US1325574A - Secret-signaling system - Google Patents

Description

Patented Dec. 23,1919.-

H'. w. NICHOLS.

SECRET SIGNALING SYSTEM.

APPLICATION FILED SEPT II. I9l5.

QN W w M. m #0 m ,W lJTh W/fnesses:

' UNITED STATES PATENT OFFICE.

HAROLD WILLIAM NICHOLS, OF MAPLEWOOD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORA-' TION OF NEW YORK.

SECRET-SIGNALING SYSTEM.

Specification of Letters Patent. Patented De 23, 1919 Application filed September 11, 1915. Serial No. 50,150.

To all whom it may concern:

Be it known that I; HAROLD WILLIAM NICHOLS, a citizen of the United States, residing at Maplewood, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Secret- Signaling Systems, of which the followlng is a full, clear, concise, and exact description.

This invention relates to a method of and apparatus for secret transmission of intelligence.

Its object is to'transmit signals which shall be intelligible only at a properly equipped receiving station.

A further object is tomake possible continuous transmission suitable for commercial telephony, that is, transmission in which there is no appreciable time interval between the production of a signal and its transmission to the receiving station.

A fundamental requirement of commercial telephony is that there shall be no delay in the transmission of signals, that is, a.

signal must be transmitted immediately upon its production. This requirement precludes the use of code sending as ordinarily understood, because such sending would necessarily introduce a delay equal to the time required for translation to code; stated in other words, this requirement means that there must be no storage of signals.

In order to accomplish these objects, this invention proposes to so distort the signal transmitted from the sending station that it shall be unrecognizable in the interval between transmitting and receiving station, to receive the signal, and, by means of supplementary modifying apparatus at the receiving station, to restore the orlglnal character of the signal and finally to translate it in a suitable manner. A fundamental condition for this kind of distortion is that the order of electrical states which make up the signals shall not be changed, although the intervals elapsing between successive states may be changed in any arbitrary manner. If this condition is not fulfilled the result will be either delay in the transmission of the signal or else superposition of one part of the signal upon another part, making the resultant message unintelligible.

The nature of this invention will be clear by reference to the drawing, which shows thls invention as applied to radiotelephony. In this arrangement signals are produced by the telephone transmitter, distorted by the apparatus intervening between the transmitter and antenna, transmitted to a receiving station, received and restored to their original forms, and finally translated to audible sounds by the telephone receiver. Referring to the drawing, 1 represents an iron wire or tape driven by the rotatable elements 2, 3 is an electro-magnet which is energized by means of the battery 5, and mlcrophone 4, in circuit with battery 5 and magnet 3, serves to vary the current through the magnet in accordance with speech vibrations. The result of impressing speech vibrations upon the microphone is to alter the magnetic state of the wire 1, as in the magnetic detector or telegraphone, these variations in magnetic state being permanent and carried along withithe wire' or less faithful copy of the current, in mag net 3. The magnet 6 is rigidly connected to the arm 17 which passes through guides and is driven by the cam mechanism 8. This cam may be driven by a separate source of power, or the same source of driving power may be used for the cam and for the driving pulleys 2. The purpose of this cam-driven magnet 6 is to so alter the wave form of vibrations induced in it, with respect to those produced in 3, as to be unrecognizable when transmitted from the antenna as explained later.

It will be obvious that if the motion of the wire 1 is uniform and if the magnets 3 and 6 are relatively at rest, the signal induced in 6 will be practically an exact copy of that produced by the microphone. On the other and, if there is relative motion of-magnets 3 and 6, it is obvious that the signal induced in 6 will be distorted, as the time phase relation between succeeding portions of the signal wave will be modified. The object of this device is to so distort the signal that it will be unintelligible except by a properly equipped receiving station. In designing and operating this cam-driven mechanism, it is essential that the relative speed of mag nets 3 and 6 shall never be great enough to cause superposition of different parts of the message. In order to efi'ace the record of the signal, after it is communicated to 6, and to place the wire 1 in a condition suitable for the recording of a new message, the permanent magnet 9 is placed below the tape, as shown in the figure. Transformer 10 serves to impress the vibrations in magnet 6 upon the input circuit of a thermionic element 11 of the audion type. By means of transformer 13, oscillations of power value, comparable with those produced in 6, are impressed upon the same input circuit by means of the alternating current generator 12. In this figure this is shown as a thermionic oscillator having its input circuit connected with its output circuit. This particular arrangement is the invention of Ralph V. L. Hartley, for improvement in oscillation generators, filed June ,1, 1915, Serial No. 31,476. It is obvious, however, that another type of alternatingcurrent generator may also be used. 14 is a battery placed in the input circuit of the thermionic element and 15 another battery in its output circuit. In order to obtain effective modulation, it is desirable to operate the thermionic device 11 over a range of impressed electromotive forces throughout which the curvature of its characteristic curve is large. Battery 14 serves to impress upon the input circuit an initial electromotive force corre sponding to a point in this range. The thermionic element 11, therefore, serves, in connection with magnet 6 and the oscillation generator 12, as a device for producing in its output circuit modulated high frequency oscillations. This modulating scheme is the invention of Van der Bijl and is described and claimed in his application for radiocommunication, Serial No. 46,643, filed Air gust 21, 1915. By means of transformer 16, these oscillations are transferred to the tuned circuit comprising one winding of 16 and the condenser 17. Across the terminals of 17 is placed a group of amplifiers 18 arranged in parallel. The function of battery 19 is similar to that of 14, and that of battery 20 to that of battery 15, except that in the case of the amplifier the potentials of these batteries are so adjusted as to cause the amplifier to operate over the straight line portion of the characteristic curve. These amplifiers, therefore, produce a'ugmented modulated high frequency oscillations in the output circuit. By means of transformer 21, these oscillations are transferred to the sending antenna 22 through which electromagnetic Waves in the other are orlgmated.

- the same direction as the tape, greater than the speed of the tape. Except 130 These waves impinge upon antenna 23 of the receiving station and are transferred, by means of transformer 24, to a tuned circuit containing condenser 25. The amplifier 26 increases the energy of oscillations in this tuned circuit, and this increased energy, by means of transformer 29, is transferred to the input circuit of a thermionic element 33. 27 and 28 are batteries for use in connection with the amplifier. The condenser 30 performs the same function as condenser 25. In the grid circuit of element 33 is placed condenser 31 shunted by the resistance 32. The function of element 33 is to detect the incoming high frequency modulated oscillations with the result that only the envelop of the oscillations appears in its output circuit. Battery 34 supplies the direct current necessary for this output circuit. Transformer 35 serves to transfer the power from the output circuit of element 33 to the receiving magnet 36. This magnet is similar and similarly mounted to magnet 6 in the distorting device at the sending station. 38 is an iron Wire or tape similar to 1, 39 a magnet similar to 3, 41 a permanent magnet similar to 9, and 40 a telephone receiver connected with magnet 39. 37 is a driving cam whose function is similar to that of 8 at the sending station.

The operation of the device is as follows:

The distorting devices at the two stations are started in synchronism and in phase by means of a predetermined signal. The cams may be driven by clm-kwork, for example, 100 in order to maintain the necessary degree of synchronism. 'hcn a signal is impressed upon the tape 1 by means of magnet 3, it would normally. if magnets 3 and .6 were at restand the tape moving uniformly, require 105 a certain definite time to be transmitted to the mproducing magnet 6. If, however, magnet 6 is in motion with respect to 3, the time clapsing between the production of a signal at 3 and its reproduction at 6 will be 110 variable. and therefore the message sent out from the sending antenna 22 will no longer be an exact copy of the impressed message.

At the receiving station this distorted message is transmitted to the thermionic ele- 115 ments, being amplified in element 26 and transformed into low frequency form in element 33. It is then impressed upon the receiving magnet 36, whose motion is similar to that of 6; The distorted message is, there- 1 fore, received from the tape 38 in its normal form, due to the relative motion of 36 and 39 and is then picked up by magnet 39 and reproduced in undistorted form in the receiver 40.

As stated before, it is essential that the speed of the moving magnet, during that part of its motion in which it is moving in shall not be for this restriction the motion may be. arbitrary.

While the invention has been described as applied to radiotelephony it will be obvious to those skilled in the art that it is applicable as well to either radio or wire systems of telephony, telegraphy or other forms of communication involving transmission of varying electrical energy. The inventlon resides not only in the system as a whole but in various features of the system as pointed out in the appended claims.

What is claimed is:

1. The method of distorting a signal wave form which consists in modifying the time phase relation of succeeding portions of said signal wave.

2. The method of distorting a signal wave form which consists in alternately increasinfg and decreasing the time phase relation 0 succeeding portions of said signal Wave.

3. The method of secret signaling which consists in distorting the time phase relation of succeeding portions of a signal wave, and in translating said distorted wave into its original undistorted form.

4:. The method of secret signaling which consists in distorting the time phase relation of succeeding portions of a signal wave, modulating a carrier wave in accordance with said distorted Wave, in transmitting,

receiving and detecting the modulated wave, and in restoring the detected distorted signal Wave to its original. form.

5. A signal transmission system comprising means for producing audio frequency signaling currents, means for distorting the wave form of said signaling currents, means for transmitting and means for receiving energy varying in accordance with said distorted Wave form, and means for deriving from said received energy currents having the wave form of said audio frequency signaling currents.

6. In a system for secret transmission of intelligence, a source adapted to generate electrical impulses corresponding to a signal to be sent, means practically simultaneously cooperating with said source to alter the mutual phase relations of such impulses, transmitting and receiving apparatus for said altered signal impulses, means cooperating with said receiving apparatus for restoring said mutual phase relations of the altered impulses received, and a translating device responsive to said restored impulses.

7. In combination with a system for the transmission of intelligence, a distorting device having an input circuit and an output circuit, means for supplying currents of a given character to said input circuit, and means for varying the mutual relations of said circuits, whereby said output circuit is adapted to supply currents of a different character.

8. In combination, a magnetizable record, a magnetic recordmg device, and per1od1- cally acting means for causing an-irregular I relative motion of said record and said recording device.

9. The combination of a magnetizable member. means for moving said member, a I

recording magnet and a reproducing magnet adjacent said member, and periodically acting means for varying the relative posi-' tions of said magnets during operation.

10. The combination of a record element, a recorder for modifying said element in accordance with signaling waves, a reproducer in operative relation to said element, and means for varying the relative positions of said recorder and reproducer to cause a distorted reproduction of said signaling waves.

11. The combination of a record element, a recording device and a reproducer associated therewith, and means for causing motion of said record element both with respect to said recording device and said reproducer and for periodically changing said motions by the same amounts. 7

12. A signal transmission system comprising means for producing audio frequency signaling currents, means for distorting the waveform of said signaling currents, means for transmitting and means for receiving energy varying in accordance with said distorted Wave form, and means responsive to said receiving means for restoring the original wave form of said signaling currents.

13. The method of signaling comprising producing signal -waves, distorting said waves, transmitting energy varying in accordance with said distorted waves, receiving said energy, and restoring the original wave form.

14. The method .of signaling comprising producing signal waves, distorting said waves, transmitting energy varying in accordance with said distorted wave, receiving said energy, restoring the original wave form, and producing signal indications by the resulting energy.

15. The method of producing a magnetic record by means of a magnetizable member and a magnet acting thereupon which comprises producing constantly varying relative motion between said member and said magnet.

16. A signaling system comprising means for producing signal waves, means for distortmg said waves, means for transmitting energy varying in accordance with said distorted waves, means for receiving said distorted energy, and means for restoring the original wave form of said received energy.

17. The method of signaling which comprises recording a signal upon a record, reproducing the signal from the record, and cyclically varying the relation between the and means for partly or wholly compensating for such distortion.

19. The combination with means for pro-- ducin a high-frequency wave modulated in accor ance with voice waves, of means for distortingsaid voice waves, and means for partly or-wholly compensating for-such distortion.

20. The combination with means for producing a high frequency wave, a source of voice current waves and a modulator for modulating said high frequency waves in accordance with said voice current waves,'of means for distorting the voice current waves, and means for partly or wholly compensating for such distortion.

21. The method of signaling comprising producing speech waves, distorting said speech waves, transmitting energy varying in accordance with the distorted speech ing means for producing voice currents,

means for distorting the wave form of said voice currents, means for transmittingand means for receiving energy varying in accordance with the distorted voice currents,

and means for deriving from said energy currents having the form of said voice currents.

23. A signal transmission system comprising means for producing currents corre sponding to speech, means for distorting the wave form of said currents, means for transmitting and means for receiving energy varying in accordance with the distorted wave form, and means for deriving from said received energy currents in their restored wave form corresponding to speech and for reproducing speech from the restored currents.

In witness whereof, I hereunto subscribe my name this 8th day of September, A. D., 1915.

HAROLD WILLIAM N IOHOLS.

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