US2302690A

US2302690A - Electric oscillator

Info

Publication number: US2302690A
Application number: US167618A
Authority: US
Inventors: Germeshausen Kenneth Joseph
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-03-09
Filing date: 1937-10-06
Publication date: 1942-11-24
Anticipated expiration: 1959-11-24

Description

Nov. '24,.1942. K. J. G ERMEsHAU SEN 2,302,690

ELECTRIJCOSCILLATOR Original Filed-March 9, 1937 INVENTOR ATTORNEY Patented Nov. 24, 1942 ELECTRIC OSCILLATOR Kenneth Joseph Germeshausen,

Cambridge, Mass.

Original application March 9, 1937, Serial No.

Divided and this application October 6, 1937, Serial No. 167,618

24 Claims.

The present invention relates to electric oscillators, and more particularly to oscillators of the multi-vibrator type. The present application is a division of application, Serial No. 129,837, filed March 9, 1937, Patent No. 2,201,166 granted May 21, 1940.

An object of the present invention is to provide a novel electric oscillator.

A further object of the invention is to provide a novel oscillator for controlling the flashing rate of a stroboscopic lamp.

Another object is to provide a novel method of controlling the frequency.

Still another object of. the invention is to provide a novel means for calibrating the frequency scale of the above oscillator.

Other objects will be explained hereinafter and will be particularly pointed out in the appended claims.

' For a consideration of what I believe to be .novel and my invention, attention is directed to the accompanying description and the claims appendedthereto.

The single figure of the accompanying drawing is a circuit diagram illustrating a preferred complete stroboscope circuit, with .a conventional power supply to furnish direct current from the alternating-current mains, a. separate oscillator embodying the invention for driving the stroboscopic lamp so as to cause the lamp to flash at the desired frequency, means for calibrating the,

oscillator, means for operating the lamp so as to cause it to flash at the frequency of the alternating-current supply voltage from the line, and a contactor device for controlling the flashing rate.

The tube I may be of the type illustrated in my application, Serial No. 48,669, filed November 7, 1935, Patent No. 2,185,189 dated January 2, 1940, or a modification of the same, illustrated in Fig. 1 and described more at length in a copending application, Serial No. 129,838, filed March 9, 1937, Patent No. 2,201,167 dated May 21, 1940. It comprises an evacuated glass envelope-filled with a suitable gas, suchas neon, or any of the other noble gases, such as argon or helium. The pressure of the gas in the tube may vary, the usual pressure being from one to two centimeters. The tube contains several electrodes, namely, a solid cathode 2, an anode or plate 5, and one or more grids, inner and outer grids being shown at 3 and 4 between the anodeand the cathode. The grid 3 is at zero potential with respect to the cathode 2 and the grid 4 is positive with respect to the grid 3. The source of the electrons is a bright cathode spot on the surface of the cathode.

Either grid may be usedas the control grid, depending upon the polarity and the magnitude of the control voltage.

As explained in the said Patent No. 2,185,189, the grid 3 may, in normal use, he placed close to the cathode 2, say-,xnot more than a, few millimeters from the cathode, and may be of such shape that the cathode will sputter a thin surface layer or coating of a material of low work-function, such as caesium, on the grid surface during the normal operation of the tube. A-thin surface coating or layer of the caesium or other material of low work-function is thus maintained on the grid 3. As explained in the said Patent No. 2,201,167, however, the grid 3 may, under some circumstances, be precoated.

The form of the arc stream between the anode and the cathode is a column of small diameter which has high intrinsic brilliance, with substantially all the light emitted from the concentrated arc stream. This discharge is easily distinguished from a glow discharge, which occupies substantially the whole interior of the tube, with a discharge of low intrinsic brilliance, the greatest brilliance being at the surface of the cathode.

In the illustrated stroboscopic circuit, the anode 5 and the cathode 2 of the tube are shown connected across a condenser H, which is continuously charged, by way of conducting wires 1 and 8, from a suitable direct-current source of, say, 300 to 400 volts, connected through a variable current-limiting impedance l2, which may be a resistor, or a-combination of resistance and inductance. The source may be constituted of thermionic. or gaseous-discharge rectiflers for producing direct current from alternating curcathode 2 and the grid 3.

rent, as illustrated, or any other-source of direct current.

In the illustrative circuit, a transformer 18, a double-anode rectifier tube 11 and a condenser 69 form a conventional power supply to give any desired direct-current voltage, say, 300 volts, from the 110-volt alternating-current mains.

The discharge condenser II is used for highfrequencyoperation of the stroboscope circuit; for low-frequency operation, a condenser I3 is connected in parallel with the condenser II by means of a switch 66.

Impedances l9 and are shown connected between the cathode 2 and the grid 4, and between the grid 4 and the anode 5, respectively; and an impedance 8| is shown connected between the The bias is so adjusted on the grid 4 by means of these impedances, which may be resistors, and the supply the voltage between the anode 5 and the cathode 2 much greater than the voltage required to cause a glow discharge between the grid 4 and the grid 3,v and the tube will thus stay-in a non-conducting state when the condenser I I is fully charged. The lamp circuit comprises the said two discharge condensers II and I3, the said currentlimiting resistor I2 and the three resistors 8|, 80 and 18. v

Current is also supplied from the power supply to conductors I00 and I32. The conductor I32 is connected, through a resistor I24, to a switch 88, adapted to occupy two positions A and B. The conductor I 00 is connected, by a contactor device 81, to a contact member with which the switch 88 is adapted to contact in position B. The circuits of the hereinafter-described multivibrator are open when the switch 88 occupies the position B. The switch 88 is connected by a conductor 58,

through a condenser 83, to the grid 3. The switch 88 is connected also to the source of alternating current, by way of a conductor 20, and through a resistor 84, by a switch 85. The contactor 81 may beperiodically opened and closed in any desired manner; that is not shown in order to simplify the drawing.

With the switch 88 in position B, and the switch 85 open, the lamp I can be triggered at the desired instant by means of the contactor device 81, which causes a momentary surge through the condenser 83. When the contactor device 81 closes, therefore, the grid 3 is given a negative voltage pulse equal to the voltage existing between the conductors I00 and I32. The condenser 83 then discharges through the resistor 8| and the grid 3 to the cathode 2, allowing the voltage of the grid 3 to return to zero. The discharge circuit extends from one side of the condenser 83, through the resistor 8I and the grid 3 and the cathode 2, in parallel, by way of the conductors 8, 85 and I00, and through the

switches

81 and 88, the latter in the position B, to the other side of the condenser 83. Once the contactor 81 becomes closed, it may remain closed without the stroboscope flashing on again when the condensers II and I3 build up their voltages. The operation is independent of the length of time that the contactor 81 remains closed, the

complete function being performed at the moment it first becomes closed. The contactor 81, therefore, gives only one impulse of voltage at each closing, and the length of time the contactor 81 remains closed does not affect the operation of the tube.

The voltage applied between the grids 3 and 4 should be sufllcient to cause an initiating glow discharge between the grid 4 and the coating on the grid 3. The voltage at which this discharge takes place is low and substantially constant, due to the fact that the grids 3 and 4 shield the field between the grids from charges on the glass. To start the glow discharge between the grids may require a voltage of only about a hundred volts and a current of only a fraction of a mililampere, so very little power is required.

The use of the controlling oscillator, for impressing its oscillations upon the grid 3, makes it possible to operate the stroboscope without any moving parts.

The illustrated multivibrator oscillator is simple and cheap, it possesses constancy of frequency irrespective of variations in applied voltage and an abrupt or saw-tooth wave form, and it has a comparatively high voltage output. The directcurrent power supply for the oscillator may be obtained from the power supply for the stroboscope circuit through conductors 84 and and a resistor 81. A filter condenser 88 is provided to remove any slight alternating-current ripple in the direct-current voltage.

The oscillator circuit comprises a pair of electron-

discharge vacuum triodes

88 and 88, a pair of anode or plate resistors or other impedances I22 and I 24, the grid resistors or other impedances I38 and I38 that are connected to the grids or control electrodes I I4 and I I8 of the

triodes

88 and 88, the grid condensers or electron-storage devices I25, I28, I21 and I28, and the condenser I28. The frequency-control circuit of the said oscillator comprises the variable, calibrating resistors or other impedances I2I and a biasing source of energy. The biasing source of energy is illustrated as comprising the potentiometer I I8. The set of electrodes of the vacuum triode 88, comprising the filament or cathode 88, the grid or control electrode H4 and the anode 82, and the set of electrodes of the vacuum triode 88, comprising the filament or cathode 88, the grid or control electrode I I8 and the anode 84, may be in separate envelopes, or in a single envelope. It is usually more convenient to combine the two in a single tube. ,The voltage from the voltage source is applied to the oscillator by way of the conductors I00 and I32, between which the oscillator is connected. The calibrating resistor |2| is'connected between resistor 81 and conductor I32. The second calibrating resistor I30 is connected, in series with the potentiometer I I8, to the conductor I00. The potentiometer H8 is thus connected between the calibrating resistors I2I and The cathodes of the

oscillator tubes

88 and 88 are connected to the conductor I00. The anodes of the oscillator tubes are connected to the conductor I32 and the resistor I2I through the resistors I22 and I24. The pair of resistances I22 and I24 thus connect the anodes 82 and 84, respectively, to the upper end of the potentiometer I I8, which is positive with respect to the

cathodes

88 and 88 by reason of the fact that it is connected by the conductor 84, through the resistor 81, to that terminal of the rectifier 11 that is positive with respect to their cathodes. The resistor I22 and I24, therefore, maintain the anodes 82 and 84 positive with respect to the cathodes. The switch 86 is connected, in position A, to the anode 84 of the triode 88. The anodes 82 and 84 are thus connected to one side of the source of voltage by the conductor I32, through the resistances I22 and I24. The cathodes 88 I33, through the resistor I38, to the grid II4.

The input circuit of the triode 88 may similarly be traced from the filament 88, by way of the conductor I00, through the calibrating resistor I30, the lower portion of the potentiometer H8, and the adjustable arm I34, and by way of the conductor I33, through the resistor I38, to the grid II8. One of the ends of each of the respective resistances I38 and I38 is thus connected other ends are connected to a potential position' with respect to the

cathodes

96 and 98, byway of the conductor I33, to the adjustable arm I34 ofthe potentiometer H8. The said other ends of the resistors I 36 and l38 are thus maintained positive with respect to the

cathodes

96 and 98; The output circuit of the triode 89 may be traced from the filament 96, by way of the conductor I00, through the calibrating resistor I30, the potentiometer H8, and the calibrating resistor I2I and, by way of the conductor I32, through the resistor I22, to the anode 92. The output circuit of the triode 88 may similarly be traced from the filament 98, by way of the conductor I00, through the calibrating resistor I30, the potentiometer H8 and the calibrating resistor I2I and, by way of the conductor I32, through the resistor I24, to

the anode-94, =The condenser I isconnected between the [grid II6 of the electron-discharge device 88 and the anode 92of the electron-discharge device 89, and the condenser I26 may be connected in parallel therewith. The condenser I2! is similarly connected between the grid I I4 of the electron-discharge device 88 and the anode 94 of the electron-discharge device 88, and the condenser I28 maybe connected in parallel therewith.

With the switch 86 in the position A, the output of the oscillator, taken from the plateof one of the triodes, is connected to the stroboscopic lamp I through the coupling condenser83 and the conductor 58.

The principles of operation of .the oscillator and its production of a saw-tooth wave form are" well understood in the art and hence will not be gone into here. In the usual oscillator, the conductor I33, joining the ends of the grid resistors I36 and I38, is connected to the cathode circuit of the triodes, represented by the conductor I00. The frequency ,of the oscillator is then varied by varying the resistors I36 and I38. Since the resistors I36 and I38 are of considerable magnitude (say, 1 megohm), they are not conveniently procurable in the variable form and, furthermore, varying these resistors gives a non-linear frequency scale of the exponential type.

According to the present invention, the frequency of the multivibrator is controlled linearly by adjusting the slider I34 back and forth on the potentiometer II8 to vary the positive bias on the grids of the

triodes

88 and 89 in a linear fashion. This yields not only a linear frequency scale and a wide frequency range,as much as six to one.

- The potentiometer I I6 is calibrated in flashes per minute of the stroboscope lamp, with the aid of a vibrating reed I40 and the calibrating resistors I2I and I30. It has a direct-reading scale of frequency against resistor setting, instead of an exponential scale, as formerly obtained. Asomewhat greater frequency range occurs, moreover, with reasonable values of resistance in the potentiometer II8.

The potentiometer H8 is provided with two linearly calibrated or uniformly divided scales (not shown), with a four-to-one factor between them. The frequency of the oscillator is shifted by this factor by means of the condensers I26 and I28. Connecting these condensers in the circuit by means of their accompanying switches reduces the frequency of the oscillator and shifts the whole frequency scale in linear fashion, the amount of the shift depending on the values of the condensers. The stroboscope may have a I22 with condenser I25, and the time constant of resistor I24 with condenser I21, be appreciably less than the shortest interval between oscillations at the high-frequency end of the scale. The condenser I29 may be connected across the conductors I00 and I32, in parallel with the resistors I2I and I30 and the potentiometer II8, to correct a slight curvature at the lower end of the scale.

There is a tendencyfor the scale or scales (not shown) to have a further slight curvature in the region of operation of the oscillator with the bias voltage on the grids at the lower end, near the zero, of the scale. This may be corrected for by having the minimum value of the resistor I30 not less than about ten per cent of the potentiometer I I8. In actual practice, the variation in frequency per unit adjustment of the slider I34 may be slightly greater or less than that indicated on the scale. sistors I2I and I 30, however, serve to adjust the calibration of the frequency scale by matching the oscillator to the scale. The resistor I2I adjusts the frequency of the oscillator at the high end of the scale to correspond to the scale markings (not shown), without appreciably affecting the lower end of the scale, and the resistor I30 similarly adjusts the lower end of the scale, without affecting the higher end. Both resistors I2I and I30, at their respective ends of the scale, serve to adjust the rate at which the frequency of the multivibrator changes in response to changes in the applied bias voltage. By means of these resistors it is possible so to calibrate the oscillator as exactly to match the frequency to the linearly calibrated scale provided, regardless of slight variations in the oscillator circuit due to manufacturing errors or aging of the parts.

The invention also provides a means for checking the calibration'of the oscillator. According to the specific embodiment of the invention that is illustrated and described herein, the checking apparatus comprises the vibrating reed I43, driven by means of a solenoid I42 in exact synchronism with the alternating current of the line. To this end, the solenoid I42 is connected in circuit with a switch I44 and conductors I46 and I48 across the alternating-current supply. At most localities, the frequency of the alternating mains is controlled with suflicient accuracy to enable the vibrating reed I 40 to serve as a standard. The reed is placed so that the light from the flashing lamp falls upon it so that, when the flashing rate of the lamp is the same as the frequency of the reed, the reed appears to stand still. When this occurs, the slider I34 of the potentiometer III should be at a marked calibrating point. If it is not, it may be brought to the proper point by adjustments of the calibratingresistors I2I and I30. The check is easily and quickly made and serves to compensate for factors that may impair the calibration. -The resistors I2I and I30, as before explained, enable setting of frequency of the oscillator in terms of the 60-cycle reed I40 to correspond to the scale markings at both ends of the scale, without disturbing the linear variation of frequency with adjustment of the slider I34 over the potentiometer H8. The resistors I2I and I33 may be said to serve the function of so tipping the whole frequency scale that the value, say 3600, checked at one frequency by means of the reed I40 shall correspond to all frequencies The before-mentioned variable re-' throughout the length of the scale. Uniform rate of change of frequency corresponding to the adjustment of the slider I34 is thus preserved throughout the length of the scale.

An alternative method of checking the calibration is shown by a glow lamp I50 and a resistor I49, connected in series to the alternating-current supply at one anode of the rectifier I1 and to the anode 5 of the stroboscope lamp. When the frequency of the alternating-current supply and the stroboscope are the-same and in phase, the glow lamp will be extinguished. When the frequency is slightly different, the glow lamp will go on and off at a rate equal to the difference in frequency. This is the familiar beat method of matching frequencies.

By closing the switch 85, an alternating-current voltage is applied to the oscillator from the transformer 18 through the resistance 84 and the conductor 20. This causes the oscillator to run at the frequency of the line voltage and in exact synchronism therewith. This is useful in certain applications of the stroboscope.

The light produced by this stroboscope, obtained from a 115-volt, 60-cycle alternatingcurrent source, is sufficient to permit good stroboscopic observation of mechanisms, particularly when the light is concentrated by means of a parabolic reflector. Because of the calibrated frequency scale, the stroboscope is particularly useful in measuring the speed of rotating or vibrating mechanisms.

Modifications will occur to persons skilled in the art, and all such are considered to fall within the scope and spirit of the invention.

What is claimed is:

1. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers conn cted, re-

spectively, between the grid of each of the sets and the impedance of the other set, and means for adjusting the potentiometer to vary the bias on the grids in order to control the frequency of the multivibrator.

2. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, and input circuit connectrd between the filament and the grid of each set. an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes. a potentiometer connected in both output circuits, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, and a variable impedance connected between one end of the potentiometer and the filaments.

3. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set. an output circuit connected between the filament and the plate of each set, an impedance c nnected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, and a variable impedance connected between one end of the potentiometer and the plates.

4. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a late, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits, two condensers connected, respectively, between the grid of eachof the sets and the impedance of the other set, and a variable impedance connected between one end of the potentiometer and the plates in series with the respective two first-namedimpedances.

5. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, 9. potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, means for adjusting the potentiometer to vary the bias on the grids in order to controlthe frequency of the multivibrator, and a variable impedance connected between one end of the potentiometer and the filaments.

6. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, means for adjusting the potentiometer to vary the bias on the grids in order to control the frequency of the multivibrator, and means for calibrating the potentiometer.

'7. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament andthe grid of each set, an output cir-' cuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively,

between the grid of each of the sets and the impedance of the other set, means for adjusting the potentiometer to vary the bias on the grids in order to control the frequency of the multivibrator, means for calibrating the potentiometer, and means for adjusting the calibration.

8. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the sets and the impedance ofthe other set, means for adjusting the potentiometer to vary the bias on the grids in order to control the frequency of the multivibrator, and means for calibrating the potentiometer comprising a variable impedance connected between one end of the potentiometer and the filaments.

9. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, means for adjusting the potentiometer to vary the bias on the grids in order to control the frequency of the multivibrator, means for calibrating the potentiometer, and means for checking the calibration.

10. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, means having a scale for changing the frequency of the multivibrator, a vibrating member, and means for adjusting the scale of the frequency-changing means in accordance with the vibrations of the vibrating member.

11. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of th sets of electrodes,

plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other-set of electrodes, two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, and means for applying an adjustable positive voltage to the input circuits ,to adjust the frequency of the multivibrator. 13. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between thean adjustable positive voltage across the potenan impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of" each of the sets and the impedance of the other set, means for adjusting the frequency of the multivibrator, a vibrating member energized to vibrate at a predetermined frequency, and additional means for adjusting the output frequency of the multivibrator, thereby to calibrate the output frequency of the multivibrator.

12. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the tiometer to apply an adjustable positive voltage to the input circuits, thereby to adjust the fre-,

quency of the multivibrator.

14. An electric system comprising an oscillator having an input circuit and an output circuit, a source of alternating voltage, and means for calibrating the oscillator comprising a glow lamp connected to the output circuit and the source.

15. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes,

an impedance connected in the output circuit oi! the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, two condensers connected, respectively, between the grid of each of the'sets and the impedance of the other set, and means for adjusting the potentiometer to vary the bias on the grids in a linear fashion in order to control the frequency of the multivibrator linearly.

16. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits to bias the grids positively, a scale associated with the potentiometer, and two condensers connected, respectively, between the grid of each of the sets and the impedance of the other set, the'time constant of each condenser and the impedance to which it is connected being appreciably less than the shortest interval between oscillations. at the high-frequency end of the. scale.

17. A multivibrator comprising two sets of electrodes, each comprising principal electrodes, namely, a filament and a plate, and also a grid, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an imother set of electrodes, a potentiometer connected in both output circuits, two condensers connected, respectively, between the grid of=each of the sets and the impedance of the other set, and an impedance connected between one end of the potentiometer and one of the principal electrodes.

18. A multivibrator comprising two sets of electrodes, each comprising a filament, a grid and a plate, an input circuit connected between the filament and the grid of each set, an output circuit connected between the filament and the plate of each set, an impedance connected in the output circuit of one of the sets of electrodes, an impedance connected in the output circuit of the other set of electrodes, a potentiometer connected in both output circuits, two condensers connected, respectively, between the grid of each electrode of the other discharge device, a pair of resistances, means for connecting one end of each resistance to said control electrodes, and means for maintaining the other ends of said pair of resistances positive with respect to said cathodes and negative with respect to said anodes.

20. An oscillator for producing a saw-tooth wave form comprising a pair of electron discharge devices each of which includes a cathode, a control electrode, and an anode, means including anode resistances for maintaining said anodes positive with respect to said cathodes, means including electron storage devices for connecting the anode of each discharge device to the control electrode of the other discharge device, and

means including a pair of resistances for con-- necting said control'electrodes to a source of potential positive with respect to said cathodes.

21. An oscillating circuit for producing a sawtooth wave form comprising a pair of electron discharge tubes each including an anode, a control electrode, and a cathode, means including a pair of resistances for connecting said anodes to a source of potential positive with respect to said cathode, a condenser connected between, the anode of each tube and the control electrode of the other tube, a resistance connected to the control electrode of each tube, and means for connecting the other end of the control electrode resistances to a potential positive with respect to said cathodes.

22. A multivibrator comprising two sets of electrodes, each comprising a cathode, a control electrode and an anode, an input circuit connected between the cathode and the control electrode of each set. an output circuit connected between the cathode and the anode of each set, an impedance connected in the output circuit of one of the sets of electrodes for maintaining the anode of the said one set of electrodes positive with respect to the cathode of the said one set of electrodes, an impedance connected in the output circuit of the other set of electrodes for maintaining the anode of the said other set of electrodes positive with respect to the cathode of the said other set of electrodes, two condensers connected, respectively, between the control electrode of each of the sets and the anode of the other set, and means for energizing the output circuits and for applying an adjustable positive voltage bias on the control electrodes in order to control the frequency of the multivibrator.

23. A multivibrator comprising two sets of electrodes, each comprising a cathode, a control electrode and an anode, an input circuit connected between the cathode and the control electrode of each set, an output circuit connected between the cathode and the anode of each set, an impedance connected in the output circuit of one of the sets of electrodes for maintaining the anode of the said one set of electrodes positive with respect to the'cathode of the said one set of electrodes, an impedance connected in the output circuit of the other set of electrodes for maintaining the anode of the said other set of electrodes positive with respect to the cathode of the said other set of electrodes, two condensers connected, respectively, between the control electrode of each of the sets and the anode of the other set, means for energizing the output circuits and for applying an adjustable positive voltage bias on the control electrodes in substantially linear fashion in order to control the frequency of the multivibrator substantially linearly, and means for adjusting the rate at which the said frequency changesdn response to changes in the applied bias voltage.

24. A multivibrator comprising two sets of elec trodes, each comprising a cathode, a control electrode and an anode, an input circuit connected between the cathode and the control electrode of each set, an output circuit connected between the cathode and the anode of each set, an impedance connected in the output circuit of one of the sets of electrodes for maintaining the anode of the said one set of electrodes positive with respect to the cathode of the said one set of electrodes, an impedance connected in the output circuit of the other set of electrodes for maintaining the anode of the said other set of electrodes positive .with respect to the cathode of the said other set of electrodes, two condensers connected, respectively, between the control electrode of each of the sets and the anode of the other set, means for energizing the output circuits and for applying an adjustable positive voltage bias on the control electrodes in substantially linear fashion in order to control the frequency of the multivibrator substantially linearly, the last-named means including an impedance, and means for varying the last-named impedance to adjust the rate at which the said frequency changes in response to changes in the applied bias voltage.

KENNETH J, GERMESHAUSEN.