US2365568A - Signaling system - Google Patents

Description

Dec. 19, 1944. N. LANGER SIGNALING SYSTEM 2 Sheets$heet 1 Filed July 20, 1942 azfa. W

HTTOANEY Dec. 19, 1944. LANGER 2,365,568

SIGNALING SYSTEM Filed July 20, 1942 I 2 Sheets-Sheet 2 m m v INVENTOR. ANCHOL /75 A fiNE/P HTTOR/VEY Patented Dec. 19, 1944 SIGNALING SYSTEM Nicholas Langer, New York, N. Y., assignor to Central Commercial Company, Chicago, 111., a corporation of Illinois Application July 20, 1942, Serial No. 451,581

8 Claims.

This invention relates to signaling systems and particularly to electrical systems employing gaseous discharge tubes as signal sources from which predetermined tone signals are adapted to be selectively transmitted to an electroacoustic translating device for conversion thereby into audible sound.

As those skilled in the art know, oscillators employing gaseous discharge tubes, such as glowdischarge tubes, neon tubes, and the like, are generally based on the property of such tubes that there is a difference of definite and more or less constant character between the break-down voltage of 'the tube, at which it becomes conductive,

and the extinction voltage of the tube, which is the lowest voltage at which the tube still is conductive after discharge through the tube has been initiated. The extinction voltage is substantially lower than the break-down voltage, depending upon various factors, such as principally the type of gas included within the tube, its pressure, the shape and arrangement of the electrodes, etc. Tubes of this type may be connected in various ways with capacities, resistances and a source of direct current to produce electrical oscillations by alternately charging and discharging the capacities in the circuit. The principal advantage of these oscillators is their small dimensions and inexpensive character, particularly when twoelcctrode gaseous discharge tubes with a cold cathode are employed.

One of the disadvantages of these oscillators Was the relatively small amount of oscillatory energy that could be directly obtained, particularly when the more inexpensive and smaller coldcathode gaseous discharge tubes having only two electrodes, were used. This relatively low output was in part caused by the relatively small amount of current passed by the cold-cathode, two-electrode tube in the conductive state, and was also due to the fact that a relatively high resistance of the order of several hundred thousand ohms up to several meghoms had to be connected in series with the tube, in order to produce oscillations. Obviously, this greatly reduced the output of the oscillations produced.

An object of my invention is to take advantage of the low production and maintenance cost, recognized simplicity, durability, longevity, small size and other favorable characteristics of gaseous discharge tubes, and to arrange same in an electrical frequency generating and distributing system so that, as oscillation sources, said tubes will generate substantially more useful voltage than heretofore has been possible.

Another and more specific object is to provide an oscillation generator in which two-electrode gaseous discharge tubes, of each individual group of tubes employed function collectively to produce oscillatory energy at a voltage which is the sum of the individual tubes of said group of tubes and wherein the resultant Waveform of useful voltage is always maintained exactly in accordance with predetermined calculations.

It is a further object to provide a frequency generating and distributing system in which each individual oscillation generator employed, itself consists of substantially identical two-electrode, cold-cathode glow-discharge tubes connected in series for substantially simultaneous and synchronous break-down and extinction of the serially connected discharge paths, whereby the tubes function in electrical coaction with each other to insure the handling of increased oscillatory energy.

Still another object of the present invention is to provide a group of oscillators, each employing a plurality of serially connected, two-electrode, cold cathode, gaseous discharge tubes, said oscillators being approximately tuned to harmonically related frequencies and being automatically maintained in the exact harmonicall related frequencies by impressing oscillatory energy obtained from each oscillator upon at least another one of said oscillators.

It is also within the contemplation of the invention to provide an electrical frequency generating system in which a large number of oscillation generators is employed, each including a plurality of serially connected glow-discharge tubes, said oscillators being arranged in groups including only harmonically related frequencies, high oscillatory potentials derived from each oscillator being impressed upon at least another one of said oscillators by means of an external, capacitively operative electrode, to maintain their predetermined harmonic relationship constant.

Another important object of the invention is to provide a plurality of groups of harmonicall related oscillators and switching means under the control of an operator to draw oscillatory energy from any desired number of oscillators at a time, means for normally maintaining said group in an inoperative condition, and means operable by said switching means to initiate the operation of such groups from which at least one oscillation is to be withdrawn.

Other and further objects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates the circuit diagram of an oscillator embodying the principles of the present invention in which a pair of serially connected gaseous discharge tubes is employed;

Fig. 2 depicts a circuit diagram of a similar oscillator in which three series-connected glow-discharge tubes are incorporated;

Fig. 3 shows an oscillation generator circuit, which is a modification of the circuit illustrated in Fig. 1;

Fig. 4 is a diagrammatic circuit of an oscillator group including five harmonically related oscillators, each oscillator employing a pair of serially connected tubes provided withexternal electrodes for the purpose of stabilizing the harmonic relationship of the several oscillators; and

Fig. 5 is the circuit diagram of a portion of an electrical organ employing groups of harmonically related frequency stabilized oscillators, means being provided for selectively withdrawing oscillatory energy from the several oscillators and for disabling all of the oscillators when no oscillations are required.

Broadly stated, in accordance with the principles of the present invention, I provide a plurality of gaseous discharge tubes connected with each other in such a manner as to have their respective discharge paths in series with each other. The resulting discharge path is connected with capacities and resistances so that the capacitor is alternately charged and discharged at a predetermined rate. Thus, for example, a condenser may be connected across the common, or resultant gaseous discharge path, and a high resistance may be connected in series with such discharge path. When now a source of direct current having a voltage higher than the sum of breakdown voltages of the individual discharge Paths is connected across the resulting structure, the condenser across the common discharge path will be gradually charged from the source of direct current through the resistance until its charge potential reaches the break-down voltage of the combined discharge paths. At that time the combined discharge paths become conductive and discharge the condenser until the voltage across the condenser will drop below the extinction voltage of the combined discharge paths. Thereafter charging of the condenser will be resumed and the described cycle will be repeated at a rate determined by the capacity of the condenser, the value of the resistance, the voltage of the source of direct current and the constants of the discharge rpaths, particularly their break-down and extinction voltages. I have found that although there may be a very substantial difference between the critical voltages of the individual serially connected gaseous discharge paths, current will start and stop flowing through them in such close sequence that for most practical purposes it may be assumed to be simultaneous. This surprisin fact may be to some extent explained by considering that when, for example, two individual discharge paths are connected in series and a source of direct current potential is connected across the same, the potential of the source will b divided between the two, initially non-conductive discharge paths in a more or less uniform manner, particularly when the tubes are of the same general type and have similar electrode arrangement, gas filling, etc. As soon, however, as one of the discharge path has become conductive, its resistance will suddenly drop from a very high value to a very low value, generally speaking from several hundred megohms to l0-50,000 ohms, or less. This will concentrate practically all of the potential drop between the electrodes of the remaining non-conductive tube which will break down practically instantaneously. In other Words, the break-down 0f the serially connected discharge paths will occur in such rapid sequence as to be practically simultaneous. The same conditions of operation apply to circuits in which more than two serially connected discharge paths are employed.

A similar oscillatory circuit includes a plurality of serially connected gaseous discharge paths which are connected in series with a high resistance and with a source of direct current having suitable potential, a condenser bein connected across the resistance. In this case the gaseous discharge paths will break down practically instantaneously and will charge up the condenser. After the condenser is charged, its potential will oppose that of the source of direct current and the discharge paths will be extinguished. At the same time, however, thecondenser begins to be slowly discharged through the shunting resistance. When the potential of the charge of the condenser becomes sufliciently low, the voltage of the source of direct current becomes again effective and the charging cycle begins anew. Oscillations will be produced in the circuit, the frequency of which will be determined by the same factors as in the circuit referred to in the foregoing.

In addition to these representative circuits, various other circuits are possible for the production of electrical oscillations. As a matter of fact, it could b generally stated that in any circuit embodying gaseous discharge tubes, a plurality of serially connected tubes of the same type may be substituted for each tube, provided that the voltage of the source of direct current is correspondingly increased. The advantages of the present invention may thus be readily obtained, these advantages residing particularly in the possibility of obtaining a greatly increased oscillatory current and potential output with standard parts and with readily obtainable standard gaseous discharge tubes of low cost and small dimensions. These and other important advantages following from the application of the principles of the present invention will more fully appear from the following detailed description of certain representative circuits into which the invention may be incorporated.

Referring now more particularly to Fig. l of the drawings, a preferred embodiment of the invention will be described. Two glow-discharge tubes G-l and (3-2 are connected in series with each other and and with a resistance R-l. A source of direct current B-l is connected across the serially connected tubes and resistance to apply a constant potential thereto. A condenser 0-! is connected across the two tubes G-l and G4. It will be found that oscillations of determined frequency will be produced in a circuit of the described typ provided that the voltage of B-l exceeds the sum of the break-down voltages of G-l and (3-2.

Upon completion of the circuit, condenser C-l will be gradually charged through resistance R-l. The tubes G-I and G-Z being originally nonconductive, they do not have any appreciable effeet on the rapidity of the charging of the condenser, this being solely determined by the capacity of C-l the resistance of R-l and the voltage of B-l.

As soon as condenser C-l has been charged up to a potential corresponding to the combined break-down voltages of G- l and G-2, the tubes will become conductive substantially simultaneously (as it has been explained in the foregoing), and the condenser will start to discharge through the serially connected gaseous discharge paths of G-l and G-Z. This discharge will continue until such time as the potential of the condenser charge decreases below the extinction voltage of the two tubes, this being the lowest voltage at which the discharge can be still maintained, once it has been initiated. At this time tubes G-l and G-Z become non-conductive and charging of condenser C-| is resumed. This cycle comprising alternate charging and discharging of the condenser is continuously maintained until direct current potential is applied to the system in which oscillations of substantially constant frequency will be produced. The frequency of the oscillations is determined by the capacity and resistance and also by the voltage of the source of direct current. Of course, the critical voltages of tubes (3-! and G-2 (the break-down and extinction voltages) have also a definite effect on the frequency. Generally speaking, the frequency of the oscillations produced decreases with increasing resistance and capacity and increases with increasing operating voltage, and vice versa. For example, audio-frequency oscillations may be produced with resistances from 1 megohm to 20 megohms, capacities of 0.0001 to 0.01 microfarad and voltages of 150 to 300 volts. These ranges, however, are by no means critical and wide variations are possible. Obviously, the same frequency may be obtained by an infinite number of combinations of values of RFI, C-l and of the voltage of B-l, a higher capacity may be compensated for by a lower resistance, or higher voltage, and vice versa.

The oscillatory output may be taken off in a number of different ways. For-example, the primary winding of an output transformer may be connected in series with any portion of the circuit and the output may be taken off through the secondary winding of the transformer. As an alternative, a bleeder resistance may be connected in any branch of the circuit and the oscillatory voltage drop along this resistance may be utilized. Particularly when the load has a very high impedance, such as the grid circuit of a thermionic tube, or the external electrode of a glow-discharge tube, a direct connection of such grid or electrode, etc., is possible to a point of the circuit where the potential with respect to a point of fixed potential of the circuit is greatly varying at the oscillatory rate determined by the frequency of the oscillations produced. Such a point is, for example, the junction point of the serially connected tubes Gl and G-2, and resistance R-l, denoted by reference character A-l. It will be noted that when tubes G-l and G-Z are non-conductive, practically all of the potential drop will be across the tubes so that the potential at A-l will closely approximate that of the positive terminal of the source of current. As soon, however, as both tubes G-l and G-Z become conductive, their internal resistance will decrease from a large number of megohms to a few thousand ohms. In other Words, the potential of point A-l will be shifted considerably closer to that ,of the negative terminal of source of current B-l. The voltage fluctuation at A-l with respect to a point of constant potential in the circuit nected discharge paths of the three tubes will may reach very high values, well over volts and more. A substantially lower oscillatory potential is obtainable at the junction point of the two tubes G-I and G-Z, denoted by reference character A-Z.

Fig. 2 depicts an oscillatory circuit which is in all respects similar to that shown in Fig. 1, with the only difference that three glow-discharge tubes are connected in series. Of course, the voltage of source of current B-Z has to be generally higher than the sum of the break-down voltages of the three tubes.

The circuit of Fig. 2 includes three two-electrode, cold-cathode, gaseous discharge tubes, such as glow-discharge tubes (3-3, G4, and G-5. These tubes are connected in series with each other and with a resistance R-2, tubes and resistance being collectively connected across the positive and negative terminals of source of direct current B-Z. A condenser 0-2 is connected across the serially connected tubes G3, G-4, and G5. For all practical purposes the serially confunction as a single gaseous discharge path having considerably higher break-down and extinction voltages, although it may be pointed out that conduction of current through the various tubes is not exactly simultaneous at all times. The operation of the circuit of Fig. 2 is exactly the same as that of Fig. 1 and will be readily understood by those skilled in the art without any detailed explanation. It will be sufficient to state that electrical oscillations of determined frequency will be maintained in the circuit and may be withdrawn in any suitable manner by means of capacitive, inductive, or galvanic coupling means. Reference character A-3 denotes the junction point of resistance R2 and serially connected tubes G-3, G-4 and G-5, from where 0s cillatory potential of the highest value may be obtained. Junction points A-4 and A-5 of tubes G-3, G-4 and (3 1-, G-5, respectively, can provide oscillatory potentials of lower values, that of A-4 being higher in value than that of A-E, for obvious reasons.

It will be readily appreciated that more than three gaseous discharge tubes may be connected with equal or similar results, and thereby oscillations of correspondingly increased amplitude may be produced. Of course, when increasing the number of serially connected tubes, the voltage of the source of direct current has to be likewise increased.

The oscillation producing circuit shown in Fig. 3 is likewise closely similar to that shown in Fig. 1. In this case the difference consists in connecting the condenser across the resistance in the circuit, rather than across the tube. This will produce a somewhat difierent waveform, as it will appear from the following description of the circuit and operation of this oscillator.

The circuit of Fig. 3 comprises a pair of glowdischarge tubes G-6 and G-! connected in series with a resistance R-3 and with a source of direct current B3 of appropriate voltage. A condenser 0-3 is connected across resistance R-3. Provided that the voltage of the direct current source is higher than the sum of the break-down voltages of G-6 and G4, upon completion of the circuit the two tubes will break down at once and condenser C-3 will be charged up. As soon, however, as condenser 0-3 is charged, its electro-motive force will be opposed to that of B-3 so that the discharge through the tubes will be interrupted.

At the same time condenser C-3 will begin to discharge through resistance R-3. After a certain time the voltage of the condenser charge will decrease sufiiciently to cause break-down of tubes G-6 and (1-7 under the effect of the voltage of 3-3 and a new cycle of charging and discharging of the condenser will begin. The frequency of the oscillations produced in the circuit is determined by the same factors as in the case of circuits l or 2.

It is worth noting that while in the circuits of Fig. l and Fig. 2 the condenser is charged gradually through the resistance and is discharged practically instantaneously through the tubes, in the circuit of Fig. 3, the condenser is charged practically instantaneously through the tubes and is discharged gradually through the resistance. In other words the waveforms obtained by circuits Fig. l and Fig. 2 on the one hand, and by circuit of Fig. 3 on the other hand show a more or less reversed configuration, the frequency obtainable by both types of circuits being substantially the same, provided the physical constants of the respective circuits are the same. In view of the fact that the waveform of the oscillations generated has great influence on the tone colors ultimately produced, selective and judicious application of these two basic types of oscillators makes it possible to obtain a wide range of musically valuable tone qualities. The oscillatory output of the circuit of Fig. 3 may be withdrawn in any of the ways described in connection with the circuits of Fig. l or 2. For example, a high oscillatory potential may be taken off at the point A-6, and a somewhat lower oscillatory potential maybe taken olT at A4.

In Fig. 4 a plurality of harmonically related oscillators of the type illustrated in Fig. 3 are shown, means being provided for impressing oscillatory potential derived from each oscillator upon the following one, thereby to maintain the harmonic relationship between the various oscillators constant. In Fig. 5 five oscillators O-l, O-Z, O-S, O4 and O-5, tuned in octaves, are illustrated although, of course, any desired number of oscillators may be employed. Oscillator O-l comprises a pair of glow-discharge tubes G-8 and G-9 connected in series with a resistance R4, a condenser C-4 being connected in series with a resistance R- l, a condenser C-4 being connected across the resistance. Oscillators O-2, O-3, O4 and O5 comprise pairs of tubes G-ltl and (3-H; G-l2 and G-l3; G-M and G-l5; and G-IE and G-l'l, respectively, connected in series with resistances R-5, R-B, R-l, and R-B, condensers C-5, C-6, C1 and C-8 being respectively connected across the corresponding resistances. All oscillators are connected to a common source of direct current B-4 whereby electrical oscillations will be set up in each oscillator. The electrical constants of the various oscillators are so determined that they will produce oscillations the frequency of which is approximately in octave relation. In other words, the frequency of the oscillations produced by oscillators O4 to O-5 are approximately in the proportion of 16f, 8f, 4f, 2], and f. To facilitate approximate tuning of the several oscillators to such respective frequencies, condensers O4 to C-8 may be of the variable type.

Tubes 64 to G-l1 are each provided with an external electrode E-I to E-IO, respectively. The object of these external electrodes on the tubes is to influence, or to trigger the starting and stopping of a discharge through the respective tubes by means of a potential impressed upon such electrode. Although somewhat loosely, it could be stated that the external electrode has to some extent a similar effect upon the current flow through the tube as the grid of a thermionic tube upon the plate current.

The external electrodes of tubes in the same oscillator are connected in pairs. Thus, external electrodes 12-3 and 13-4 of oscillator O-Z are connected to the junction point of serially connected tubes G-8, G-9 and resistance R4 of oscillator O-|, denoted by reference character A-8. Likewise, external electrodes 13-5 and E-B on the tubes of oscillator 0-3 are connected to the corresponding junction point A-9 in oscillator O-Z, external electrodes E-'[ and E8 of oscillator 04 are connected to the corresponding junction point A-IB Of oscillator O-3, and external electrodes E-S and E-lfl of oscillator 0-3, and external electrodes E9 and E-lll of oscillator O-5 are connected to the corresponding junction point A-ll of oscillator O-4. In view of the fact that at points A-8, A-S, A-IU and A-H strongly varying oscillatory potentials are present, such potentials will be impressed upon the tubes of subsequent oscillators and thereby will stabilize the frequency relationship thereof. As oscillators O-l to O-S are approximately tuned in octave relation, the triggering voltages on the external electrodes of the tubes will time the break-down and extinction of the discharge through the various tubes in such sequence that the octave relation will be permanently and accurately maintained even though some or all of the physical constants of the several oscillators may vary to a substantial extent. Experiments have shown that after a group of cascaded oscillators of the type shown in Fig. 4 has been locked in the desired harmonic relation, even intentional attempts to tune one of the oscillators away from the original frequency, for example, by changing the capacity of C, the resistance of R or the voltage of B are of practically no effect upon the oscillators which thus may be maintained at the proper relative pitch indefinitely. It has been found that the voltage of 34 could be changed by as much as 20 or 25 volts, without disturbing the relative pitch of the oscillators, although, of course, the absolute pitch would change with the voltage. In order to maintain also the absolute pitch likewise constant, which is of great importance in various electrical systems primarily designed, adapted and intended for the generation and transmission of predetermined tone frequencies, it is in some cases desirable to impress a stabilizing oscillatory potential of constant frequency upon oscillator O-l by means of external electrodes E-l and E4. This external stabilizing voltage may be taken from any oscillation producer having a high stability, such as a thermionic tube oscillator of suitable construction, a tuning fork oscillator, etc., and its frequency may be identical with that of the desired frequency of oscillator O-l, or at least is harmonically related thereto. In this manner, both the absolute pitch and the relative pitch of the oscillators will be positively maintained.

In my U. S. Patent No. 2,252.189, issued to me on August 12, 1941, I have disclosed systems of harmonically related glow-discharge tube oscillators in which the desired accurate frequency relationship is maintained by impressing a signal from a point of strongly varying oscillatory potential from each oscillator upon the next following oscillator. The present invention constitutes an improvement over the circuits and the principles disclosed and broadly [claimed in the said patent. The principal advantage of the cirouits disclosed herein resides in the series arrangement of a plurality of glow-discharge tubes or similar gaseous discharge devices whereby a much higher oscillatory potential may be obtained. Due to the fact that the stabilizing circuit shown in Fi 4 provides oscillatory stabilizing voltages several times as high as obtainable by the circuits disclosed in the said patent, the stabilizing effect is substantially improved so that even under rather unfavorable operating conditions excellent and practically permanent stability of the oscillations produced is obtained.

While I shall now make specific reference to adaptation of m invention to electric organs wherein accurate generation and selective transmission of harmonically related tone frequencies are factors normally determining the success of such instruments, this is by way of illustration only and to make clear the functional advantages of my invention when used in this particular environment. Persons skilled in the art will readily appreciate the many advantages of my invention when employed in various signaling systems in which the main purpose thereof is the production of dependable oscillatory potentials at harmonically related tone frequencies. Thus, for example, in an organ having a range of '7 octaves and tuned in the tempered scale from C to C, 85 oscillators are necessary. Preferably, these 85 oscillators are subdivided in twelve groups, each group including seven oscillators tuned in octave relation to the same note of the tempered scale, with the exception of the C note group, which includes 8 octaves. Each group has the octavely related oscillators arranged in substangially the same coordination as shownin Fig.

In cascaded oscillators arranged in plurality of note groups, generally twelve, corresponding to the number of notes in a single octave of the tempered scale, c, Ct, d, di, e, fit, g, gt, a, at, b, it was heretofore unavoidable to have all of the oscillators of all of the note groups producing oscillations all of the time and to provide suitable keying or switching means whereby oscillatory energy is withdrawn from certain of the oscillators in accordance with the musical composition which is to be interpreted. This conventional practice introduced grave problems in the way of shielding to avoid cross-talk, cross modulation and similar parasitic oscillatory phenomena which formed a background noise or 4 interfered with the proper tone color or the purity of the musical sounds ultimately produced. This will be readily appreciatedif it is considered that in an electrical organ of practical construction as many as 85, or even more, oscillators have to be maintained in continuous oscillations. In view of the fact that the power supply of all oscillators is generally in common in order to simplify wiring and to reduce cost, there is usually some remaining coupling between the several oscillators. In addition, even with careful shielding, leads carrying different frequency oscillations have to be located in close proximity and some pickup of oscillatory energy is difli cult to avoid unless each oscillator, or at least each note group is Very carefully decoupled and also shielded. The problem of adequate shielding is further aggravated in the keyboard and associated contacts in which leads and contact blades are necessarily arranged in close proximity to each other and where conventional methods of shieldin are executed only with great difficulty. As a result, prior electrical organs embodying cascaded oscillators generally suffered from a certain amount of background noise which was almost impossible to avoid unless extremely complete shielding was practiced at great inconvenience and expense.

I have discovered that this problem of cross talk in any electrical system having for its purpose the generation and frequent simultaneous use of different tone frequencies is now solved in a remarkably simple and inexpensive manner by departing from the conventional practice of having the groups of cascaded oscillators oscillating all of the time. Instead 'of this old and unsatisfactory practice, I prefer to have all groups of cascaded oscillators normally inoperative and to start the complete group oscillating only when any one of the notes in the particular group is required. In other words, only those groups are operating and producing oscillations at any time, from which at least one note is needed at that particular moment. Thus, for example, when the player desires to produce a C major chord including the notes 0, E, and G, depression of the corresponding keys of the keyboards will first start the corresponding note group oscillators operating and immediately after will withdraw oscillatory energy from the particular oscillators of such groups corresponding to the depressed keys. In this manner, when the above mentioned cord is played, the rest of the note group oscillators will be inoperative and consequently no non-harmonic parasitic oscillations may be picked up, even in the complete absence of any shielding. Even though some very slight amount of oscillatory energy may be picked up from some of the oscillators of the same name as the notes played, these will be harmonically related to the played notes and will not influenc the desired musical effect, except perhaps for a slight enhancing of some of the harmonics of the said notes.

This simple, but at the same time extremely valuable novel principle in the design and construction of electrical organs will be better understood by referring to the circuit of Fig. 5 in which the wiring of a single note group with a keyboard and associated contacts is illustrated, embodying the principle broadly stated in the foregoing.

Referring now to Fig. 5 of the drawings, the note group embodying the principles of the present invention comprises five octavely related glow-discharge oscillators 0-6, 0-1, 0-8, 0-9 and 0-H). These oscillators each include a pair of glow-discharge tubes G-I8, G-I9; G-ZIJ, G-2 I; G-ZZ, G-23; G-24, G-25; and (3-26, G-Z'I, respectively, connected with a condenser of adjustable capacity C-9, C-Ill, 0-4 I, C-IZ and C-l3, respectively, and a bleeder resistance lit-I4, R45, R-IB, R-II, and R-I8, respectively.- The bleeder resistances are of a relatively low value, a few thousand ohms, and their object is to obtain a potential drop which may constitute the signal to be selectively introduced into the output sysem by means of key-controlled switches, as it will presently appear. Oscillators 0-6 to O-IlI are all connected across the positive and negative terminals of a source of direct current 3-5, the voltage of which may be adjusted within a narrow range by means of a potentiometer P connected across a portion thereof.

High resistances of the order of several megohms, R-9, R-III, R-I I, R-IZ and R-I3 have One of their ends respectively connected to the point of junction of the serially connected tubes and of the variable condensers of the oscillators 0-8 to 040, while the other end of all of these resistors is connected to a common bus bar D. This bus bar is normally disconnected from the negative terminal of source of direct current B-5 so that all of the oscillators are inoperative. Switches S-l, 8-3, 5-5, 3-1, and 8-9, respectively operable by depression of keys K-l, K4, K-3, K- i, and K-5 are connected between common leads F and H of which F is connected to bus bar D and H is connected to the negative terminal of B5. Thus, depression of any one of the playing keys K-! to K-5 will cause closing of one of contacts S4, S-3, S-5, S-l, S-9 and thereby will connect bus bar D to the negative terminal of 3-5. This will complete the circuit of oscillators 0-6 to O-l 0, all of which will produce oscillations of determined musical frequencies.

Tubes G-l8 to (3-21 are each provided with an external electrode E-l l to E-ZD, respectively, connected in pairs coordinated to tubes of the same oscillator, These pairs of external electrodes are electrically connected to points of highly varying oscillatory potential in the preceding oscillators.

Thus, external electrodes E-l3 and E-M are connected to the junction point of serially connected tubes G-IB, G-IS and condenser C-9; electrodes E4 5 and E-! 5 are connected to the junction point of tubes (3-20, G-2l and condenser C-it; elecspectively. Adjustment of potentiometer P connected across a portion of 13-5 makes it possible to change the operating voltage of all oscillators at the same time so that their pitch may be simultaneously raised or dropped without, of course, affecting their relative pitch or intervals, which will remain that of an octave throughout. In some cases it may be desirable to impress an external stabilizin voltage derived from a stable oscillator, such as thermionic tube oscillator, tuning fork oscillator, etc., and preferably having the frequency of 16 upon external electrodes E-ll and E-l2.

Each of the keys K-l to K-5 is provided with a second contact or switch, S-Z, S-4, S45, S-8,

and S-lfl, respectively. These contacts have the I object of controlling the withdrawal of oscillatory energy from the various oscillators in accordance with the wishes of the operator.

The oscillatory energy or signal is withdrawn through decoupling resistors R-l9 to R-23 of the order of 10,000 to 50,000 ohms. One end of these resistors is connected to the upper end of bleeder resistances R44 to R48, respectively, while their other end is connected to the upper contact spring of switches S2, 5-4, S-B, 5-8, and S-IO, respectively. The lower contact of said switches is connected to a common bus bar I, and thereby to one terminal of the primary winding of an output transformer T, the other terminal of which is connected to the negative terminal of source of direct current 13-5,

From the foregoing description, the operation of the stabilized group of harmonically related oscillators will be readily understood by those skilled in the art. In the normal condition of Oscillators 0-45 to O-lU are aprest, that is when none of the keys is depressed, oscillators O6 to O-lll are imperative. There being no oscillations produced, the problems of shielding and of parasitic oscillations, cross-talk, etc., are non-existent. Upon depression of any one of keys K-l to K-S, bus bar I) is connected to the negative terminal of B-5 by the upper one of the key switches and all of the oscillators of the group start oscillating. A fraction of a second after, the second or lower switch of the same key is likewise closed whereby oscillatory output corresponding to the depressed key is introduced into the primary winding of output transformer T. l'he secondary winding of this transformer may be electrically associated with an amplifier and a sound producing means (not shown) whereby the oscillations withdrawn are amplified and converted into sound. In case more than one key is actuated at the same time, output of the other oscillator will be likewise withdrawn and impressed upon the same transformer with similar results. In view of the interposition of decoupling resistances R-l9 to R43, which are relatively high in value in comparison to resistances R-lfl to Rr-la, the reflection of energy from one oscillator to the others, robbing" of one oscillator by another and the like undesirable phenomena are avoided at the time when more than one key is operated simultaneously.

Obviously, in a complete electrical organ a number of note groups are employed, preferably twelve, corresponding in number to the number of notes within an ctave of the tempered scale. Each of the groups of octavely related oscillators includes a plurality of octavely related oscillators, such as 6 or I, in accordance with the desired range or gamut of the organ. Oi course, certain of the elements of the note groups may be in common for all groups, such as the output transformer, the amplifier and speaker and the source of direct current whereby the circuit may be considerably simplified.

It will be noted that the principles of the present invention provide a number of important advantages. First of all, a. novel and improved oscillator is provided employing gaseous discharge tubes and capable of a substantial output of oscillatory energy.

It is to be also observed that the oscillators embodying the present invention make it possible to obtain substantial outputs of oscillatory energy varying at an audio frequency rate by employing gaseous discharge tubes, particularly glow-discharge tubes of conventional design and of small dimensions.

Moreover, oscillatory potentials of very high value may be readily obtained whereby harmonically related groups of oscillators may be maintained in their accurate frequency relation indefinitely without requiring any complex circuits. The present invention also teaches the provision of an electrical organ of extremely simple and inexpensive construction which may be provided at a fraction of the space and cost requirements of prior electrical musical instruments and at the same time is free from the problems of crosstalk, arasitic oscillations, and the like which made the construction 01' prior electrical organs involved and expensive.

Although the present invention has been disclosed in connection with a few preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles or the present invention. Thus, while I prefer to employ glowdischarge tubes of the type in which two cold electrodes are arranged in a sealed vessel containing neon gas under reduced pressure, twoelectrode tubes containing other gases, such as argon, etc., may be employed with equal or similar results. Likewise, it is possible to employ two-electrode tubes in which the cathode is heated to facilitate ionization, three-electrode tubes with heated or unheated cathode, with or without gas filling, etc. I consider all of these variations and modifications as within the true spirit and scope of the present invention, as disclosed in the foregoing description and defined by the appended claims.

I claim:

1. In a signaling system, an oscillation producer comprising a plurality of serially connected glow-discharge tubes, each of which has but two electrodes; a source of direct current, and a resistance, all in series and forming a circuit; and a condenser connected across and in common for said-tubes and alternately charged through said resistance and discharged through said tubes during substantially synchronous periods of nonconduction and conduction thereof, whereby oscillatory energy is produced in said circuit.

2. In mechanism of the class described having cascaded groups of harmcnicall related oscillators, means for selectively withdrawing oscillatory energy from said oscillators, and means for disabling each group of oscillators while no energy is withdrawn from any one oscillator in such group.

3. In mechanism of the class described having a plurality of groups of harmonically related oscillators and switching means under the control of an operator to draw oscillatory energy from any desired number of oscillators at a time, the combination of means for normally maintaining said groups in an inoperative condition, and means operable by said switching means to initiate the operation of such groups from which at least one oscillation is to be withdrawn.

4. In mechanism of the class described, the combination comprising a plurality of groups of normally inoperative harmonically related oscillators, key-controlled switching means for each of said oscillators to withdraw oscillatory energy from any desired number of oscillators at a time, and control means for each group operable by any one of the switching means of the group to initiate operation of the complete group of oscillators upon actuation of at least one of the switching means of each group.

5. In mechanism of the class described, the

combination comprising a plurality of groups of harmonically locked octavely related oscillators, a key-controlled switch for each of said oscillators for arbitrarily withdrawing oscillatory energy therefrom, said oscillators being normally inoperative, and control means for each group operable by any one of the switches of the group to initiate operation of the complete group of oscillators upon actuation of at least one of the switches 'of such group before said actuated switch becomes fully effective for the withdrawal of oscillations.

6. In mechanism of the class described, the combination comprisingv a plurality of groups of octavely locked oscillators, a playing manual having a key for each of said oscillators, a notecontrolling switch and a group-controlling switch for each of said keys, said note-controlling switch being operable upon depression of the corresponding key to connect the oscillator to a common output, and said group-controlling switch having means associated therewith adapted to normally disable all of the oscillators of the group and to render all of said oscillators operative upon depression of said key.

7. In mechanism of the class described, the combination comprising a multiplicity of normally inoperative groups of oscillators, each of said groups including a plurality of oscillators approximately tuned to successive octaves of a note of the tempered scale and permanently locked in accurate octave relation, a playing manual having a key for each of said oscillators, a pair of switches for each of said keys, and an output circuit in common for all oscillators, one of said switches being adapted upon depression of a key to connect the corresponding oscillator to said common output circuit, and the other of said switches being adapted to initiate operation of all oscillators of the corresponding group.

8. In mechanism of the class described, the combination comprising a plurality of groups of glow-discharge tube oscillators each of said groups comprising a plurality of at least three glow-discharge tube oscillators tuned to successive octaves of a note of the tempered scale and each of said oscillators including a plurality of serially connected tubes having a resistance connected in series therewith and a condenser, a source of direct current in common for all of said oscillators, an external electrode on the tubes of at least two of said oscillators connected to the common terminal of tubes and a resistance in another one of the oscillators of the same group having the nearest frequency to interlock said oscillators with each other and to maintain their relative frequency constant, a key-controlled switch for each of said oscillators to connect any desired number of them to a common output circuit, and control means for each of said groups adapted to normally disable the oscillators of the group and operable by said switches to render the groups operative from which at least one oscillator is connected to the output.

NICHOLAS LANGER;

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