US2283383A - Signaling system - Google Patents

Description

y 19, 1942- J. T. MCNANEY 2,283,383

SIGNALING SYSTEM Filed Nov. 6, 1940 3 Sheets-Sheet 2 k m p s s & Q

Petent e y 9, I r 2,283,383

UNITED STATES PATENT OFFICE 2,283,383 srcmnmc SYSTEM Joseph T. McNaney, Baltimore, Md.

Application November 6, 1940, Serial No. 364,489

14 Claims. (01. 250-141) This application is a continuation in part of type utilized in the transmitting portion of my my copending application, Serial No. 341,196. system,

My invention relates to signaling systems and Figure 3 is a view partly in section exemplifyit has a particular relation to high speed systems ing the manner in which the perforated tape is of the type wherein a perforated tape or the like utilized for the purpose of providing a plurality is utilized at the transmitter and means at the of groups of electrical impulses, each group of receiver are utilized for making a permanent mpulses being epresentative of a messa e-charrecord of a received message. acter.

Heretofore, in systems of the general type to Figure 4 is Oircuit d a a e e plifyi the which my invention pertains, the limitation upon utilization of photo-electric currents for the purthe speed of transmission and reception has been D Of co ro l t e odu ation of a translargely mechanical. That is to say, referring for e example to teletype systems, the inertia of the Figure 5 is a circuit diagram of a receiver uti moving parts at the receiver prevents ultra high lized in my y speed and in printing telegraphs the samelimita- Figure 6 is a eonventienalized View, P y in tion appear section, of my novel cathode ray translating tube It is, accordingly, an object of my invention to and exemplifying the manner in which the tube provide a signaling system wherein the speed of is employed for t e p pose o p ap cally transmission and reception is substantially unrecording an n ng messag limited, within reason, and a permanent record Figure 7 is a View in Vertical Section of a of t message is f n-ned element of the cathode ray tube shown in Figure Another object of my invention is to provide a system of the type described that shall be Figure 8 is a view in vertical elevation of the substantially unaffected by static. electron gun assembly exemplified by Figure Another gbje t f my invention is to provide, looking into the tube from the recording end in a signaling system of the type referred to, rethereof,

ceiving apparatu th t 1 ,11 enable the making 7 Figure 9 is an enlarged elevational view of a of a photographic record of an incoming message. portion of the apparatus Shown in Figure 7.

Another object of my invention is to provide Figure 10 is a n i udinal vertical cross secnovel receiving t wherein incoming elec, tional view of a receiving tube comprising an trical impulses representing message-characters altemative embodiment of y invention. may be translated into light and the light there Figure 11 is a vertical cross-sectional view of from is of such nature that it may be utilized the tube shown in Figure 10 taken along he for the purpose of making a photographic record. line A still further and more specific object of my Figure 12 Is an elevational view f a po tion invention is to provide a novel receiving tube of the cathode Shown in Figures 10 d of the cathode ray type that shall be capable of In accordance with my invention. I provide translating incoming electrical impulses repre means for transmitting two modulated carrier senting characters of a message into visible rewaves by wlre radio, the Said Waves being utiplicas of the said characters, which replicas may 40 the receiving end of the System or debe utilized for photographic recording termimng the momentary angles of deflection of The novel features of my invention are set forth locally generated cathod? the coordinates with particularity in the appended claims; the of the position of the ray in turn determining a invention itself, however, both as to its orgam particular character of a transmitted message,

zation and its method of operation, together with if g ff jf g e g; zgi gg ggg i g additional objects and advantages thereof, will system I i two radio g best be understood from the following descrip- 3, two carrier frequency generators 5 d 1 two tion of a specific embodiment when read in con- 0 signal frequency generators, 9 and H, and two nectron with the accompanying drawings, wherem t l3 and Is, h percentage of moduin: lation in each modulator being determined,

Fi ure 1 1s a diagrammatic vlew, hlghly e nsimultaneously, by the output from two photo vent o e z d, of a signa ng sys em e body electric cells I I and I9. At the receiving end, it my invention, being understood that the two transmitters send Figure 2 is a view of a perforated tape of the on different carrier frequencies, I provide two receivers 2| and 23 permanently tuned to the carrier frequencies and two converters 25 and 21 for changing the incoming signals to D. C. po-

tentials, which potentials are simultaneously impressed across pairs of deflecting plates 23 and 3| in a cathode ray receiving tube.

For the purpose of providing message modulated light for the two transmitting photo-electric 'xpair of light sources and 31, the light falling on the phototubes being limited by two slots 39 and 4| in a mask 43 interposed between the said tubes and the light sources.

Referring still to Figure 2, it will be noted that the tape carries a plurality of paired groups of perforations disposed at each side of the center thereof, the groups extending transversely of the tape in alignment with the respective slots in the mask, whereby, when the tape is .caused to advance between the light sources and the phototubes the amount of light reaching each tube is determined by the number of perforations momentarily interposed between it and its individual light source. It will also be noticed that the several transverse slots in the mask are narrower than any perforation through the tape, considered in the direction of the travel thereof, whereby each group of the said perforations dwells for a short space of time before the slot corresponding to it. The slots in the actual apparatus are much narrower than shown in the drawings.

In Figure 2, I have made no attempt to exem plify an actual message but have shown instead the manner in which the transverse paired groups of perforations may be so designed as to the relative number of perforations per group that 49 separate and distinct characters may be transmitted. It may be pre-punched by any suitable device.

The manner in which each one of the two photoelectric cells is utilized in the transmitter to modulate a carrier wave is exemplified by the transmitter diagram of Figure 4. The space current path in a photo tube is connected in series with a source 45 of potential and a biasing resistor 41, which resistor is included in the input circuit of a thermionic tube 49 in series with .an additional adjustable resistor across which a modulating frequency at constant amplitude is impressed. The modulating frequency, for example, may be within the audible range, such as one thousand cycles or the like, and it is preferably the same for both photo tubes. The anode circuit of the thermionic tube includes the primary coil 53 of a transformer, a. source 55 of potential and a self-bias resistor 51 shunted by a by-pass condenser 59.

The secondary coil 6| of the transformer is included in the anode circuit of a modulator tube 63, in series with an impedance device such as a tuned circuit 65. The carrier frequency is impressed upon the input circuit of the modulator tube 63 from an oscillator (not shown) and appears across the impedance device, modulated by the signal frequency which is introduced into the anode circuit thereof from the secondary winding of the transformer.

The percentage of modulation of the carrier frequency depends upon the amplitude of the signal frequency supplied to the anode circuit from the photo-cell-controlled tube 49; the said signal frequency amplitude, in turn, is a function of the negative bias applied to the grid of the tube 43 and the strength of the input thereto from the signal frequency generator.

It will be noted from inspection of Figure 4, that the direction of current flow through the photo tube and the resistor 41 is such that increased current produces a more negative potential upon the grid of the thermionic tube 43 connected thereto lessening amplification therein. In the operation of the apparatus, when no light through the perforated tape reaches the photo electric cell, the resistor 5i across which the signal frequency is impressed is so adjusted that the normal self-bias applied to the grid from the cathode resistor 51 is just suflicient to permit 100% modulation of the carrier frequency in the modulator tube. Obviously, when light falls upon the cathode of the photoelectric cell, the bias applied to the tube becomes more negative, thus lessening the percentage of modulation. The amount of modulation of the carrier of each transmitter from maximum, or 100%, toward zero is controlled in seven discreet steps depending upon the number of perforations in the group of perforations that momentarily permits light to reach the corresponding photocell.

Referring once more to Figure 2 of the drawings, it will be noted that the paired groups of perforations allocated, respectively, to each of the forty-nine characters are so chosen that the light simultaneously reaching the two photo tubes differs, the amount of difference depending upon the particular character momentarily being transmitted. For example, the paired groups of perforations representing the character A are equal. Thus, when A is being transmitted, each photo-cell receives the same amount of light, this amount being the greatest of the seven different amounts controlled by the perforations, and the percentage of modulation of each carrier will be changed from to the lowest of the seven predetermined amounts. Again, if the character G is being transmitted, it will be noted that one unit of light reaches one of the photo-tubes while seven units of light reach the other tube. In that event, one carrier is modulated at the highest percentage of the seven predetermined amounts below 100% while the other carrier is modulated at the lowest of the seven predetermined percentages.

Each character is represented by analogous dissimilar paired groups of perforations. This feature of my invention is very important because, as will be clear to those familiar with mathematics, each character may be denoted by XY coordinates. As an example, referring also to Figure 8, A could be represented by 7X, 'IY; G by X, 'IY; T by -2X, 5Y, and so on with the remaining characters, each character thus being capable of being represented by a definite locus in a plane. The manner in which I take further advantage of the geometric relation between the perforation-groups and of the consequent geometric relation of the percentages of modulation of the two carrier waves, in the reaaeasa's that the carrier waves may be transmitted either by radio or over line wires or the equivalent.

As shown in Figure of the drawings, the receiver and converters are conventional in design comprising a detector 81 and amplifier and a thermionic tube Ii having an auxiliary diode circuit on which the detected and amplified signal is impressed. The last mentioned tube functions in a manner well known to those skilled in nite X-Y coordinates as explained in connection the art and provides, across a resistor II in- 10 cluded in the output circuit thereof, a D. C. potential proportional to the amplitude of modulation of the incoming carrier wave. Inasmuch as each receiver is provided with A. V. C., the

100% modulated portions of the several carriers,

corresponding to darkness at the transmittin photo cells, may be kept at a definite level which will serve as the upper limit of a guage or a voltage. The varying momentary "drops" from this constant level will be voltages that represent the coordinates of a message character as hereinbefore explained.

For the purpose of making use of the voltages representing character coordinates, I prefer to utilize a composite cathode ray tube of novel de- 5 sign exemplified by Figure 6 of the drawings. Such a tube has at one end thereof a thermionic cathode 15, a grid 11, an electron gun I! and two pairs of deflecting plates 29 and ii. At the extreme opposite end of the tube the interior sur- 30 face carries a layer 8l of fluorescent material such as Willemite or the like. At the position intermediate the two ends of the tube is disposed a transparent screen 83 coated, on the side facing the deflecting plates, with a layer 85 of fluorescent material.

Preferably, the composite tube takes substantially the form of a double cone with the fluorescent screen interposed at the junction of the bases thereof and the electron guns lll mounted tery illl, is positioned, to the other end thereof which is connected to a high positive terminal of the battery and through which the electrons are ejected in the form of a stream having the same cross-section as the outline of the emitter H8.

with the description of my transmitting tape. The potential may be derived from any suitable source such as a battery iii, the most positive point in the source being connected to a focusing anode I83 mounted within the tube. The portion of the tube, extending toward the deflecting plates, is also supplied with an interior focusing anode I" which is maintained at a high positive potential with respect to the thermionic cathode 'l'l.

In the operation of the receiving tube. potentials determined by the light received by the several transmitting photo-cells, as the tape moves before them, are impressed from the two-receiver converters, respectively, across the several pairs of deflecting plates. When these two potentials are equal and maximum, corresponding to the no-signal condition, the cathode ray assumes a position designated 0 in Fig. 8. If now the letter A is transmitted and received, the modulation of each carrier is reduced seven units, and the ray is deflected to a position on the main fluorescent screen 85 in front of the auxiliary gun having an emitter H5 conforming in contour to that letter. Such position might be represented by the notation 'IX, '15! Analogous dissimilar pairs of potentials, each less than the maximum corresponding to 100% modulation at the transmitter, cause proportional deflections of the cathode ray which ray dwells on the proper spot on the screen for the space of time required for a row of perforations to travelbetween the photo-cells and the light sources in the transmitter.

Light emitted by the main fluorescent screen 85, at any given position of the deflected ray, falls uponthe electron emitter H5 allocated to that position and causes the emission of photoelectrons therefrom that are accelerated through the corresponding gun ill to ultimately impinge upon the small fluorescent screen 8i at the recording end of the tube. As the stream of electrons emerges from the gun, it has a cross section corresponding to the contour of the character-electron emitter H5 positioned at the mouth of each gun I". For example, if the gunemitter H5 is provided with an A-shaped outline, as shown in Figure 9, only those electrons corresponding to the A will pass therethrough and will be shot against the fluorescent screen 8| at the extreme end of the tube and thereat will be reconverted into a visible image of the said char- The electron emitters H5 consist of photo-emis sive material positioned on a metallic surface of sputtered gold and the like on the substantially transparent partition 83. Thus these emitters H5 are electrically interconnected bythis thin; metal coating.

The ring-shaped electrodes of the guns I" are connected to successively more positive points on the current supply source llil and it will therefore be observed that the electron streams from these guns may be focussed so that each of said streams has the cross-section corresponding to the character H5 associated therewith. It will also be noted from an inspection of Figure 6 that the guns ii! are trained upon the center of the fluorescent screen 8|.

Viewing these guns from screen 8!, their arnations and electron emissive areas, having defl actor for the purpose of recording the said character.

A lens system II" is provided which focuses light from the fluorescent screen onto a moving strip I89 of photo-sensitive material. A diaphragm Iii having an opening H3 therethrough may be interposed between the lens system and the moving light sensitive material. Obviously, the entire apparatus may be enclosed in a lighttight housing .to prevent the light-sensitive material from receiving any light other than that transmitted to it from the fluorescent screen by way of the lens system. The specific arrangement of the housing and the other details of the film advancing mechanism form no part of my present invention and, for that reason, they have not been illustrated.

The film or other light-sensitive material is given continuous motion past the opening in the mask, the rate of travel being commensurate with the rate of travel of the perforated tape of the transmitter. By this, I mean that the linear speed of the record-receiving material should be mitting photo cells, the photo-sensitivity of the record receiving material and the maximum speed at which the said material may be caused to pass through the apparatus. My research into these problems has lead me to the conclusion that the ultimate speed obtainable by my improved system is much greater than with any other system heretofore utilized, although at this time I am unable to state with certainty the maximum number of words per minute the system is capable of handling.

Instead of generating a single cathode ray in the receiving tube and causing it to be angularly deflected in accordance with the coordinates of a message character, it lies within the scope and spirit of my invention to generate a plurality of parallel rays of electrons, or, so to speak a bundle of rays and to cause the entire "bundle to be deflected in accordance with the resultant of the two potentials supplied simultaneously by receivers M and 23.

The alternative embodiment of my invention is exemplified by Figures and 11 and comprises a planar cathode I25 mounted at one end of an evacuated cylindrical container I21. The cathode is made from a conductive non-emissive material and it is disposed perpendicular to the long axis of the container.

Disposed within the other end of the container is an anode I29 having a central opening through which cathode rays may pass to impinge upon a small fluorescent screen I3I formed upon the inner surface of the end of the container.

Alternatively, the anode may be constituted by a conductive coating deposited upon the entire inner surface of the end of the container and the fluorescent screen I 3I may be limited to a small central portion of the coating.

Referring to Figure 11, the surface of the cathode facing. the anode is provided with 49 electron-emissive characters I33, preferably corresponding in position to the disposition of the minor electron guns in the receiving tubes first described. These characters may be composed of electron emissive material well known to those skilled in the art, Among such materials may be mentioned barium, thorium, strontium and cerium oxides.

Obviously, when the entire cathode structure is heatedv to a temperature sufilcient to cause the emission of electrons from the several characters formed thereon and if the anode is maintained at a positive potential with respect to the cathode a bundle of electron streams will travel toward the anode, each stream having a crosssection corresponding to one of the characters.

If desirable the surface of the cathode not covered by the emissive characters may be coated with non-emissive material I35 such as carbonblack.

For the purpose of causing the electron streams from the message characters to maintainparallism during their travel from the cathode toward the anode I29, I dispose a solenoid I39 around the container; the solenoid is supplied with direct current from a source I and maintains a longitudinal magnetic field in the space between the cathode and the anode.

In order that the entire bundle of cathode rays may be caused to move across the opening in the anode I29, I provide two pairs of deflecting coils I43, I45 and I41, I49. The first mentioned pair is supplied with unidirectional current from the receiver 23 and the second pair from the receiver 2|.

Inasmuch as the several pairs of deflecting coils are disposed at opposite sides of the container, as clearly shown in Figure 11, these coils have the same function as the deflecting plates in the tube first described, and take the place of the resistors 13 shown in Figure 5.

The plate supply for the receivers 2| and 23 is exemplified by the battery I5I.

For the purpose of adjusting the tube to the no signal" condition I provide direct current sources I53 and I55 in series with resistors I91 and I59 respectively for causing direct current to flow through the receiving coils in opposition to the normal plate current drawn by the converters 25 and 21.

When the receivers 2| and 23 are active the control grids in the converters 25 and 21 are swung negatively to potentials determined by the transmitting tape thus causing a proportional change in the currents in the deflecting coils I43, I45 and I41, I49. The change in the current in the mentioned coils causes the-bundle of rays to be deflected both vertically and horizontally, thus momentarily exposing the fluorescent screen "I to electrons emitted from a given one of the 49 characters on the cathode.

It is, of course, substantially immaterial how the cathode I25 is heated, such heating means-being designated in Figure 10 by the heater IBI and the battery I63. cathode I25 functions as does the well known oxide-coated cathode utilized in radio tubes, and is maintained at a negative potential with respect to the anode I29 by means of any suitable unldirectional sources such as battery I62.

From the foregoing description of my invention it will be seen that it offers practically unlimited possibilities insofar asrapidity of transmission and reception are concerned. Transients, such as static, will affect both receivers to substantially the same degree and, consequently they will give rise to equal decrements of potential acrossthe pairs of deflecting plates. Even if strong, static will only urge the cathode ray diagonally of the screen toward the zero position thereon corresponding to modulation. If, as a result of static, therefore, a character is omitted from the recorded message it may easily be interpolated by reference to a chart such as shown in Figure 8. The appearance of any recorded character itself cannot be marred by interference, because the ray must dwell for an appreciable length of time on a given portion of the screen to give rise to a photographic representation of the character.

No synchronization of the transmitter and the receiver is necessary as in other well known systems because the transmitter tape does not have to run at the same speed as the film.

The receiver being free of moving parts and electrical contacts is less likely to give trouble, at the same time being more reliable.

The high speeds possible will permit greater use of expensive land lines and submarine cables.

A signaling system of this type has possibilities for secret signaling.

Essentially, therefore, the

Although I have shown and described a few specific embodiments of my invention, many other modifications thereof will be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be limited except by the prior art and by the spirit of the appended claims.

I claim as my invention:

1. A cathode ray tube comprising an elongated container, ray generating and ray deflecting means at one end of said container, a fluorescent screen at the other end of the container, means interposed between the ray generating means and the screen for deriving a plurality of minor electron streams from the cathode ray, each stream having a cross-section corresponding to a message-character, and means for causing all of said minor streams to be focused upon substantially the same portion of the fluorescent screen.

2. A cathode ray tube comprising an elongated container, ray generating and ray deflecting means disposed in one end of thecontainer, a fluorescent screen disposed in the opposite end of the container, a plurality of relatively small electron guns mounted within the container intermediate the ray deflecting means and the screen, the axes of the guns being directed toward a common point on the screen and the open ings thereof that lie toward the ray generating means being substantially in a surface normal to the long axis of the container, means for focusing the cathode ray and directing it toward said surface, means whereby each relatively small electron gun under the influence of the cathode ray may be caused to emit a stream of electrons having a cross section corresponding to a message character, and means for causing each of said streams to be focussed upon substantially the same portion of the fluorescent screen.

3. The invention set forth in claim 2, wherein the means for causing a small gun to emit electrons comprises fluorescent material for translating the cathode ray into light and photo-sensitive material for re-translating the light into electrons.

4. A cathode ray tube comprising an elongated container, ray generating and ray deflecting means disposed in one end of said container, a small fluorescent screen disposed in the other end of the container, a relatively large fluorescent screen disposed within the tube intermediate the small screen and the ray deflecting means and lying in the path of travel of the ray when deflected, means for translating light emitted by the large screen, under impact of the ray, into electrons, means for causing said electrons to fall onto the small screen to cause luminescence thereof, and means for causing the cross section of the stream of electrons reaching the small screen to vary in accordance with the coordinates of the loci of the cathode ray upon the intermediate screen.

5. A cathode ray tube comprising an elongated container, a transparent screen disposed within said container and substantially intermediate the ends thereof, a plurality of spaced-apart areas of photo-emissive material disposed up n one surface of said screen, a layer of fluorescent material disposed upon the opposite surface thereof. cathode ray generating and ray deflecting means disposed in the end of the container opposite the fluorescent layer. a small fluorescent screen disposed in the end of the container opposite the areas of photo-emissive material, each of the said areas simulating a message-character, and means for directing electrons emitted from said areas, under the influence of light from said fluorescent screen, toward a common point on the small fluorescent screen in the end of the container.

' 6. A cathode-ray tube comprising a container, means within said container for providing a plurality of independent electron streams, means for forming the cross section of said electron streams in the shape of predetermined characters, and means for selectively converting different ones of said streams into light.

7. A cathode-ray tube comprising a container, a cathode within said container, for providing a plurality of independent electron streams, means for forming the cross section of said electron streams in the shape of predetermined characters, a fluorescent screen and means for selectively causing different ones of said electron streams to impinge upon said screen.

8. A cathode-ray tube comprising an elongated container, a planar conductive element, mounted in one end of said container transversely of the long axis thereof, one surface of said element having a plurality of discrete electron emissive areas, the said areas having the configuration of message-characters, means for raising said areas to the emissive temperature, and an anode disposed within said tube parallel to said element and spaced apart therefrom and means for selectively converting different ones of the electron streams from different ones of said emissive areas into light.

9. In combination, an evacuated container, means within said container for providing a plurality of independent electron streams the cross sections of which are representative, respectively, of message-characters, a fluorescent element within said container, and selection means whereby anyone of said independent electron streams may be caused to impinge upon said fluorescent element.

10. The invention as set forth in claim 9 additionaiiy comprising focusing means for causing said electron streams to maintain substantial parallelism, each to the others, during their travel from the loci of emission toward the fluorescent element.

11. Apparatus as set forth in claim 9 wherein said first means is constituted by a planar conductive element one surface of which is provided with a plurality of discrete electron emissive areas, the said areas having the configuration respectively of message characters.

12. Apparatus as set forth in claim 9 further:

message characters.

JOSEPH T. McNANEY.

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