US2471246A

US2471246A - Electronic apparatus

Info

Publication number: US2471246A
Application number: US537276A
Authority: US
Inventors: Lester C Smith
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1944-05-25
Filing date: 1944-05-25
Publication date: 1949-05-24
Anticipated expiration: 1966-05-24

Description

,May 24, 1949.

1.. 0. SMITH 2,471,246

ELECTRONIC APPARATUS Filed May 25, 1944 llllll CENTERING CONTROL \NTENSITY CAT HODE.

TO CON 0L AAAAAA INVEN TOR. L. c. smm-u.

ATTORNEY Patented May 24, 1949 2,471,246 ELECTRONIC APPARATUS Lester C. 'Smith,

of Delaware Westmont, N. J., assignor to Radio Corporation of America,

a corporation Application May 25, 1944, Serial No. 537,275

10 .Claims.

The present invention relates to an improvement in cathode ray Oscilloscopes, and more particularly to-oscilloscopes"wherein single sweep deflection provisions are present.

'-In U. S. patent application entitled Deflection circuits flled by this applicant concurrently-herewith as Serial'No. 53-'7',2'75, issued December 10, 1946, as Patent No. 2,412,542, a circuit arrangement isshownand described wherein voltage variations be used for deflecting a cathode ray beam in -a-cathode ray oscill'oscope. The circuit arrangement 'is of such a nature that the cathode ray beam may -be de'flected across the screen of the viewing tube each be observed is applied thereto, the beam bein normally maintained :in a static condition in the absence \of :such transient conditions. By "means :of the circuit arrangement, single sweep deflections of a cathode ray beam may be produced.

Since transient phenomena do not, in most instances, :occur at regular intervals, single sweep provisions must be made :in order that an apparently stationary trace may be produced on the screen or rta'rget area of the :cathode ray tube 'used it)! :observation purposes. In some instances, it is possiblerthata transient phenomena :may .OCCllIliIl relatively widely spaced time :intervals, whereas in other instances the same transient phenomena may-occur in rather rapid succession. If ;a :single sweep deflection geniera'tor is -usedawhich will respond to each transient condition, then the horizontal deflection aOf theucathode ray,=beam, in the oscilloscope will be deflected-,atsuch intervals when the transient condition :occurs, with :the result that the horiizontal deflections oi the cathode :ray beam may ioccur during rather spaced intervals or the .sweep deflection may ;be produced in relatively .rapid successionzover. afperiodof time. By reason -;of this inconsistencyin the :frequency of occurrence of the transient phenomena and the resultant inconsistency in the repetition frequency of the cathode :raybeamz-sweep deflections, certainlundesirablereffects will result in a conventional deflection amplifier and in the circuits associated with the cathode .ray tube which will acause a change in-lthe biasing or static conditions present in the circuit.

More specifically, :in' cathode ray oscilloscopes a provisionris .made whereby the hori- :.zontal :position of .a cathode :ray beam as well lras'the area traversedzby thexbeam'duringits hori- Isontal deflectionimayube controlled manually are developed which may time .a transient signal to w I for centering purposes. applies a predetermined static bias to the de- This centering control fleeting plates of the cathode ray tube so that when the sweep deflection potentials (of properly adjusted intensity) are superimposed :thereon, the cathode .ray beam will be deflected between predetermined prescribed limits and over a predetermined portion of the viewing screen. It is naturally desirable that this predetermined bias potential that is applied to the .deflecting plates of the :cathtode ray tube remain substantially unchanged (unless a change is deliberately made) since any change in the biasing potentials applied to the plates will cause a shifting of the :area transversed by the beam during its deflections.

Due to the nature of circuit arrangements usually associated with. cathode ray tube tin toscilloscopes, when the sweep deflection rates are rapidly varied a.gradual change in the average potential of the-deflecting plates takes place, with the result that after a series of rapidly successive deflections, the .area traversed by the cathode ray beam may shift in one direction or another and the produced image is accordingly shifted. iSuch an operation is undesirable since it is preferable that the produced image or trace remain apparently stationary.

The same or a-similar situation exists in re- ;gard to a deflection amplifier tubes that are associated with the deflection plates of the cathode ray tubes.

A purpose of the present invention, therefore,

resides in the provision of means in a cathode ray oscilloscope whereby the deflection potentials :applied to the cathode ray beam are maintained within the desired range regardless of the frequency at which the cathode ray beam is deflected across the screen of the viewing tube.

Another purpose of the present invention resides in the provision of means in a cathode ray oscilloscope wherein single stroke deflection provisions are available whereby the area or .region traversed by :the cathode ray beam during its sweep deflections remains unchanged regardless of whether the deflections are widely separated in point .of time or whether they occur in rapid succession.

Still another purpose of the present invention resides in the provision of means whereby the centering or bias potential applied to the deflecting electrodes of a cathode ray oscilloscope will remain within the desired range regardless of the particular superimposed deflection voltages applied therefore.

A still further purpose of the present invention resides in the provision of means in a deflection amplifier for a cathode ray oscilloscope whereby the bias potential applied to the deflection amplifier tubes remains within the desired range regardless of the wave form of the applied voltage variations.

Other purposes and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description wherein:

Figure 1 represents a preferred form of the present invention: and

Figure 2 shows a curve used in explaining the operation of the system.

Referring now to the drawing, a pair of defiection tubes and are used for causing horizontal deflections of the cathode ray beam. These tubes each include a cathode, a control electrode and an anode. The cathode l2 of tube It and the cathode 22 of tube 20 are connected together, and are connected to ground or a source of fixed potential by means of a series arrangement of

resistances

32, 34, 36 and 33.

The control electrode M of tube it? is connected to input terminal 40 by way of coupling condenser 42 and a relatively small oscillation suppression resistance 44. A grid resistance 33 is connected to extend between the junction of the coupling condenser 42 and the resistance i l and the junction of resistances 32 and 3d. This connection afiords a certain amount of self bias for tube H], the extent of the bias being determined by the combined resistance of the

re sistance elements

34, 36 and 38.

The control electrode 24 of tube 23 is connected to the junction of resistances 3i; and 38 by means of a relatively small oscillation su pression resistance 48 and grid resistance 56. This connection affords a bias between the oathode 22 and. control electrode 24 of tube 23 in an amount determined by the potential drop across resistance 38. The junction of the resistance 38 and the grid resistance 50 is connected to ground by means of a relatively large condenser 52.

The anodes It and 26, respectively of tubes ill and 23 are connected, by way of a load circuit, to terminal 54 to which a source of positive potential is applied. Each anode load circuit in. cludes a load resistance 56 and may include a peaking coil or inductance 58. Voltage variations present at the anodes l6 and 23 of the deflection tubes I 3 and 20 may then be applied to the horizontal deflecting plates of a cathode ray tube.

In the circuit arrangement so far described, tubes l3 and 20 afford cathode ray beam deflection potentials in an out-of-phase relationship so that a push-pull action may result. Only a single input is provided at terminal it, and by reason of the circuit arrangement associated with tubes l3 and 29, a phase inversion or pushpull operation is accomplished. It will be noticed that the bias potential applied to control electrode I 4 relative to the cathode i2 is determined by the potential drop across the three

series resistances

34, 36 and 38, whereas the bias potential applied to the control electrode 23 relative to cathode 22 is determined by the voltage drop across resistance 38 only. By proper choice of the relative size of these resistances, the tubes l0 and 20 may be biased at different static conditions.

It will also be observed that the control electrode 24 is efiectively connected to ground ins0- far as an alternating current component is con cerned by means of relative large condenser 52. This precludes any modulation of the potential applied to the control electrode 24. The input potentials which are applied to the terminal to are impressed upon the control electrode 54 of tube Hi and the electron stream in tube 23 is subjected to cathode modulation.

Referring now to Figure 2, there is shown a curve representing the plate-current/grid-potential characteristic of tubes l0 and 28, and the

resistances

34, 36 and 38 are so chosen that the normal bias applied between the control electrode and cathode of tube I0 is of a value similar to that, for example, represented by the dotted line E10 of Figure 2. Furthermore, since only the voltage drop across resistance 33 is utilized in biasing the control electrode 24 of tube 251 relative to its cathode, the bias potential on tube 28 will be materially less than that applied to tube It! and the value of resistance 38 is chosen such that this bias potential will be approximately as represented by the dotted line E20 of Figure 2, indicating a rather low bias condition.

With this arrangement, when signals or voltage variations extending in a positive direction, such as represented by curve 60, are applied to the input terminal 40, the potential of the con trol electrode I4- is modulated in a positive direction relative to the cathode l'2 which reduces the bias applied to tube IE], and accordingly increases the amount of current permitted to pass through the anode circuit of tube I0. This increased current causes a fluctuation in the potential of the cathodes l2 and 22 in a corresponding positive direction so that the cathode 22 of tube 29 is modulated in a positive direction, which results in a reduction in the amount of current permitted to flow in the anode circuit of tube 20.

The application of positive impulses or voltage variations to the input terminal 49, therefore, results in momentary increases in the current permitted to flow in the anode circuit of tube ill and corresponding momentary decreases in the current permitted to flow in the anode circuit of tube 20. These momentary increases and decreases in current in the two anode circuits produce, respectively, corresponding negative and positive potential variations in the anode circuits of the two tubes, as indicated by the curves Gill and 632. A push-pull deflection action is, therefore, produced although only a single input is provided.

Referring again to Figure 2, it will be seen, therefore, that the bias potential on tube It is normally that represented by E10 and the bias potential on tube 20 is normally that represented by E20. When signal potentials extending in a positive direction are applied to the input terminal, the bias potential applied to tube I l is decreased from the value represented by the dotted line E10 and simultaneously the bias potential of tube 20 is increased from the value represented by the dotted line E20.

Figure 1 also shows a portion of a cathode ray tube 62 which includes

horizontal deflecting plates

64 and 66, as well as a pair of vertical de fleeting plates 68. The signal to be observed is naturally applied to the vertical deflecting plates 68, and since such circuit arrangements are well known to those skilled in the art no provision is indicated for applying a transient signal or other voltage variation to be observed to the vertical deflecting plates. The horizontal the secondanode able contact of potentiometer 90 in order to afford a focus control, and

. Stand 96 is connected to:

cting plate 64, is connected to the anode H or deflection tube H) by means of a coupling conde ser 10. A series connected peaking induct- ;anoe 12' may be included in the circuit and the 'may be effectively applied to the horizontal defleetin Plates 64 and as.

" For reasons ofsimplicity the electron gun structure of the cathode ray tube 62, is not shown, but as is the usual custom, negative potentials may be applied to the cathode and control electrode of the electron, gun structure, relative to the gun anode in order that a desired cathode may be generated. The highvol-tage negative poray beam tential may be connected to terminal 82- with the associated-positive potential connected to the terminal: 84. Between these two terminals is connected the usual bleeder resistances including potentiometer g6, resistance 88, potentiometer 9t,

resistance 92-, andparal-lelly connected centering '

potentiometers

94 and 96.

The cathode of th electron gun structure may be connected to the junction of-

resistances

86 and 88, as indicated in the drawing, in which case the control electrode would be connected to a movable contact of' potentiometer 86. Similarly,

would be connected to the movthe first anode of the cathode ray tube may be connected to ground or to a potential approximating that applied to the terminal 84.

Due to the current flowing through this series of resistances including the centering

controls

94 and 96, the potential along the potentiometers variable and the adjustable contact associated with each of these potcntiometers is the deflection plates 6,4 and 66 by 'way of relatively high resistances 98 and IjOil, re-

spectively. By an adjustment of the position of the movable contacts along potentiometers 94 and 96-, a horizontal adjustment of theposition of the cathode ray beam is made possible.

Preferably the two centering controls, i. e., the movable contacts associated with potentiometers 9 4 andjfifi are ganged. together for simultaneous operation. Such a procedure is well known to those skilled in the art. The movable contacts associated with, these centering potentiometers are connected to ground by way of condensers I02 and IM in order to preclude the possibility of any possible rapid, potential fluctuations on the potentiometers from reaching the deflecting elecrodes- "I hecircuitarrangement as so far described affords a, means for causing deflections of a cathode ray beam, the deflecting potentials bein applied to the deflecting electrodes in. a push pull manner in response to the application of a single voltage variation toinput terminal 40. If the cathode ray oscilloscope is to be used, in, a conventional manner where the deflection potentials are regularly recurrent at a predetermined rate determined. by thev frequency of operation of the deflection generator, the cathode ray beam will be deflected repea dly n. a orizontal direction.

f: the eflection. voltage. variations. ecapplied to tr einputterminalmll: arenot regularly recurrent but are derived from a single sweep deflection generator, then, under certain conditions, certain undesired efiects will take place. For example, the bias E10 normally present between control electrode and cathode of tube I0. is determined by the voltage drop across

resistances

34, 36. and 38. This bias is applied to the control electrode by way of grid resistance 46, and a coupling condenser 42 is included between the input terminal 41] and the grid end of the grid resistance. 4:6,.

Suppose, for example, that no deflection voltage variations are applied to the input terminal, then the static bias condition will, of course,

,prevail on tubes lit and 20. If a recurrent transient condition occurs, then for each transient condition a deflection voltage variation extending in a positive direction will be applied to the input terminal Ml from the. single sweep. deflection generator (an example of which is shown and described in the above mentioned L. C. Smith application). These deflection voltage variations may occur at rather widely spaced intervals or they may occur in relatively rapid succession. The deflection voltage variations, as applied to input terminal All, extend in a positive direction to modulate the control electrode IA of tube 10 in a positive direction from its normal static bias potential E10 of Figure 2. If the individual single sweep deflection voltage variations are widely separated in time, then the modulation of the control electrode M will. be in a positive direction and very little or no distortion will result.

If, however, a series of rapid or closely spaced deflection voltage variations are applied to the input terminal 40, after a few cycles the alternating current axis will shift (due to the presence of condenser 42) with the result that the voltage swing in a negative direction from E 10 will become appreciable and may in fact approach the swing in positive direction from E10. Such a conditiOn is undesirable since appreciable potential, changes in a negative direction from Em would drive. the control electrode potential of tube [0 beyond cutoff and result in serious diSlEOr iO 0 the defl ction wave form.

In order to overcome this undesirable operation some provision must be made to prevent excessive excursions of the control electrode IA of tube It) in a negative direction fromlilio, regardless of the wave form or characteristics of the input signal. For this purpose the diode it is included in. the circuit as described above. The diode is connected across grid resistance 46 so that any potential change of the control electrode l=4 in= a direction appreciably negative with respect to the potential E10 causes the cathode of the diode M0 to become negative with respect to its anode with the result that the diode becomes conductive. Due to the conduction of the diode I I0 a potential is produced across resistance 46 thus causing a charge to accumulate on condenser 42 which displaces the average potential of the control electrode M in a positive direction withv the result that the control electrode is never driven in a negative direction from potential E10 by any appreciable extent. Accordingly, distortion is prevented and the control electrode modulations are always in a positive direction with respect to potential E10 regardless of the frequency of occurrence of the sweep deflection potential variations to input terminal 4:0.

For similar reasons, and in the absence of the diode I20, it is possible for the control electrode 24 of tube 20 to be effectively modulated by asubstantial amount in a direction positive with respect to the potential E20. Since it is desired that the potential difference between the control electrode 24 and the cathode 22 of tube 20 be confined primarily to the region between E20 and E10, a diode I20 is included in parallel with the grid resistor 56. The operation of this diode upon the presence of a series of closely spaced deflection potential variations is similar to the operation of the diode I I and results in precluding any appreciable effective modulations of the control electrode 24 in a direction positive with respect to the potential E20. Actually the modulation of the electron stream in tube is by cathode modulation while the undesired operation is prevented by a change in the potential of the control electrode by reason of the operation of diode I20. The applied deflection wave form will, therefore, be amplified without distortion regardless of the frequency of occurrence of the sweep deflection voltage variations.

When diodes H0 and I20 are included in the circuit it is possible, therefore, to apply sweep voltage variations to tubes I0 and 20 where such voltage variations are subjected to amplification, and the degree of amplification remains constant and without appreciable or objectionable distortion regardless of the rate or frequency at which the voltage variations are applied and regardless of the rate at which their frequency of application varies. Amplified deflection voltage variations are then present at the anodes of tubes I0 and 20 and at the coupling condensers '10 and 16.

These deflection voltage variations are applied to the

horizontal deflecting plates

64 and 66 of the cathode ray tube 62.

Since the sweep voltage variations may be rather widely separated or closely spaced in point of time, a change in the position (average) of the trace on the screen of the cathode ray tube may occur by reason of a shift in the alternating current axis of the voltage variations present at the coupling condensers I0 and 16. If the alternating current axis shifts appreciably, as when a rapid succession of deflection voltage variations occur, the produced trace will gradually shift horizontally across the screen and such shifting is, of course, objectionable.

In order to preclude a horizontal shifting of the position of the trace on the cathode ray oscilloscope tube, diodes I and I26 are employed and these are effectively connected in parallel with resistances 98 and I00, respectively. The anode of diode i 2 2 is connected to the cathode ray beam deflection plate 64, i. e., to the end of the resistance 98 which is subjected to the deflection voltage variation. The cathode of diode I24 is connected to the centering control end of resistance 98, which point in the circuit is effectively connected to ground, insofar as any alternating current component is concerned, by reason of the inclusion of condenser I02.

The diode I26 is poled in an opposite manner since the undesired change in potential of the conductor connected to the deflecting plate 65 is in a direction opposite to that which occurs in connection with the other deflecting plate. In this case, the cathode of the diode I26 is connected to beam deflection plate 66 and to the end of resistance I 06 that is subjected to full deflection potential variations. The anode of the diode I26 is connected to the centering control end of resistance 1106, which point in the circuit is effectively connected to ground, insofar as any alternating current component is concerned, by reason of the inclusion of the condenser I04.

As explained above, under static conditions the potential at the coupling condenser 10 and at the deflecting electrode 64 is maintained at a predetermined value. When a series of deflection voltage variations are successively transmitted through the circuit the alternating current axis of the voltage variations present at coupling condenser I0 shifts and after a few cycles the potential deviations as applied to the deflecting electrode 64 will become effective on both sides of the normal average potential of the electrode I54v with the result that the negative peaks will not cause as great a deflection of the beam from the electrode 64 and the positive portion of the deflection voltage variations will, in fact, cause the beam to be attracted nearer the electrode 64 resulting in a shift of the trace toward the left across the screen. It is desired that the deflection voltage variations cause a repulsion only of the beam and that these variations do not extend in a direction appreciably positive with respect to the normal bias potential of electrode 64.

When diode I2 5 is included in the circuit as described above, any variation of the potential of electrode 6% in a direction positive with respect to the normal bias potential determined by potentiometer :3 causes the diode to conduct which results in the production of a potential drop across resistance 98. The end of the resistance adjacent coupling condenser I0 becoming negative with respect to the other end so that the tendency for the trace to shift is compensated. This change in potential of the end of resistance 98 may be looked upon as resulting in a change in the average potential of the deflecting electrode 64 in a negative direction by an amount corresponding to the shift in the alternating current axis so that the potential deviations of electrode 64 may always extend in a negative direction from the normal static potential of electrode fill with Very little or no deviation in potential in a positive direction from that static potential value. By reason of the diode I 24, the trace remains in a fixed position and does not shift horizontally regardless of the rate or change in rate at which the deflection voltage variations are applied.

Similarly, diode I26 prevents a similar effect from taking place with respect to deflecting electrode 6B. This diode is poled oppositely with respect to diode I24 since the deflection voltage variations present at coupling condenser I6 are in push-pull relation to those at condenser I0. Diode I25, therefore, produces a potential across resistance we so that the potential deviations of electrode 66 are always in a direction positive with respect to the normal static bias potential of the electrode regardless of the wave form applied thereto.

By reason of the present invention, it is possible to apply single sweep deflection potentials to the deflecting circuit amplifier and to the deflecting plates of a cathode ray tube at any desired rate and in any wave form without in any Way affecting the operation of the system. The inclusion of the diodes II 0 and I20 prevents a shift in the grid modulation range of tubes I0 and 2d, and the inclusion of the diodes I 24 and IE6 prevents a shift of the oscillographic trace on the screen of the cathode ray tube. It is,

therefore, immaterial whether the deflecting potential variations occur in regular sequence and, in fact, a Wide deviation in the rate of application of the deflection potentials to the circuit is entirely possible without affecting the operating characteristics of tubes I0 and 20 and without causing 'anyshift whatever in the horizontalrpositioniri'g oilthe trace on the screen of the cathode raybscilloscope tube.

Although the have tion is described more or less in detail, and although push-pull operation is shown,- asingle amplifier may also be used in whichthe present invention is employed and the deflectingv potentials may be applied to one plate only of the horizontal deflecting plates. Furthermore, the present invention may be applied to any type amplifier where a similar situation exists and need not be confined to oscilloscope use.

Various other alterations and modifications may bemade therein without departing from the spirit and scope thereof, and it is desired that any and all such alterations and modifications be-considered within the purview of the present invention, except as limited by the hereinafter appended claims. I

Having now described the invention, what is claimed is: I v

1. A cathode ray oscilloscope including an amplifier tube having a cathode, a control electrode and an anode, means for applying a predetermined static bias potential between the control electrode and the cathode of said tube, condenser means for applying voltage variations extending in a predetermined potential direction and of varying wave form to the control electrode of said tube, a unilateral conducting device associated with the co trol electrode of said tube toconfine the operation of the tube to a predetermined portion of its operating characteristic so that amplified voltage variations are present at the anode of said tube, a cathode ray tube lncludinga pair of cathode ray beam deflecting electrodes, means for applying a predetermined static bias potential to one of the deflecting electrodes relative to a point of fiXcd potential, condenser means for applying the amplified voltage variations to the said one deflecting electrode, and means including a unilateral conducting device for preventing a shift in the area traversed-by the deflected cathode ray beam by reason of changes in the wave form of the applied voltage variations.

2. A cathode ray oscilloscope including an amplifier tube having a cathode, a control electrode and an anode, -xrieans for applying a predetermined static bi'as potential between the control electrode and the cathode or said tube, means for applying voltage variations of varying wave form to the control electrode of said tube, a unilateral conducting device included in the control electrode circuit of said tube to confine the potential variations of the control electrode of the tube to a predetermined potential direction from the bias potential so that consistently uniformly amplified voltage variations are present at the anode of said tube, a cathode ray tube including a pair of cathode ray beam deflecting electrodes, means including a resistance for applying a predetermined static bias potential to one of the electrodes relative to a point of fixed potential, means for applying the amplified voltage variations to the said one deflecting electrode, and means including a unilateral conducting device connected in parallel with said resistance for preventing any alteration in the area traversed by the deflected cathode ray beam by reason of changes in the wave form of the applied voltage variations.

3. A cathode ray oscilloscope including an amplifier tube having a cathode, a control electrode variations are present at with each resistance for sition of the beam,

and an anode, means including a resistance for applying a predetermined static bias potential between the control electrode and the cathode of for applying voltage variations.

said tube, means to the control electrode of said tube, a unilateral conducting device connected in parallel with said resistance to confine the operation of the tube to a predetermined portion of its operating characteristic regardless of the wave form of the applied voltage variations so that amplified voltage the anode of said tube, a cathode ray tube including a pair of cathode ray beam deflecting electrodes, means including a second resistance for connecting one of the. defleeting electrodes to a point of fixed potential,- means for applying the amplified voltage variations to the said one deflecting electrode, and means including a diode connected in parallel with said second resistance in the deflection limits of the ray beam by reason of changes in the wave form and the applied voltage variations.

4. A cathode ray oscilloscope apparatus in-.

cluding a push-pull deflection amplifier comprising two tubes each including a cathode, a control electrode and an anode, means for connecting the cathodes of the two tubes together, means including a resistance to connect the cathodes to a point of fixed potential, a first grid resistor connecting the control electrode of one of the tubes to one point along said resistance, a second grid resistor connecting the control electrode of the other of the tubes to another point along said resistance, whereby a difierent bias potential is maintained on the two tubes, means to apply modulating voltage variations of variable wave form to the control electrode of one of the tubes to thereby modulate the bias potential of the tubes in a push-pull manner and in opposite directions by the voltage variations, and means to confine the potential modulation to a predetermined deviation range relative to the bias potential of each tube regardless of the Wave form of the applied voltage variations, said lastnamed means including a unidirectional current conducting device connected across a portion of the resistor in the control electrode circuit of each of the amplifier tubes.

5. A cathode ray oscilloscope including a cathode ray tube having a pair of cooperating defiecting electrodes for deflecting the cathode ray beam in a predetermined plane, means for applying a predetermined static bias potential to the deflecting electrodes to determine the static pomeans for applying a deflection voltage variation in push-pull relationship to the deflecting electrodes in order to cause deflection of the cathode ray beam and means for preventing a shift in the area traversed by the cathode ray beam due to a change in the alternating current axis of the applied voltage variations, said means including a pair of unilateral conducting devices.

6. A cathode ray oscilloscope adapted to include a cathode ray tube having a pair of cooperating deflecting electrodes for deflecting the cathode ray beam in a predetermined plane, means including a high resistance for connecting each deflecting electrode to a point of fixed potential, means for applying a variable wave form deflection voltage variation in push-pull relationship to the deflecting electrodes to cause deflections of the cathode ray beam at variable intervals, and means including a diode associated preventing a shift in for preventing a shift deflected cathode 1 l the average position of the cathode ray beam due to a change in the alternating current axis of the deflection voltage variations caused by a change in wave form.

7. A cathode ray oscilloscope adapted to use a cathode ray tube having a pair of deflecting electrodes to which deflection potential variations may be applied comprising, means for applying a predetermined static bias potential to at least one of the electrodes relative to a point of fixed potential, means for applying deflection voltage variations of widely different wave forms to one of the deflecting electrodes relative to a point of fixed potential in order to cause deflection of the cathode ray beam in a predetermined plane, and means for preventing a shift in the area traversed by the deflected cathode ray beam due to changes in applied wave form, said lastnamed means including a unilateral conducting device for producing a potential difference so that the potential deviations of the said one deflecting electrode will primarily extend in a predetermined direction from the static bias potential of that electrode regal dl-ess of the wave form of the applied deflection voltage variations.

8. A cathode ray oscilloscope in which a cathode ray tube is used which includes a pair of deflecting electrodes to which deflection potential variations are applied, means including a resistance for applying a predetermined static bias potential to one of the electrodes relative to a point of fixed potential, means for applying voltage variations of widely different wave forms to said one of the deflecting electrodes relative to a point of fixed potential in order to cause dcflection of the cathode ray beam, and means for preventing a shift in the region traversed by the deflected cathode ray beam due to changes in wave form of the applied deflection voltage variations, said last-named means including a unilateral conducting device connected in parallel with said resistance for effectively producing a change in the bias potential of the electrode so that the potential deviations of the deflecting electrode will always extend in a predetermined direction regardless of the wave form of the applied deflection voltage variations.

9. A cathode ray oscilloscope in which a cathode ray tube having a pair of deflecting electrodes may be used including means for applying pushpull deflection voltage variations to the deflectl2 ing electrodes in which the voltage variations extend in predetermined and opposed potential direction at the electrodes, circuit means including a pair of resistances for individually applying a predetermined static biased potential to the deflecting electrodes relative to a point of fixed potential, a pair of unilateral conducting devices each including an anode and cathode, and means for respectively connecting each of the unilateral conducting devices in parallel with one of said resistances, whereby the potential deviations of the said deflecting electrodes always extend in a predetermined potential direction from the static bias potential of the electrodes regardless of the wave form of the applied deflection voltage variations.

0. A cathode ray oscilloscope in which a cathode ray tube having a pair of deflecting electrodes may be used including a source of variable wave form deflection voltage variations in which the voltage variations extend in a predetermined potential direction, circuit means including a resistance for applying a predetermined static biased potential to one of the deflecting electrodes relative to a point of fixed potential, means for applying the deflection voltage variations to the said one deflecting electrode, a unilateral conducting device including an anode and cathode, and means for connecting the unilateral conducting device in parallel with said resistance, whereby the potential deviations of the said one deflecting electrode primarily extend in a predetermined potential direction from the static bias potential applied to that electrode regardless of the wave form of the applied deflection voltage variations.

LESTER 0. SMITH.

REFERENCES CITED The following references are of record in the file oi this patent:

UNITED STATES PATENTS Number I Name Date 2,153,140 Diehl Apr. 4, 1939 2,173,497 Schlesinger Sept. 19, 1939 2,231,591 Pieplow Feb. 11, 1941 2,240,605 Bingley May 6, 1941 2,267,120 Mathes Dec. 23, 1941 2,286,894 Browne et a1 June 6, 1942 2,319,139 Koch May 11, 1943