US2890380A

US2890380A - Movable center-blanked horizon line forming apparatus and saturable reactor pulse forming network for use therein

Info

Publication number: US2890380A
Application number: US677873A
Authority: US
Inventors: William F List
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1957-08-13
Filing date: 1957-08-13
Publication date: 1959-06-09
Anticipated expiration: 1976-06-09
Also published as: BE570333A

Description

June 9, 1959 w, s 2,890,380

MOVABLE CENTER-BLANKED HORIZON LINE FORMING APPARATUS AND SATURABLE REACTOR PULSE FORMING NETWORK FOR USE THEREIN Filed Aug. 13, 1957 4 Sheets-Sheet l 49 F|g.l. ,1"

r I 12. g 43 INVENTOR William F. List ATTORNEY June 9, 1959 Filed Aug. 15, 1957 w. F. LIST I 2,890,380 MOVABLE CENTER-BLANKED HORIZON LINE FORMING APPARATUS AND SATURABLE REACTOR PULSE FORMING NETWORK FOR USE THERE'IN 4 Sheets-Sheet 2 A v A wdvnna a N v PrlmorylS Woveshope Resistor 2| Ll Ll Prim ory 26 A Woveshap. v \l k \l 7 Primary 32 l I V A I Wovuhope l I Terminol45 Woveshbpc 0 I90 200 M20 4C )O 50 0 BO O 7C2O 80 0 900 Elac'rical Degrees Fil'ed Aug. 13, 1957 June 9, 1959 2,890,380

W. F. LIST MOVABLE CENTER-BLANKED HORIZON LINE FORMING APPARATUS AND SATURABLE REACTOR PULSE FORMING NETWORK FOR USE THEREIN 4 Sheets-Sheet 3 Amplifier Amplifier Intensify X AXIS Switch Y Axls Switch Z Axls Switch Switch Gate Generator June 9,1959 w. F. LIST MOVABLE CENTER-BLANKED 2,890,380 HORIZON LINE FORMING APPARATUS AND SATURABLE REACTOR PULSE FORMING NETWORK FOR USE THEREIN 4 Sheets-Sheet 4 Filed Aug. 15, 1957 IZA wyill Time MOVABLE CENTER-BLANK'ED HORIZON LINE FORMING APPARATUS AND SATURABLE RE ACTOR PULSE FORMING NETWORK FOR USE THEREIN William F. List, Linthicum Heights, Md., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 13, 1957, Serial No. 677,873

11 Claims. (Cl. 315-26) This invention relates to apparatus for generating a movable center-blanked horizon line for use in conjunction with a cathode ray tube breakaway cross symbol, and particularly to such apparatus employing saturable reactors for obtaining pulses of the desired wave forms needed in the production of the line and symbol.

As is well known in the art to which the invention pertains, it is common practice in aircraft to employ instruments for visually providing the pilot with information regarding the attitude of the wings of the aircraft. One conventional type of such instrument employs movable or tiltable line forming means to indicate departure from the normal wing attitude, the movable line being associated with a large X or cross to provide a breakaway command when the attitude of the aircraft wings approach the limits of safety, or some other hazard exists such as dangerous proximity to other aircraft or a ground obstruction, the horizon line being center-blanked and rotating about a point corresponding substantially to the center of the breakaway cross or X symbol, to indicate the instant attitude of the wings of the aircraft, as aforestated.

The presentation of this information on a cathode ray tube type indicator requires a special circuit for producing the center-blanked horizon 'line, and heretofore the generation of the necessary pulses and signal Wave shapes to provide the center-blanked movable horizon line has required the use of a number of electron tu es with attendant circuit complexities and limitations in the apparatus by reason of the susceptibility of the tubes ,to excessive shock, acceleration and other influences.

The apparatus of the instant invention overcomes the disadvantages of the prior art by employing saturable reactors in conjunction with semiconductor diode recti- :fiBI'S and a number of resistors for generating pulses of the necessary shapes.

Accordingly, a primary object of the instant invention is to provide new and improved apparatus for generating .a center-blanked movable horizon line for use in conjunction with a breakaway cross symbol, for application to aircraft wing attitude indicators.

Another object is to provide a new and improved sat- :urable reactor circuit for generating pulses having wave- .forms suitable for use in aircraft wing attitude indicators.

Other objects will become apparent after a study of the following specification when read in connection with the accompanying drawings, in which:

Figure 1 is a view of the display provided by apparatus embodying the instant invention and including a cross or X to indicate a breakaway command and a movable center-blanked horizon line; i

Fig. 2 is a schematic electrical circuit diagram of apparatus employing saturable reactors and diodes for producing pulses of the necessary waveforms to provide for the indication of Fig. 1;

Fig. 3 is a graph of a number of pulse and voltage waveforms illustrating the operation of theapparatus of Fig. 2;

Fig. 4 is a schematic electrical circuit diagram largely 2,890,380 Patented June 9, 1959 in block form, of apparatus for providing wing attitude information including the center-blanked horizon line and the breakaway command symbol of Fig. 1; and

Figs. 5A, 5B, 5C and 5D are graphs or curves further illustrating the operation of the apparatus of Figs. 1, 2 and 4.

Particular reference should be made now to the drawings, in which like reference numerals are used throughout to designate like parts, for a more detailed under standing of the invention and in particular to Fig. 1 thereof. The reference numeral 10 generally designates the screen of a cathode ray display tube shown in Fig. 4 and generally designated 11. The line 12, Fig. l, is the center-blanked horizon line which changes its slope in accordance with the variations in the attitude of the wings of the aircraft, \and a large X symbol 13 is provided for indicating the danger condition to be presented by the indicator, such as dangerous proximity to other aircraft;

Particular reference should be made now to Fig. 2 in which an electrical circuit employing saturable reactors is shown for producing the necessary pulse wave shapes to provide the indications of Fig. 1. The reference numeral 14 generally designates a saturable reactor having a primary winding 15,

secondary windings

16, 17 and 18 which are provided for purposes to be made hereinafter more clearly apparent, and a saturable core 19 which it is understood is composed of a suitable material which becomes saturated when the magnetic flux therein attains a preselected value with the result that the impedance of the primary winding varies markedly at saturation and that signals or voltages induced in the secondaries aforementioned vary markedly or quickly at the moment of saturation, in a manner which will become hereinafter more clearly apparent. One terminal of the primary 15 is connected by way of lead means 20 to a suitable source of substantially sinusoidal voltage with reference to ground having a phase a as indicated by the curve A of Fig. 3. The other terminal of primary 15 is connected by way of lead 23 and resistor 21 to ground 22. The last-named terminal 15 is also connected by way of lead 23, resistor 24, and lead 25 to one terminal of the primary 26 of a secondary saturable reactor generally designated 27, the reactor 27 having a pair of

secondaries

28 and 29 and a saturable core 30. The other terminal of the aforementioned primary 26 is connected to ground 22.

A. third saturable reactor generally designated 31 is provided having a primary 32, secondaries 33 and 34 and saturable core 35. The terminals of the primary 32 are connected, one terminal by way of resistor 36 and lead 37 and the other terminal by Way of lead 38 to a voltage of sinusoidal wave form and of an amplitude corresponding to the amplitude of the aforementioned voltage a applied to lead 20, and having a phase be which lags the voltage fa by as indicated by graph A of Fig. 3.

The adjacent terminals of the aforementioned secondaries 33 and 3.4 of saturable reactor 31 are connected together by lead means 39 and to ground 22. The other terminal of secondary 33 is connected by way of lead 40 to one terminal of the aforementioned secondary 17 of the saturable reactor or transformer generally designated 14, and the other terminal of secondary 17 is con nected to an output terminal 41. In like manner, the other or lower terminal of the secondary 34 as seen in Fig. 2 is connected by lead 42 to one terminal of the aforementioned secondary 16 of the saturable reactor generally designated 14, and the other terminal of secondary 16 is connected to an output terminal 43.

The aforementioned secondary 18 of the saturable reactor or transformer generally designated 14 has one terminal thereof connected to ground 22 and the other terminal thereof connected by way of capacitor 44 to an output terminal 45. Output terminal 45 is also connectedby way of resistor 46 to ground 22. The capacitor 44 and'resistor 46 form a differentiating network which is provided for purposes to be made hereinafter more clearly apparent.

The

aforementioned secondaries

28 and 29 of the aforementioned saturable reactor generally designated 27 have their adjacent terminals connected to each other by way of lead 47 and to ground 22. The other terminal of secondary 28 is connected by way of resistor 48, lead 49 and rectifier 50 to ground 22. Lead 49 is also connected by way of resistor 51 and lead 52 to an output terminal 53. The other terminal of the aforementioned secondary 29 is connected by way of resistor 54, lead 55 and rectifier 56 to ground 22. Lead 55 is connected by way of resistor 57 to lead 52. Lead 52 is further connected by way of resistor 58 to ground 22. The aforementioned rectifiers 50 and 56 may be of the silicon diode type.

A transformer generally designated 59 is provided as shown in Fig. 2 having a primary 60, a core 61 and a secondary 62. Core 61 is not of the saturable type. One terminal of the primary is connected to ground 22, and the other terminal of the primary 60 is connected by way of lead 63 across a suitable source of alternating current potential with reference to ground of sine wave form having a phase b which lags phase "a" by 60, phase 11 being related to the aforementioned phases a and be as indicated by curves or graph A of Fig. 3. The voltage of phase 12 is of substantially the same amplitude as the voltage of phases a and be. The three voltages having the phase relationships indicated by curves a, b, and be of graph A of Fig. 3 may be obtained by any convenient means, for example, they may be obtained from a transformer connected to a conventional three-phase source.

The aforementioned secondary 62 of transformer 59 has one terminal thereof connected to ground 22 and the other terminal thereof connected by way of resistor 64, lead 65 and capacitor 66 to ground 22. Lead 65 is connected by way of capacitor 67, lead 68 and variable resistor 69 to ground 22. Lead 68 is connected to one terminal of one winding 70 of a resolver generally designated 71, the other terminal of winding 70 being connected to ground 22. Resolver 71 has an energizing winding 72 connected to any suitable source of potential, and an additional pair of

movable windings

73 and 74, one terminal of each being connected to ground 22, winding 73 having an output lead and winding 74 having an output lead 76. Suitable position means 77 is provided for positioning the movable windings '73 and 74 of the resolver 71, and the positioning means 77 may be connected to a roll and bank responsive or control device which may be a gyro, as will be readily understood by those skilled in the art.

In the operation of the apparatus of Fig. 2, it should be recalled that the primary 15 of reactor or transformer 14 is connected across phase a in series with a resistor 21 shunted by the primary 26 of reactor 27 and a series resistor 24. The relative impedance of these branches are preselected so that the load is effectively resistive. The voltage applied to the circuit on the aforementioned lead 20 causes the voltage to build up sinusoidally across the primary 15 of reactor 14 until the core 19 of this reactor saturates, when the voltage across the reactor primary 15 falls to nearly zero because of the change in impedance of the primary windinng 15 at saturation. Pr or to this, the voltage across the series resistor 21 was slowly increa n s u o d t h v ltss dividing proportionally to the impedagioes. Since the impedance o the p ma 15 is ar rri r Q saturatin s'joliiiiaied to the value of resistor 21', the voltage across the resistor former 27 is nearly zero prior to the saturation of core 19. When saturation of the core 19 of reactor 14 occurs, the voltage across the resistor 21 increases substantially to the instantaneous value of the applied voltage on lead 20. The voltage across the primary 26 of reactor 27 increases to substantially the applied voltage level on lead 20 and follows sinusoidally until the core 30 of reactor 27 saturates, thereby reducing the voltage across the primary 26 of reactor 27 to substantially zero and causing the remaining portion of the applied wave shape to appear across the resistor 24 in series with the primary 26. Voltage wave shapes are generated in the

secondaries

16, 17, 18, 28 and 29 of both of the

reactors

14 and 27 by transformer action. The uses of these secondaries will be disclosedin more detail hereinafter.

in Fig. 3, to which particular reference is now made, the voltage across the aforementioned primary 15 is shown .by curve B, the wave shape of the voltage across resistor 21 is shown by curve C, and the wave shape of the voltage across the primary 26 is shown in curve D, in accordance with the aforegoing explanation. The

aforementioned secondaries

28 and 29 of reactor 27 are con nected as aforedescribed in a manner such that positive pulses are attenuated through the series resistors and silicon diodes and only the negative pulses appear in the output on terminal 53. This output signal on terminal 53 is illustrated by the adjacent pulses, and is further illustrated by curve G of Fig. 3. Terminal 53 is connected to the Z-axis switch of an intensity control circuit shown in Fig. 4 and hereinafter toibe described in more detail.

The primary 32 of the aforementioned reactor 31 is connected in series with a current limiting resistor 36 and energized with voltage of phase bc" separated by 90 from phase a of curve A of Fig. 3. The voltage wave form across the primary 32 of reactor 31 behaves in a manner similar to that of the previous description of the voltage waveform across the

primaries

15 and 26 of

reactors

14 and 27 respectively. The

secondaries

33 and 34 of reactors 31 are interconnected as shown and aforementioned with two of the secondaries, namely, 17 and 16 respectively of the aforementioned reactor or transformer 14 to form the'breakaway symbol, the voltage outputs of secondaries 16 and 17 being applied to

terminals

43 and 41, as shown, and having waveshapes as shown by graphs H and I of Fig. 3.

The remaining secondary winding 18 of reactor 14 is connected as aforementioned to a'ditferentiating circuit including capacitor 44 and resistor 46 to provide trigger pulses on output terminal 45 for a multivibrator or gate generator the indicator circuit of 'Fig. 4, such, for example, as a two hundred cycle multivibrator. The shape of the triggering pulse at terminal 45, Fig. 2, is shown adjacent terminal 45 and is further illustrated by curve F of Fig. 3.

The voltages for forming the aforementioned attitude line as seen at 12 on screen 10, Fig. Lare generated in the above described circuit of Fig. 2by supplying one winding of the aforementioned resolver "71 from phase b through a two-section filter including resistor 64,

capacitors

66 and 67 and variable resistor 69. The variable resistor 69 makes it possible to accurately center the blanking pulses about the signal voltage wave shape, as will be discussed in connection with Figs. SA-SD. The two output components of the resolver 71 as developed on the aforementioned leads 75 and 76 are connected to appropriate X axis and Y axis switch channels, in a manner to be hereinafter more fully described in connection with Fig. 4. i

It should be noted that the blanking pulses are preferably initiated at substantially 40 electrical degrees after the voltage of phase a has passed the zero axis and are terminated at substantially 80electrical degrees after the voltage of phase a has passed the zero axis. 'This results 'in' the pulse starting 20 degrees before'and ending 20 degrees after the voltage of phase b crosses the zero axis, it being recalled that phase b lags phase a by 60 degrees.

Particular reference should be made now to Fig. 4 which shows an electrical circuit diagram for utilizing the output pulses and voltages from the apparatus of Fig. 2 to provide the indication shown in the aforementioned Fig. 1. V

In Fig. 4 there is shown a block generally designated 78, it being understood that the block 78 includes the aforementioned transformer 59, the aforementioned filter

circuit including resistors

64 and 69 and

capacitors

66 and 67 and the aforementioned resolver 71, the voltages on

leads

75 and 76 being varied in accordance with movement of the aforementioned positioning means 77.

Three switches are provided for each of the three beam axes of the aforementioned cathode ray tube 11 including an aforementioned X axis switch shown in block form and generally designed 80, an aforementioned Y axis switch shown in block form and generally designated 81, and a Z axis switch shown in block form and generally designated 82. The

switches

80, 81 and 82 are provided and connected as shown, being necessitated because the breakaway or X signal 13 of Fig. l and the horizon line 12 of Fig. l are alternately put on the screen of the cathode ray tube generally designated 11 in Fig. 4. All of the

switches

80, 81 and 82 have applied thereto on lead 83 a gating pulse obtained from a gate generatoror multivibrator shown in block form and generally designated 84, the gate generator 84 being of any convenientdesign, for example, a two hundred cycle multivibrator. The gate generator 84 is operatively connected by lead 85 to the aforementioned output terminal 45 of the pulse generator 79, and receives as an input a series of triggering pulses such, for example, as those shown in Fig. 3F. Every positive pulse from terminal 45 causes a switch gate to be generated at 84, and this gate is applied by lead 83 to all three

switches

80, 81, and 82 and operates the three switches simultaneously. Every time the switches operate, they operate to alternately produce on the screen 10 either the horizon line 12 or the breakaway symbol 13', in the manner which will become hereinafter more clearly apparent. Any convenient switching circuits could be employed at 80, 81 and 82, and constitute no part of this invention.

A direct current voltage is supplied on lead 86 to the Z axis switch 82 from a suitable source of direct current potential, now shown, which may be of the order of 10 to volts and may, if desired, have the negative terminal thereof connected to lead 86 and the positive terminal thereof connected to ground 22, depending upon the circuit arrangement of the switch and an associated amplifier hereinafter to be described.

The aforementioned outputs from the resolver 71 are applied by

leads

75 and 76 to the X axis switch 80 and the Y axis switch 81 respectively. Terminal 41 of the pulse generating apparatus of Fig. 2 is connected by lead 87 to the Y axis switch 81 whereas terminal 43 is connected by lead 88 to the X axis switch 80. The aforementioned terminal 53 of the apparatus of Fig. 2 is connected by lead 89 to the Z axis switch 82. a

The output obtained from the X axis switch 80 is applied by lead means 90 to an amplifier shown in block form and generally designated 91;-the output from the Y axis switch 81 is applied by lead means 92 to an amplifier shown in block form and generally designated 93; and the output of the Z axis switch 82 is connected by lead means 94 to an amplifier 95.

As aforementioned, a cathode ray display tube generally designated 11 is provided, the tube 11 having a screen which may correspond to the screen 10 of Fig. 1, having

vertical deflection plates

96 and 97, horizontal deflection plates 98 and 99, a cathode 100 and an intensity control grid 101. The cathode 100 is connected to ground 22; the intensity control grid 101 is connected by lead 102 to the aforementioned amplifier the

vertical deflection plates

96 and 97 are connected by

leads

103 and 104 to the aforementioned amplifier 93; and the aforementioned horizontal deflection plates 98 and 99 are connected by

leads

105 and 106 to the aforementioned amplifier 91.

Particular reference should be made now to Figs. 513- 5D inclusive, all the curves of which are plotted on the same time base. Curve 5C shows the aforementioned blanking pulses at terminal 53. In curve 5B, both the voltages represented by thesolid line and the dashed line represent a voltage at the deflection plates which produces or paints a symbol indication. The solid line represents a properly phased voltage, and it will be noted that the voltage represented by the solid line passes through zero at an instant corresponding substantially to the center of the corresponding blanking pulse of Fig. 50, whereas the improperly phased voltage of the dashed line of Fig. 5B passes through zero at a time well ahead of the center of the blanking pulse.

The curve of Fig. 5D represents the combined results of the voltages of Figs. 5B and 5C, and shows how the blanking pulses periodically eliminate portions of the voltage at the deflection plates.

In Fig. 5A, the center-blanked horizontal line indicates the attitude symbol 12 at the scope, the portions of the attitude line being designated 12A and 12B in Fig. 5A, the portions being of uniform brightness throughout.

The lower broken or center-blanked horizon line of Fig. 5A represents the results of improper phasing. Portion 12A is seen to have thin-line tail or end sections m and n, and line portion 12B is seen to have thin-end or tail sections p and q. Tail sections m, n, p, and q are of diminished brightness.

There has been provided then, apparatus well suited to perform and accomplish the aforedescribed objects of the invention.

In some applications of the invention, for example, fire control, it is desirable that the X symbol to provide a breakaway command not appear on screen 10 until the dangerous condition occurs. In such applications, any convenient means, not shown, may be provided for applying a voltage on lead 86 for selective passage by the Z-axis switch 82 to intensity modulatethe beam of cathode ray tube 11 and cause the X symbol 13 to appear in response to the occurrence of the dangerous condition.

Whereas for convenience of illustration a voltage of phase be lagging the phase a by 90 degrees has been shown and described as energizing the primary 32 of reactor-transformer 31, any sine wave voltage of proper amplitude which lags the voltage of phase a by more than 40 degrees is suitable.

Whereas the line 12 has been referred to herein as a horizon line, it should be understood that the line could be used to indicate the value of any variable quantity supplied to the resolver 71 by means 77.

Whereas the invention has been shown and described with reference to an embodiment thereof which gives satisfactory results, it should be understood that modifications may be made and equivalents substituted without departing from the spirit and scope of the invention.

I claim as my invention:

1. In cathode ray tube indicator apparatus for providing an indication of a movable center-blanked line symbol and a fixed breakaway symbol, in combination, cathode ray tube means, signal obtaining means including resolver means and saturable reactor means for obtaining a plurality of signals having a plurality of preselected wave shapes and a plurality of preselected time relationships therebetween, and means operatively connected to the signal obtaining means and to the cathode ray tube means for alternately applying some of said signals and the remainder of said signals to said cathode ray tubemeans, said cathode ray tube means being constructed and arranged to utilize the signals applied thereto to alternately provide said movable line symbol and fixed breakaway symbol.

2. In cathode ray tube indicator apparatus for providing a movable 'lirie symboland a breakaway symbol in conjunction therewith'jin combination, first signal obtaining means for providing a pair of signals having preselected wave shapes, amplitudes 'and time relationships With respect to each other, means operatively connected to said first signal obtaining means for altering said pair of signals in accordance with variations in'a variable quantity, saturable reactor signal obtaining means for providing a plurality of other signals having preselected amplitudes, wave shapes and time relationships therebetween, cathode ray tube means, and means operatively connected to the first signal obtaining means, to the cathode ray tube means, and to the saturable reactor signal obtaining means for alternately applying said pair of signals and said plurality of other signals to said cathode ray tube means, said cathode ray tube means being constructed and arranged to utilize the pair of signals to provide a movable line symbol and said other signals to provide said breakaway symbol.

3. In cathode ray tube indicator apparatus for providing a movable line symbol in conjunction with a breakaway symbol, in combination, cathode ray tube means, voltage obtaining means adapted to have applied thereto a variable input corresponding to the instant value of a variable quantity, said voltage obtaining means being constructed and arranged to utilize the variable input to provide a pair of variable voltages, saturable reactor means for obtaining a plurality of signals having a plurality of preselected wave shapes, amplitudes and time relationships therebetween, and switching means alternately operatively connecting said voltage obtaining means and said saturable reactor means to said cathode ray tube means, said cathode ray tube means being constructed and arranged to utilize the voltages and signals applied thereto to provide the line and breakaway symbol indications.

4. Apparatus for providing a movable line indication of a variable quantity and a stationary indication adjacent thereto which is adapted to establish limits for the variable quantity comprising, in combination: cathode ray tube means, first signal obtaining means including saturable reactor pulse forming means, switching means, means including said switching means operatively connecting said first signal obtaining means to said cathode ray tube means, said cathode ray tube means being constructed and arranged while some of the signals from the first signal obtaining means are applied thereto to produce said stationary indication, second signal obtaining means adapted to have a variable input applied thereto which varies in accordance with variations in the quantity to be indicated, and means including said switching means operatively connecting said second signal obtaining means to said cathode ray tube means, said cathode ray tube means being further constructed and arranged to utilize the signals from the second signal obtaining means and at least some of the pulses from the saturable reactor pulse forming means to provide said movable line indication with a predetermined portion thereof blanked out.

5. Apparatus for providing a movable line indication of a variable quantity and a stationary indication adjacent thereto comprising, in combination, cathode ray tube means including switching means and a cathode ray tube, first signal obtaining means including saturable reactor pulse forming means operatively connected to said cathode ray tube means for obtaining first signals including signals for providing the stationary indication, and second signal obtaining means adapted to have a variable input applied thereto which varies in accordance with variations in the quantity to be indicated and to provide variable second signals for forming said movable line indication, said second obtaining means being operd d at -E t s l9 t il Pfitl sttls ray tub mea said switching means providing for alternate use by the cathode'ray tube of signals from the second signal obtaining means and some of the signals from the first signal obtaining means, said cathode ray tube means being constructed and arranged to utilize other of the signals from the first signalobtainin'g means .to' blank out a predetermined portion of said line indication.

6. In apparatus for providing a movable line indication of avariable quantity, in combination, cathode ray tube means including means adapted to have a variable input applied thereto which varies in accordance with variations in the quantity to be indicated and to pro vide variable signals for utilization by the remainder of the cathode ray tube means to provide said movable line indication, and saturable reactor pulse forming means operatively connected to said cathode ray tube means, said cathode r b ns bein construc ed and arra ge to ut ize th pul f o the s tura re ctor p e o ing means to blank out a predetermined portion of said line.

7. In apparatus for providing a movable line indication of a variable quantity, in combination, cathode ray tube means, means adaptedto have a variable input applied thereto which varies in accordance with variations in the quantity to be indicated, said last-named means being operatively connected to said cathode ray tube means and constructed and arranged to provide a variable signaloutput to the cathode ray tube means, said cathode ray tube means being constructed and arranged to utilize the variables ignal output to provide said movable line indication, saturable reactor means for obtaining pulses having preselected characteristics and predetermined time relationships to said 'variable signal output, and means operatively connecting said saturable reactor means to said cathode ray tube means, said cathode ray tube means being" further constructed and arranged to utilize said pulses to blank out a predetermined portion of said line.

8 In apparatus for providing 'amovable line indication of a variable 'quantity, 'in'combination, resolver means adapted'to have a variable input applied thereto which varies in accordance with variations in the quantity to be indicated, said resolver means being constructed and arranged to provide two variable signal voltages, cathode ray tube means having vertical and horizontal deflection plates and intensity control means, means operatively connecting said resolver means to said cathode ray tube means, said cathode ray tube means having said two signal voltages applied to the vertical and horizontal deflection plates thereof and utilizing said two signal voltages to form said movable line,'s'atur able reactor means for forming pulses having a preselected polarity, ampli tude, and wave shape and a predetermined time relationship to said two signal'voltages, and means operatively connecting said saturable reactor means to said intensity control means in a manner whereby said pulses blank out a predetermined portion of said line.

9. Apparatus for providing a movable line indication of a variable quantity and a stationary indication adjacent thereto comprising, in combination, cathode ray tube means including switching means, first'satur'able reactor signal obtaining means operatively connectedt os'aid cathode ray tube means, said cathode ray tube means being constructed and arranged to utilize first signals from the first saturable reactor signal, obtaining means to provide the stationary indication in accordance with the setting of the switching means, other signal obtaining means operatively connected to the cathode ray tube means and adapted to'ha've a variable input applied thereto which varies in accordance 'with variations in the quantity to be indicated and to provide variable second 'signals'fo'r forming said movable line indication in accordance'with the setting of the "switching means, said switching means providing for alternate use by the cathode ray' tube means of the first and second signals, second satljrable' reactor means operatively connected to the first saturable' reactor means for obtaining blanking pulses having predetermined time relationships to the first and second signals, and means operatively connecting the second saturable r'eactor means to said cathode ray tube means, said switching means passing said blanking pulses simultaneously with the passage of said second signals, said cathode ray tube means being constructed and arranged to utilize the pulses from the second saturable reactor means to blank out a predetermined portion of said line.

10. In cathode ray tube indicator apparatus, in combination, first voltage obtaining means for obtaining first and second voltages having preselected wave shapes, cathode ray tube means including a pair of vertical deflection plates, a pair of horizontal deflect-ion plates, and an intensity control grid, first and second switching means interconnecting said first voltage obtaining means and said cathode ray tube means, said first and second switching means being adapted while in preselected settings to apply said first and second voltages to said pairs of deflection plates to provide a line indication on the screen of said cathode ray tube means, other voltage obtaining means including saturable reactor means for obtaining other voltages, said other voltage obtaining means being connected to said first and second switching means, third switching means interconnecting said other voltage obtaining means and said cathode ray tube means, said other voltage obtaining means providing a blanking voltage which, while said third switching means is in a preselected setting, is applied to said intensity control grid to blank a portion of the line indication on the screen of said cathode ray tube means, said other voltage obtaining means also providing a series of trigger pulses, a switch gate generator operatively connected to said other voltage obtaining means to have said trigger pulses applied thereto and providing for the generation of a switch gate upon the application thereto of at least certain ones of said trigger pulses, means connecting said switch gate generator to all of said first, second, and third switching means to operate the same, said switching means being constructed and arranged to alternately apply to the deflection plates of said cathode ray tube means voltages from the first voltage obtaining means and some of the voltages from the other voltage obtaining means, said other voltage obtaining means while the remainder of the voltages therefrom are applied to said cathode ray tube means providing for the generation of a cross symbol on the screen of said cathode ray tube means.

11. Apparatus for use on aircraft for providing a movable center-blanked horizon line and a breakaway cross symbol cfor use in conjunction with said line to indicate to the pilot of the aircraft that variation of the horizon line from its normal position has passed a safe limit comprising, in combination, cathode ray tube means including a viewing screen, a pair of vertical deflection plates, a pair of horizontal deflection plates, and an intensity control grid, means :forming an X axis switch, a Y axis switch, and a Z axis switch, means operatively connecting all of said switches to said cathode ray tube means,

each of said X, Y, and Z axis switches having first and second settings, voltage obtaining means for obtaining a pair of voltages, means operatively connecting said X axis switch and said Y axis switch to said voltage obtaining means for applying one voltage of the pair to each of the X and Y axis switches, other voltage obtaining means including saturable reactor means for obtaining a blanking pulse, means connecting said Z axis switch to said other voltage obtaining means for applying the blanking pulse to the Z axis switch, said X, Y and Z switches being constructed and arranged while in first settings thereof to apply said pair of voltages and said blanking pulse to the deflection plates and intensity control grid of said cathode ray tube means to provide a center blanked horizon line, said voltage obtain-ing means including means adapted to have a variable turning input applied thereto for causing the horizon line to rotate about its center point, said other voltage obtaining means being operatively connected to said X axis switch and said Y axis switch, said X axis switch and said Y axis switch being constructed and arranged while in second settings thereof to apply the voltages from the other voltage obtaining means to the horizontal and vertical deflection plates, the voltages from said other voltage obtaining means having preselected characteristics and causing an X symbol to appear on the screen of said cathode ray tube means, said other voltage obtaining means including means for providing a series of trigger pulses having predetermined time relationships to the voltages from the Voltage obtaining means and the voltages from the other voltage obtaining means, and switch gate generator means operatively connected to the other voltage obtaining means and having said trigger pulses applied thereto, said switch gate generator means being constructed and arranged to utilize at least some of the trigger pulses to provide switching gates, said switch gate generator means being operatively connected to all of said X, Y and Z axis switches, said X, Y and Z axis switches being further constructed and arranged to utilize the switching gates to alternate between first and second settings to thereby selectively connect the ouput of the voltage obtaining means and the blanking pulse from the other voltage obtaining means to said cathode ray tube means, and thereafter selectively connect only the other voltages from the other voltage obtaining means to said cathode ray tube means.

References Cited in the file of this patent UNITED STATES PATENTS 2,208,379 Luck July 16, 1940 2,318,197 Clark May 4, 1943 2,435,207 Dimond Feb. 3, 1948 2,437,275 Skene Mar. 9, 1948 2,646,530 Goodell July 21, 1953 2,662,197 Comte Dec. 8, 1953 2,674,812 Hales Apr. 13, 1954