US2495738A

US2495738A - Cathode-ray pulse time modulation multiplex system

Info

Publication number: US2495738A
Application number: US567414A
Authority: US
Inventors: Labin Emile; Donald D Grieg
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC; Federal Telephone and Radio Corp
Priority date: 1944-12-09
Filing date: 1944-12-09
Publication date: 1950-01-31
Anticipated expiration: 1967-01-31
Also published as: GB603188A; BE469040A; CH259614A; FR938192A; ES172611A1

Description

Jam, mi, 1950 E. MEIN Erm.

CATHODE-RAY PULSE TIME MODULATION MULTIPLEX SYSTEES Filed Dac. 9, 1944 4 Sheets-Sheet l BY v/ff Jan, 3H, 1950 E. LABHN HAL 294959733 cAmoDE-RAY PULSE TIME MODULATION MULTI? sysma Filed Das.. 9, 19M @shaw-sheet 2 INVENToRs Amm? Jan. 319 E950 E. LABIN ETAL 2,495,733

cA'monE-RAY PULSE 'rmE MoDuLA'rIoN MULTIPLEX SYSTEM IN V EN TORS Anon/VW Jan. 3L H950 Filed Dec. 9, 1944 UML L A T05 E. LABIN Erm. 2,495,738

CATHODE-RAY PULSE TIME MODULATION MULTIPLEK SYSTEM 4 Sheets-Sheet 4 TYNEY Patented Jan. 31, 1950l sacarse CTHODE-RAY PULSE TME MODUATION MULTKPLEX SYSTEM Emile Lubin, New nous una nonne n. Grieg,

Forest Hills, N. Y.,

assignors to Federal Tele phone and Radio Corporation, New York, N., Y., a corporation ot Delaware Application December 9, 1944, Serial No. 587.41@

lill. 332-13) 30 minima.

This invention relates to electrical signal transmission systems and more particularly to multi-s channel transmission by means of time modulated pulses.

The usual generation of time modulation multichannel wave forms for signal transmission purposes require:

l. Generation of e. series of basic pulses;

2. Retarding or phasing by different amounts, dierent ones ci these pulses so as to obtain an individual series o pulses for each of a plurality of channels;

3. Modulation of each series of channel pulses according to a given source of signals; y

4. Amplification of the modulated pulses;

5. Limiting the extent of modulation to prevent "break through between channels;

6. Generation of marker or synchronizing pulses; and

7; The nal mining of channel and synchronizing pulses into one interleaved train of pulses for transmission.

If conventional tubes and circuits are used to accomplish these steps, a relatively large number of tubes and circuits are required in addition to a great deal of accompanying auxiliary equipment. For example, with a :Z4-channel system using conventional tubes and advanced circuit techniques heretofore known, approximately 60 tubes are required for the multiplex time modulation steps listed above, and many of these tubes are double tubes in single envelopes. In addition to this larger number of tubes, there are the necessary accompanying circuit elements, delay and phasing lines, shaping units, etc., together with a large power supply requirement.

One of the objects of this invention-is to provide a simplified multi-channel transmitter; and in particular, a multi-channel pulse time modulater requiring much less equipment and tubes than heretofore required for multi-channel systems of alike number of channels. A

Another object of the invention is to provide l a multi-channel pulse time modulator capable of accomplishing any one, or combination, of the multi-channel transmission functions enumerated above, that is, generating and phasing the pulses required for multi-channel operation. time modulating and amplifying the pulses, limiting the maximum displacement of modulation, providing pulses for a synchronizing channel anclmixing the pulses into a single train for transmission.

A further object of the invention is to provide an improved modulator for producing a series of piulg time modulated according to a modulating s One of the features of the invention is the employment of a cathode ray tube or other electron 'beam producing apparatus and means to cause the beam to sweep through a given movement together with a series oi special electrodes which coact with the beam and a target arrangement to produce the multiplexing operations referred to above. The signals of the dierent channels are applied to these special electrodes so that deection of the beam is effected by the increment oi signal energy occurring at the electrode during the presence of the :beam in its sweep movem ment adjacent thereto. The target is arranged to present a plurality of electron responsive areas. one for each signal channel. 'Ihese areas are arranged in series relation so as to be traversed in succession by the beam during its sweep movement. The areas when traversed by the beam produce by secondary emission, ior example, pulse flow of electrical energy.

To effect time modulation of the pulse energy, the cross-section of the beam or each .beam responsive areas maybe made narrow and disposed at an acute angle to the direction of the signal beam deflection. This relationship causes the beam to traverse the responsive area sooner or later vin time depending upon the signal val-ue applied to the special electrode which controls deflection of the beam. Thus, the output pulse energy for each channel is time displaced relative to an average time position according to the instantaneous value of the modulating signal.

The shaping of `the target area or the crosssection of the beam if desired may include end portions disposed parallel to the direction of the signal beam deflection so as to provide maximum limits of pulse displacement. This prevents break-through from one channel to the next upon the occurrence of signals of unusually high value.

Another feature of the invention is the manner in which deflection of the beam is effected. According to one embodiment the -beam may be deected directly in response to the signal while according to another embodiment the signal energy controls acceleration of the electrons o! the beam during their movement in the eld of a given deiiecting potential. This increasing or decreasing of the electron acceleration controls the degree of deflection produced.

A further feature of the invention includes commutation of the beam. This is accomplished by providing a commutating plate having as many apertures as there are channels. or means for commutation keying of the grid, whereby the beam is divided into segments for modulating treatment by signals to be transmitted. This commutating feature provides individual beam segments per channel, thereby avoiding crosstalk that may otherwise occur if the deflection produced by signals of one channel were permitted to be carried over by the beam to the next defiecting zone of an adjacent channel.

The above and other objects and features of the invention will become more clear upon conslderation of the following detailed description to be read in connection with the accompanying drawings, in which:

Fig. 1 is a diagrammatical illustration of a multi-channel pulse time modulator according to the principles of this invention;

Fig. 2 is a graphical representation of the time modulating operation employed in Fig. l;

, Fig. 3 is a graphical illustration showing a period of multi-channel pulses and control waves employed in the modulator;

Fig. 4 is a diagrammatic showing of a second modulator embodiment according to this invention;

Fig. 5 is a graphical illustration representing the modulating operation of the modulator of Fig. 4; and

Fig. 6 is a diagrammatic showing of a third modulator embodiment of the invention.

Referring to Figs. l, 2 and 3, a multi-channel pulse time modulating system is shown for eleven signal channels, I to II and a synchronizing channel I2. One period or cycle of multi-channel pulses is shown in graph b of Fig. 3, the pulses of signal channels I to II being of a given pulse width and the synchronizing pulses I2 being of a greater pulse Width, whereby the latter can be separated from the signal channel pulses at the receiver by a suitable pulse width discriminator.

While we have shown our system for I2 channels in all, it will be understood that a great many more channels may be provided, the number per modulator tube being limited largely by the size of the tube, the character of sweep movement selected for the beam, the maximum time displacement per channel, the guard intervals between pulses of adjacent channels and the widths of the pulses.

Referring more particularly to Fig. 1, a modulator is shown in the form of a cathode ray tube I3. While this form of modulator is shown to illustrate the invention. it will be understood that other forms of electron beam producing arrangements may be employed; also it will be understood that the tube illustrations in Figs. 1, 4 and 6 are purposely exaggerated as to the relative proportions and spacing of elements to assist in explaining the principles of the invention, and therefore do not represent the ultimate proportions desired for commercial embodiments.

The tube I3 contains electron beam producing elements I4, I5 and I6, preferably of the character capable of producing a iine beam of electrons. The beam of electrons is caused to have a sweep movement by means of horizontal and vertical (1v-axis and y-axis) deecting plates I1, I8 and I9, 20. The sweep movement chosen for the purpose of illustrating the present invention is circular and the deiiecting waves for producing this sweep movement are obtained from an oscillator 2I and a phaser 22. The control waves obtained from phaser 22 are represented in graph a of Fig. 3 by sine waves 23 and 24, separated in phase by 90. Sweep movements other than circular may be used, for example, a sweep pattern such as used in television scanning may be employed.

A commutator plate 25 having a series o! apertures 26, 21, etc., arranged in a circular manner divides the beam during its sweep movement into segments. The apertures for the signal channels are preferably shaped in the form of sectors, the sides thereof being defined by the radii of the plate 25. This shape, however, is not essential except where a maximum number of channels is required. The aperture 28 for the synchronizing channel need not b e of this shape even where a maximum number of channels is desired, it may instead be of narrow rectangular form.

To effect signal deflection oi the beam segments, a circular electrode 29 is provided with a series of small electrodes 30, 3i, etc., disposed in series relation about the edge of the electrode 29. The electrodes 30, 3I are arranged so that the corresponding beam segments passed by apertures 26, 21, etc., occur between them and the central electrode 29. The signal is applied to the small electrodes, the electrode 30 being connected to the input circuit of channel I as indicated at 32. The input signal is preferably stepped up by transformer 32a before application to the electrede.

The target system with which the electrons of the beam cooperate to produce pulse energy flow comprises a modulator plate 33 and a secondary electron emission plate 34. The potential of the plate 33 is higher than the ring 34 so that when electrons impinge upon the ring 34, the ring emits electrons which flow to the plate33. The plate 33 is provided with narrow slots 35, 36, etc., one for each channel, for passage of the beam for impingement upon the area of ring 34. The central portion of the slots for the signal channels are preferably disposed at an acute angle with respect to the direction of signal deflection produced by the potential differences between the small plates, 30, 3l, etc.. and central electrode 29. The end portions of the slots, however, are disposed parallel to the direction of signal deflection. The slot 3l for the synchronizing channel is disposed parallel to the direction of signal deflection. This relationship of the slots of plate 33 and the beam sweep movement is shown at a larger scale in Fig. 2.

The dotted line 38 in Fig, 2 represents the sweep path of the beam 39 in the absence of signal modulation. It will be noted that this path traverses the center of the central portion 48 of the slot 35. The beam for this normal sweep movement causes secondary emission of electrons from plate 34, thereby producing a pulse flow of energy substantially as indicated at 4I.

Assume now that a signal occurs on electrode 30 of a positive value such as to cause a deflection of the beam 39 to the path indicated at 42. This will produce a pulse flow displaced from the pulse timing at 4I as indicated at 43. The vertically extended portion 44 of the slot 35 is provided as hereinbefore stated to limit the time displacement for exceptionally large signal values. The output pulse such as indicated at 43 will occur for any displacement of the beam along the length of portion 44. If the slot 35 were terminated at the end of the central portion 48 no output pulse would be obtained for a signal causing deflection beyond such end. For a negative swing of signal on electrode 30 the beam 39 will be shifted to a path below the path 38. Such a negative sacarse `maximum negative displacement for the pulse similarly as in the case of the vertical end portion 44. The slot 31 for the synchronizing channel is shown in Fig. 2 to be a vertical narrow slot, although it may take the form of a small square slot since for the synchronizing channel no deflectlng potential need be provided. The slot 31 preferably is elongated as shown to accomodate any oil-set bias that may bel normally imposed upon the system, such for example as by controlling the amplitude of the deflecting waves supplied to electrodes I1 to 20.

Referring back to Fig. 1, the potentials applied to the diierent elements of tube I3 are indicated. The elements I1, 20, 25, 29 and 33 are all provided with the same high voltage potential as indicated at 48. The control grid I5 is shown to be provided with a high negative voltage potential by connection 49 while the cathode element I4 is provided with a less negative potential by the interposltion of a resistor 50. The beam shaping or focussing element I6 is provided with a more positive potential than the cathode I4 by means of resistors 5| and 52. The anode target ring 34 is provided with a less positive potential than the modulating plate 33 by means of the interposed

resistors

52, 53 and 54. The output oi' the

circuit elements

33, 34 is applied to a cathode follower 55, the output energy of which may be applied to the usual carrier frequency modulator for transmission. It will be noted here that this output circuit is independent of the electron beam circuit. This is of advantage because the secondary emission function of the

elements

33 and 34 is in eiTect an amplification of the signal energy. For example, the targets may be madea part of the beam circuit whereby the beam current controls the output of the tube. In such cases, however, the beam current controls and in order to get desired amplication amplifiers are required.

From the foregoing description it can be readily seen that the combination of the apertures of the modulation plate 33 and the anode ring 34 provide the pulse generation, and the sequential distribution of the apertures provide the necessary delay or phase difference between the pulses of adjacent channeis. The deection system 29-30, 3|, in conjunction with the shape of the apertures of the modulator plate 33 provide the modulation translationof signal increments from amplitude variations into time displacements of pulses. Further, the shape of the apertures of plate 33 allows modulation limitation for each channel. The width of the apertures of plate 33 determines the width or duration of the channel and synchronizing pulses, the aperture for the synchronizing channel being wider distinguishes the synchronizing pulses from the signal channel pulses. Finally, the combinations of the modulator plate 33 and the anode ring 34 provides for the mixing of the channel and synchronizing v pulses into a single train of pulses for transmission. Such a train of pulses is shown in graph b of Fig. 3, the period of which corresponds to the period of the beam control Waves shown in graph a.

In Fig. 4, we show an alternative modulator tube construction for production of a similar multi-channel train of pulses. This tube includes the same circuit elements shown in tube I3 of Fig. l except that it is provided with a beam shaping plate 55 and the apertures of the commutating plate and the modulator plate differ in shape. The plate 55 is provided with an aperture of a configuration corresponding to the desired crosssection of the beam. That is to say, instead of 5 providing the modulator plate 33a with slots oi' the character shown at 35, Figs. 1 and 2', the beam shaping plate 56 is provided with a slot of that shape. While the slot 51 is shown to have vertical end portions or ears similar to slots 35. 36, 10 etc., in plate 33, Fig. 1, it is recognized that their function as deflection limiters is true to a maxi- ,mum degree only for the top and bottom channel l opening in plate 33a, Fig. 4, and to a lesser degree for the channel openings in between. If desired, these vertical end portions or ears may be omitted. 'I'he plate 33a is provided with small apertures of uniform shape, preferably round (although other shapes maybe used) for each signal channel. The beam shaped according to the shape of slot 51 is caused to have a sweep movement as described in connection with Fig. 1 and the apertures of plate a commutate the beam to provide segments, one for each channel. The

y Abeam segments thus formed are deflected as de- 25 scribed in connectionwith Fig. 1, and depending upon the point of interception between the apertures of plate 33a and the cross-section of the beam, controls the timing of the pulse output of the combination

modulator elements

33a, 34. This will be clear from a study of Fig. 5 wherein beam position 58 represents the path of beam sweep in the absence of signal modulation, and positions 59 and 60 represent beam deection positions in response to positive and negative signal deflection of the beam. It willbe understood, of course, that the degree of modulation per channel will diiler depending upon lthe relative angle between the plane of the beam and the direction of deflection. This angle varies because of the anplane of the beam being selected so that no chan- `nel deection occurs parallel thereto. Best operation, of course, will be had when the deflection for each channel is at right angles to the plane of the beam.

In order to obtain a synchronizing pulse of greater duration than the signal channel pulses. an aperture 31a of length greater than aperture 35a is provided. The output pulses for these two apertures are indicated at Ia and I2a. The ends of the beam cross-sections shown in Fig. 5 provide maximum modulation limits for signals greater than a predetermined value for those channels represented by apertures at the top and bottom of plate 33a, the limiting effect being less for those in between. Should deflection cause the ears of the beam to coincide with the channel aperture on the right or left hand side of plate 33a, the resulting pulse in the output circuit will be of greater duration than the other pulses, depending of course upon the angular relationship of the ears with respect to the direction of deflection.

As regards the electron density of the cross section of a beam, it is to be noted that a maximum build-up time of a pulse in the output circuit is determined by the density of the beam as measured inwardly from the outer extremityl rising abruptly from zero to maximum. In the case of the iiattened beam of Fig. 4, the width of gular relation of the apertures in plate 33a, the' the beam in cross-section should be as tine as possible and the density should likewise risc abruptly from zero to maximum. In the s-ystem of Fig. 4 the build-up, amplitude and decay time of the output pulses are also controlled by the shape of the apertures of plate 33a.

In Fig. 6, We show still another alternative form of modulator. The modulator tube I3b differs from the tube I3 of Fig. l in that the grid is keyed according to a commutating control wave which replaces thecommutator plate 25 used in the tube of Fig. l, and the signal deflecting arrangement is replaced by a signal acceleration-deection system. .The commutation control of the grid I5 keys the beam on and oi according to the channel `timing desired. This is accomplished by applying the base wave of oscillator 2i to a multiplier 5I to obtain the proper channel frequency. The output wave of multiplier SI is phased at 62 and applied to a shaper 63 which may be a multi-vibrator 'or other wave shaping means capable of transmitting a sine wave into a substantially rectangular wave form. The rectangular wave thus obtained is applied to the grid I5 which is normlly biased to cut 01T.

The signal acceleration-deflection of the beam is eiiected by first providing a circular electrode 64 spaced from an annular electrode 65 to which a potential difference is applied as indicated at 66. The potential dlierence between these ,two elements provides a Aconstant deflection force for the beam passing therebetween. Each signal channel is provided with a hollow cylindrical element, such as indicatedat 61 for channel I, through which a beam segment passes, one for each sweep cycle of the beam. It will be understood of course that the sweepmovement will be synchronized with the keying operation so that .a beam segment occurs in proper time relation for each of the hollow cylindrical electrodes of the several signal channels. As the beam segment flows through the hollow cylinder 61 the potential applied thereto will accelerate or decelerate the electrons according to the value of the signal applied. A given positive bias vmay be applied as indicated at 68 for each channel so that the positive and negative values of signals will cause the electrons of the beam to accelerate and'decelerate proportionately. This change in acceleration of the beam electrons coacts with the constant defiecting potential of

electrodes

64 and 65 to vary the amount of deflection of the beam relative to the apertures ofthe modulator plate 33. It will be clear that this variation is veffected in accordance with the signal and that the output pulse is time displaced in proportion to the signal value.

It will be understood that vwhile the acceleration .deflection feature ot. :the'invention is disclosed with a commutator plate having slot shaped apertures disposed at an acute angle to the direction of deflection, it may also 'be used in connection with the modulator arrangement of Fig. 4 where the beam is specially shaped. It will also be understood that the keying of the beamby means of the grid I5 may also be applied to the systems shown in Figs. 1 and '4 in place of the commutator plates therein shown.

It is realized that many additional variations and arrangements of the tube elements and associated circuits are possible without departing from the invention, and it is accordingly stressed that the diierent embodiments herein shown and 8 described are intended for illustration purposes only and not as a limitation on the scope of the invention as set forth in the objects and the appended claims.

We claim:

1. In a multichannel pulse modulator, means to produce a beam of electrons, means to causel the beam to have a given sweep movement, a plurality of signal channel input circuits, means associated with said input circuits to control de: iiection of the beam successively during its sweep movement according to increments of the input signals of said circuits, and beam responsive means to produce pulses of energy time modulated according to the corresponding signal deflections of said beam, said means for controlling deflection of the beam including means to provide a given beam deflection potential, and means to control according to said input signals the acceleration of the electrons of the beam in passing through the field of said deilecting potential.

2. In a multichannel pulse modulator, means to produce a beam of electrons, means to cause the beam to have a given sweep movement, 'a plurality of signal channel input circuits, means Aassociated With said input circuits to control deflection of the beam successively during its sweep movement according to increments of the input signals of said circuits, and beam responsive means to produce pulses of energy time modulated according to the corresponding signal deflections of said beam, said beam responsive means including an element having a secondary electron emitting area in the path of the sweep movement of the beam and an apertured plate disposed in front of said element, the apertures of which outline the portions of said area upon which said beam of electrons may impinge during said sweep movement.

3. In a multi-channel pulse modulator, means to produce a beam of electrons, means to cause the beam to have a given sweep movement, channel commutating means for producing beam segments with respect to said sweep movement, a pluraity of signal channel input circuits. means associated with .said input circuits to control defiection of the beam segments successively dur- -ing its sweep movement according to increments of the input signals of said circuits, and beam responsive means to produce pulses of energy time modulated according to the corresponding signal deections of said beam segments.

4. A modulator according to claim 3, wherein the channel cominutating means includes' a member having apertures disposed in the path of beam movement.

5. A modulator according to claim 3, wherein the channel commutating means .includes means for keying the beam on and olf.

6. A modulator according to claim 3. wherein the means for controlling deflection of the beam includes beam deecting electrodes, and means for connecting said circuits each to a separate beam deecting electrode.

`7. A modulator according to claim 3, wherein the means for controlling deflection of said beam segments includes means to control the acceleration of the beam, and means responsive to changes in acceleration of said beam to deiiect the beam with respect to said beam responsive means.

' 8. A modulator according to claim 3, wherein the beam responsive means includes an element having a secondary electron emitting area in the path of the sweep movement of the beam and an vapertured plate disposed yin front oi' said element, the apertures of which outline the portions of said area upon which said beam of electrons may impinge during said sweep movement.

9. A modulator according to claim 3, wherein the beam responsive means includes means for presenting narrow target areas for impingement by electrons of said beam to produce current ilow, said narrowtarget areas being disposed at an acute angle to the direction of signal deflection of said beam.

10. A modulator according to claim 3, wherein the beam responsive means includes means for presenting narrow target areas for impingement by electrons of said beam, the central portion oi' said areas being arranged at an acute angle to the direction of signal deilection of said beam, and the ends of said areas being arranged parallel to the direction of said deflection.

11. A modulator according to claim 3, wherein the beam producer includes means to render the beam narrow in cross-section and disposed at an acute angle to the direction of signal deflection.

12.` In a multi-channel pulse modulator, means to produce a beam of electrons, means to give the beam a given shape in cross-section, means to cause the beam to have a g-iven sweep movement, a plurality of signal channel input circuits, means associated with said input circuits to control deilection of the beam successively during its sweep movement according to increments of the input signals of said circuits, and beam responsive means presenting areas each arranged to coact with the beam during its impingement thereon to produce pulse ilow of current, the timing of the pulse occurrence being determined by the degree of beam deflection when the beam trav` erses said areas.

13. A modulator according to claim 12, wherein the beam shaping means includes means to renderthe beam narrow `in cross-section and disposed at an acute angle to the direction of signal deilection of the beam.

14. A modulator according to claim 12, wherein the beam shaping means includes means to render the-beam in cross-section long and nar- -row'with the center cross-section portion disposed at an acute angle to the direction of signal deiiection of the beam and the cross-section ends of the beam disposed substantially parallel to the direction of said signal deection.

15. A modulator according to claim 12, wherein the beam shaping means includes means to render the beam needle-like in character, and the beam responsive means includes means for presenting long. narrow target areas for impingement by electrons of said beam to produce pulse flow of energy, said narrow target areas being disposed at an acute angle to the direction of signal deection at said beam.

16. .A modulator according to claim 12, wherein the beam responsive means includes means for presenting long narrow target areas for impingement by electrons of said beam, the central portion of said areas being arranged at an acute angle to the direction of signal deflection of said beam and the ends-of said areas being arranged substantially parallel to the direction of said deiiection.

17. A modulator according to claim 12, wherein the beam responsive means includes means providing a beam responsive area shaped different from the beam responsive areas of the signal channels to provide a series of pulses difl0 tering in character from Ithe signal pulses for synchronizing purposes.

18. In a pulse time modulator, means to produce a beam o! electrons, means to cause said beam to have a. given sweep movement, means responsive to said beam to produce a pulse flow oi.' energy when impinged upon by the electrons of said beam, means to effect deflection of said beam according to a signal, said beam responsive means having an area arranged to coact/with the beam during impingement thereonto time modulate said pulse of energy according to the signal deflection imposed upon said beam, said beam responsive means having means to limit the time modulation of pulses between predetermined signal values.

19. In a pulse time modulator, means to produce a beam oi.' electrons, means to causel said beam to have a given sweep movement, means responsive to said beam to produce a pulse flow of energy when impinged upon by the electrons of said beam, means to establish a given deflecting potential across the sweep path of said beam, an electron accelerating control means for eiecting change in acceleration of the electrons in said given detlecting potential, and means for applying signal energy to said control means.

20. In a pulse time modulator, means to produce a beam of electrons, means to cause said beam to have a given sweep movement, means responsive to said beam to produce a pulse flow of energy when impinged upon by the electrons of said beam, means to eiect deection of said beam according to a signal, said beam responsive means having an area arranged to coact with the beam during impingement thereon to time modulate said pulse of energy according to signal deection of said beam, and means to render said beam narrow in cross section with at least the central portion thereof disposed at an acute angle with respect to the direction of signal deection of the beam.

21. A modulator according to claim 20, wherein the beam narrowing means comprises a beam shaping element having a narrow aperture with the central portion disposed at an acute angle with respect to the direction of beam signal deiiection and the end portions thereof disposed substantially parallel to the direction of beam signal deection, and said responsive means includes means presenting a substantially circular shaped area across which said beam is caused to sweep, the timing of coincidence of the beam and said area. being controlled by the deflection of the beam according to said signal.

22. A multi-channel pulse modulator comprising means to produce a beam of electrons, :c-axis and y-axis deecting means, a source of control wave energy, means for applying said control wave energy to said derlecting means to causev the beam to have a circular sweep movement, a plurality of signal channel input circuits, means associated with said input circuits to control deflection of the beam successively during its sweep movement according to increments of the input signals of said circuits, and beam responsive means presenting narrow target areas for im-= pingement by electrons of said beam, one for each signal channel, said target areas being disposed at an acute angle to the direction of signal deection of said beam for the corresponding signal channel to produce pulses of energy modulated according to the corresponding signal deflections of said beam.

23. A modulator according to claim 22, where- Memisa includes a pair of circular` electrodes spaced apart in concentric relation to provide an annular passage for the beam during its circularsweep movement, means to maintain a given potential difierence between said electrodes, an electron acceleration contrl means for each signal channel arranged inv sequence in iront of said annular passage, and means for connecting said input circuits each to one of said acceleration control means, whereby the acceleration of the electrons o! the beam is' controlled according to said input signals, the changes in acceleration of said electrons resulting in proportional variations of beam deflection during passage thereof between said pair of electrodes.

25. A modulatoraccording to claim 22, wherein the ends oi said areas are substantially parallel to the direction of such signal deflection.

26. A modulator according to claim 22, in combination with an aperture plate disposed in front 'of the signal ldeilecting means, said plate having an aperture for each signal channel, whereby the beam is divided into beam segments prior to signal deflection thereof.

-27. A modulator according to claim 22, in combination with means for keying the beam on and on' at a rate proportional to the number of communicating channels included in each cycle of the-beam sweep movement.

'28. A modulator according to claim 22, in combination with means for keying the beam on and oil. said keying means comprising a control grid for said beam, means for multiplying the frequency of control wave energy according to the number of channels of communication, and means to shape the resultant wave to provide a keying wave for said grid.

29. A multi-channel pulse modulator comprisin'g means to produce a, beam of electrons, z-axls and y-aids deliectlng means, a. source ot control wave energy, means for applying said control wave energy to said deectln'g means to cause the beam to have a given sweep movement, a plu rality of signal channel input circuits. means associated with said input circuits to control deection of the beam successively during its sweep movement according to increments oi' the input signals of said circuits, and beam responsive means to produce pulses of energy modulated according to the corresponding signal deections of said beam, the beam producing means including means to render the beam long and narrow in cross section and disposed at an acute angle to one of the axes of said :caxis and y-axis deflecting means.

30. A multi-channel pulse modulator comprising means to produce a beam of electrons, :lr-axis and y-axis deflecting means, a source of control wave energy'. means for applying said control wave energy to said deflecting means to cause the beam to have a given sweep movement, a plurality of signal channel input circuits, means associated with said input circuits to control deiiection of the beam successively during its sweep movement according to increments of the input signals of said circuits, and beam responsive means to produce pulses of energy modulated according to the corresponding signal deections of said beam, the beam producing means including an element having an aperture'therethrough for shaping the beam, the central portion of the aperture as viewed in cross section with respect to said beam being narrow and disposed at an acute angle to one of the axes of said z-axis and 'y-axls deflecting means, with the ends of said aperture disposed substantially parallel to said one of the axes.'

EMILE LABIN. DONALD D. GRIEG.

REFERENCES CITED The following references are-of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 2,057,773 Finch Oct. 20, 1936 2,361,766 Hadekel Oct. 31, 1944