selected with such values of inductance and capacity that the two middle sections will constitute a wave filter having a cut-off limit at about the frequency of 2,000 cycles per second. Any disturbances introducedby the power limiting device 9 or other elements in the path 6 which are higher than this frequency will be attenuated in the network 13 due to its action as a low pass filter.
At the sending station X, the line 3 has superposed thereon signaling current from the circuit 19, confusion currents by means of the transformer 16 and control currents from the current path 5. If this line 3 were connected to an ordinary receiver, the combined signal and confusion currents would be translated into the original signal which would have superimposed a complex noise which would mask the signal and render the same unintelligible. The currents the line 3 are utilized to modulate, by means of any suitable modulator M, the carrier currents supplied by a suitable source G. The modulated currents sent from antenna 52 are received by antenna 53 where they are selected by means of any suitable detector D which supplies the detected currents to line 54. If a receiver is connected to line 54 the signal will be confused in the same manner as if the receiver L I is connected to the line 3. In order that the signal originating in circuit 19 may be received free from confusion at the proper receiving station Y, confusion currents of opposed phase to those'supplied by the transformer 16 are combined with the superimposed confusion and signal currents received at that station.
At the station Y, the line 54 is connected to the signal or other translating circuit 20 through the paths 21 and 22. In the path 21, the amplifier 56 serves to increase the amplitude of all of the incoming cur- The telephonic speech signal to be suppressed by means of the filter 23 so that the transformer 24 serves to impress amplified signal and confusion currents to the circuit 20. The input end of current path 22 is tuned to the frequency of the control oscillations by means of the condenser 25. The control oscillations selected by the tuned circuit comprising the condenser 25 and the inductance 26 are supplied to the amplifier 27 which is coupled to a tuned circuit 28 which is also tuned to the frequency of the control oscillations. By means of the adjustable resistance R, inductance L and capacity C, the phase of the control oscillations supplied to the transformer 29 is adjusted so that the two current paths 21 and 22 supply the signal circuit 20 with confusion currents .which are opposed in phase. The control currents, which are properly adjusted in phase by means of L, R and C, are supplied to the power limiting device 30 which is similar to the power limiting device 9 above described. The currents having a flat top or complex'wave form supplied by the device 30 are impressed on the oscillation network 31, filter 32 and amplifier 33, which are similar to the oscillation network 13, filter 14 and amplifier 15 at the station X. The superposed confusion and signal currents supplied by a transformer 24 are combined with the opposite phase confusion currents supplied by the amplifier 33, whereby the confusion currents originally superimposed are suppressed and the signal currents are received in the circuit 20 free from con-' fusion.
In the modified form of sendin station shown in Fig. 2, instead of using a generator such as 4 to continually supply the 4 control oscillations, these oscillations are generated by means of the .voice currents so that, upon the cessation of the voice cur-v rents, the generation of the control oscillations will also cease and no current will be transmitted over the line ,3. This method of generating control currents is more fully described and claimed in applicants copending application Serial No. 124,958, filed October 11, 1916. The current paths 5' and 6 are identical with the corresponding paths 5 and 6 shown in Fig. 1. Inductively related with the coils 34 and 35, which, are traversed by the signal currents, is the .coil 36 which transfers the speech currents to the amplifier 37, the output circuit of which is tuned by means of the condenser 38. to the control frequency. The control oscillations may be further amplified by means of the amplifier 39 and supplied by means of the coil 40 to the coils 7 and 8. The coils 34 and 35 are included in the input circuit of a vacuum tube 41, which is essentially unilaterally conducting, in order to prevent a local circulation of power from either of the paths 5 and 6' through. the control current path136, 37, 38, etc.
, It is-proposed to change from time to time, the character of the confusion cur rents transmitted by changing the values of the capacity or inductance in the sections of the network, the receiving station having its network correspondingly changed.
The novel features believed to be inherent in the invention are defined in the appended claims.
What is claimed is:
1. The method of secret telephony which comprises generating currents representing speech, generating confusion currents, having at least one frequency coinciding with the'frequency range of said first mentioned currents, transmitting simultaneously and together the superposed speech and confusion currents, and receiving -a relatively wide band of frequencies of the speech representing currents free from the confusion currents.
2. The method of secret telephony which consists in generating speech representing currents, generating confusion currents having a frequency component within the range of audible frequencies to be received, simultaneously superposing and transmitting together the speech and confusion currents, eliminating the confusion currents at the receiving station and receiving thereby a relatively wideband of the essential speech frequencies free from the confusion current component within the desired range.
3; The method of secret signaling which consists in superposing' confusion currents having frequencies within the range of 200 to 2,000 cycles per second upon the outgoing talk tablishing the desired phase difference be-' tween said currents, and maintaining said phase difference constant by supplying the currents at both of said stations from a common source of frequency other than the frequency of said currents.
5. The method of secret signaling which consists in generating (onfusion currents from control currents, transmitting the control, confusion and signal currents to a distant station, generating other confusion currents from the control currents received 7 at said station, adjusting the phase of said other confusion currents and in combining from the produced waves, means for pro ducing amplified waves of the selected fre- 13 quencyrange, means for producing from theamplified waves other waves of changed frequency, means for selecting from the other waves of changed frequency alternatin current waves of a frequency range di erent from the received waves and different from the first named selected waves, means for producing amplified waves of the frequency range last selected from the selected waves, and a utilization circuit for the amplified waves energy thus produced whereby the energy 'level in each amplifying device is kept small, whereby each amplifying device is prevented from being loaded wit-h undesired energy, and whereby singing is pre- 30 vented by the operation of the selective means preceding each amplifying device in attenuating currents of frequencies which are not attenuated by the selective means preceding the other amplifying device;
35 7. The method of transmission which comprises modulating a carrier wave in accordance with a signal wave and in accordance with at least two'control waves of-different frequencies, and controlling a oo- 40 operating receiver by the conjoint action of the control waves.
8. The method of secret signaling which comprises superposing confusion currents of more than one frequency on the speech ourrents to be transmitted, simultaneously transmitting the superposed speech. and confusion currents and in receivingthe speech currents free from the confusion currents.
9. A high frequency transmission system comprising a modulator and an input source of waves for said modulator, said source comprising in tandem electrical elements having definite upper and lower cut-ofi" limits whereb the waves transferred to said modulating evice from said source are limited to a. definite band or frequency range.
10. The method of masking a talking signal which consists in periodically superimposing upon and transmitting with said signal, trains of electric waves having several frequencies located throughout the range of audibility. -1
11. The method of renderin a talking 08 signal unintelligible which consists in auto- 1,4so,217 Y causingthe control current variations to eliminate the confusion current at a receiving station. 14. A signal transmitting system including a generator of control currents, an oscillation network, means whereby said generator causes confusion currents having frequency components other than the control current frequency to be generated in said network, and means for transmitting the confusion current and. the control current simultaneously.
15. A system for--generating noise currents comprising the combination of a source of currents, a damped sectional network having a plurality of diiferent natural periods adapted to be supplied by said source, and an output circuit for said network containing a filter for limiting the output of said network to currents of frequencies corresponding to the natural periods thereof.
16. In a system for generating noise currents, the combination of a source 0 low frequency currents, a sectional loaded artificial line adapted to be supplied thereby, each of the sections of said line comprising inductance, capacity and resistance, and an output circuit for said network containing a filter for extinguishing currents of the frequency of the low frequency source.
1 A signaling system comprising a source oftele honiospeech frequency currents, means or superposing thereon con- I fusion currents of speech frequency and transmitting them simultaneously with said telephonic currents, and means forsubstantially uniformly receiving a band of said telephonic currents covering a range of over fifty cycles per second free from confusion currents.
18. A signaling system comprising a source of telephonic speech frequency currents, means for superposing thereon and transmitting simultaneously therewith confusion currents having several frequencies within the speech frequency range for confusing the'signal to be transmitted, means for transmitting a band of over fifty cycles per second inwidth of said waves with ap- 20. In a signaling system, the c'ombina-,
- tion of a source of signal currents, means for supplying confusion currents for confusin the signal to be transmitted, means inclu ing phase regulating means for supplying other confusion currents of opposite phase to said first mentioned confusion currents, means adapted to combine the resaid ceived confused signal with said confusion currents of opposite phase for clarifying the signal at a distant station, and means for translating the clarified signal.
21. In a signaling system, the combination of means forsupplying oscillations, a line, a. pair of current paths adapted to connect said supplying means to said line, one of said paths comprising a source for producing confusion current having a characterist1c frequency component dependent on a frequency characteristic of said oscillations and another characteristic frequency component independent thereof, and means for preventing the other of said paths from sending current through said one path.
22. In asignaling system, the combination of means for supplying oscillations, a line, a pair of current paths adapted to connect said supplying means to saidline, one of said paths comprising means for producing confusion current together with means for regulating said confusion current, and a unidirectionally conducting device in one of said paths for preventing the other of said paths from sending current through said one path.
23. In a signaling system, the combination of means for supplying oscillations, a line,
a pair of current paths adapted to connect said supplying means to said line, one of said paths comprising means for roducing currents of audible frequency ans a space dischar e device in each of said paths, said device fiaving an input circuit connected to a grid and a cathode, and an output circuit connected to a cathode and an anode, whereby current is unilaterally conducted from said supplying means through said paths to line. 24. The combination of means for supplying variable currents and a plurality of circuits ada ted to be energized by said means, each of said circuits comprising an oscillation network having a plurality of modes of natural vibration, and means for adjusting the relative phase of the currents supplied to said circui 25. In a signaling system, the combination of a source of signal currents, means for supplying confusion current for confusing the signal to be transmitted, means for supplying other confusion currents of opposite phase to said first mentioned confusion currents, a phase adjuster for maintaining the phase opposition between the two said confusion currents, and means for translating said signal currents'free from confusion.
26. In a signaling system, the combination of a source of signal currents, means for supplyingv confusion currents for confusing the signal to be transmitted, means for supplying other confusion currents of opposite phase to said first mentioned confusion currents, and'a source of control oscillations for maintaining the phase oppo sition between the two said confusion currents, and means for translating said signal currents free from confusion. I
In a signaling system, the combinat1on of a source of signal currents, means for supplying confusion currents for confusmg the'signal to be transmitted, means for supplying other confusion currents of opposite phase to said first mentioned confusion currents, and a source of control currents for energizing both of Said supplying means, whereby the two said confusion currents are maintained in phase opposition,
and means for receiving sald signal currentsfree from confusion.
28. In a, receiving system, the combination of an incoming conductor for supplying a confused wave having a signal component and a confusion component, with signal clarifying means for deriving from energy incoming over said conductor a neutralizing wave and appl ing it to the confused wave, and means or causing a characteristic of the neutralizing wave to vary in response to changes in a characteristic of the confused wave.
29. The combination of an incomin line for supplying control currents, CODIfilSlOn currents and signal currents, an outgoing line for supplying a clarified signal, a pair of current aths connecting said lines, one of said pat s comprising means for Selectively transmitting the signal and confusion currents, the other of said paths comprising means for deriving, rents, confusion currents of opposite phase to said first mentioned confusion currents and means for selectively transmitting said confusion currents of opposite phase.
30. The combination of an incomin line for supplying control currents, con sion cu rents and s gnal currents, an outgoing from said control curline for sup lying a clarified si al, a pair of unilatera ly conducting amp ifying current paths connecting said lines, one of said confusion currents of opposite phase.
31. A secret signaling system comprising.
a source of control oscillations, means. for derivin confusion currents from said control oscillatlons, a source of signal currents,
a line adapted to be supplied by said condevice.
trol oscillations and by said signal and said confusion'currents, means at a receiving stationfor selectively receiving said control oscillations and for deriving therefrom confusion currents of opposite phase to, sald first mentioned confusion currents, and a translating circuit in which said signal and said confusion currents supplied to said line are adapted to be combined with the confusion currents of opposite phase whereby signals may be received free from confusion. i
32. A telephone si aling system comprising means for pro ucing speech currents and means for producing confusion currents, a means which is operative in the ab sence of confusion currents for transmitting speech currents, means for superposing the confusion currents on the-speech currents, and means for receiving speech currents free from the confusion currents, said -last mentioned means comprising a plurality of se.
lective energy transferring channels terminating at a common signaltranslating 33. In a signaling system, a enerator of sustained waves, a modulating evice, a plurality of circuits connecting said generator and said modulating device and translating devices of diflerent character in said conne ting'circuits respectively, whereby electric l waves of one characteristic are supplied through one of said circuits -to 'said modulator during the operation of said generator, and of a different characteristic through the other of'said circuits.
34 The method of wave transmission which comprises receiving electrical wave energy of two kinds, having distinctive freqllilency characteristics, at a receiving station, 0 anging the phase of one of said kinds of waves to a predetermined relationship with respect to the other thereof, deriving current energies from said waves of changed phase and other waves, and combining the energles. 35. The'method of synchronously product mg two wave energies at a receiving station which comprises producing a controlenergy verting them to imposed variations, and receiving said sound wave signaling variations free fromconfusion variations.
37. The method of radio telephony which consists in radiating signaling current energy in the form of high frequency waves modified in accordance with signaling variations and confusion variations of the same general frequency range and at a receiver detectin the high frequency waves, and selective y entinguishing the confusion variations.
38. The method of telephony which comprises'receiving incoming signal wave energy, transmitting art of the received energy through one patli to an indicating device, transmitting another part of'the received 1 energy through another path to the same indicating device, and changing the frequency of the energy traversing one of said paths.
39,. The method which comprises generating a control wave at one station, utilizing part of the control wave energy for transmission to a cooperatin station, and causing energy of said contro wave frequency to synchronously generate other waves at each of said stations. v n
40. A transmission system comprising two co-operating stations, means for generating a control wave of a given frequency at one of said stations, means for simultaneously producing energy of the control frequency at the other station, and .means vi lhereby said control wave energy controls t e simi ar waves having a frequency other than the frequency of the control wave,
generation at each of said stations of- 41. The method of radio reception which comprises successively utilizing at oneostation the energy of received waves to produce other waves of different frequency, increasing the frequency in at least one instance, and selectin a frequency component of the energy pro uced b each frequency change includin the se ection of the energy of increase frequency in at least one instance of frequency lncrease.
' 42. The method of radio reception which comprises receivin waves, successively connally produce waves of lower frequencies, filtering-said waves of lower frequencies by freely transferring a Ill relatively wide band offrequency comporelatively Wide band of Waves of the proin duced frequencies having frequencies below a definite frequency and attenuating accompanying waves of all higher frequencies.
In Witness whereof, I hereunto subscribe y A. D., 1921.
Joint MILLS.
name this 22nd day of December 15
US530528A 1922-01-20 1922-01-20 Method and means for signaling Expired - Lifetime US1480217A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US530528A US1480217A (en) 1922-01-20 1922-01-20 Method and means for signaling

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US530528A US1480217A (en) 1922-01-20 1922-01-20 Method and means for signaling

Publications (1)

Publication Number Publication Date
US1480217A true US1480217A (en) 1924-01-08

Family

ID=24113954

Family Applications (1)

Application Number Title Priority Date Filing Date
US530528A Expired - Lifetime US1480217A (en) 1922-01-20 1922-01-20 Method and means for signaling

Country Status (1)

Country Link
US (1) US1480217A (en)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418119A (en) * 1943-04-10 1947-04-01 Sperry Gyroscope Co Inc Secret communication
US2448055A (en) * 1944-02-21 1948-08-31 Standard Telephones Cables Ltd Wobbled frequency carrier wave communication system
US2476337A (en) * 1943-01-22 1949-07-19 Sperry Corp Secret radio communication
US2505594A (en) * 1944-09-06 1950-04-25 Us Executive Secretary Of The Atmospheric static simulator
US2710343A (en) * 1950-08-09 1955-06-07 Dale Belford Secrecy system for transmitting television signals
US3016519A (en) * 1956-06-12 1962-01-09 Herbert G Lindner Synchronization for maximum correlation
US3071752A (en) * 1958-01-02 1963-01-01 Strasberg Murray Interference reduction apparatus
US3478169A (en) * 1964-02-24 1969-11-11 Matsushita Electric Ind Co Ltd Secret sca communication systems and apparatus
WO2009139807A2 (en) * 2008-05-16 2009-11-19 Alcatel-Lucent Usa Inc. Service induced privacy with synchronized noise insertion

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2476337A (en) * 1943-01-22 1949-07-19 Sperry Corp Secret radio communication
US2418119A (en) * 1943-04-10 1947-04-01 Sperry Gyroscope Co Inc Secret communication
US2448055A (en) * 1944-02-21 1948-08-31 Standard Telephones Cables Ltd Wobbled frequency carrier wave communication system
US2505594A (en) * 1944-09-06 1950-04-25 Us Executive Secretary Of The Atmospheric static simulator
US2710343A (en) * 1950-08-09 1955-06-07 Dale Belford Secrecy system for transmitting television signals
US3016519A (en) * 1956-06-12 1962-01-09 Herbert G Lindner Synchronization for maximum correlation
US3071752A (en) * 1958-01-02 1963-01-01 Strasberg Murray Interference reduction apparatus
US3478169A (en) * 1964-02-24 1969-11-11 Matsushita Electric Ind Co Ltd Secret sca communication systems and apparatus
WO2009139807A2 (en) * 2008-05-16 2009-11-19 Alcatel-Lucent Usa Inc. Service induced privacy with synchronized noise insertion
WO2009139807A3 (en) * 2008-05-16 2010-01-07 Alcatel-Lucent Usa Inc. Service induced privacy with synchronized noise insertion

Similar Documents

Publication Publication Date Title
US1480217A (en) Method and means for signaling
US1624966A (en) Ambulatory repeating system
US2014081A (en) Wave transmission system
US1882653A (en) Signal transmission system
US1836824A (en) Wave transmission with narrowed bands
US1951524A (en) Variable frequency multiplex system
US1480216A (en) Transmission system
US1565091A (en) Wave-transmission system
US1624601A (en) Secret communication
US1507887A (en) lubjslioo
US1447773A (en) Radio transmission control system
US1569003A (en) Signaling system
US1526335A (en) Secrecy transmission system
US2695927A (en) Multichannel carrier telephone system
US1740859A (en) System of secret radiant telephony and telegraphy
US1757729A (en) Wave-transmission system
US1668674A (en) Directive radio repeating system
US1502889A (en) Method of and system for radiosignaling
US1544910A (en) Repeater for multiplex systems
US1593365A (en) Method and system of high-frequency transmission
US1738000A (en) Means for and method of volume control of transmission
US1465357A (en) Radiocommunication
US1603582A (en) Carrier-wave transmission system
US1660072A (en) Duplex transmission system
US1811915A (en) Means to control cross talk