US1671143A

US1671143A - Wave translator

Info

Publication number: US1671143A
Application number: US739638A
Authority: US
Inventors: George A Campbell
Original assignee: American Telephone and Telegraph Co Inc
Current assignee: AT&T Corp
Priority date: 1924-09-24
Filing date: 1924-09-24
Publication date: 1928-05-29
Anticipated expiration: 1945-05-29

Description

G, A.. CAMPBELL WAVE 'TRANSLATOR Filed Sept. 24, 1924 4 Sheets-Sheet l IN VEN TOR 6'; Calm/ne@ L 6l A TTOQNEY G. A. CAMPBELL WAVE TRANSLATOR Filed Sept. 24, 1924 4 Shee'S-Sheet- 2 d/ -AL I +0 y nl. I -#w i BY W A TTORNEY G., A. CAMPBELL WAVE TRANSLATOR Filed Sept. 24, 1924 Lamm@ 4 Sheets-Sheet 3 ATTORNEY May 29, 192s. @Win43 G. A. CAMPBELL WAVE TRANSLATOR Cou/duly Plates INVENTOR ATTORNEY Patented May 29, 1928.

UNITED STATES GEORGE A. CAMPBELL,

OF UPPER MONTCLAIR, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONE AND ',IELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

WAVE TRANSLATOR.

Application filed September 24, 1924. Serial No. 739,838.

This invention relates to wave transmission and more particularly to a method of and means for operating upon a wave in such a manner as to change the time required for transmission of short portions of the wave.

The method of transforming the wave is based upon the Doppler principle; the input wave is propagated through a guiding medium with which coupling is made by a device which moves with respect to the medium. The Wave thus produced in the coupling device may be transmitted by usual methods to any desired stat-ion, there propagated through a second guiding medium and by a second moving coupling device transformed lo its original state. The input wave is divided by the mechanism into portions of equal duration. By employing the Doppler principle, motion of the coupling device in the direction of propagation of the input wave, at a velocity less than that of the input wave, will increase the duration in the coupling device of a given portion. The portion, the duration of which has been thus increased, is said to be expanded, and to an amount denoted by the ratio of the duration of the portion in the coupling device to its duration iu the ,guiding medium. This ratio is called the degree of expansion. Similarly. motion of coupling device contrary to the direction of propagation of the input wave will shorten the duration of a portion in the coupling device. or compress it to an amount denoted by the degree of compression. or ratio of the duration of a portion in thc guiding medium to its duration in the output of the coupling device. If the wave is periodic, expansion results in reducing the frequency. and compression results in increasing the frequency, of the in- A put wave.

MoreI specifically, the invention contemplates compressing portions of a. wave each to l/nth its duration and repeating each compressed portion n times. Where the system involves modulation the compression may take place either before or after mo'dulation. The compressed iva-ve is then transmitted by wire or radio to a distant station and, by expansion of compressed portions and superposition of repetitions (either before or after modulation), given its original duration. In a radio system this method of transmission may be use'd to i'educe the effect of static by reason of the fact that each portion of the output signal at the receivingend will be built up by an n-fold repetition, whereas the static impulse will, in general, not occur in synchronism with the repetitions in the compressed wave and so will not be built up to an n-fold amplitude.

The invention also makes possible the simultaneous transmission in one channel of n times the normal frequency band-widt of the signals from ynehannels. The n input waves are compressed portion by portion but not repeated and the compressed portions are so arranged in the single resulting compressed wave that there is one compressed portion from each signal in each sequence of n compressed portions. This multiplex compressed wave is transmitted to a distant station and there expanded in such a way that the n different signals are separated and taken up by u different channels. Such a method of transmission offers a frequency saving over those systems using n channels of normal width in that it eliminates the bands which are necessary in those systems to separate the channels.

The invention also provides means for attaining secrecy in transmission. The input wave is divided into portions, without compression or expansion, but with each portion reversed with respect to time. This transformed wave consisting of successive reversed portions is transmitted to a distant station and there reversed again, portion by portion, reproducing the time relations of the input wave. Furthermore, in the method of compressed, repeated transmission each compressed port-ion may be reversed with respect to time at the transmitting station and so expanded and reversed at the receiving station as to reproduce the time relations of the input wave, combining the advantages of reversion with those of reducing the effect of static.

The invention may be more fully understood from the following detailed description thereof when read in connection with the accompanying drawings. Figure 1 is a simplified diagram showing how the wave compressor and the wave expander are arranged and combined to cooperate with each other in a Signaling system; Fig. 2 is a chart versely as the frequency of a simple periodic illustrating the states of the wave between the transformations in the apparatus of Fi". 1; Fig. 3 is a diagram showing in some detail the apparatus used either in connection with a Wave compressor or with a wave eX- pander; Fig. 4 is a simplified diagram showmg how the apparatus of Fig. 3 may be applied as a wave compressor at the transmltting station of a. radio system; Fig. 5 is a similar diagram showing how the appara tus of Fig. 4 may be applied as a wave eX- pander at the receiving end of a radio system; Fig. shows how apparatus similar to that of Fig. 4 may be applied to the simultaneous transmission in one channel of input Waves from several channels and Fig. 7 shows the apparatus ot' Fig. 4 used to receive the compressed Wave transl'nittedtrom the apparatus of Fig. 6. A

It is neither practicable nor desirable to transform more than a short portion of a wave ,as a unit. Compression of a portion of a Wave corresponding to a complete message or even a complete sentence would require an inconveniently long guiding medium. It is desirable, furthermore, in two- Way communication, that one station be able to interrupt the other at any instant, without waiting for the completion ot' the message or sentence started. To secure repetitions means must be provided for the coupler to move a given distance back along the guiding medium in a minimum of time. Both these requirements, i. e., division of the input wave into short portions and apparatus permitting the coupling device to move back over a given distance along the guiding medium with suiiicient quickness, are met most easily by using a guiding medium which is circular in shape with a coupling device rotating about the center of the circle, the gap between the points where the Wave enters and Where it leaves the circle being made very small.

The degree of expansion or compression is given directly by the fundamental expression for the Doppler `principle (Barton,l

Sound, p. 97). In Fig. 1, the incomplete circles represent the guiding mediums: an artificial line in the case of electromagnetic Waves, or an air tube Jfor sound Waves. The wave enters at A and leaves at B, where there is a suitable termination to avoid retlection. Mounted on an arm which rotates about the center of the circle is a coupling device, C, which is excited by the wave in the artificial line. If the wave and the arm travel around the circle in T seconds and t seconds, respectively,y the ratio of their velocities, it/T, has the positive or the negative sign it the velocities are in the same or the opposite directions, respectively. Substituting in the equation cited. and noting that a wave portion will be transformed inwhere P is the duration of a wave portion, and lI the duration ot' the corresponding transfmmed portion.

llxamiuation ot' Equation (l) shows that, depending on the ratio T/t, the input -Wave is transformed in one of seven ways, which considering only cases in which P/P is au integer or the reciprocal of an integer, are as follows: i

(l) For 'ly/ 0, the. input wave is compressed and repeated by portions completely.

(2) For 'I`/?f=(). the `input wave suffers no change in time relations.

(3) For O 'l`/ l, the input wave is expanded by portions, with certain portions omitted.

(si) For 'l1/trai., there is no resulting' ware 1n the coupler.

(5) For l 'l`/f 2. the input wave is expanded by portions. with certain portions omitted, but with the expanded portions` reif'ersed with respect to time.

(6) For 'Il/#22, the input wave is reversed by portions completely, 'but without change in the duration of a portion.

(7) For 'l`/I Q. the input Wave is compressed and repeated by portions completely, with each compressed portion reversed with respect to time.

The words compression and expansion, unless specifically qualified, will he taken hereinafter to 'refer to C. es (l) and (Si)` respectively. that is. to transformation witliout reversion. Cases (l) and (3) will be considered in detail. information concerning the other cases can be derived by analogous considerations.

For compression, Case (l),the ratio of the velocities ofthe coupler and the input wave is negative: tliereiore. using subscript c to denote compression, the degree of compression is Suppose that. beginning at any instant when the coupler` C. is vertical, the input wave is divided into portions t.. seconds long. B v Equation (2) the arm makes Contact with n such portions each revolution, and also h'v Equation (2) the artificial line is ot .such length as to contain (nf-1) portions. Contining our attention to the case Where n is an integer. a given portion passes completely through the artificial line in n revolutions. It is consequently repeated in compressed form n times. the first appearance occurring While the portion is in the first nth of the artificial line. the second in the second nth. and so on. At an instant when the arm is llt) lil() vertical it has just lnade contact for the first time with a certain portion. Since the arti- {icial line colltains (1t-1) portions, the first of which is the portion in question, the coupler must make contact with (ft-2) intervening portions between each repetition in the compressed wave; ltherefore repetition of identical points occurs at intervals of ('n-1)/n seconds.

`For example, referring to Fig. 2, it, beginning at any instant when't-he coupling arln is vertical, the order of portions in the inputI wave be denoted by letters as in row (1), then for n=4 the order of compressed portions in the compressed wave is that. shown in low (2), the subscripts denoting the order of appearance of repetitions.

For expansion, Case. (3). the velocity ot' the coupler is positive` that is, the coupler moves in the direction ot' propagation of the wave. Using subscript c to denote expansion, to attain a degree of expansion n the velocities nlustbe suchlthat Writ-T2 Suppose that beginning' at any instant when the coupler is vertical the input wave is divided into portions (te-Te) seconds long'. By Equation (3 n such portions enter the artificial line uring each revolution, also b Equation (3) the artificial lille is of such eligtll as to contain (n-1),sueh portions. The (n-l) portions in the artificial line. at the beginning of a revolution of the coupler'are omitted, since the coupler moves more slowly. than the wave, and one portion (te-Te) seconds long entering the artificial line as the revolution begins is expanded during each revolution. However, if n equally spaced coupling'arms are used, the entire wave will be. expanded once and only once, since the arms follow each other by (te-Te) seconds. Successive portions of the'input wave are. expanded by successive arms.

For example, referring to Fig. 2, it', beginning at any insta-nt when coup-ling arln l is vertical, the order of portions (tc-T.) seconds long entering the artificial line be denoted by letters as in row (2), then for a=4 the order of portions expanded by the four coupling arms is shown by rows (4) Vto (7) inclusive.

An input wave which has been compressed and repeated in the manner described for Case (1) is transformed to its original time relations by means of expansion in the manner described 'for Case (3), subject to the re quirements that the degree ot expansion equal the degree of compression, the length of the portion (te-Te) .seconds long which is expanded equal the length tc/n seconds of a compressed portion, the length of the p0rtion T., seconds long whiclris omitted by the te=t and lTfr-Tc. (4)

Or, the coupling arms of the expander revolve at the same rate as the coupling arm ot the compressor, and the wave is propagated through the Lartificial line ot' the expander 11y times as rapidly as through the artificial line of the compressor.

If n equally spaced coupling arms are used in the expansion of a compressed lepeated wave each one will reproduce the original input wave, since the length of the portion omitted by each coupling arln of the expander has been made equal to the length of the compressed portions between the same appearances of successive portions. The outputs of the various arms will not, however, be ill synchronism. for repetitions of the same point of the. Wave appear at intervals of zf(n-1)/n seconds. In order to superpose the outputs, each lnust be retarded sufliciently to synchronize with that from the arnl which expands last appearances of portions inthe compressed Wave. Calling this arm number l and numbering the. arms in the order in which they follow this arln, the output from the th arm must be retarded t, (1w-1) (n-1)/n, or (ZP-1) Ic/n seconds.

Detailed consideration of aV special case will make these relations clear. Fig. 1 shows a system using a wave compressor vand a wave expander for the ease in which 71:4.' The compressor arln carrying the coupler, C, revolves in thedirection opposite that of the propogation ot the wave and in t, seconds. The wave travels from A to B in 3a., seconds, where it is dissipated in a non-reflecting termination. The expander has four arms a quarter revolution apart which rotate together in the direction of the wave in t, seconds. The wa`ve passes through the expander in .3h/4 seconds. The first coupling arm is connected directly to the output circuit, the second to the output circuit through al retarding line or network producing a de lav of 31h/4 seconds, the third through, in effect. two such l'etarding lines, Sotllat the delay is 315/2 seconds, and the fourth through three retarding lilles producing a delay of 91?../4 seconds.

The chart of Fig. 2 illustrates the successive states of an input wave between the various transformations. Each roW of the' y vRow (2) shows the vthe input wave,

Q chart is divided intotime intervals of the same magnitude, but, unless otherwise noted, each row has a different origin of time.

Row (1) shows the `division of the input wave, beginning at an instant when the comprcssor nrin is vertical, into portions cach A.,

seconds long, thcl portions in order being denoted by thedetters A, B, C, 1),-ctc.

order and relative duration of compressed portions in the coinl are separated by two other compressed portions; therefore repetitions of the same point of the input wave, the beginning of portion D, for example, occur at intervals of Ste/4 seconds.

The compressed, repeated wave shown in i'ow (2? is transmitted to thereceiving station. w 1ere it enters the artificial line of the expander. The rtation of the coupling arms of the expander is so arranged that an arm is in the vertical position at the instant aI compressed portion reaches point A 'of the artificial line.` Row (3) of the .chart shows the order in which the compressed portions are individually picked up by the several arms of the expander. Arm 1 icks up l'ast appearances in the compressed repeated wave of successive portions of the input wave;

arms

2, 3 and 4 pick 'up third, second and `first appearances, respectively. Each arm accordingly produces a wave having the time relations of the input'wave. The waves in the several arms are not nchronous, as shown in rows (4), (5), (6) and (7) of the chart. which are drawn with a common origin of time. The effect of the associated retarding lines, however, is to retard the waves produced by

arms

2, 3 and 4 until they synchronize with the wave produced b v arm 1, as shown in rows (8), (9), 10) and (11), which have a common origin of time. These synchronous reproductions of the input wave are then supeiposed to form the output wave.

If the reception of a momentary static impulse should occur during the reception of compressed portion D2, for instance, the distorting effect of the static impulse will only appear as a distortion of D2 in row (10) of the chart, consequently in only one of the four-fold repetitions from which the output wave is built up. The ratio of the magnitude of the static effect to the total signal (D,ID2ID,+D4) is accordingly reduced to 1/4; this reduction increases with the degree of compression used.

It is to be noticed that in expanding a compressed, repeated wave two operations must be performed before the expanded reptating the coupler arms at l/wtli the rale of the compressor arm. The outputs of the expander arms may then be s uperposed at once to v'form the output wave.

It has been pointed out that the successive repetitions of portions in a compressed wave are made in successive arcs l21r/a ofthe artificial line of the compressor. If each arc 21r/n of the artificial line be assigned, each.

with proper termination, to n different chanl nels of input wave, the compressed wave Twill consist of sequences of n com ressed portions, each one from a different cliannel. Each portion of each input wave will be compressed and appear once in the compressed wavc. If each of the input'waves occupies a frequency band of a certain width, the compressed wave, carrying all n signals, will occupy a channel n times as wide. If such a wave be received by an expander of the type illustrated in Fig. 1, each of the n arms will reproduce one of the input Waves, since the portion expanded is exactly the length of a compressed portion and the portion omitted is exactly the length of the (iz-1) compressed portions belonging to other input waves. Each arm may then be connected to the circuit of a different out?.

going channel.

By considerations similar to the it can be shown that an input wave, transformed in the manner of Case (7) of Equation (1), i. e., compressed and repeated by port-ions, with each portion reversed with respectto time, may be given its original time relations by means of a transformation in the manner of Case (5).

As in the case of unreversed compression and expansion, the expander Ais provided with n equally spaced coupling arms each of which produces a wave having the time relations of the input wave. The waves from the coupling arms may be superposed, after suitable retardations, .to form an output wave having the time relations of the input wave.

foregoing Apparatus to accomplish a transformation I' out change in the duration 'of a portion. The resulting reversed wave is transmitted to the receiving station where by means o apparatus identical with the reversing apparatus the reversed wave is given the time relations of the input wave; Such transmitting and receiving apparatus can be used to attain secrecy in transmission.

In any system, involving wave compression followed by expansion, there will be distortion of the signal if the coupling armsvary in speed. This distortion takes the form of over or under compression accompanied by more than n repetitions or less instant a compressed port-ion of signal is entering the artificial line. This type of distort-ion may be avoided by mountin the artificial line so that it may be turne around its center, the correct position to be found by monitoring either on the signal or a control signal. Precise equations are not given concerning the efi'ect of attenuation, since the method of compensating for it depends on the type of line and the type of coupling employed. In general, attenuation in the artificial line can be compensated for in the compressor by a coupling which decreases exponentially as the arm goes from B to A of Fig. l; and in the expander by coupling which increases similarly from A to B. If no compensation were provided, and a simple periodic wave entered the compressor artificial line (Fig. l), the amplitude 0f the compressed, repeated wave would increase exponentially during the time of each revolution of the coupling arm.

It is apparent that apparatus to accomplish the wave transformations described can be constructed in a variety of ways. To

' cite only three examples, sound Waves may be transformed directly by using a microphone which rotates in a circular air tube; a telegraphone provided with a moving magnet may be used to transform electromagnetic waves; or electromagneticwaves may be transformed by direct coupling.

Details are given here only for one method -of accomplishing the last named result. The

guiding medium used is an artificial line of the ladder type shown in Fig. 3, with series inductance, L, shunt capacity, C, terminated in mid-shunt by its iterative impedance, K.

Such an artificial line acts as a low-pass.

filter. From the time of propagation per f neededfwhich is fixed by the de section, given by the theory of artificial lines, and the total time of; propa tion ree o compression used and the rate o revolution chosen for the coupling arm, the number of 7n sections needed for the compressorl is:

where p/21.- and4 11e/2n are the frequency of 75 the input Wave and the cutoff frequency of the artificial line, respectively.

Equation (5%J shows that the various frequencies of a and will not be compressed uniformly, the higher frequencies being compressed by a greater amount than the lower ones. Distortion from this cause may be reduced to a negligible amount by choosing the cutoff frequency sufficiently high in comparison with the highest frequency it is desired to reproduce. The expression for the anti-sine may then be replaced by the first term of its series, and, to a degree of accuracy discussed below:

The expanderarms, by previous theory,

rotate at the same rate as the compressor arm. The cutoff frequency of the expander l artificial line must be fn times that of the compressor, and its time of propagation must be 1 /nth that of the compressor artificial line. Using thel same approximation for 10 anti-sine as in deriving (6), then, the number of sections of artificial line needed for the expander is the same as for the compresser.

The suitable minimum value for the cut- Where f is any frequency and' f, the cutoff frequency of the compressor. The effect of the complete transformation is a decrease in all the frequencies. If a variation of 2() higher powers than the cycles at a frequencyY of 200() be taken as the 12o maximum permissi e, for 'n=3 the cutoff` frequency of the compressor mustA be approximately 9500 cycles, that of the expander 28,500 cycles.

\Vith the cutoff frequencies fixed by (7) 126 and the iterative impedance determined by the apparatus to which the artificial lines are connected,-the values of the inductances and capacities required may be computed by well-known formulae.

byv expansion. Dropping The retardin lines for the expander arms can convcnientliv be made up of lengths of the type of artificial line usedV for compression. Each length must have N/nI sections.

Formula (6) shows the number of sections with which coupling is made each second. This number is large. For instance, if n=3 it is approximately 60,000. The values .of N and t, depend, therefore, on a compromlse between the cost of building a large number of sections and that ot constructing a suit able highspeed coupling device. In the case cited, if 500 sections are used, the arm must run-at 7 200 revolutions per minute.

Because of' the high speeds involved, coupling by direct contact is impracticable. An electrostatic method is shown in Fi 3. Metal plates, a. connected directly to Junction points of the artificial line, are sunk in the face of a stationary wheel, b, and insulated 'from one another. Coaxial with b, and as near it as possible is a rotating wheel, e, which carries an insulated plate, (l, for compressing, or n equally spaced insulated plates for expanding. The plate d is large enough to cover one or several, as may be best, of the plates a. From d runs a conductor, e, to amplifiers, etc. There is some coupling between d and all the plates, a, but coupling is a maximum with the plates directly opposite d. It is desirable to keep the coupling so low as to have a negligible reaction on the wave in the artificial line. Calculation shows that the coupling between adjacent artificial line plates, a, can be neglected.

Figs. 4 and 5 illustrate how the compressor and expander may be applied to the transmitting and receiving stations respectively of a system of radio intercommunication. The particular case illustrated in Figs. 4 and 5 involves a degree of compression n=3. In Fig. 4, 10 designates a te1ephone transmitter which is connected to an artificial line, 11, of the type illustrated in Fig. 3, said line has connections from its various sections to the plates (not .illustrated) of the stationary Wheel, b. d is the revolving plate of the coupler and is connected by a conductor, 12, to the radio transmitter apparatus, 13, comprising the usual amplifier modulator, etc. The upper termi nal of the artificial line, 11, is also connected t0 the radio transmitter and the transmitter is associated with a radiating antenna, 14, in a Well-known manner.

In Fig. 5, 15 designates a receiving antenna having associated therewith the usual radlo receiving apparatus comprising a demodulator, etc. One terminal of the radio receiving apparatus is connected to the u per terminal of the artificial line, 16, said artificial line being of the type illustrated in Fig. 3. Connections are made from the various sections of the artificial line to the plates (not shown) of astationary wheel, li', of the type shown in Fig. 3. The expander is provided with three equally spaced. revolving plat-es d1, tlg, and d3, each bemg similar to the plate (Z of Flg. 3. The plate d1 is connected directly to the lower terminal of an outgoing telephone line or an amplifier in said line. The second plate, (Z2, is connected to the lower input terminal of a retal-ding line, L. said retarding line lbeing ot the' same general type as the artificial line illustrated in Fig. 3 and said line being so designed as to produce the necessary retardation of the wave transmitted from the -plate d2. The plate d, is connected to the lower input terminal of a similar retarding line, L3, which is connected in series with the retarding line L2 so that the Wave components picked up by the plate da will be retarded twice as much as those picked up by the plate d2., A terminating impedance, K', is connected across the input terminals of retai-ding line, L J, the upper one of Which is connected directly to the upper terminal of the terminating impedance, K, of the artilicial line 16. The operation will be apparent from the theoretical discussion already given.

Figs. 6 and 7 show the application of the compressor and expander to a multiplex system of' inter-comnmnication. The particular case illustrated also involves a degree of compression '1i/:3 and permits theI simultaneous transmission of Waves from three channels in one channel three times the normal frequency width and provides means for their separation at the receiving end. Fig. 6 shows the compressing apparatus. The three incoming channels, designated as lines A, B and C are connected to artificial lines A, 13 and C, respectively. Each of these artificial lines is of the general type shown in Fig. 3 and each is terminated in its iterative impedance, K. The section points ot each line are connected to the plates (not illustrated) of the stationary wheel, b, in such a way that the Wave in each artificial lille travels along a third otthe circumference of b. l is the revolving plate ot' the coupler, moving in a direction opposite that of the waves. d is connected to an amplifier which in turn actuates radio transmitting apparatus or a telephone line in the usual manner. The upper terminals of the artificial lines and the amplifier are connected in series.

In Fig. 7 is shown the expander to be used at the receiving end with the output of the compressor in Fig. 6. It is essentially the same as the apparatus shown in Fig. 5, except that no retarding networks are needed and the output from each arm is connected to the lower terminals of amplifiers associated with channels A, B and C, respectively. The upper terminals of these method of construction of' the apparat-us and the inter-relations between the transmitting and the receiving elements are apparent from the principles and apparatus heretofore described.

It will be obvious that the general principles herein disclosed mayv be embodied in many other organizations widely different from those illustrated without departing from the spirit and scope of the invention as defined in the appended claims.

What `is claimed is:

1. The method of wave transmission which consists in progressively producing upon successive elements of a transmission medium effects corresponding to the progressive variation of a wavewith time so that the wave is in effect propagated from element to element along the medium, producing in a conductor a wave having variations corresponding to saidsuccessive effects, and moving said conductor with respect to said medium during the propagation of a wave along the medium to change the time relations of the variations of the produced wave as compared with the time relations of the corresponding variations of the original wave.

2. The method of wave transmission which consists in transmitting a wave through an artificial line, producing in a conductor a wave having variations corresponding to tit) the successive effects in the sections of said artificial line, vand moving said conductor with respect to the elements of said artificial line to change the time relations of' the variations of the produced wave as compared with the time relations of the corresponding variations of the original Wave.

3. The method of compressing a wave which consists in progressively producing upon successive elements of a transmission medium effects corresponding to the progressive variations of the wave with time so that the wave is in effect propagated from element to elementalong the medium, producing in a conductor a wave having variations corresponding to said successive effects, and moving said conductorwith .respect to said medium in a direction opposite to that in which the wave is being propagated along said medium, thereby reducing the time relations of the variations of the produced wave as compared with the time relations ot' the corresponding variations of the original wave.

4. The method of compressing a wave which consists in propagating a wave from section to'section of an artificial line, producing in a conductor a wave having variations corresponding to the variations in the wave propagated along the artiicial line, and moving said conductor with respect to said artificial line in a direction opposite to the direction of propagation over the line, thereby reducing the time relations of the variations of the produced wave as compared with the time relations of the vcorresponding variations of the original wave.

5. The method of increasing the frequency of a wave which consists in progressively producing upon successive elements of a transmitting medium effects corresponding to the progressive variations of the Wave with time so that. the wave is in effect propagated from element to element along the medium, producing in a conductor a wave having variations corr xsponding to said successive effects, and moving said conductor with respect to said medium in a direction opposite to that in which the wave is propagated over the medium, thereby increasing the frequency at which succeeding elements of the wave follow each other as compared with the frequency at which similar elements of the original wave recur.

6. The method of increasing the frequencyv of a wave which consists in propagating said wave from section to section of an artificial line to produce in each section effects corresponding to the progressive variations of the wave with time, producing in a conductor a Wave having variations corresponding to said successive effects, and moving .said conductor with respect to said artificial line 1n a direction opposite tothat in which the wave is propagated along said artificial line, thereby increasing the frequency at which succeeding elements of the wave follow each other as compared with the frequency at which similar elements of the original wave recur. l

7. The method of expanding a wave which consists in progressively producing upon successive elements of a transmitting mediu1n efiects corresponding to the progressive variatlons of the wave with time so that the wave is in effect propagated from element io element along the medium, producing in a conductor a wave having variationsicorresponding to said successive effects` and moving said conductor with respect to vsaid medium in the same direction as the direction of' propagation of the wave along said medium and at. a rate slower than the rate of propagation of the wave along the medium, thereby increasing the time relations of the variations of the produced wave as con'ipared with the time relations of the corresponding variations of the original wave.

8. The method of expanding a wave which consists in -propagating said wave from section to section of an artificial line to produce effects in each 'section correspondu gli ing to the progressive variations of the wave cessive etlccts, and moving said conductor Y with respect to said artiticial line in the saine direction as the direction of propagation ot the wave over said line and at a rate slower than the rate ot propagation over said line, thereby increasing the time relations of the variations ot the produced wave as compared with the time relations ot'the corresponding variations ot the original wave.

9. The method ot' decreasing the t'requency ot a wave which consists in progressively producing upon` successive elements of the transmitting medium eti'ects corresponding to the progressive variations of the wave with time so that the wave is in etl'ect propagated troni element to element along the medium, producing in a conductor av wave having variations coi'responding to said successive ett'ects, and moving said conductor along "aid medium in the saine direction as the direction of propagation ot the wave along' said medium and at a rate slower than the rate of propagation along said medium, thereby decreasing the trequency at which succeeding elements of the wave follow each other as compaia-al with the frequency at which similar elements ot the original wave recur.`

10. The method oi decreasing the 'frequency ot' a wave which consists iii prop-.igating said wave t'roin section to section ot an artificial line to produce eti'ects iii each section corresponding to the progressive variations of the wave with time, producing in a conductor a wave having` variations corresponding to said successive ett'ects. and moving said conductor along said artiticial line iii the saine direction as the direction of propagation of the wave along ifaid line and at a rate slower than the rate of propagation ot' said wave over said line. thereby decreasing the frequency at which succeeding elen'ients o'l. the wave t'ollow cach other as coinpared with the trequency at which siinilail elements of the original wave recur.

1l. rlllie method ot" wave transmission which consists in compressing a wave by "uccessive portions each to a Atraction of its original length, and repeating each coinpressed portion a number ot' times equal to the ratio ot the original length ot' the wave to its conq'iressed length.

12. The method ot wave transmission which consists in compressing a wave by successive portions each to a traction of its original length and repeating each compressed portion at separated intervals a number of times corresponding to the ratio ot the original length of the wave to its compressed length, the intervals between successive repetitions of a given portion of the wave being sutliciently great to enable other compressed ortions to be repeated during said interva s.

13. The method of wave transmission which consists in increasing the frequency ot successive. portions of a wave, portion by portion, and repeating each portion at an increaf'ed trequency a number ot times corresponding to the ratio of its increaseditrequency to its original Jfrequency.

14. The method ot wave transmission which consists in increasing the frequency ot successive portions ot' a wave, portion by portion, and repeating each portion at an increased frequency during separated intervals a number of times corresponding to the ratio ot the increased frequency ot' the wave to its original frequency, the separation between successive repetitions of a given wave portion being sufficiently great to permit of the repetition otl other portions ot' the. wave during said intervals.

15. The method of wave transmission which consists in compressing a wave by successive portions to a traction of its original length. repeating each compressed portion a number of times equal to the ratio of the original length of the wave. to its conipressed length. transmitting the wave thus translated, and expanding eaehcoinpressed lportion to its original form.

16. The method ot' Wave transuiission which consists in compressing a wave by successive portions to a fraction of its original length, repeating each compressed portion a number of times equal to the ratio of thev original length of the Wave to its conipressed length, transmitting the wave as thus translated, expanding each coii'ipressed portion to its original form, and changing the time relation ot the several expanded repeated portions so as to bring the components corresponding to the saine portion into synchronism with each other.

17. The method lot wave transmission which consists in increasing the frequency ot successive portions ot a wave, portion by portion, repeating each portion at an increased frequency a number of times correspending to the ratio of its increased trequency to its original frequency, transmitting the portions thus translated, and eX- panding each portion to its original form.

18. The methodl of wave transmission which consists in increasing the frequency ot successive portions of a wave, portion by portion, repeating each portion at an increased frequency a number of times correspending to the ratio of yits increased frequency to its original frequency, transmit.- ting the wave portions thus translated, expanding each portion to its original form, and changing the time relation ot repeated components ot the same portion so as to ino . ing to the bring the several components corresponding to the same portion into synchronism with each other. l

19. In a signaling system, a transmission medium upon the successive elements of which e'ects may be impressed corresponding to the progressive variation of a wave with time so that the Wave is in eect propagated from element to element along the medium. a conductor inductively related to said medium so that variations corresponding to said successive effects may be impressed thereon, and .means to move said conductor with respect to said medium during the propagation of a Wave along the medium to change the time relations ofthe variations of the produced wave as compared with the time relations of the corresponding variations of the original wave.

20. In a signaling system, an artificial line comprising a succession of sections upon which may be impressed eects corresponding to the progressive variation of a wave with time,.a conductor inductively related to said artificial line so that the successive effects in the sections ot said artificial line may be induced therein, and means to move said conductor with res ect to the sections of said artificial yline to c ange the time relations of the variations of the produced wave as compared with the time relations of the corresponding variations of the original Wave.

21. In a signaling system, a transmission medium .upon the successive elements of which eiects may be impressed corresponding to the progressive variation of a wave with time so that the Wave is in effect propagated from element to element along the medium, a conductor inductively related to said medium so that variations corresponding to said successive effects may be impressed thereon, and means for moving said conductor with respect to said medium in a direction opposite vto that in which the wave is being propagated along said medium, thereby reducing the time relations of the corresponding variations of the original wave.

22. In a signaling system, an artificial line comprising a succession of sections upon which may be impressed effects correspondprogressive variation of a wave with time,.a conductor inductively related to said artificial line so that the successive eiects in the sections of said artificial line may be induced therein, and means to move said conductor with respect to said artificial line in a direction opposite to the direction of propagation over the line, thereby increasing the frequency at which succeedlng elements of the Wave follow each other as compared With the frequency at which simi.

lar elements of the original wave recur.

23. In a signaling system, a transmissmn medium upon the successive elements of which effects may be impressed corresponding to the progressive variation of a wave' with time so that the wave is in eii'ect propagated from element to element along the medium, a conductor inductively related to said medium so that variations corresponding to said successive effects may be impressed thereon, aud means for moving said conductor with respect tov said medium in the same direction as the direction of propagation of the Wave along said medium and at a rate slower than the rate of propagation of the Wave along the medium, thereb increasing the time relations ot' the varlations of the produced wave as compared with the time relations of the corresponding variations of the original wave.

24. In a signaling system, an artificial line comprising a succession of sections upon which may be impressed effects corresponding to the progressive variation of a wave with time, a conductor inductively related to said artificial line so that the successive effects in the sections of said artificial line may be induced therein, and means to move said conductor along said artificial line in the same direction as the propagation of the wave along said line and at a rate slower than the rate of propagation of said wave over said line, thereby decreasing the frequency at which succeeding elements of the Wave follow each other as compared .with the frequency at which similar elements of the original wave recur.

25. In a signaling system, a Wave compressor comprising a transmission medium having a high time constant arranged in the form of an open circle, means to impress a wave upon said transmission medium at one terminal, and means to take off the Wave at the other terminal after propagation over the medium, a rotating coupler adapted lto be continuously rotated along said medium in a direction opposite to the direction of transmission through Vsaid medium, thereby producing in the coupler successive Wave portions, each corresponding to portlons of the wave transmitted through said medium, each a fraction of the length of the original portion, and each portion thus compressed being repeated a number of times equal to the ratio of the original length of the portion to its compressed length.

26. In a signaling system, a Wave compressor com rising an artificial line havlng a number o sections arranged in the form of an open circle, means to impress a wave upon said artificial line at one end thereof, means at the other end for taking off said wave after propagation through said artificial line, lated-to said line and adapted to be rotated in a direction opposite to the direction of propagation along said line, thereby produca rotating coupler inductively reing in the coupler successive wave portions, each corresponding to portions of the Wave transmitted throu h sald artificial line, each a fraction of the lgength of the voriginal portion, and each portion thus compressed being repeated a number of times equal to the ratio of the original length of the portion to its compressed length.

27. In a signaling system, a Wave compres-A sor comprising a transmission medium having a high time constant arranged in the form of an open circle, means to impress a wave upon said transmission medium at one terminal, and means to take oil the wave at the other terminal after propagation over the medium, a rotating coupler adapted to be continuouslyrotated along said medium in a. direction opposite to the direction of transmission through said medium, thereby producing in the coupler successive Wave portions, each corresponding to portions of the wave transmitted through said medum, each a fraction of the length of the original portion, each portion thus compressed being repeated a number of times equal to the ratio of the original length of the portion to its compressed length, means to transmit the wave as thus translated, a wave expander, said wave expander comprising a transmitting medium having a high time constant larranged in the form of an open circle,

means to impress the translated waves upon one endof sald medium, means to take ofi' said waves fromvthe other end of said medium after propagation along said medium, anda rotating coupler rotating in synchronism with the coupler of said compressor and in the same direction as the direction of propagation along the transmitting medium of said expander, whereby each compressed September, 1924.

portion will be expanded to its original length.

' 28. In a signaling system, a wave compressor comprising an artificial line having a number of sections arranged in the form of an open circle, means to impress a wave upon said artificial line at one end thereof, means at the other end for taking ofi' said wave after propagation through said artificial line, a Vrotating coupler inductively related to said line and adapted to be rotated in a direction opposite to the direction of propagation along said line, thereby producing in the coupler successive wave portions, each corres ending to portions of the Wave transmittedp through said artificial line, each a fraction of the length ofthe original portion, each portion thus compressed being repeated a number of times equal to the ratio of the original length of the portion to its compressed length, means to transmit the Wave' portions thus translated, a Wave expander comprising an artificial line having o plurality sections arrangedv in the form of an open circle, means to impress the translated waves upon one end of said articial line, means to take oi'l' said Waves after propagation over said artificial line, a rotating coupler associated with said line and adapted to rotate at the same rate of speed as the coupler of said compressor and in the same direction as the direction of propagation along the artificial line of said expander whereby' each compressed portion will be expanded to its original length.

' In testimony whereof, I have signed my name to this specification this 22nd day of GEORGE A@ CAMPBELL.