US2076253A - Television - Google Patents

Description

C. SELZ TELEVISION April 6, 1937.

Original Filed May 12, 1932 VIIIVVIV INVENTOR CHARLES SELZ Y (Lam W ATTORNEY Patented Apr. 6, 1937 PATENT OFFICE TELEVISION Charles Selz, New York, N. Y., assignor to Telegralight Corporation, .a corporation of New York Application May 12, 1932, Serial No. 612,075

Renewed June 24, 1936 16 Claims.

The present invention relates to discharge lamps, and to certain structures embodying the same, for use in sound-on-fllm recording, television, and allied and other arts.

Heretofore, in the art of scanning, in television reception, two general methods have been employed in the translation of the incoming high frequency signal into a visible image. In one of ertures,'is rotated before a pulsating light. This method, because of the mechanical inertia of the movable mass of the scanner, presents the dif- -ficulty and problem of attaining proper synchronization between the receiving and the transmitting scanning disks, and this problem has, thus far, for all practical purposes, remained unsolved. The other method is the so-called cathode-ray method, in which a stream of electrons is directed from the cathode in a vacuum tube against ,the fluorescent surface therein, causing a spot of light to appear thereon. This stream of electronsis then deflected and swung over the fluorescent surface in such manner as to form a screen pattern thereon. The inherent defect of this second method is the low illumination obtained.

An object of the present invention is the eliminationin television devices of scanning" disks and other moving parts having the undesirable inertia mentioned,--while still providing illumination superior to that had by any of the devices mentioned.

In attaining the'above results, in television reception, as more fully hereinafter described, the present invention involves the use of a tube, which I have termed a telegralight, and which in this adaptation of the invention, is preferably filled with an inert gas. Contained in this tube is a screen, composed of anode and cathode electrodes, preferably in the form of parallelly arranged resistance wires, one such pair for each desired line of the screen, and which electrodes of each line are connected back ,and stepped down from the endj'of one line to the beginning of the next line so that the several pairs of such electrodes, one for-each screen line, are electrically continuous through the screen. In the television reception of the present invention, a

spot of light and not necessarily visible to the eye is caused to show on the screen at the point of highest potential across the gas space and between the anode and cathode, and to traverse the several reaches of the electrodes from end to end of the screen on each half cycle of alternating current therein. The intensity of such (Cl. 178-6) K light spot is made to vary, in intensity, in the different positions thereof, on the face of the screen, in accordance with the television signal beingv received. In this manner, and by means hereinafter more fully described, a moving light spot of variable intensity, is made to produce a highly luminous image on the screen, in proper lights and half lights, and without the use of these, a disk, perforated spirally with small ap-' moving mechanical parts.

In television transmitting, as heretofore practiced, there have also been used scanning disks and other moving mechanical parts having objectionable inertia; and there has also been distortion of the image and loss of a large part of the light which would otherwise have been available for scanning, by reason of the fact that the cross-section of light beam for scanning, has been progressively introduced into and removed from the areas of the apertures of the revolving scanning disks, and so has been fully effective only when fully within such apertures.

In connection with television transmitting, it is an object of the invention, again, (as in the use thereof in television receiving) to eliminate all inertia such as is inherent to moving parts; and it is a further object of the invention in the 4 use thereof for television transmitting, to avoid distortion of image, such as has heretofore been caused by changes in intensity of light due to the above mentioned progressive introduction into, and removal from, the aperture of the revolving disk, of the cross-section of the light beam. In this connection, it is a further object of the invention to provide means whereby losses of available and desired light are eliminated in te scanning operation. I

In the adaptation of-the invention for television transmitting, as hereinafter more fully described, there is employed a modified form of the screen bulb or telegralight above mentioned. The applied low frequency potential along the cathode, (in television transmission coated with light-sensitive material), causes a high potential field to move along this electrode in the same manner that the light spot moves in the receiving scanning tube. This effect is achieved by reason of the fact that the low frequency potential which is, in this case local to the cathode, (as in the receiver structure), effects an electronic motion; the instantaneous direction of which is dependent on the sign of the current at any instant. This electronic action tends to move the light-sensitive spot, be-

cause that spot is really a point of moderate ionization, (the lamp being gas filled). The entire action is therefore identical with the receiving screen, except for the added activity of the light sensitive material. Here again, therefore, the invention provides means for scanning 6 without the use of moving mechanical parts.

The telegralight, in its use in television transmitting, is therefore generally distinguished from its form and function as a television receiver in that as a receiver it is the spot of light, of 10 varying intensity, which traverses the screen, whereas in television transmitting it is the point of critical potential for electronic flow between the electrodes which traverses the screen and in both cases hereinafter referred to generically as a light spot. In the telegralight' as a transmitter, the cathode is coated with photo-electric material for variation in intensity of electronic flow atdifferent points of the screen, whereas in television receiving such coating is absent. Further, in the use as a transmitter, the telegralight may be a vacuum tube, whereas in the use as a receiver the' telegralight preferably contains an inert gas and has its cathode uncoated with photo-electric substance. I

Referring to the basic showing in Fig. 1, there is illustrated a glass tube Ill in which is sealed an atmosphere of inert gas. Separated from each other and extending longitudinally within the tube are two electrodes H and I2 including resistors I3 and i4 hereinafter referred to respectively as anode and cathode. Externally of the tube, the positive or anode resistor l3 at its opposite end connects through leads 23 and 23 with the opposite ends of a resistance 24 from the electric .center or mid-value point of which a lead. 25 connects through a variable resistance 19 with the positive pole 26 of a high potential supply B of direct current. A lead 36 from the right hand end of the electrode |2 connects to lead 31 and thence to one end of the secondary 48 of a transformer and similarly a lead. 38 connects the left hand end of electrode |2 with the opposite end of the secondary 48. From the electric center or point of mid-value of the secondary 48, a lead 28 connects the negative terminal 21 of the direct current supply. Terminals for the application of alternating current of any 'desired frequency are shown at 49 and 4| with terminal 48 connected by lead 42 with one end of the primary 43 of the transformer and lead 46 extends from the other end of the primary to the 3' terminal 4|. With this arrangement there will be a light spot in the tube II) at the point thereof where the potential between the resistive electrodes ||--|3 and |2-|4 is above the ionization or striking valve. If now, the potential is varied by means of the variable external resistance 19, the area of the light spot in the tube III will vary proportionately. Again, if the point-of engagement of lead 25 with resistance 24, or, if the point of engagement of lead 28 with the resistance forming the secondary 48 be moved in directions electrically opposite to each other, the time axis of the resulting sine curve is shifted up or down the length of the tube.

Various other objects and advantages of the invention will be in part obvious from an inspection of the accompanying drawing and in part will be more fully set forth in the following particular description of one form of device embodying the invention, and the invention also consists in certain new 'and novel features of construction and combination of parts hereinafter set forth and claimed.

Fig. 1 is a diagrammatic view showing in simplified form a telegralight constituting a preferred embodiment of the invention;

Fig. 2 is a diagrammatic view of the telegralight in which theimpedances of three-element vacuum tubes are used and showing the layout as a television-receiving system;

Fig. 3 is a view similar to Fig. 2 showing the telegralight used in a television transmitting system;

Fig. 4 is a detailed view of the telegralight lamp as used in television receiving; and

Fig. 5 is a detailed view showing the light sensitive coating' on the cathode in the lamp of Fig. 4 when the telegralight is used in television transmitting system.

The showing in Fig. 2 follows in general the disclosure in the basic Fig. 1 and utilizes vacuum tubes V and V of the three-element type in the circuits containing the anode and cathode. In this case a lead 3| from one end of the transformer secondary 48 leads to a resistance 29. From the left hand end of the electrode M a lead 38-connets, by way of lead 39, to one end of the secondary I of another transformer, and from the other end of the secondary 47 a lead 38 connects to the other end of the resistance 29. From the electrical center or point of mid-value of the resistance 29, a lead 28 connects to the negative pole 21 of the high potential supply. The circuit thus far described is closed across the electrodes l3 and I4 when the voltage in the tube I0 is sufficiently high.

The plate circuits of the vacuum tubes V and V are as follows. From the positive pole 26 of the high potential supply, through lead 25 to the mid-value point of resistance 24, thence forking through leads 23 and 23' to leads 20 and 22 and to the plates 2| and 2|" of the tubes V and V respectively. From the plates 2| and 2|", the

- plate circuits continue through the filaments 32' and 32", resistances 33 and 33", to leads 30 and 3|, and thence through resistance 29 bridged by a condenser 29' to the negative terminal of the high potential supply. The grid circuits of the upper end of the primary 43 for the secondary 41 in the grid circuit for tube V and from the lower end of primary 43 a lead 46 extends to the upper end of primary 45 for the secondary 48 in the grid circuit of the tube V The lower end of primary 48 is connected by lead to the other alternating current input terminal 4|. It follows that due to the connection of the lower end of primary 43 with the upper end of primary 45, the tubes V and V willfunction out of phase with each other. Hence when tube V is drawing the maximum current, tube v V has its minimum current, and vice versa.

The voltage in the local cathode circuit, which includes the secondaries 41 and 48, the resistance 29 and cathode structure I 4, produces a flow of electrons in that local circuit, thereby causing movement of the point of ionization which has been struck or created by the potential existing between the electrodes l3 and I4.

It is to be understood that any field of ionization is positive in nature, and hence that the visible portions of an ionization field are apparent at the surface of the cathode. The cathode creates a field of electronic density where the positive elements of the ionization field can neutralize themselves, in accord with their tendency,

by combination with the electrons at the cathode. I set the dense electronic field in the neighborhood of the cathode in motion by means of the local cathode circuit. The action at the surface of the cathode is now analogous to friction; the ions following in the path of the cathode electrons, due to their natural afiinity.

From the foreg'oing,'it will be seen that there is no mass factor or inertia in the movement of the light spot; and that there can be no appreciable lag of the position of the light spot relative to the instantaneous current value of the plate frequency. This latter is at least true up to fairly high frequencies such as 30 to 40 kilocycles.

Referring now to Fig. 3, which more specifically shows the application of the invention to telelvision, the circuit structure is as follows:-As

in Fig. 2, the electrode resister I3 is bridged, externally ofthe tube ID, by the conductor 23 and 23, having therein the resistance 24, from the mid-value point of which a lead 25 is connected to one terminal of the input source of energy. In this instance, the lead 25 is extended by a lead 50 to the positive terminal 5| of the high potential supply. The terminals of the resister electrode l3 are again shown as connected by leads 20 and 22 respectively to the plates 2| and -2l" of the vacuum tubes V and V respectively. The filaments 32' and 32" of the tubes V and W are supplied from an alternating current source external to this circuit, and bias resisters 33- and 33" are connected at a point of electrical center of the filament circuits by leads 30 and 3| respectively to the extremities of resister 29,

bridged by a condenser 29'.

, been effected; and the instantaneous position of the light spot atlany point of the cycle, deter.- mined- For use in television, however, the intensity of the light spot, in the different positions thereof in the lamp l0, must be modulated or varied to produce the lights and half lights of dark areas which go to make up the picture. Variations in intensity of the light spot will accord to variations in the current passing through the gas in the tube In at the point of the light spot therein. Suchcurrent variations are effected as follows:-

A third three-element vacuum tube is shown at V The plate circuit of this tube may be traced from the positive end of the high potential supply, through the resistance 53 in the lead 50, to the plate 54 of the tube V and thence through the filament 55 of the tube V to the lead 56, and to the negative end of the high potential supply. In the lead 58 of the grid 51 of tube W is the secondary 59 of a transformer, the primary 60 of which is in the high frequency output circuit of the television signal amplifier. The grid circuit is continued by the lead 58 through a resister 53" to the filament 55.

The frequency in the primary 60 will be that 'of'the transmitted signal, and it follows that the e tire structure shown in Fig. 2 must be adapted t the desired frequency of such signal. In operation, the voltage fluctuations in the secondary 59 of the grid circuit are combined, additiveiy and subtractively, on each cycle, with the voltage drop at the resistance 58", thus effecting the grid swing in the grid circuit of tube V; and by reason thereof, corresponding variations in the plate circuit of the tube V Except for the resister 53 in the plate circuit, the light spot which follows the moving path of least resistance in the traverse of the latter along'the electrodes of the tube l0, would be of fixed intensity. The potential drop across the resister 53, however, varies by reason of the variations of currentin the plate circuit of the tube V and thus modulates and varies the current in the bridge circuit, including the electrodes l3 and I4, in which latter circuit the resistance 53 is, as above' described, located between the positive pole of the high potential supply and the tube 1 0. The modulations or variations of current in the electrodes l3 and I4 eifect changes in the intensity of the light spot as the latter traverse the length of the electrodes in the tube In in unison with the passage of the .path of least resistance there along. As otherwise stated, the voltage change across the resister 53, due to variations in the amount of current drawn by the plate 54, regulates the value of the applied potential across the entire structure between the poles of the high potential supply, varying, in amplitude, the voltage between the mid-point of resister 24 and the mid-point of resister 25, in accordance with the potential applied to the primary 60.

Further, in connection with the foregoing, it is to be noted that'the variations in amplitude of the voltage in the primary 60, do not change any of the conditions of the bridge circuit, the bridge of which is composed of the two electrodes, l3

and. ll, of the tubes V and V The balance of this latter circuit does not depend upon the voltage applied, but-upon the resistance values in the bridge elements. In other words, the balance of the bridge circuit is a function of equality in the plate impedances of the tubes V and V, and of equality in the resistance values of electrodes i3 and I4. When there is no current in the grid circuits of tubes V and V the point of highest potential along the electrodes I3 and I4 will be at the electrical center of these units. This is also the case at the instant when the alternating current value in the grid circuits of the tubes V and V is zero. When there is an unbalanced condition of the circuit, the highest potential along the electrodes will be other than at the electrical center of the electrodes. This unbalanced condition exists at all moments during the various phases of the cycle except when the alternating current values in the grid circuits are zero; and when balance does not exist, the point of highest potential in the lamp i0 is in transit between the electrical center and one of the extremities of .the electrodes I3 and I4.

To the lamp or tube I0 I have given the general appellation telegralight'. In television this telegralight is the scanner. For scanning purposes, however, the lamp will ordinarily not be in the simple form shown in Fig. 2, of an elongated tube with the electrodes or resistances l3 and i4 in but one reach each; but is preferably of a form is the lead 36' of Fig. 3. This lead, in the form of a low resistance wire, passes up the post 62 to the top thereof, where it emerges therefrom at its point of connection with the resister l4. 5 This resister l4, as to the upper reach thereof,

crosses to and enters the post 63, where it connects with a wire 66 of negligible resistance;

which is turned downward and crossed back to the post 62; where it connects with a second reach l4 of the resister I4. This second reach l4 of the resister crosses to the post 63, parallel to and below the first mentioned reach of the resister l4. Again, a wire 66' of negligible resistance, connects the resister reach I4 back to the post 62, and to another reach M" of the resister M. In this manner the resister l4, in

a series of reaches, corresponding in number to the desired number of scanning lines in the scanning screen, is led and connected, zigzag, laterally and downward, in the plane of the two posts 62 and 63; to be finally connected to the lead 36 of Fig. 3, at the right hand lower part of the lamp 6|.

The front of the lamp 6! will be considered that side of the lamp in which lies the plane of the posts 62-63, with the resister l4. The resister l4, being the cathode resister, will be the resister which is illuminated when the scanner is used in receiving. The plane of the posts 64 and 65 may therefore be said to be to the rear portion of the lamp 6i.

The lead 20, of Fig. 2, is shown as entering the lamp 6| of Fig. 4 at the lower left, whence it passes into the post 64, and to the top of the latter, there connecting with the anode resister l3.

This resister [3, in a series of reaches, (connected by wires of negligible resistance, 67, 61', etc.,) is extended between, and supported by, the posts 64 and 65, and is stepped downward in the same manner as above described in connection with the resister I4. For each reach of the resister there is a reach of the resister I3, cooperating therewith, as described in connection with Fig. 2 These co-operating, or pairs of reaches of the resisters I3 and it, are shown in Fig. 4 as lying in planes perpendicular to the uprights 62, 63, 64 and 65. The anode-resister l3 finally connects, at the lower right hand, portion of the lamp, with the lead 22 of Fig. 2.

- It will thus be seen that by using the four terminals of a screen of electrodes so constructed,

and connecting the screen so that the terminal leads thereof will be represented, as inFig. 2, by leads 2!), 22, 36 and 36', there will be no change in the circuit described in connection with Fig. 2. It follows that the point of least resistance in the circuit will move from one terminal extremity of the screen, to the other and back again, for each cycle of the frequency induced into the secondaries 41 and 48. It can be seen that the progres-' sion of the scanning is in the same manner as a printed page is read; but the opposite direction of scanning would act similarly.

In Fig. 4 the modulation or attenuation of the light spot is, of course, dependent upon the action of the vacuum tube V, as described in connection with Fig. 2. The number of the separate lines of the electrode pairs, shown in Fig. 4, will be determined by the nature of the desired transmission scanning, and it will be realized that the entire device is flexible to variations in the frequency at which it is to be operated. In other words, there is practically no limit to the number of light spots, or rather light spot positions, per line of the screen. It will also be seen that by mechanical television transmitting scanner.

superposing the images produced by two such screens, functioning at right angles to each other, and by similar duplication in the transmitting system the limits of possible scanning frequency will only be limited by the ability of the human eye to view such images.

If scanning in one direction only is desired, rectification of the induced frequency in coils 4'! and 48 will be such that only one-half of the wave is effective in the circuit. The scanning may, however, be caused to function in both directions relative to the terminal extremities of the screen. For each complete cycleof the frequency applied to the coils 41 and 48 from the adjacent circuit, the point of least resistance will move the length of the electrode circuit, and back to the starting point; and it follows that successive or alternate scannings may be had in opposite directions along the electrodes of the screen. In fact, such alternate scannings in opposite directions are the natural functioning of the device in response to the full wave of the low frequency used forsynchronization applied at the coils 41 and 48; and so, for double canning, there is no complexity. The reversal direction in scanning, on each half cycle of irequency will, however, have no optical effect; because the human eye cannot follow the movement of the light spot, but gathers only the aggregate effect of all light produced by the spot in transit. Thus, in reality, it makes no difference, so far as the eye is concerned, whether the light spot is actually moving in one direction or the other, or both.

Transmitting The structure shown in Fig. 2, as hereinbefore stated, is a layout for receiving television signals. With certain modifications in the lamp iii of Fig. 4, and in the layout in which the same is employed, the telegralight may be used as a non- As will presently appear, in the action of the telegralight as a photo-electric cell, the light sensitive spot in the telegralight' will be at that point of the negative electrode which, at any given instant, is the point of least resistance on the electrode; it being understood, of course, that this point of least resistance passes along the entire length of the electrode, and back, on each cycle.

The aforementioned point of least resistance, which is a dynamic spot of ionization, can be best understood as a typical alternating potential node, which proceeds along the electrode'in the gas as a space charge actually moving from one extremity of the electrode to the other. As the moving space charge produces violent ionization, (when the tube is gas filled), at the position where it instantaneously exists, the, effects of its presence appear in the form of photo-electric emission in the transmitter, or as glowing spot in the receiver. All the discernible effects are of course relative to the nature of the cathode surface, the pressure of the surrounding atmosphere, and the potential applied to the anode.

The area of screencr scanning action in the photo-electric cell need be of but small size; because the image of the transmitted scene may, by proper lenses, be reduced to the desired area of scanning action.

In the use of the telegralight as a photo-electric cell for television transmitter, it is of course apparent that the telegralight is the source of alternating current in varying amplitude instead of being the sink thereof, as in the Fig. 2 use of the telegralight in receiving. This distinction is reflected by difierences in the wire-diagram or layout, now to be described.

5 For transmitting, the modification in the lamp,

or telegralight itself, consists simplyin depositing, as indicated in Fig. 5, upon the negative resister l4 in the several reaches thereof, a coating 68 of photo-electric material, such for instance, as potassium or caesium. The telegralight used as a photo-electric cell may be gasfilled, or,a vacuum, according to the nature of the response desired. The circuit layout in which the telegralight is used as a transmitting scanner is shown in Fig. 4. Fig.- 4 is a duplication at the transmitting end of certain of the layout shown in Fig. 2 for the receiving end, and that the parts in'Fig. 4 are numbered as in Fig. 2,

chronization may be effected by means well known in the art.

30 In the transmitting layout of Fig. 4, a threeeiement vacuum tube V is shown, having filament 69, plate and grid H. The filaments 32' and 32" of the tubes V and V are supplied from an alternating current source external to 35 this circuit, and bias resisters 33' and 33" are connected at a point of electrical center of the filament circuits by leads 30 and 3| respectively to the extremities of the resister 29, bridged by a condenser 29', from the mid-value 40 point of which resistance, a lead 28 extends to the negative terminal 21 of the high potential supply, B. The high potential supply terminals are indicated B- and 3+ with a third terminal B'+, between which latter terminal and the 45 terminal 3+, is shown the bleeder resistance 12 and. a bridging condenser 13. The local plate circuit of the tube V is shown as extending by a lead 14, containing a primary 15 of a transformer, to the plate 10; thence through 50 the filament 69, lead 16 and lead 11 to the B'+ terminal of .the high potential supply. The circuit of the bridge across and through the photoj electric cell or telegralight I0 is shown as extending from the B'+ terminal of the high 55 potential supply, through the lead 11 to alead 18, in which lead 18 is a resistance, or grid resister 19. The lead 18 connects to the grid II and to the lead 25, and thence to the mid-value point 01' the resister 24 in the bridge. The line 0 is here forked to the two extremities of the anode resistance in the photo-electric cell of telegrelight 10. Upon electronic flow between the resistances l3 and I4 in the photo-electric cell, the circuit is continued by leads 36 and 38, and 5 3'! and 39, through the transformer secondaries 41 and 48, respectively, to the leads 30 and 3|. and thence through the resistance 29 to the midvalue point thereof and by the lead 28 to the negative terminal 21 of the high potential sup- 70 P y Asshown in Fig. 5, the resistance I4 within'the photo-electric cell or telegralight is covered or coated as at 68 bypotassium, caesium, or the like. At whatever point of the resistances or 75 electrodes, l3 and I 4, within the photo-electric cell, the critical potential for the moment may exist (as heretofore explained in connection with Figs. 2 and 3), an electronic flow, completing the synchronizing current at 41 and 48. l0

Since the electronic flow, and consequently .-the current in the bridge across the photo-electric cell, varies according to the intensity of light on a given point of the image opposed to the point of the screen, or of the electrodes, where 15 the potential of possible electronic flow for the moment exists, the current in the bridge circuit through the resistance 19 correspondingly varies. This variation of current in the resister l9 correspondingly affects the potential drop across 20 this resister to which the grid ll of the tube V is connected; and this variation in the potential at the grid ll correspondingly affects and modulates the current in the plate circuit of the tube V This modulated, pulsating current in the plate circuit may, by means of the transformer, whose primary I5 is in the plate circuit,

be suitably amplified for transmission.

In the foregoing description, and in the drawing, the telegralight has been shown as having both anode and cathode in the form of an elongated resistance; and, in the screen structure, the anode has been shown as having reach for reach with the cathode. Itis not necessary, however, that both anode and cathode comprise the elongated resistance: this resistance may be absent from either one or the other of these electrodes, provided it is presentin the other. Furthermore, the resistance, when not present in the anode, need not formthe cathode itself. It may be outside the lamp bulb, but connected into the cathode from stage to stage thereof; and the cathode itself may be an elongated strip of negligible resistance, provided it is properly associated with the elongated resistance somewhere properly placed in the bridge circuit and connected thereto. Again, the anode need not be an elongated piece, nor, in the screen structure parallel the cathode, reach for reach: it may be a single piece or plate cooperating with one or more reaches of cathode, and it may be be of a variety of shapes and sizes.

I claim:

1. Apparatus for use in television, sound-recording, and the like, comprising a discharge lamp having therein a cathode resistance piece, and an anode, means for energizing the lamp to create a spot-field of ionization therein at a point of the cathode, and a circuit comprising a source of alternating current, and of which 0 said cathode-resistance piece forms an element; so that, upon passage of such alternating current through said last-mentioned circuit, and through the cathode-resistance piece, said spotfield of ionization is caused to move along the 5 cathode on each cycle of the current 2. Apparatus for use in television, sound-recording, and the like, comprising a discharge lamp having a pair. of electrodes forming a cathode resistor, and an anode, connections from said electrodes to a source of potential sufliciently high to create a spot-field of ionization in the lamp at a point of said cathode, a circuit local to and containing said cathode-resister, anda source of altemating current in said local cirsaid spot-field of ionization is caused to move along the cathode on each cycle of the current.

3. Apparatus for use in television, sound-recording, and the like, comprising a discharge lamp having an elongated cathode resistance piece, and an anode at least one of which is within the lamp, a closed local circuit containing the anode and containing a resistance external to the lamp, a closed local circuit containing the cathode and containing another resistance external to the lamp, a source of potential sufficiently high to energize the lamp and to create a spot-field of ionization therein at a point of the cathode, a connection from one pole of said source to the electrical center of said anode loop circuit, a connection from the other pole of said source to the electrical center of said cathode loop circuit, and means for generating in said cathode loop circuit an alternating current, so that said spot-field of ionization is caused to move along the elongated cathode on each cycle of the current from said last-mentioned source.

4. Apparatusfor use in television, comprising a discharge lamp having an elongated cathode resistor stepped therein over the desired scanning area, an opposed anode, a source of direct current for energizing the lamp to create a spot-field of ionization therein at a point of the cathode, a

circuit comprising a source of alternating current, andof which said cathode-resister forms an element, whereby, upon passage of such alternating current therethrough, said spot-field of ionization is caused to move along the cathode on each cycle of the current from said lastmentioned source, a television signal-amplifier, and means electrically coupling said amplifier to the first-mentioned energizing circuit, whereby to eifect variations of luminosity of the spotfield of ionization in accordance with the instantaneous voltage-values of the television signals.

5. Apparatus for use in television, comprising a discharge lamp having an elongated cathode resistor stepped therein over the desired scanning area, an opposed anode, a source of-direct current for energizing the lamp to create a spotfield of ionization therein at a point of the cathode, a circuit comprising a source of alternating current, and of which said cathoderesister forms an element, whereby, upon passage of such alternating current therethrough, said spot-field of ionization is caused to move along the cathode on each cycle of the current from said last -mentioned source, a thermionic television-signal amplifying tube, and a resistance in the plate circuit of said tube, which resistance is also in the aforesaid lamp-energizing, direct current circuit, whereby to effect variations of luminosity of the spot-field of ionization in accordance with the instantaneous voltage-values of the television signals.

6. Apparatus for use in television, sound-recording, and the like, comprising a discharge lamp having an elongated cathode resistor, and an opposed anode, means for energizing the lamp to create a spot-field of ionization therein at a point of the cathode, and a circuit comprls 70 ing a source of alternating current, and of which said cathode-resister forms an element; so that,

pon passage of such alternating current through aid last-mentioned circuit, and through the cathode-resister therein, said spot-field of ioniza- 75 tion is caused to move along the elongated cathode on each cycle of the current from said last-mentioned source, and means for imposing signal voltages upon the lamp-energizing circuit in such manner as to efiect corresponding fluctuations in luminosity.

7. A photo-electric cell, having an anode and having a light sensitive substance formed as an elongated or line-cathode, means for applying to said electrodes a direct current of potential less than striking value, but suflicient to produce electronic emission from the cathode in the presence of light, a source of alternating current potential in circuit with the cathode, of value suflicient to suppress the emission at all but the dynamic point of maximum difierence between the anode and cathode, and to move said emission point along the cathode as a function of such applied alternating current.

8. A photo-electric cell, having a pair of electrodes, one forming an anode and the other including a light sensitive substance formed as an elongated or line-cathode, means for applying to said electrodes 2. direct-current of potential less than striking value, but sufiicient to produce electronic emission from the cathode in the presence of light, a source of alternating current in circuit. with the cathode, of value suflicient to suppress the emission at all but the dynamic point of maximum diiference between the anode and cathode, and to move said emission point along the cathode as a function of such applied alternating current.

9. A photo-electric cell, having a pair of electrodes, one forming an anode and the other including a light sensitive substance formed as an elongated or line-cathode, said cathode being extended in a set of lengths or reaches stepped from one another to form a screen, means for applying to said electrodes a direct current of potential less than striking value, but suflicient to produce electronic emission from the cathode in the presence of light, a source of alternating current in circuit with the cathode, of value sufficient to suppress the emission at all but the dynamic point of maximum difierence between the anode and cathode, and to move said emission point along the cathode as a function of such applied alternating current.

. 10. A photo-electric cell, having a pair of electrodes, one forming an anode and the other including a light sensitive substance formed as an elongated or line-cathode, said cathode being extended in a set of lengths or reaches stepped from one another to form a screen, means for applying to said electrodes 9. direct current of potential less than striking value, but sufficient to produce electronic emission from'the cathode in the presence of light, a source of alternating current in circuit with the cathode, of value sufficient to suppress the emission at all but the dynamic point of maximum diflerence between the anode and cathode, and to move said emission point along the cathode as'a function of such applied alternating current, and a thermionic television signal amplifying tube in circuit with one of the electrodes of the photo-electric cell, and having a resister in the grid circuit thereof, whereby the different lights of an image imposed upon the screen give signals in the form of alternating current of varying potential amplitude.

11. Apparatus for use in television, sound recording, and the like, comprising a discharge lamp havin'g. elongated anode and cathode resistances therein, a source of direct current for energizing the lamp to create a spot-field of ionization therein at a point of the cathode, and a circuit comprising a source of alternating cur rent'and of which said electrode resistances are elements; so that when said alternating current is imposed thereon, said spot-field of ionization is caused to move'along and traverse the cathode on each cycle .of the alternating current.

12. A discharge lamp having a pair of electrodes forming a cathode and an anode, at least one of which is within the lamp, means for energizing the lamp to create' a light spot to form in the region adjacent one of the electrodes and means including the cathode forming an alternating current circuit acting to cause the spot to traverse one of they electrodes in synchronism with a cyclonic function of the alternating current and means for varying a characteristic of the current in said alternating current circuit thereby to vary at least one characteristic of said light spot and information conveying mechanism operatively controlled by and thus responsive to the variations in said variable character-' istic of the light spot. 0 13. A discharge lamp having a pair of electrodes forming a cathode and an anode, at least one of which is within the lamp, means for energizing the lamp to create a light spot to form in the region adjacent one of the electrodes and means including the cathode forming an alternating'current circuit acting to cause the spot to traverse one of the electrodes in synchronism with a cyclonic function of the alternating current and means for varying a characteristic of 5 the current in said alternating current circuit 15. In a device of the class described, the combination of means defining a path of travel for a spot of ionization, control means for preliminarily locating the center of motion of the spot in said path and means including a source of alternating current electrically coupled with the first named means for causing the spot to traverse its path of travel on each cycle of the alternating current. a

16. A photo-electric cell comprising a tube having two electrodes extending therethrough, one of said electrodes constituting an anode and the other constituting an elongated or line cathode covered with a light sensitive substance, both the anode and cathode each extended in sets of length or reaches stepped from one to another to form an anode and a cathode screen, said cell provided with means for connecting both of the electrodes to a source of direct current and provided with means for electrically coupling the cathode with a source of alternating current.

CHARLES SELZ.

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