May 8, 1934. H, SHORE 1,958,212 MODULATOR OSCILLATOR Fillied Jan. 30, 1932

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NVENTOR "77%.HENRY SHORE . . ATTORNEY Patented May 8, 1934 1,958,212

UNITED STATES PATENT OFFICE

1,958,212 MODULATED OSCILLATOR, Henry Shore, Elizabeth, N. J., assignor to Radio Corporation of America, a corporation of Dela ware Application January 30, 1932, Serial No. 589,857 2 Claims. (C. 178-5) The present invention relates to a System for frequency may be maintained constant while directly modulating constant frequency gener varied directly as to its annplitude and thus make ated oscillations So as to produce changes in the it possible to shift the amplitude of the gen amplitude of these OScillations in accordance With erated OScillations in proportion to the intensity 5 a predetermined type of message transmission. of the record Subject for transmission. Inher 60 Fundamentally the invention is designated for ently, the dynatron is an extremely stable device use with radio communication Systems, although and when the frequency of oscillation is once it is to be understood that it is likewise appli established there is substantially no tendency cable to or network transmission by making, toward variation, due to changing load circuits 0 where necessary or desirable, a Suitable adjust or similar disturbing influences. 65 ment of the frequency of the generated OScil Therefore, as an object of the present inven lations. tion, I have SOught to provide Ways and means In connection with facsimile transmission Sys by Which the dynatron, as an oscillator, may tems and also With television transmission SyS be used at the same time as a modulating ele ... 5 tems it is quite desirable to have the exploring ment for facsimile or picture record signals for medium of the System, by which is meant, the transfinission. 70 photo cell, oscillator and amplifier-modulator A further object of the invention is to simplify combination, together with the necessary optical to a considerable extent the existing means for System of the greatest simplicity possible. In transmitting picture record signals. 20 facsimile apparatus the Scanning head, Which Another object of the invention is to provide 75 includes the illumination System for illuminating a modulated Oscillator wherein the input signal the picture record of which the image is to be may be of relatively Small strength and still transmitted, together with the Optical System by produce a relatively great change in output which the variations in light and Shadow of the amplitude. 2 5 record subject are transferred to a photoelectric Still a further object of the invention is to element, usually includes also an amplifier from provide a modulating system which is simple in 80 the output of which signals are fed to a modul its construction and arrangement; a system lating device to which energy of a frequency which is inherently stable; a system which will corresponding to a source of oscillations is also follow faithfully all changes in intensity of input 30 connected. With most facsimile apparatus this energy to produce a correspondingly modulated entire assembly is mounted Within a container output; and a system of modulation which can 85 and is positioned adjacent the record carrying be arranged through the use of a correct com drum and as the record is explored either the bination of elements and circuit characteristics record is moved relative to the Scanning head, at present obtainable. 5 or the scanning head is moved relative to the Other objects and advantages of the inven 90 record. tion Will, of course, become apparent and at To provide a system which is considerably once suggest themselves to those skilled in the simplified it has been an object of this inven art to which the invention is directed, by reading tion to utilize the dynatron type of oscillator the following Specification and claims in connec 40 and to modulate this oscillator directly from the tion with the accompanying drawing, wherein output energy of a photo tube which has been Figure i illustrates conventionally one form of 95 subjected to light of varying intensities, which circuit arrangement which the invention may variations take place in accordance With the aSSume, and Figure 2 indicates a Series of curves change between light and dark on Successive ele plotting plate current against plate voltage for 45 mental areas of a record subject of which the different grid voltages to illustrate the extent image is to be transmitted. of response of the System to varying potentials 00 It has been found from experiments that a Supplied to the . dynatron is extremely sensitive to Small changes Referring now to the drawing, the picture in grid potential and that these changes in grid record for transmission, assuming the invention 50 potential tend to produce a considerable change is to be applied to facsimile message transmis in the output current from the tube when the Sion, is carried upon a record holder 1 which 105 dynatron is operating at a point Substantially rotates in a direction shown by the arrow. The near the cut-off point. It is these character picture carried upon the record holder 1 is ill istics of the dynatron which have been used here luminated from a light Source 3 whose light is in to provide a system wherein the oscillator directed by means of an optical System, conven 2 1,958,212 tionally shown as a lens 5, to a point 7 from In Order to illustrate the characteristics of the which the diffusely reflected light is focussed by dynatron, Figure 2 shows various operating curves wherein the ordinate represents the plate means of a Second optical System, conventional Current and the abscissa lepiesents the Supplied ly shown as the lenS 9, upon the light sensitive 80 3 of a photo tube 13. In Order to init plate Voltage, and aSSulning that modulation the amount of light reaching the photo tube, a takes place within the tube by virtue of varying diaphragm or the equivalent i5, which may be potentials supplied to the grid 23 Various curves adjustable in two directions, that is, vertically to show the change in current occurring between and horizontally, although illustrated only in black and white on the picture record carried On the record carrier 1 have been illustrated. 85 O the horizontal plane, has been provided between the record holder and the optical system 9. In this connection the curve ESG=K1 may rep As light falls upon the light Sensitive Cathode resent one extreme intensity on the picture lec 11 of the photo tube 13 electrons are emitted Ord and the curve ESG=K3 may represent the Op from the light sensitive element and flow toward posite extreine, with the curve ESG=K2 represent the or positive 17 of the photo ing the intermediate value Such as medium gray. 90 tube. The photo tube anode 17 is Supplied With The dotted portion of the Curve immediately be Operating Voltages from a source 19 and conse low the Zero Value of plate current is intended quently with changes in the electron stream to illustrate the operating region of the tube and the fluctuation in current appearing in the Output flowing within the tube, due to varying light in 95 20 tensities falling thereon, variable drops in volt is a function of the amplitude changes on the age will be produced across a 21 Con grid electrode for varying changes in light in nected across the photo tube . The tensity On the picture record or subject as af resistor 21 is also connected with the grid and fecting the photo tube 13 So that the current may vary Within the limits of the dotted line por filament electrodes 23 and 25 respectively of the 100 25 multi-electrode tube 27 through a grid biasing tion of the characteristic curves. source 29. The tube filament or cathode 25 is It is, of course, to be understood that the preferably grounded at 31. The remaining Cold Curves illustrated are not intended to be exact electrodes commonly known as the screen 33 and curves of the operation but are merely drawn anode or plate 35 are connected with a Source from a family of curves obtainable in the region of potential conventionally shown as 37. Where dynatron action may take place with vary 05 30 In order to provide dynatron action within ing operating voltages supplied to the grid elec the tube 27, that is, to provide a tube wherein trode 23, and, therefore, these curves and the secondary electron emission takes place, the curve illustrating the variation in current flow screen electrode is connected to the most posi Within the tuige must be regarded as merely illus tive point of the potential Source 37 and the trative and not limiting. 110 35 plate or anode electrode is connected through a While the invention has been shown in only a Single One of its preferred forms, it is, of course, tuned circuit 39 comprising the usual inductance to be recognized that the disclosure is capable of 41 and capacity 43, each of which may be Wari many changes and modification without depart able where desired, to a point on the potential 115 40 source 37 which is less positive than the point ing materially from its spirit and scope and I of connection of the screen electrode. therefore believe myself to be entitled to make By tuning the oscillatory or resonant circuit and use any and all of these modifications such 39 by adjusting the value of the capacity and in as those which would suggest themselves to those ductance or both 43 and 41, the period of oscil skilled in the art to which this invention relates, lation of the system may be changed. Due to provided, of course, that such changes and modi 120 45 the secondary electron emission Occurring Within fications fall fairly within the spirit and scope the tube, in order to form an oscillating al of the hereinafter appended claims. rangement there need be no direct circuit cou Having now described my invention, what I pling between the plate and screen electrodes 33 claim and desire to secure by Letters Patent, is the following: 125 50 and 35 since these are strictly dependent upon the . - - 1. An analyzing System for converting picture If, now, a load is to be applied to the System 1'ecords into modulated electrical energy sig it will be noted that the frequency characteris nals which comprises means to produce fluctuat tic will not vary but will remain Substantially ing currents of Values proportionate to the inten Sities of light and shadow on successive elemental 130 5 Constant. This load which, in the Suggested form of the invention, may include a thermionic areas of a record Subject of which an image tube 43, is coupled by way of a capacity coupling is to be produced, a multi-electrode through the capacity 45 and the grid Voltage having its input circuit connected with said light supplied to the tube 43 is taken across the poten Converting means, an oscillatory circuit connect tioneter 47 by means of a variable tap conven ed. With the plate electrode of said tube, means 135 (60 tionally shown as 49. Biasing potentials for the for applying operating potentials to the other grid of the coupling 43 are shown as being sup electrodes of Said tube so as to cause secondary plied from the 51. electron emission within the tube and to produce In the plate circuit of the tube 43, which con an OScillatory output of a frequency determinable ; nects to the potential Source 37, is a primary by the resonant period of said oscillatory circuit, 140 winding 53 of a whose secondary 55 and means provided by the connection of said connects with output terminals 57 from which light translating means With the input circuit energy may be supplied to a radio transmitter of said tube for modulating the resulting output or to a wire line for tranSmission purposes. It energy. is, of course, to be understood that the coupling 2. An analyzing System for converting picture 145 tube 43 is not an essential part of the invention records into modulated electrical energy signals and that any other form of load circuit may be which comprises means to produce fluctuating connected with the capacity 45 or that the direct Currents of values proportionate to the intensities connection may be made from the capacity to a of light and shadow on Successive elemental areas of a record Subject of which an image is to be 75 transmitting circuit. 1,958,212 3 produced, a multi-electrode vacuum tube having the resonant period of said oscillatory circuit its input circuit connected With said light convert means provided by the connection of Said light ing means, an Oscillatory circuit connected with translating means With the input circuit of Said the plate electrode of Said tube, means for ap 5 tube for modulating the resulting output energy, plying operating potentials to the other electrodes and a load circuit capacitively coupled With Said 80 of Said tube So as to cause Secondary electron OScillator. emission within the tube and to produce an os cillatory output of a frequency determinable by HENRY SHORE. 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