US2847616A - Electronic circuits for controlling illumination intensity in ionizable gas display tubes or the like - Google Patents

Description

Aug. 12, 1958 D D. HANSEN TUBES OR THE LIKE Filed April 19. 1954 FIG. I

5 Sheets-Sheet 1 Sec. l-C

Station Amplifie rUniT 26 25 24 A MosTerlOonTrolunir o i IZM Seal-8' DAYNE D. HANSEN, Sec. Inventor Attorney g- 12, 1953 D. D. HANSEN 2,84

ELECTRONIC CIRCUITS FOR CONTROLLING ILLUMINATION INTENSITY IN IONIZABLE GAS DISPLAY I TUBES OR THE LIKE Filed April 19. 1954 5 Sheets-Sheet 2 I w Th raTron PIaIe CIrcuII Cu rvenI' How. 0 5 IO I5 H6 2 Time (Seconds) SI N E 50 50 Grid 5305 on c ThgraIron Tube \1 '0 5' no I5 FIG 3 I E m Grid B'Ias of me OuTpuI' of I41 FIG 4 53 53 1-, W PIare CurrenI FIow Tube I8 0 5 I0 I5 I FIG 5 54 5s 54 53 54- 53 E VoITaqe Across l Capac'flor 23 o 5 I0 l5 FIG 6 Grid Bias To "STaIIon UnII D YN NSEN LIghT OuIpuT of E Eag Neon Tubes B 15 of W AIIm-ney g- 12, 1953 D. D. HANSEN 2,847,616

ELECTRONIC CIRCUITS FOR CONTROLLING ILLUMINATION INTENSITY IN IONIZABLE GAS DISPLAY TUBES OR THE LIKE Filed April 19, 1954 Sheets-Sheet 3 FIG. 9 I W Muster Control Umt Sec.9-D

/25a 49a -fl a zoa g W 34 i 18 S 9 x 5 D g B a? 38 2m l. FIGJZ 7 I IO W W?! H" DAYNE D. HANSEN, Inventor L g Sec.9 A BY 4 A v o m I j no v Attorney Aug. 12, 1958 D N ELECTRONIC CIRCUITS FOR CONTROLLING ILLUMINATION INTENSITY IN IONIZABLE GAS DISPLAY Filed April 19, 1954 RED TUBE TUBES OR THE LIKE 5 Sheets-Sheet 4 DAYNE D. HANSEN mvenTor BY Attorney United States Patent ELECTRONIC CIRCUITS FOR CONTROLLING.

ILLUMINATION INTENSITY IN IONIZABLE- GAS DISPLAY TUBES 0R THE LIKE Dayna D. Hansen, Seattle, Wash.

Application April 19, 1954, Serial No. 424,990

17 Claims. (Cl. 315-481) My invention and discovery relates to gaseous. tube display lighting and the production and automatic control of varying brilliance of said display lighting, and more particularly to an all electronic control circuit so employed, the same being capable of operating: without power driven or mechanically moving parts, such as motors or solenoids.

In general, it is a primary and fundamental object of my invention to provide a circuit, that may be employed in any electric circuitin which an automatically varied or variable current or potential. is. desired to electronically control such. circuit without employing motor driven or mechanically moving parts.

Also, be it noted, my invention and discovery may be applied to producing a wave of desired form in producing correlated effects in experimentation.

This application is a continuation-in-part. of; my ap: plication, Serial Number 364,415, filed June. 26, 1953, entitled Non-Mechanical and Wholly Electronic Controlled Circuit, which application was copending here with and has been abandoned in favor of the. present application. 1

While my invention and discovery is set forth for purpose of clearness of description and. illustration in connection with sign lighting, the scope thereof; is not to be so limited but is coextensive where like. problems or conditions exist in whole or in part.

Also, more particularly my invention and discovery relate to the production and control of the brilliance, especially of a gaseous tube sign, by providing a master voltage control circuit which controls the magnitude of current of an amplifying means and this in turn controls the current of the sign and therefore its brilliance, while at the same time providing voltage ofv a substantially constant value at all times of. such magnitude asmay. be required to maintain ionization of such gaseous medium in the sign-all this without employing mechanically moving parts either for the production of such varying brilliance or for the control thereof. By the terms gaseous and gaseous medium itisto be understood there are to be included for example, neon, argon, and mercury vapor which are cited by vway of. illustration and not limitation.

A primary object of this invention and.discovery is. to provide electronic means for varying. brilliance. of a gaseous electric sign whereby a gradual dimming of the light emanating from such gaseoustube sign may beaccomplished, followed by a gradual return of the lighttto its normal brilliance, and soon alternating in predetermined timed cycle.

A further primary object of the. inventionis, inthe fields of both outdoor and indoor gaseous, tubeillumination, to eliminate the expensive and'bulkycontrol equip- Pent heretofore employed. In outdoor sign illumina- "P particularly, installation space is limited and'often M u of access. The equipment, moreover, cannot concealed as readily as when indoors. gjm ther primary object is. to avoidthe presenhgem 2,847,616 Patented Aug. 12, 1958 2 erally adoptedpractice of custom building of. the control equipment, that. is, specially and. individually. building equipment for each particular: signinstallation.

My invention involves (a) a Master Control Unit" and (b) a Station Amplifier Unit; In myinvention, in. contrast with. such specially and individually custom built equipment, I provide. a Master Control Unit which can be constructed of like parts throughout,.i. e., standardized, for all magnitudes of currentjbeing controlled inthe. Station Amplifier Unit. or. in a. number of such. Station Unit Amplifiers. Also the parts of the. Station Amplifier Unit of my inventionv may be. constructedv alike and interchangeable, i. e.,.standardized, withsthe; exception ofthe amplifying vacuumtriode: Thistubeiis selected. according to different rangesof. magnitude of. current. required. For example, one. size of said tubefwill accommodate magnitudes of. current ranging from one milliampere to 60 milliamperes as is:employ.ed. inucomm'on practice; Another sizeof: such tubeis employedxwherel the magnitude of current'is in thelrange ofj60 milliamperes to 500;milliamperes. Obviously, a tube oftasize'for SOOtmilliamperes will accommodate a current of from 1. milliamp'ere to 500 milliamperes, but this would b.e.:uneconomical=when sogreatly in excess of the range: sufficient to operate a given sign; As a. matter of'practice, the current of neon tubes for sign.installationfalligenerally in the ranges-of l to 60.. milliarnperes and 60 milliamperes to 500? milliamperes. For: eighty to; ninety percent (80% to 90%) of thesign tube'installations, the current ratings. offthe neon. tubes fall'in the range of l to 60.n1illiamperes. This interchangeability; and: versatility. of the device: of

. my invention provides. for great economy in: the sign installation and maintenance.

It is particularly'a primaryobject of my inventiontand discovery to provide'a completely electronicusystem which employs no motor or. mechanically moving parts, to achieve all of the lighting effects herein set forth. To.- ward. this objective, itJWill beseen that the invention produces a. whole'new series of effects, including wide variation in speed: of change of brilliance, period of maximum brilliance: andi dirnness, and smoothness of blending of lights of different colors in the field of electrical advertising: and decorative lighting;

It.is also a primary and fundamental object of very great importanceiof my invention totprovideua neonsign of marked :and especially great economyvin manufacture, and, above all, of. especially great economy in installation and maintenance the device of myinvention' being characterized by its eflicicncy in operation, eliminating the. consumption of. current by auxiliary motors by: direct consumption and by heat dissipation by resistors.

Afurther primary object ofmy invention is to provide a neon sign whose brilliance may belchanged gradually either, automatically or manually.

A further and fundamental primary. object of my inventionis to-provide:for changes of color in timed cycles and for. theprecise'; synchronization ofsuccessive changes of color by different gaseous tubes in a giveninstallation:

Other objects of anduses. to which. the invention: may be directed-Will be readilyapparent to those skilled in the art as the description proceeds. For example (by way of. illustration and. not-of limitation.) may benamed the following: The invention can. be used toicontrol air field. tower markers to :prevent airplane pilots' from losing distance perspective. Also in experimental work, further,,the control provided. by the invention can be employed in generating signals of low frequency ofanydesired wave formas respects voltage or currentcmagnitudes. Further, the invention is adaptedato operate 35111651301111- dary marker for airplane fields or runways; The speed of the ;lighting up of the arunway is adaptableito adjustment 3 so as to function as a basis of comparison for the pilot in judging his landing speed, or other aid.

The invention and discovery is well adapted for testing devices which are subject to vibration; by Way of illustration and not limitation, among such applications may be cited the following: In testing vibrations of airplane wings, the device or invention would be useful in rendering uniform and definitely controlled the force producing the low frequency vibration of the wings; in short, the invention and discovery is useful in controlling and rendering uniform the force for developing frequency of vibration of selected frequency and magnitude, whether of uniform or unequal magnitude and with either gradual or abrupt changes in said forces.

Tubes employed in advertising, which are filled with an ionizable gas such as mercury or neon vapor, have the same voltage-current characteristics as any gaseous discharge tube, in that if the voltage is high enough it will ionize the gas in the tube and when a certain minimum of current is provided light will be given off. The ionized gas will then conduct electricity as in the case of any metallic conductor as long as the circuit is maintained. In anygaseous discharge tube, the voltage must remain above a certain minimum value to overcome resistance in order to keep the gas ionized, but the intensity and brilliance of the light given off is dependent upon the amount of current flowing rather than upon the amount of the voltage. Hence, in order to vary a neon tube light over a wide range of light intensities, it is necessary to be able to vary the flow of current while maintaining an almost constant voltage, i. e. sufiicient to overcome the resistance, i. e. provide for continued gas ionization. In installations where results other than those involving the illumination effects mentioned above, the current may be kept substantially constant and the voltage may be varied. Such results (by way of illustration and not of limitation) might be the production for study of desired voltage wave forms, in which study there would be involved characteristics of tubes and values of resistors and condensers.

Devices of the prior art, for varying illumination intensity, have been applied to neon gas tubes but have usually failed because they were unable to maintain a constant voltage with variation in the amount of current employed. When they did not fail in this requirement, they were accompanied with serious disadvantages. As an example, in one existing control system the length of neon tubing ordinarily carried as full load for a transformer is reduced to a third or a half of such full load length-thus tripling or doubling the cost. Also heretofore, when a decrease of voltage has occurred, the tube has failed completely to give off light, due to the de-ionization of the gas, and for many years, this effect has been avoided by employing a flasher, i. e., a device operated by a separate motor, thus involving mechanically moving parts which can only turn the sign or portions thereof off and on, as distinguished from variation in degree of brilliance.

A primary object of my invention is to provide economy of control involved in all the above features as well as others.

Some devices of the prior art, where mercury vapor is involved, to a limited extent have accomplished changes in light intensity by decreasing the footage of the tubes allotted to each transformer by about fifty percent. However, this decrease in footage is impractical for economic reasons. Furthermore, there is apt to be a constant flicker in the gas-filled tubes when the intensity of light decreases by employing the devices and methods of the prior art, as for illustration, motor driven auto transformers.

Known methods and equipment for dimming neon and mercury gas-filled tubes for the most part have not been satisfactory because the equipment needed for the desired effect requires a great deal of installation space and also relatively great weight, sometimes several hundred pounds, making it generally impractical for use in sign work since for one reason, said equipment must be hidden and often located in elevated and relatively inaccessible positions.

Moreover, such prior methods of sign brilliance control equipment involve motor and mechanically moving parts and even with all such they do not operate to provide a substantial constant voltage. Let it be noted that a driven choke type of means for altering the current is inherently a voltage dropping device and therefore does not provide a constant voltage while, moreover, involving a decrease in tubing footage. Such footage must be near maximum to meet optimum economic considerations. However, such motorized and mechanical moving means must be special, that is, custom made, for each particular installation and are relatively much more complex than the invention herein set forth. Furthermore, all such choke means must operate upon alternating current only, while, in definite contrast, the device of my invention is capable of controlling either an alternating or direct current supply and meets optimum economical considerations.

The maintenance of the systems of the prior art is expensive, since each installation must be custom-built due to the fact that very seldom do two sign installations require the same amount of electrical energy consump tion; that is, each sign installation involves a diiferent length of tubing and therefore draws a different amount of power, and to control by motor driven means this amount of power for the particular installation, obviously requires the building of control means of special rating for the particular installation. Hence, it follows that each piece of control equipment would be of a diiferent size or rating and the parts would not be interchangeable. Experience dictates that it is desirable to have versatility in the desired lighting effect since no two installations have the same locations and surroundings to make any one lighting eflect pleasing. In short, different locations and surroundings dictate different installations to render the sign readable and of pleasing and desired attractive effect, as for example, the speed of change and degree of brilliance. Current, voltage, speed of cycling, and other factors should all be variable for best results, but with the systems of the prior art these effects cannot be readily, efliciently or economically accomplished. In the case of my invention and discovery, all such factors may be varied by a simple adjustment as by turning a dial and therefore interchangeableness and versatility are provided, and custom construction of the control units eliminated.

According to the present invention, the system comprises two basic unitsa Master Control Unit, and a Station Amplifier Unit. One such Station Amplifier Unit is employed for every so many feet of neon or mercury gas-filled tubing, but such unit can be built beforehand and applied in any lighting installation regardless of the size or effect desired, since in the device embodying my invention-the Master Control Unit is of a construction which is characterized by being able to control all such variations in the Station or Amplifier Unit by a simple adjustment or presetting of the resistors in connection with the capacity of the condenser in said Master Control Unit. I have discovered a new, so far as I know, Master Control Unit which may be employed to continuously and automatically produce and control the desired varying brilliance of the sign regardless of the number of said station units employed-said station units all being of like parts and construction for any given range of magnitude of current, i. e., only the vacuum triode tube rating need by preselected as hereinabove set forth.

The electronic system of this invention produces no flicker of light during the dimming or increasing of the brilliance of the neon sign when properly applied and adjusted. Its cost of maintenance is relatively very small due to the fact that ,the units can be fabricated before- Station Amplifier Unit. One unit may be interchanged for one in its range already installed which has failed by long use. The units of my invention anddiscovery require very little space, a most important factor as it avoids the necessity of providing a new housing; and weigh but a few pounds, as of theorder of seven pounds in contrast to fifty to one hundred pounds for mechanically driven control devices. The sign voltage is'maintained substantially constant irrespective of range of current magnitude.

The invention has the further very important advantage that it iseven applicable to neon sign installations already in use. Due to the versatility of the Master Control Unit, which may be readily adjusted, the effects obtainable relate to all of the important factors of a neon sign operation such as, the overall length of the cycle, the time required for the sign to gradually become dim, the length of time it remains dim, the length of time required to return to full brilliance, the length of time it remains at full brilliance and the degree of brilliance and degree of dimness.

Briefly summarized, and therefore incompletely set forth, the invention and discovery involve the following:

The providing of a Master Control Unit of like and interchangeable parts which function to exert a variable control signal on the grid of one or more triode tubes in the Station Amplifier Units provided by the invention, while at the same time providing voltage of a substantially constant magnitude as maybe required to maintain ionization of such gaseous medium. The function of the invention as a whole; that is, the Master Control and the Amplifying Units, is to exert an adjustable control upon the current delivered to the neon sign whereby the operator is enabled to make a setting by simply adjusting a dial which results in a light cycle of brilliance-fadingbrilliance at desired intervals, said factors being more fully set forth herein.

The disclosure of my invention relates in general to two forms, one, a very simple form as illustrated in Figure 1 herein, and the other, a more complicated form of my invention which is particularly adapted to effect a gradual change and blending of colors in the lighting system which has some of the tubes provided with mercury vapor and some with neon gas, as illustrated in Fig. 10.

The above mentionedgeneral objects of my invention, together with others inherent in the same, are attained by the mechanism illustrated in the following drawings, the same beingpreferred exemplary forms of embodiment of my invention, throughout which drawings like reference numerals indicate like parts:

Figure l is a diagram of a simplified form of electric circuit embodying my invention and discovery particularly adapted for varying the brilliance of the light emanating from the sign in -an automatic timed cycle;

Fig. 2 is a representation of the normal current wave form with respect to time which characterizes the normal operation of the thyratron plate circuit, i. e., a circuit which is either conducting or non-conducting;

Fig. 3 is a representation of the wave form of the signal voltage impressed upon the thyratron tube grid;

Fig. 4 is a representation of the output voltage signal wave form with respect to time at the output of sec. 1-A;

Fig. 5 is a representation of the plate current flow of the vacuum triode tube with respect to time in sec. lB;

Fig. p is a representation of the voltage wave form with respect to time of the combinedtor final wave form produced by sec. l-A and sec. 1 B atthe output of sec. 1-B;

Fig. 7 is another or separate representation of thecombined or final form of wave as received 'by the Station Amplifier Unit; i. e. it is a portion ofthe alternating (A.-C.) component of output of sec. l-B, from which a portion of the direct current (D.-C.) component .has been removed;

Fig. 8 is a representation of the light output of the neon tube of the sign, thereby indicating the brilliance and dimming cycle;

Fig. 9 is a diagrammatic illustration of a modified electric circuit comprising a Master Control Unit and a Station Amplifier Unit according to my invention and discovery, especially adapted for use with other similar units in a sign having a plurality of gaseous tubes, each of a different color or effect, which plurality of tubes is to be operated in synchronization successively, but also adapted to produce the result or operation of the circuit of Fig. 1, only one such .circuit and one such gaseous tube being shown;

Fig. 10 is a diagrammatic illustration of the electric circuit embodying in united and connected representation a plurality of the units set forth and illustrated in Fig. 9 where the same are connected for successive and synchronized operation of colored tubes;

Fig. 11 is a diagrammatic illustration of an electric circuit of my invention illustrating a modified form of sec. 1-A of Fig. l;

Fig. 12 is a diagrammatic illustration of a modified form of the Station Amplifier Unit employingan impedance element;

Fig. 13 is a view of Fig. l with the valves of the elements set forth in the drawings; and

Fig. 14 is a view of Fig. 11 with the valves of the elements set forth in the drawings.

In Figure 1, for purposes of description the Master Control Unit which may be otherwise termed a lowfrequency control signal generator, has been separated into two sections, sec. 1-A and sec. 1-B, by .the dotted line B-B. Also the Master Control Unit as a whole has been separated bythe dotted line A-A from the Station Amplifier Unit, sec. 1C so designated.

Master Control Unit Referring to see. 1A thereof, a transformer 11 delivers alternating current power from the source lines 10, and thence to a rectifier 12 when main switch 12M is closed. Parenthetically, let it be noted 3 that here the description hereinafter set forth will proceed in the direction of the electron flow, as contrastedtothe direction of positive current flow, to provide clear and full disclosure. The rectifier 12 may be of any type, but that shown is a full-wave vacuum tube type in combination with a center tap type transformer 11, which is considered the preferred and most practical type. transformer for this use. Electron flow starts from the center tap of transformer 11, thence through impedance 49, adjustable variable resistor13, through and charging the condenser 14, thence from resistor 13 and condenser '14 through the variable resistor 15 and condenser 16 to the cathode of tube 17. Tube 17 is a gaseous type gridcontrolled rectifier tube, known as a thyratron, and is supplied with power from transformer 11 and rectifier 12.

Thus an alternating current as a source of electrical energy in conductors 10 is connected to a transformer 11 and the plate of a rectifying tube 12 to produce a pulsating source of direct current. Of course an equivalent of this would be any of the several well known means for producing a pulsating direct current. From the plate of tube 17, electrons flow back to the rectifier tube 12, to complete the direct current (D. C.) circuit. Impedance 49 functions to limit the peak current flow through the thyratron plate circuit and also to provide greater variety charged. The grid of tube 17 is connected to condensers 14 and 16. Hence, when condenser 16 becomes charged, the potential on the grid of tube 17 is negatively high. This high negative grid potential results in a sudden extinguishing of the flow of current through tube 17. Condensers 14 and 16 primarily discharge gradually, an adjustable time constant being provided by variable bleeder resistors 13 and 15. Since the negative voitage drops as the condensers 14 and 16 discharge, the negative potential on the grid of tube 17 must drop also. When such bias is low enough, the cut-off point of tube 17 is exceeded, and the current will again flow, as described above. Thus, sec. 1-A of the Master Control Unit of Figure l is what may be termed a free-running relaxation oscillator.

As set forth above, the negative bias on the grid of tube 17 is for the purpose of momentarily interrupting, that is, shutting 011 the current fiow through gaseous tube 17. This interruption of current has the effect of automatically and inherently interrupting the current supply to resistor 13 and condenser 14. Such interruption allows the condenser 14 to discharge at a rate depending upon the capacitance thereof and the impedance value of resistor 13. All such operation of charging the said condensers 14 and 16 and controlling their discharge through said resistors 13 and 15 is for the express purpose of generating a wave form of voltage which is illustrated in Fig. 3.

More explicitly, when the switch 12M is closed, the current momentarily flows across condenser 16 and through tube 17. Such flow is only momentarily at the time of closing said switch. In the next interval of time, the current commences flowing through resistor 15, imposing a negative bias, i. e., voltage on the grid of tube 17 which, as stated above, definitely shuts off the current flow through tube 17. The circuit shown in sec. l-A, including transformer 11, resistor 13, condenser 14, condenser 16, resistor 15, tube 17, and rectifier 12 creates as its output a wave form as shown in Fig. 4. In the present disclosure, resistor 15 may be of relatively high or low impedance value in comparison to resistor 13 depending upon the output wave form desired. The sudden flow of the electric current through tube 17 provides a voltage represented by the vertical components 50 (Fig. 3). Thereupon resistor 15 imposes a gradual discharge of the voltage and is represented by the curve 51.

In a device already built embracing this invention, the above cycle or repetition rate is variable within the following limits: From one cycle a second to one cycle per twenty minutes, and as a practical matter, this is the range required. However, inherent characteristics of the invention permit a much wider range. The length of the cycle depends on the resistance and adjustment of bleeder resistor 13 and resistor 15 which discharges condensers 14 and 16 and on the capacitance of condensers 14 and 16.

The second section of the master control unit, sec. l B, lying between dotted lines A-A and B-B, is the same in general arrangement as the first section 1A, and current flow is basically the same, with but two exceptions. Gaseous tube 17 is replaced by tube 18, a pliotron, which is a vacuum or hard. Hence, tube 17, (a gaseous triode) which has the function in sec. 1-A of allowing a current to be on or off, has been replaced by tube 18 (a vacuum triode) which has the function in sec. 1-B of affording a predetermined varying control over the amount of the current flowing through tube 18. Resistor 15 and condenser 16 are replaced by a potentiometer 19 across the terminals of condenser 14 of the first section lA. This potentiometer 19 provides a control signal between the cathode and grid of tube 18, thus connecting the circuits of sec. lA and sec. l-B.

The electron flow in sec. l-B may be traced as follows: Electrons leave the center tap of the transformer 24 and flow through the impedance 49M, the variable, i. e., predetermined adjusted resistor 22, charging the condenser 23, thence flowing through triode tube 18, through rectifier tube 21, and thence to transformer 20, to complete the circuit. Impedance 49M functions to limit the peak current flow through the vacuum triode plate circuit. However, impedance 49M may be omitted when not required or desired. Rectifier 21 may be any type of rectifier, a full wave rectifier being presented for illustration.

The electron flow just described occurs only when the negative potential from sec. lA on the grid tube 18 is low enough negatively to permit the electrons to flow in said circuit. When the negative potential on the grid of tube 18 becomes too high to permit the electrons to flow through tube 18, the condenser 23, which has become charged from the line flow of current, begins to leed or discharge through resistor 22, until the negative grid potential is again low.

As stated above, the function of the pliotron tube 18 is to provide a predetermined adjusted or so called, in practice, a variable control over the amount of the current flowing through tube 18.

The voltage Wave form of sec. 1-B has superimposed thereon, i. e., is modified by the wave form of sec. 1A, producing at its output the voltage wave form shown in Fig. 5, i. e., the wave form of sec. l-A is inverted, in effect, in the wave form of sec. l-B. The final resulting form of simultaneous action of secs. 1-A and l-B produces the form of wave shown in Fig. 6. In Fig. 7 the wave form of Fig. 6 is separately shown and constitutes a basis for comparison with the wave form which characterizes the light output.

Thus, it will be apparent, that the purpose of the Master Control Unit, which may be otherwise termed a lowfrequency control signal generator, is to give a gradual, varying voltage, which if plotted, would appear in general pattern similar to or resembling a sine curve. More accurately the curves will be seen as exponential charge and decay curves, according to the predetermined time constants and capacitance of the respective circuits.

The desired control signal for the Station Amplifier Unit is accomplished by the condensers 14 and 23 and the bleeder resistors 13 and 22, which in combination, eliminate the necessity of employing a motor-driven varying potentiometer. It follows that the elimination of the potentiometer results in the elimination of maintenance trouble, repair and costs of current or power for the motor.

The exact form of the voltage curve referred to, may be varied in magnitude and periodicity to produce the desired ultimate effect in the dimming and brightening cycle of the neon gas-filled tubes as above explained.

Station Amplifier Unit Reference is made now to the Station Amplifier or Unit, sec. 1-C, divided from the Master Control Unit by the dotted line AA for the purpose of illustration. The Station Amplifier Unit is electrically connected to said Master Control Unit by the leads 25 and 26 and the potentiometer 24. The lead 25 is connected to the grid of the triode tube 34 of the Station Amplifier Unit. The Master Control Unit biases the grid of tube 34 with a predetermined, automatically varying control signal, as

desired. The Station Amplifier Unit consists of power were ' leads 30 and 31 and four tubes, 35, 36, 37, 38, con- 34, through tube 38 and thence out through lead 31.

On the other half of the cycle, the electrons flow from lead 31, through tube 35, thence through tube 34 and thence through 37 to lead 30. The conventional neon or mercury gas-filled tube 32 in the form of a sign or portion of a sign is connected between the leads 30 and 3.1, as shown. Other gas-filled tubes or electrical loads can be. substituted for the sign 32. A transformer 33 is connected as shown to provide the desired output voltage.

Since the grid voltage of tube 34 is controlled by the Master Control Unit, the flow of electrons between the cathode and plate of tube 34 is controlled by the Master Control Unit. Thus, in turn, the flow of electrical energy between leads or conductors 30 and 31 is controlled by the voltage on the grid of tube 34. Thus, the timed cycle of dimming and brilliance of the sign lighting or output is provided entirely electrically and without, be it noted, any mechanical moving parts. i

The resistor 49 throughout the drawings is a current limiting resistor, same being true for 49M, 49N, 49a, 49b and 490.

In the event that the sign represented by tube 32 herein is not of such length as to produce an overload, then it would be possible under such circumstances to employ the Master Control Unit to operate additional instrumentalities by inserting or connecting the same in the conductor leading from tube 34 to 38 or from tube 36 to tube 34.

While the invention has been designed particularly for neon tube brilliance control, it is, nevertheless, obvious that it could be employed in any circuit in which an automatically varied or variable current or potential is desired to be electronically controlled without employing mechanically moving parts since, with the arrangement shown, the operator can change the form of the wave representing the voltage by proper setting of the resistors and preselection of the other circuit components to produce various periodic cycles and forms of curves. For example, by adjusting the impedance value of resistor 15, the over-all length of time for the cycle period is determined; by adjusting the impedance value of resistor 13, the length of time required for dimming the sign. Of course, it would be understood that increasing the impedance value of the resistors will increase the period or the curve component of the wave both in dimming and in increasing the brilliancy. In further adjusting the circuit time constants, the potentiometers 19 and 24 must be considered. By selecting a particular setting of the said potentiometers the degree of sharpness of the curves can be altered; that is, they can be softened, rounded or rendered more smooth and the change in the brilliancy of the sign would not be so abrupt. The maximum brilliancy and the maximum dimness can be controlled by the setting of the potentiometer 24. If the resistance setting of potentiometer 24 between leads 25 and 26 is increased, then the brilliance in the neon tube will be decreased and vice versa.

As illustrated, an alternating current as a source of electrical energy in conductors is connected to a transformer 11 and the plate of a rectifying tube 12 to produce a pulsating source of direct current. Of course, an equivalent of this would be any means for producing a pulsating direct current.

The source of energy for sec. l-B that is the modifier unit for said half cycle may be derived from the alternating current of conductors 10 with transformer 20 and rectifier tube 21. As an equivalent any source of direct current may be employed so that the transformer 20 and Since the invention is designed to function 10 rectifier tube 21 maynot be necessary. This direct cur rent need not be a pulsating current. In fact, while it will work with pulsating direct current, it is preferable not to use a pulsating current if a filtered direct current source is elsewhere available.

Another procedure of following the current is as follows, same being set forth for clearness of description: The direction of positive current flow is as follows: in section l-A, transformer 11 delivers current to the plates of full wave rectifier tube 12 and from the cathode of tube 12 to the plate of thyratron tube 17. From the cathode of tube 17 the current flows through the capacitor 16, variable resistor 15 combination to the parallel combination of capacitor 14, variable resistor 13 and potentiometer 19. Out of this parallel combination the current flows back to the center tap of the secondary of transformer 11 to complete the D.-.C. circuit. Note conductor 15x connected to the grid of the thyratron tube 17, which at certain times will supply negative bias to the grid of tube 17, and thus make possible the interruption, ofcurrent fiow in the plate circuit of the thyratron. The D.-C. supply is left unfiltered to provide short deionization periods of the gas in the thyratron tube so that the thyratron grid may at certain times gain control of the thyratron plate current.

The function of variable resistor 15 is to create the negative bias on the grid element of the thyratron tube 17. The function of capacitor 16 shunted-around resistor 15 is to allow an initial instantaneous flow of plate current in the thyratron for the purpose, as will be eX- plained later, of charging capacitor 14 before the current flow through resistor 15 can cause a negative bias on the grid of the thyratron which will cut oil the flow of thyratron plate current. The high negative bias on the thyratron grid is caused by the thyratron plate currentflowing through the cathode resistor 15. In other words, plate current flow produces negative grid bias, the grid bias stops the fiow of current which created the bias and at the instant that current flow stops, the grid bias gradually decreases to zero and allows plate current to again flow in the thyratron. The gradual decrease of grid bias is obtained as follows: capacitor 16 has become charged during this instant of current flow, the charged capacitor supplies the negative grid bias to the thyratron :after plate current flow ceases and thus keeps plate current from flowing for the period of time required for the capacitor voltage to decay to almost zero. The time required for the capacitor voltage to drop is determined by the RC time constant of resistor 15 and capacitor 16. When this gradually decreasing grid voltage reaches a certain low value, it no longer stops the flow of plate current and plate current will again flow for an instant, that is, just long enough to recharge capacitor 16 At this time the grid bias becomes high and again stops the plate current flow until such time that the voltage of capacitor 16 decreased, due to bleeder resistance 15, to a value low enough to allow the flow of plate current to start the next cycle. Variable resistor 15 serves two purposes, first, as the cathode resistor to supply negative voltage to the grid of the thyratron while plate current is flowing in each cycle and, second, it serves as the bleeder resistor for capacitor 16 during the rest of the cycle. Since the. resistance of resistor 15 determines the length of time required for the voltage of capacitor 16 to decrease to a low value, it therefore, determines the frequency of the cycle.

Resistor 15 is a variable resistor which makes it possible to select the desired frequency.

The wave form of the thyratron tube 17 plate current is shown in Fig. 2 by vertical line 50. The wave form of voltage impressed upon the grid of thyratron tube 17 byresistor 15 and capacitor 16 is shown in Fig. 3 by lines 50 and 51.

It should be noted, that the initial surge of thyratron plate current which marks the beginning of each cycle, Fig. 2, cannot take place until the negative grid bias supplied by capacitor 16, shown as curve 51 of Fig. 3, has gradually decreased to a value so low that it can no longer stop the flow of thyratron plate current.

The RC time constant of capacitor 14 variable resistor 13, also included in section l-A of Figure 1, need not have the same RC time constant as capacitor 16 resistor 15 combination which determines the frequency. One of the voltage wave forms obtainable across the terminals of capacitor 14 is shown in Fig. 4 by lines 52 and 52M, that is, for any one selected frequency.

Potentiometer 19 connected across capacitor 14 of section 1A in Figure 1 supplies negative bias to the grid of vacuum triode tube 18 in section 1-B. Section l-B is basically an amplifier circuit which will be used not as an amplifier but as a means of inverting the voltage wave produced across the terminals of capacitor 14 in section l-A. One of the many possible inverted waves is shown in Fig. by lines 53 and 53M. As stated above, section l-B inverts the voltage wave of section 1A and in addition, section 1-B produces a component of the voltage wave of its own which it adds to the inverted wave. The added component of voltage wave is shown as curve 54 in Fig. 6. The resulting voltage wave is the final signal voltage that is sent to the Station Amplifier Unit in each neon tube circuit to control the light output.

It is possible for section 1-B to produce its own component of voltage wave form and add it to the inverted wave because of the parallel combination consisting of variable resistor 22, capacitor 23 and potentiometer 24, which is connected as the load on amplifier circuit section lB. The gradually increasing current flow in section lB which in a sense is the inverted wave of section 1A, Figs. 5 and 6 curve 53, gradually increases the voltage drop across resistor 22 which in turn increases the voltage impressed upon capacitor 23. The voltage across capacitor 23 will rise to its maximum value at a desired rate and will remain at this maximum voltage until such time that thyratron tube 17 starts a new cycle, i. e., is cut off. When the new cycle starts, the current flow in section l-B is instantly cut off but the voltage across capacitor 23 will decay at a rate determined by its RC time constant. Thus, the component of voltage wave form shown in Fig. 6 as curve 54 is produced.

The portion of the final voltage wave form produced by section l-B is forced to have the same frequency as the inverted voltage wave controlled from section l-A, but the wave form of the added component, curve 54 in Fig. 6, produced by section 1-B need not be symmetrical with the inverted wave form curve 53, Fig. 6.

Curves 53 and 54 can each be varied from an almost vertical position to an almost horizontal position by means of variable resistors 13 and 22, respectively, assuming the time dimension constant. Variable resistor 15 independently controls the control cycle frequency. Potentiometer 24 controls the maximum value of signal voltage to the Station Amplifier Units, yet to be described, and the potentiometer 19 will vary the shape of either the top or bottom half of the final voltage wave produced by the Master Control Unit. Thus, the Master Control Unit produces an extremely low frequency control signal where frequency, all components of wave form, and magnitude of voltage may be selected.

Station Amplifier Unit The Station Amplifier Unit circuit diagram is shown as section l-C of Figure 1. It consists of a bridge rectifier circuit using half wave rectifier tubes 35, 36, 37 and 38. A vacuum triode tube 34 is connected across the D.-C. portion of the bridge rectifier as shown. The alternating current flowing in the neon tubes is rectified so that both halves of the 60 cycle A.-C. flow as rectified unfiltered 111-0. through vacuum triode tube 34.

The low-frequency control signal produced by the Master Control Unit is impressed upon the grid of the vacuum triode 34 by means of conductors 25 and 26.v This grid bias controls the unfiltered direct current flow-- ing in the plate circuit of the vacuum tube 34 and, therefore, controls the flow of 60 cycle alternating current in the neon tubes. The 60 cycle alternating neon tube current wave is a reproduction of the voltage wave produced by the Master Control Unit.

Since the brilliance of a neon tube is a direct function of current, the light output of neon tubes will vary auto matically in a cycle of brilliance, fading and then gradual returning to full brilliance in a timed cycle as determined by the control signal from the Master Control Unit.

In the modification shown in Fig. 9 there is shown diagrammatically an electronic arrangement similar to the circuit of Fig. l and also suitable for automatically generating a varying voltage in the Master Control Unit and controlling either voltage or current in the Station Amplifier Unit.

Parts of the circuits of Fig. 9 which are the same as: in Fig. l are given the same numbers with the subscript a added thereto for facilitating the identification of parts.

This modification (i. e. the circuit of Fig. 9 as compared with that of Fig. 1) consists in eliminating some of the parts described and shown in connection with Fig. l, and replacing those parts with another circuit which will produce the same final results as achieved with the arrangement of Fig. 1 but of a character which may be employed in a plurality of circuits for a plurality of tubes to produce desired synchronization thereof.

The parts of sec. 1A not appearing in the corresponding circuit portion of Fig. 9, i. e. sec. 9-A are variable resistor 15, condenser 16, and the conductor 15x connecting these parts with the grid of tube 17. Modification, in terms of reconstruction of the circuit, is begun by connecting the cathode of the tube 17 to ground 40.

Other parts added, as shown, in Fig. 9, include the potentiometer 41 across the output of sec. 9-13 in parallel with potentiometer 24; the sec. 9-D comprising a transformer 42, triode tube 43, and a rectifier tube 44.

In Fig. 1, sec. l-A circuit is capable of operating by itself; that is, it is self starting and then it operates and impresses its operation upon the circuit sec. l-B and the resultant action of lA and lB is transmitted to lC. Relative the circuit of sec. l-A is self starting: This self starting arises by reason of the fact that the resistor 15 momentarily operates to hold back the electrons and impose a negative potential on the grid of the tube 17. However, just before this completes this complete negative operation by implanting the negative potential on the grid, there is a leaking of electrons through the condenser 16. At the first instant of each cycle the electrons flow through the condenser 16 and through the tube 17. After this first instant, the electrons will no longer pass through the condenser 16 (since same will have become charged and no longer is there a change of voltage as required for a current to pass through a condenser or as often now called capacitor), but flow through resistor 15, creating a negative bias or voltage on the grid of tube 17. This results from the following: The resistor reduces the electron flow through the resistor thereby building up a potential which-also builds up a potential on the grid. It is to be particularly noted that there is a connection 15x from the resistor to the grid. This conductor makes it possible to build negative potential on the grid.

In the embodiment of the invention illustrated in Figure 1, reviewed here for later comparison with the modification thereof illustrated in Fig. 9, the condenser 16 and the resistor 15 render the circuit of sec. 1A self starting. Further, in the sec. l-A circuit in Figure l, the electron flow passes from the transformer 11 to the resistor 13 and then to the condenser 16 during only the first instant of the cycle, and on through the tube 17.

:13 Whilethis is occurring, the potential is developed to a point that it places a negative potential on grid of tube 17, then this is sufficient to stop the flow of the electrons to the condenser 16 momentarily. Since the electron flow now has been stopped, .then gradually the negative potentialon the grid of tube 17 decreases to value so low that it loses its effectiveness and can no longer interrupt a structure of a sign for a colored display, we may have one gaseous, as a neon, tube over or laterally adjacent another gaseous tube, as for example, a mercury tube. Thus, the operation of the tubes successively must be sharply synchronized in producing the desired effect, i. e., one must be definitely terminated and the other must light up immediately thereafter to provide the proper effect. This synchronization is necessary in order to provide control of a desired blending effect for a multicolored sign.

The above requirements for synchronization are met by the circuit arrangement set forth in Fig. 9, wherein transformer 42 and rectifier tube 44 supply power to triode tube 43 which operates as an amplifier tube just as the triode tube 18 does in sec. 9-B, which sec. 9B in turn directly corresponds with sec. 1-B, of Figure 1, previously described. Across "the output of sec. 9-D is a potentiometer 45 which may be termed the load of circuit of 9-D. The selector contact of the potentiometer 41 is connected to the grid of triode tube 43 by a conductor 46. The potentiometer 45 has its selector contact connected to the grid of thyratron tube 17 by a conductor 47.

Sec. 9A is not self starting as is see. 1-A already described above. In the case of 9A, it performs its operation, and this is imparted upon sec. 9-B. When it has imparted its operation upon sec. 9B, then sec. 9A closes and shuts down operation. Sec. 9-B having been started inoperation, it performs its function in effecting the form of the voltage wave and it likewise concludes its operation and shuts down. However, it does not do so until it has in turn imparted its operation upon the circuit of sec. 9-D and started 9-D in operation. Then 9D performs its function and before it concludes its operation, however, it has a conductor returning to sec. 9A. This starts sec. 9A over again and thus the cycle ofoperation continues. Hence, this arrangement or circuit provides for a definite time of starting the circuit of sec. '9--- A and a definite time of startingof the circuit of sec. 9 B and aastarting of circuit of sec. 9D, which i. e. 9D may be termed a recycling circuit, as well as a conclusion of operation of each one of these sections.

The combined operation of sec. 9A, sec. 9-B and sec. 9D is as follows: Sec. 9A controls the operation of sec. 9B; sec. 9B controls the operations of sec. 9D, and. sec. :9-;-D controls the operation of sec. 9A. The

.time. required for the complete cycle to be developed is dependent upon the total resistance across the output of sec. 9A and sec. 9-B. Resistors 13a and22a in sec. 9A and sec. 9-B, respectively, regulate the time required to discharge condensers 14a and 23a in sec. 9A and sec. 9-B, respectively. A ground 50 is provided in connection with conductor 26a in the Station Amplifier Unit, to correspond with ground 40 of this lead in the Master Control Unit.

The above sets forth the definite operation for a one color system of sign tubing. It provides for the definite 14 starting and concluding ofincreasing the brilliance in the single tubingto high brilliance and .then to dinmess.

By employing the modification shown in Fig. 9 .it ;is possible to produce the same lighting effect ,as .is described in connection with Fig. l. Theadvantages, however, are theadded varying effects in electrical advertising, and the further applications in several industrial fields, wherein the Master Control Unit of Fig. .1 could not be employed since it would not provide the precise cycle repetition rate which characterizes the operation of the modified circuit of Fig. 9.

If it is desired to 'have a second colored tube synchronized in its operation with the first colored tube, then that would beaccomplished as set forth in themodificationof Fig. 10. In Fig. 10 is a reproduction of sections 9A, 9 B, 9C and 9-D of Fig. 9. The sections in Fig. 10 corresponding to the sectionspresented in Fig. 9 are identified as sections 10-,A, 10 B, lO-C and 10- D for one color tu be of the multi-tube system. For a second color tube, there is the reproduction oflike sections, designated as sections 10A 10-3 1().C and l0-D More particularly and in detail in, Fig. 10 is represented .said circuit of Fig.9 employed with other like .unit circuits in a .sign having a plurality of different gaseous tubes, each of a different color or effect, which plurality of tubes is to be operated sucessively in synchronization.

;In Fig. 10,,circuits of secs. 10A, lO-B, 10-C and 10- D ,are the circuits for controlling theoperating of one tube, for example, the neon or red tube. The other part of the Fig. 10, namely, the circuits of secs. l0-A ,110-'B 10-C and 10-D are the circuits for operating the s econd colored tube, namely, the mercury or blue tube.

Parts of. the circuitsof Fig. 1 0 are the same as those for the circuits of Fig. 9 and accordingly said like parts are given the same number with the subscript. (b) for the neon or red tu-beand the subscript (c) for the mercury .or blue tube.

Master Control Unit for the blue tube. .60 extends from the potentiometer 456 of the Control InFig. 10 the conductor 50 extends from the potentio meter 45b of the Master Control Unitfor the red tube to the grid ofthyratron tube .17c of sec. 10-A of the The conductor Unit for. the blue tube to the grid of .thyratron tube 17b ,of sec. lO-A of the Master Control Unitfor the red tube.

The operation of the corresponding parts ofthe circuits shown in Fig. 9 and in Fig. lO are identical in all resQects and accordingly vwill notberepeated in the interest of brevity.

Since,- as pointed out above, the operation of circuit IO-Ain a given .cycle completes its eration and then ceases to operate, but not until it has started the operation of the. circuit of l0-B. Circuit of sec. IIO-B in turn completes its operation for the given cycle and ceases to operate, but not until it has started the operation of the circuit of sec. 10.,'D. Circuit of secplO-D in turn com- .pletes its operationfor the given cycle and then ceases .to operate, butnot untilit has started or triggered the v. and 1-0.D. Sec. Ill-D doesnot cease its operation until it has started the circuit of sec. 10-A through conductor connected to the grid of thyratron tube 17b; tl1at.is, the tube in the Control Unitfor the red tube.

Since the operation of the circuit of the said sections all, operate in definite time sequence, one following the other, provision is. thus madefor precise cycle repetition rate and synchronization of the dimming and brilliance of the separately colored tubes.

Fig. 11 is a representation of a modified form of the circuit of sec. 1-A of Fig. 1. In this modifiedform, a transformer 70 delivers alternating current power from the source line71 and thence to a rectifier 72 when main switch 73 is closed. The rectifier may -be of any type, but that shown is a full Wave vacuum type in combination with a center tap type transformer 70 which is considered the preferred and most practical type for this use. Electron flow starts from the center of transformer 70, thence through impedance 49N, adjustable variable resistor 74, through and charging the condenser 75, thence from resistor 74 and condenser 75 to the cathode of tube 76. Impedance 49N functions as impedance 49 and like impedance 49, may be omitted. Tube 76 is a gaseous type control rectifier tube, known as a thyratron. The tube 76, which is herein supplied with power from transformer 70 and rectifier 72 is a gaseous triode operating on a low-pressure gas. From the plate of the tube 76, electrons flow back to the rectifier tube 72 to complete the direct current (D. C.) circuit.

The operation of the part of this modified form of circuit follows the same operation as that set forth in detail for corresponding parts of the circuit of sec. l-A of Fig. 1. The operation of sections 1B and 1D; that is, of the other sections, all operate as set forth in detail for the corresponding section of Fig. 1.

The diiferences betwen the circuit as set forth in sec. l-A of Fig. l and the circuit of sec. 11-A of Fig. 11 are as follows: In sec. 1-A, there are two independent control means, one for selection of frequency; that is by means of adjustable resistor 15, and one for selection of the wave form; that is by means of adjustable resistor 13. In the modified circuit of sec. 11-A illustrated in Fig. 11, there is but one control means; namely, adjustable resistor 74, so that when a desired frequency is selected, then there is automatically selected an inherent wave for that wave form for that particular frequency.

In choosing a load circuit for purposes of definiteness of illustration and clearness of disclosure, 2. load circuit of the character requiring a constant voltage has been adopted. It requires a substantially constant voltage to' maintain the ionization of the gas used in the gaseous tube. Accordingly, a tube 34 of a character which would supply a constant voltage has been adopted as the tube 34 in the amplifying circuit. However, in other load circuits, it may be important to have the current relatively constant and the voltage vary. When such is the situation, then a vacuum tube diiferent from that used in 34 would be employed; viz, a vacuum tube having different characteristics-one which would give a relatively constant current and permitting a varying of the voltage. The Master Control Unit would all be the same where the latter situation is desired, viz, where the current is to be maintained relatively constant and the voltage varied.

In Fig. 12, impedance 90 is connected between the cathode and plate of vacuum triode tube 34; functioning among other purposes to prolong the life of the tube, to limit the plate voltage of said tube 34, when used with neon tubes as a load, to prevent deionization of the gas; i. e. complete extinguishing of the light, and to adapt the circuit to loads other than lighting. Impedance 91 (with or without impedance 90) may be connected between electrical conductors 30 and 31 and would function in addition to those named above for impedance 90 to protect rectifier tubes 35, 36, 37 and 38, together with associated parts of said tubes such as filaments. Impedance 90 or 91 may be omitted where their respective functions are not desired or required.

In Fig. 12, the vacuum triode tube 34 is illustrated as positioned within the bridge of the station amplifier unit, i. e. it is connected in series in the D. C. portion of the bridge rectifier circuit and is in all respects electrically identical to that shown in sec. 1-C of Figure 1 and like sections of the other figures.

While for purposes of illustration several forms of this invention have been disclosed, other forms thereof will become apparent to those skilled in the art upon reference to this disclosure, and, therefore, this inven- 16 tion is to be limited only by the scope of the appended claims and prior art, when the same are construed in the light of the disclosure herein. In short, equivalents are to be deemed included herein.

My invention and discovery has been constructed and incorporated in specific embodiments in accordance with the herein specification and as set forth in the drawings Figs. 1-12 inclusive, and such embodiments have been successfully operated. The elements, tubes and equipment in these embodiments operating on a timed cycle of the range of one second to about one minute, i. e. high brilliance to high brilliance, employed circuit constants or values for the respective elements, capacitors, potentiometers, resistors, transformers and internal pressure of the discharge lamp loads as follows:

Fig. 1

Transformers 11 and 20 have primary winding 100 volts, secondary 700 volts with a center tap.

Tubes 12 and 21 are standard 5Y3 rectifier tubes.

Tube 17 is a standard thyratron tube 2050.

Adjustable resistor 15 is a one megohm potentiometer.

Condenser 16 is a one microfarad condenser, 400 volts.

Adjustable resistors 13 and 22 are each 3 megohm standard volume controls.

Potentiometers 19 and 24 are standard 10 megohm potentiometers.

Condensers 14 and 23 are each 2 microfarad condensers, 400 volts.

Resistors 49 and 49M are each 500 ohm carbon resistors.

Tube 34 is a 211 standard transmitter triode.

Tubes 35, 36, 37, and 38 are standard 816 half Wave mercury rectifiers.

Neon tube 32 may be any gaseous discharge tube of inside diameter of 20 mm. and with a gas pressure ranging from about 0.5 millimeter of mercury to about 20 millimeters of mercury.

Transformer 33 is any ordinary neon tube transformer-the one used here has a primary voltage of 110 volts, 60 cycles, and a secondary voltage of 2500 volts.

All electrical conductors 15X, 25, 26, 30, 31 and all of the conductors connecting in element sections l-A and 1-B are of ordinary number 14 gauge insulated wire insulated for 400 volts.

Tube 18 is a 6P5 standard vacuum triode.

Figs. 9 to 12 Transformers 11a, 20a and 42 have primary windings volts, 60 cycle, and secondary winding 700 volts with a secondary center tap.

Tubes 12a, 21a and 44 are standard 5Y3 full wave rectifier tubes.

Tube 17a is a 2050 standard thyratron tube.

Adjustable resistors 13a, 22a are standard 3 megohm potentiometers.

Condensers 14a and 2311 are each 2 microfarad condensers, 400 volts.

Potentiometers 19a, 24a, 41 and 45 are each rated at 10 megohms.

Tubes 18a and 43 are 6P5 standard vacuum triodes.

Tubes 34a and 34 are standard type 211 transmitter triodes.

Tubes 35, 35a, 36, 36a, 37, 37a, 38, and 38a are type 816 standard half wave mercury rectifier tubes.

Conductors 26a, 25a, 30a and 31a and all conductors connecting the component elements are all number 14 gauge insulated wire.

Neon tube 32a may be any gaseous discharge tube of inside diameter of 20 millimeters and a gas pressure of about 0.5 millimeter of mercury to 20 millimeters of mercury. fl

Transformer 33a is any ordinary neon tube transformer,

17 the one used here has a primary voltage of 110 volts, 60 cycles and a secondary voltage of 2500 volts.

Resistors 49a are all 500 ohm carbon resistors.

Fig. 10

Transformers 11b, 11c, 20b, 200, 425 and 420 each have a primary Winding 110 volts, 60 cycles, and a secondary winding 700 voltswith a center tap.

Tubes 12b, 12c, 21b, 210 are standard Y3 rectifier tubes.

Tubes 17b, 17c are 2050 standard thyratron tubes.

Adjustable resistors 13b, 13c, 22b and 22s are 3 megohrn potentiometers.

Condensers 14b, 140, 2315, 230 are each 2 microfarad condensers.

Potentiometers 19b, 19c, 24b, 24c, 41b, 41c, 43b and 450 are all rated at megohms.

Tubes 18b, 18c,43b,"43c are 6P5 vacuum triodes.

Transformers 32b and 32c are ordinary neon tube transformers, those usedhere have a primary voltage of 110 volts at 60 cycles and a secondary voltageof 2500 volts.

Resistors 49b and 49c are 500 ohm carbonresistors.

Tubes 34b and 340 are standard 211 type transmitter triodes.

Tubes 35b, 35c 36!), 36c, 37b, 37c, 38b and 38c are all type 816 'half wave mercury. rectifier tubes.

Conductors 25b,25c,26b, 26c, 30b, 30c, 31b, 31c, and 60 and all conductors connecting component units or elements are number 14 gauge insulated wire conductors, with insulation for 400 volts.

Light tubes 32b and 320 may be any gaseous discharge tubes of inside diameter of 20 millimeters anda gas pressure of about 0.5 i020 millimeters of mercury, the difrference between 32b.and 32c being-the color of the light producedbythe tubes.

Fig.1]

Transformers "70 and20-each have a primary voltageof 110 volts 60 cycles, and a-secondary voltage of 700 volts and a secondary center tap.

Tubes 72 and 121 are each type5Y3 rectifier 'tubes.

Tube 76 is a standard 2050'thyratron;

Adjustable resistors 74 and .18 are 'each 3 megohm standard potentiometers.

Condensers and .23 are 2 microgaradcondensers.

Potentiometers 19"and1 2141are'eachratedat l0 megohms.

Resistors 49N'and49M are. 1000 ohm carbonresistors.

Conductors 25 and26 andall conductors connecting component unitsor elements are 14 :gaugewire conductors with insulationl for 400 volts.

The units or elements in general have thesame values and identities as set forth for the corresponding parts illustrated in Fig. 9. Impedances 90 and '91 :were of same valueand such irnpedance Wassupplied by neon tube 32a forelement 01. Impedance 9t may be a similar and equal load (not necessarily, however, equal) and provided by a neon tube. Impedancein-thisFig. 12 may be any impedance as-thoseinvolved in applying the circuits of my invention and discovery inexperimentation as stated. As willbe understood by those skilled in the art, the range of value for such impedances may vary widely.

If desired'to increase the time cycle fromone minute to two minutes, then one would approximately. doublewthe resistance of the adjustable resistors, or leavetheresistors unchanged and double the capacitance rating of the condensers employed that is, for a, general ruleprovide resistor-condenser combinations which have a R.-C. time constantproportional to the desired increasein the, length of the time cycle.

Specific values, ratings. andcharacter of .meanshave been given by way. of illustration, not limitation. They do disclose a general relationship and teach those skilled in the art how to adapt the invention and discovery to specific applications. The invention and discovery is not 18 adapted to be defined by any all inclusive formula for values, ratings and means in all cases. But the relationship is set forth, so that those skilled in the art may readily know how to apply the invention and discovery.

I claim:

1. A low-frequency signal generator comprising a re.- laxationoscillator of the grid-controlled thyratron type having in the blocking circuit thereof a time constant network and having in the output circuit thereof a time constant network intermittently charged from a direct current source, said low-frequency signal generator further comprising means for selecting; at least a portion of thesignal developed across the second-mentioned time constant network and impressing the same on the grid of a grid-controlled vacuum tube having in the plate. circuit thereof a time constant network intermittently charged from a second direct current source, and means for, se

lecting at least a portion of the signal generated across said last-mentioned time constant network as the output low-frequency signal.

2. A low-frequency signal generator capable of wide variation in. output .waveform, comprising a relaxation oscillator of the. grid-controlled thyratron type having in the blocking circuit thereof a variable time constant network ,andhaving in the output circuit thereof a second variable time constant network intermittently charged through a rectifier, said. low-frequency signal generator further comprising variable means forselecting at .least a portion of the signal developed across said second time constant network and impressing the sameon the grid ofa grid-controlled vacuum tube having in the plate circuit thereof a variable time constant networkrintermittently charged through asecond rectifier, and variable means for selecting at least a portionof the signal generated across said last-mentioned time constant network asthe output low-frequency signal.

3. A low-frequency signal generatorcapable ofwide variation in output signal waveform, comprising a relaxation oscillator of the grid-controlled thyratron type havingin the blocking circuit thereof'a first variable means including a time constant network .for adjusting the repetition rate of the output signal, saidv thyratronhaving in the plate circuit thereof a, second variable means includinga time constant network intermittently charged throughea rectifier circuit under control of said thyratron, said second variabledmeansadjusting the rate of voltageincrease of said, output signal, ,said low-frequency signalgenerator further comprising ,a third .variable means .for selecting at least .a portion of thesignal developedacross said second-mentioned time constant network .to selectively adjust the shape of saidoutput signal at the maximum and minimurnvoltage portions thereof, such selected signal .beingimpressed upon .the grid of a grid-controlled amplifier having in the plate circuitthereof a fourth variable means including a time constant network intermittently chargedthrough, a second rectifier circuit under control of said amplifier, said fourth variable means adjusting the rate. of voltage decrease of said output signal, and a fifth variablemeans for selecting at least a portion of the signal generated' across said last-mentioned time constant network to determine the amplitude of said output signal.

4. An illumination display system comprising a gaseous display tube,..-means for supplying a high-voltage alternating current to said display tube, variable impedancemeans in circuit with said gaseous display tube, and a low-frequency control signal, generator for varying the: impedance of said variable impedance means said low-frequency signal generator comprising a relaxation oscillator of the grid-controlled thyratron type having in the blocking circuit'thereof a time constant network and having in the output circuit thereof a time constant network intermittently charged through a rectifier circuit, said low-frequency control signalgeneratorfurther comprising means for selecting at least a portion of the signal developed across the second-mentioned time constant network and impressing the same on the grid of a grid-controlled vacuum tube having in the plate circuit thereof a time constant network intermittently charged through a second rectifier, and means for selecting at least a portion of the signal generated across said last-mentioned time constant network to control the impedance of said variable impedance means.

5. An illumination system according to claim 4 wherein said relaxation oscillator is free-running.

6. An illumination system according to claim 4 wherein at least a portion of the output of said low-frequency signal generator is impressed on means developing a trigger pulse in turn connected by feed back means to the grid of said relaxation oscillator to precisely maintain the repetition rate of the low-frequency control signal generator.

7. An illumination system according to claim 4 wherein said variable impedance means comprises a bridge rectifier network with the alternating current terminals thereof connected in series with said display tube, said bridge rectifier network also including a grid-controlled vacuum tube having the plate and cathode thereof respectively connected to the positive and negative direct current terminals of said bridge rectifier network, the selected output of the the low-frequency control signal generator being impressed on the control grid of said latter-mentioned vacuum tube.

8. An illumination display system comprising a gaseous display tube, means for supplying a high-voltage alternating current across said display tube, variable impedance means in series with said gaseous display tube, and a low-frequency control signal generator for varying the impedance of said variable impedance means to cause cyclic variation in the illumination intensity of said gaseous display tube, said low-frequency control signal generator comprising a relaxation oscillator of the gridcontrolled thyratron type having in the blocking circuit of said thyratron a variable time constant network and having in the plate circuit of said grid-controlled thyratron a variable time constant network intermittently charged through a rectifier, said low-frequency signal generator further comprising variable means for selecting at least a portion of the signal developed across the second-mentioned time constant and impressing the same on the grid of a grid-controlled vacuum tube having in the plate circuit thereof a variable time constant network intermittently charged through a second rectifier, and variable means for selecting at least a portion of the signal generated across said last-mentioned time constant network to control the impedance of said variable impedance means, causing corresponding variation in the illumination intensity of said display tube.

9. An illumination display system comprising a gaseous display tube, means for supplying a high-voltage alternating current across said tube, variable impedance means in circuit with said gaseous display tube to cause variation in the illumination intensity thereof, and a low-frequency control signal generator for producing a control signal to vary the impedance of said variable impedance means, said generator comprising a relaxation oscillator of the grid-controlled thyratron type having in the blocking circuit thereof a first variable means including a time constant network for adjusting the repetition rate of said control signal, said thyratron having in the plate circuit thereof a second variable means including a time constant network intermittently charged through a rectifier circuit under control of said thyratron, said second variable means adjusting the rate of voltage increase of said control signal, said low-frequency signal generator further comprising a third variable means for selecting at least a. portion of the signal developed across said second-mentioned time constant network to selectively adjust the shape of said control signal at the maximum and minimum voltage portions thereof, such selected signal being impressed upon the grid of a grid-controlled amplifier having in the plate circuit thereof a fourth variable means including a time constant network intermittently charged through a second rectifier circuit under control of said amplifier, said fourth variable means adjusting the rate of voltage decrease of said control signal, and a fifth variable means for selecting at least a portion of the signal generated across said last-mentioned time constant network to determine the amplitude of said control signal.

10. A system according to claim 9 wherein said relaxation oscillator is free-running.

11. An illumination system according to claim 9 wherein at least a portion of the output of said lowfrequency control signal generator is inverted in phase to provide a trigger pulse, and means for impressing said trigger pulse on the blocking circuit of said relaxation oscillator to precisely maintain the repetition rate of said low-frequency control signal generator.

12. An illumination system according to claim 9 wherein said variable impedance means comprises a bridge rectifier network with the alternating current terminals thereof connected in series with said display tube, said bridge rectifier network also including a grid-controlled vacuum tube having the plate and cathode thereof respectively connected to the positive and negative direct current terminals of said bridge rectifier network, the selected output of the low-frequency control signal generator being impressed on the control grid of said lattermentioned vacuum tube.

13. An illumination control system comprising a plurality of gaseous display tubes; means for supplying a high-voltage alternating current to each of said display tubes; and a plurality of illumination intensity control means, one in circuit with each of said display tubes, each such control means comprising a variable impedance means controlled by a low-frequency control signal generator including a relaxation oscillator, each said illumination intensity control means further comprising means for impressing at least a portion of the low-frequency control signal produced by each said generator on the associated variable impedance means to cyclically vary the impedance thereof; and a re-cycling circuit for developing a trigger signal from the output of one of said control signal generators and delivering such trigger signal to the relaxation oscillator circuit of a second of the said generators to provide synchronization therebetween and produce cyclically related variation in the illumination intensity of said display tubes.

14. An illumination control system comprising a plurality of gaseous display tubes; means for supplying a high-voltage alternating current to each of said display tubes; and illumination intensity control means associated with each of said display tubes, each such intensity control means comprising a bridge rectifier network with the alternating current terminals thereof connected in series with an associated display tube, said bridge rectifier network also including a grid-controlled vacuum tube having the plate and cathode thereof connected to the direct current terminals of said bridge rectifier network, each said illumination intensity control means further comprising a low-frequency control signal generator in cluding a relaxation oscillator, each said illumination intensity control means further comprising means for impressing at least a portion of the low-frequency control signal produced by said generator on the grid of the associated grid-controlled vacuum tube to cyclically vary the impedance of the associated rectifier network; and a recycling circuit for developing a trigger signal from the output of one of said control signal generators and delivering such trigger signal to the relaxation oscillator circuit of a second of said generators to provide synchronization therebetween and produce cyclically related 21 variation in the illumination intensity of said display tubes.

15. An illumination control system comprising a plurality of gaseous display tubes; means for supplying a high-voltage alternating current to each of said display tubes; illumination intensity control means associated with each of said display tubes, each such control means comprising a variable impedance means, each said illumination intensity control means further comprising a low-frequency control signal generator including a variable frequency relaxation oscillator of the grid-controlled thyratron type; and means for impressing at least a portion of the low-frequency control signal produced by said generator on the control circuit of said variable impedance means to cyclically vary the impedance thereof; and a synchronization circuit including means for generating a trigger signal from the low-frequency control signal produced in one of said generators and means for delivering said trigger signal to the relaxation oscillator thyratron blocking circuit of a second of said generators to provide synchronization therebetween and produce cyclically related variation in the illumination intensity of said display tubes.

16. An illumination control system according to claim 15 wherein said synchronization circuit further includes means for generating a second trigger signal from the low-frequency control signal produced by said second generator and means for delivering said second trigger signal to the relaxation oscillator thyratron grid of said first low-frequency control signal generator.

17. An illumination control system according to claim 16 wherein said first and second trigger signals are related in phase to cause inverse variation in the illumination intensity of said display tubes.

References Cited in the file of this patent UNITED STATES PATENTS 1,898,827 Franklin Feb. 21, 1933 1,926,181 Schramm Sept. 12, 1933 2,005,893 Gulliksen June 25, 1935 2,008,494 Elder et al. July 16, 1935 2,275,308 Niemann Mar. 3, 1942 2,457,176 Preisman Dec. 28, 1946 2,522,492 Anderson Sept. 19, 1950 2,760,069 Cole Aug. 21, 1956

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