US2825886A

US2825886A - Cathode ray tube viewing device

Info

Publication number: US2825886A
Application number: US590041A
Authority: US
Inventors: Robert R Pittman; Louis W Erath
Original assignee: SOUTHWESTERN IND ELECTRONICS C
Current assignee: SOUTHWESTERN IND ELECTRONICS C; SOUTHWESTERN INDUSTRIAL ELECTRONICS Co
Priority date: 1956-06-07
Filing date: 1956-06-07
Publication date: 1958-03-04
Anticipated expiration: 1975-03-04

Description

March 4, 1958 R. R. PITTMAN ET AL ,8

CATHODE RAY TUBE VIEWING DEVICE Filed June '7, 1956 8 Sheets-Sheet 1 22 FIG. I. 22

r-W|NDOW| SWEEP; INTENSITY Position Width SPEED .o'| window awn 25 2s 2? 2a 29 so 31' INVENTORS ROBERT R. PITTMAN LEWIS W. ERATH BY r f ATTORNEY wmmUH 8 Sheets-Sheet 3 INVENTORS ATTORNEY ERATH n m q awo 02:60 5

R. R. PITTMAN ET AL CATHODE RAY TUBE VIEWING DEVICE March 4, 1958 Filed June '7, 1956 ROBERT R. PITTMAN LEWIS W.

March 4, 1958 R. R. PITTMAN ET AL 2,82

CATHODE RAY TUBE VIEWING DEVICE Filed June '7, 1956 8 Sheets-Sheet 5 m moEEzwo b. m n M2: 0222:. Jana WTH E ta nn w w m 11. R howci m?- d: w ocm n R u II as aw .llllllulllll l l 0F- ATTORNEY A March 4, 1958 R. R. PITTMAN ET AL 2,825,886

CATl-IODE RAY TUBE VIEWING DEVICE Filed. June 7, 1956 8 Sheets-Sheet 8 Sweep Trlgger Window Trigger LEO Recorder Magnetic Recorder Drum . INVENTORS ROBERT R. PITTMAN LEWIS W. ERATH ATTORNEY United States Patent r 2,825,886 CATHODE RAY TUBE vmwlNc nnvrcn Robert R. Pittman and Louis W. Erath, Harris County, Tex., assignors to Southwestern Industrial Electronics Company, Harris County, Tex., a corporation of Delaware Application June 7, 1956, Serial No. 590,041

24 Claims. (Cl. 340-) This invention relates to apparatus for exhibiting simultaneously a plurality of signals, and, more particularly, to a cathode ray tube viewing device operable to exhibit a plurality of voltage signals simultaneously on its fluorescent target.

Many branches of science have need for a device which will display a plurality of signals visually in simultaneous manner, so that correlation between the various signals can be observed. For instance, petroleum seismology, aerodynamics and medicine all employ vibration-type signals for analysis purposes, and such signals are converted into electrical voltages by transducers and recorded in suitable manner as an aid to such analysis. 1

This invention is particularly applicable to pertoleum seismology and will be described in that connection, but it will be evident after the apparatus of the invention has been described that it could be used in the other sciences mentioned, as well as for other applications. As a matter of fact, the apparatus to be described is usable in connection with display visually of a plurality of time base signals obtained from any source.

Petroluem seismology involves the generation of ground vibrations by detonation of one or more shots beneath the surface of the earth or dropping a weight on the earth, and detection of the vibrations at a plurality of geophones spaced from the source of the vibrations. A large amount of the energy that reaches the geophoues is in the category of noise, while a relatively small amount represents information. In order to increase the signal to noise level of the geophone outputs, it has become conventional to perform several difierent operations-on the geophone output voltages, including compositing, filtering, etc. One of the objects of the apparatus of the present invention is to furnish an apparatus which will present the geophone signals in visual form so that the waveforms can be examined while these various operations are performed on the signals.

The apparatus of the present invention is particularly adapted for use with magnetic recordings of geophone signals made in the field and then taken back to the laboratory for analysis and clarification. Filtering and phase angle correction of the signals may be performed in the laboratory, and the present apparatus can be used to give a visible indication to determine when optimum filtering or phase shift is obtained.

In display of signals such as geophone output voltages, it is particularly desirable to furnish some indication of relative time along with the signals. The apparatus of the present invention includes circuitry for displaying timing lines on the cathode ray tube face along with the signals. The apparatus also includes means for expanding the representation of a selected portion of the signals, so that portion may be more readily examined.

The apparatus of the present invention, generally speaking, includes a cathode ray tube including the usual beam sweeping elements and an intensity control means. Means are provided for sweeping the beam at high speed along one dimension of the target and at low speed along another dimension substantially perpendicular to said one dimension. The beam is normally turned off by the intensity control means, but it is turned on by circuits including'comparators which compare the signal voltages and suitable bias voltages therefor with the high speed sweep, and pulse generators which generate a train of voltage pulses for the intensity control means in response to the comparator outputs. The beam spot is thereby caused to generate a plurality of traces corresponding to the signal voltages spaced apart along said one dimension. The apparatus also includes means for displaying the timing lines along with the signal voltages, means for speeding up the slow speed sweep for a portion of the sweep to expand a portion of the representation, means for synchronizing the slow speed sweep with an appropriate event, such as the time break signal, and means for selecting the position of the faster speed sweep portion of the representation (called the window) accurately.

The apparatus of the present invention will now be more fully described in conjunction with preferred embodiments thereof, as shown in the accompanying drawings.

In the drawings:

Fig. l is a somewhat diagrammatical elevational view of the front of a cathode ray tube viewing device constructed in accordance with this invention;

Fig. 2 is a diagrammatical representation of the method of sweeping the beam of the cathode ray tube along the target and the method of indicating the signal voltages on the target; I Fig. 3 is a block diagram of the apparatus and circuits of the cathode ray tube viewing device of the invention;

Fig. 4 is a schematic diagram of a portion of the apparatus of Fig. 3 including the high speed sawtooth generator and the associated voltage comparators and blocking oscillators;

Fig. 5 is a schematic diagram of the low speed sawtooth generator and associated circuits of Fig. 3;

Fig. 6 is a schematic diagram of the intensity controlling circuits of the cathode ray tube of Fig. 3;

Fig. 7 is a more complete block diagram of the timing line sync source and the sweep and window sync source of Fig. 3;

Fig. 8 is a schematic diagram of the apparatus to Fig. 7; and

Fig. 9 is a diagrammatic representation of an alternate method for furnishing a sweep and a window trigger voltage for the apparatus of Fig. 3.

The apparatus of the present invention is particularly designed toshow a plurality of geophone output signal voltages on the target or face of a cathode ray tube. For such use, the geophone voltages are preferably played back from a magnetic recording tape wound on a recorder drum and the geophone voltages displayed on the cathode ray tube target in vertically spaced positions, with the horizontal dimension of the representation indicating time, and the vertical dimension indicating amplitude of the geophone voltages at every instant.

It is conventional in petroleum seismology to detect vibration waves caused by detonation of a shot beneath the surface of the earth or by dropping a weight onto the earth at a plurality of points spaced from the source of vibrations through transducers called geophones. The geophones may be positioned in any appropriate fashion, but it is conventional to record the outputs of the geophones for a time period of the order of five seconds after the vibrations are generated. If a shot is the source of the vibrations, the time period is measured from the socalled time break indicating the moment the shot is fired, and the time break is recorded along with the geophone outputs.

In order to represent the geophone output voltages so 777 N aisaaeaa- 3. obtained with the apparatus of the present invention, the record of those voltages is played back by rotating the record number on a drum past appropriate playback heads in continuous fashion such that thefivesecondrecord period is repeated over and over.

The geophone voltages are then displayed on the face oftarget 20 of a cathode ray tube, such as shown in Fig. 1. In that figure, beginning from the bottom of the face of the tube, the first nine traces are shown as varying in amplitude in somewhat similar manner to geophone voltages, though the showings are extremely idealized for convenience in representation. The next ten geophone traces are shown as straight horizontal lines, indicating that no geophone voltages are supplied to these channels of the viewing device.

In. order to represent time on the face of the cathode ray tube-in suchfashion. as to make it convenient to determine the relative time of any voltage change,;timing lines21 are generated and placed on the face of the tube in a manner to be described. Further, in order that a portion of the geophone output voltages may be examined more closely, that portion is expanded on the surface of the tube by increasing the speed of the sweep for a portion of the extent thereof, such as shown between timing lines 21a and 21b in Fig. 1.

The apparatus for expanding this portion ofthe sweep, called the window" will be described hereinafter.

The positions of the traces on the face of the cathode ray tube are controlled through potentiometers having screws 22 exposed along the upper surface of the" cabinet 23 which supports the face of the cathode ray tube.

The position of the window between timing lines 21a and 21b is controlled by a control knob 25, while the width: of the window along the horizontal dimension of the-tube face is controlled by a knob 26. The speed of the sweep of the cathode ray tube beam along, the horizontal dimension is controlled by a knob 27.

Several controls for the intensity of the cathode ray tube beam are provided, including

knobs

28 and 29 for controlling the intensity of the timing lines 21 which represent every one-hundredth of a second and every tenth of a second, respectively. The intensity of the portion of the sweep within the window is controlled through knob 30, while the intensity of the overall representation is controlled by knob 31.

Referring now to Fig. 2, this figure represents in diagrammatic form the method of generating a raster on the face of the cathode ray tube and intensity modulating the beam to represent the voltages on the tube face. In order to accomplish the sweepshown diagrammatically in Fig. 2, the beam is deflected vertically through a very high speed sweep voltage having aperiod of the order of 200 microseconds, while the beam. is swept along the horizontal dimension by a voltage having, a period. of the order of. about five seconds. At the beginningvof one complete sweep, the beam spot would be at the lower left-hand corner of the tube face 20 and would proceed therefrom upwardly along a nearly vertical line 35a. When the spot reaches the upper end of the tube, it is returned very rapidly to the lower end along a substantially vertical path 36a. The beam spot repeats this vertical sweep action a very large number ofv times duringa horizontal sweep cycle to describe the sweep paths shown diagrammatically in Fig. 2.

The cathode ray tube is provided with an intensity control which normally keeps the beam turned off so that the spot is not seen on the surface of the tube. However, the beam is turned on through the intensity control in accordance with a comparison between the various signal voltages and the vertical sweep, by pulses of voltage reach. ing. the intensity control from a plurality of comparator stages, to be described. When a signal voltagei's'applied. to the trace channels, the beam is caused to be turned on at points indicated by the dots in Fig. 2, so describing. the voltages supplied thetrace channels. It will be under 4. stood that the representation of Fig. 2 has been expanded considerably so as to show the sweep action of the beam. The sweep is actually very much faster than indicated in Fig. 2, with the result that the vertical sweep is very nearly perpendicular to the horizontal dimension of the tube face and the dots on the face of the tube are spaced apart by such small distances that they appear to form continuous lines.

When no signal voltages are supplied. to the. trace channels, the beam is turned on in such fashion as to generate substantiallyhorizontal lines for these channels.

General circuit description Referring now to Fig. 3, a complete apparatus for furnishing the representations shown in Figs. 1 and 2 is shown therein in block diagram form. In that figure, the cathode ray tube 40 is provided with a vertical deflection circuit 41 which is supplied with sweeping energy from. a high speed sawtooth generator and shaper 42. A horizontal deflection circuit 43 is supplied with sweeping energy from a low speed sawtooth generator and shaper 44.

The intensity controlling .means for the cathode ray tube beam includes a cathode circuit 45 and a grid circuit 46. Cathode circuit 45 is supplied with voltage pulses to turn the beam on from a video amplifier 47 which receives its input from a plurality of channels. Each of the channels providing an input to the video amplifier 47 includes a blocking'oscillator 48 and a voltage comparator 49'. One of the inputs to each of the voltage comparators 49 is a voltage from the high speed sawtooth generator 42,. while the geophone output signals provide the other inputs to the voltage comparators.

The geophone signals'arefed into the system through playback of the'record' tape on which they' are recorded on a magnetic'recorder drum 50 driven by an appropriate recorder drum drive 51. The drum moves the record tape past a plurality of playback heads 52, one for each of the geophone channels recorded. The outputs of the playback heads 52 are supplied to demodulators 53 if, as is conventional, the geophone output voltages have been frequency modulated before recording on the record tape. Each of the demodulators 53 is connected to the appropriate voltage comparator 49 to supply the geophone output voltage to the comparator for comparison with the high speed sawtooth.

'This comparison action results in the video amplifier providing a train ofvoltage pulses to the cathode circuit 45- which turns the beam on each time it receives a pulse of voltage.

The initiation of the low speed sweep is controlled by an appropriate synchronizing pulse such as that which can be obtained by recording'a'time break pulse on the record tape withthe geophone signals and playing back the time break pulse at the beginning of the playback cycle. It is conventional to record the time break pulse on a channel separate from the geophone output voltages,

' though it could as wellbe recorded along with the output voltages. As indicated above, the time break indicates the moment of initial generation of the vibrations detected by the geophones. If the time break is recorded on a separate channel, a playback head 55 is provided to detect this recording and furnish it 'to a source of synchronizing voltage indicated generally at 56 in Fig. 3 and termed time break pulse. The output of the block 56 is supplied to the control circuit 57 of Fig. 3 and, more particularly, to the sweep and window sync source 58 of the control circuit. This sync source provides a paring the low speed sawtooth voltage with a controllable bias voltage in a window comparator 60 and providingthe resultant output of the comparator to a window a portion of the horizontal sweep to increase the sweep speed.

An alternative method for controlling the window is by providing a window trigger voltage from the sync source 58 to the window multivibrator.

- In order to furnish timing lines 21, such as shown in Fig. 1, along with the geophone representations, the control circuit 57 includes a timing line sync source 65 which provides synchronizing voltage for a timing line generator 66. Generator 66 provides an input voltage for an intensity gate circuit 67 which controls grid cirsuit 46. Each time that a timing line voltage is generated, intensity gate 67 provides a pulse of voltage to the grid circuit 46 to turn the beam on during the vertical sweep corresponding to the time of the timing line voltage.

In addition, the intensity gate is provided with voltage from the window multivibrator 61 to increase the intensity of the beam during the window time period, since the higher sweep speed during this period would normally result in an apparent decrease in beam intensity.

In order to turn the beam off at the end of the trace and until the beam spot returns to the lower left-hand corner of the tube face, horizontal deflection circuit 43 provides a flyback blanking voltage to intensity gate 67.

In order that the various synchronizing sources in the control circuit 57 may be reset at the end of one complete beam sweep, a flyback pulse from the horizontal deflection circuit is provided as a reset to each of the time line sync source 65 and the sweep and window sync source 58.

Vertical sawtooth generator Referring now to Fig. 4, the circuitry of the high speed sawtooth generator and the associated blocking oscillators will be more completely described. The high speed sawtooth is generated by a blocking oscillator 70 including a triode tube 71 having its cathode grounded and its plate connected throughrthe primary of an iron core transformer 72 and a resistor 73 to a source of positive voltage indicated only as B+. The grid of the triode is connected through the secondary of the feedback transformer 72 and a capacitor 74 to ground. The primary of the transformer and the B+ source are shunted by a capacitor 75.

The well-known action of the blocking oscillator 70 results in the provision to capacitor 74 of a rectangular pulse of voltage at intervals determined by the parameters of the circuit. These parameters are so selected for the apparatus of Fig. 4 that a high frequency train of pulses is supplied by the output of the blocking oscillator. The time period of such pulses may be of the order of 200 microseconds for an appropriate design. Capacitor 74 converts these pulses into sawtooth pulses of the same frequency.

The blocking oscillator may be synchronized by pulses provided from a circuit including a Colpitts oscillator indicated generally at 76 which provides a sine wave output across a resistor 77. The sine wave voltage across the resistor is shaped into pulses by a shaper circuit 78 including a pair of triodes 79a and 79b having their cathodes connected together 'and connected through a resistor 80 to a source of negative voltage indicated as B in Fig. 4. The grid-cathode circuit of triode 79a is supplied with the sine wave voltage across resistor 77 and couples its output through a capacitor 81 to the grid of triode section 79b. The output of the shaper circuit 78 is developed across a resistor 85 which is connected to the grid-cathode circuit of a'trigger triode 86. The grid of tube 86 is biased so that'the tube is normally cut off by the combination of a resistor 87 and a source of negative voltage indicated as B, connected to the grid of the tube. Trigger tube 86 provides a train pf pulses of volt.-

circuits of all of the blocking oscillators.

6 age of high speed sawtooth frequency to the plate of the blocking oscillator tube 71 to synchronize the blocking oscillator.

The high speed sawtooth voltage developed acrosscapacitor 74 is coupled through a cathode follower stage 90 to a pair of coupling cathode followers 91a and 91b. The cathode follower 90 is designed to maintain the charging current for the sawtooth capacitor 74 as constant as possible. Coupler stage 91a is cathode coupled to a vertical driver stage 92 which includes a pentode 93. The output of the pentode 93 is developed across the primary of a transformer 94. A portion of the secondary voltage of transformer 94 is used to drive the vertical deflection coil 95. A damping circuit for the vertical deflection coil is also provided by a circuit including diode 96.

The sawtooth voltage from coupler section 91b is cathode coupled by a bus which is connected to one input of each-of voltage comparators 49. More specifically, in each of the comparator circuits, bus 100 is connected to a multivibrator 101, by connecting the bus to the grid of triode section 102a of the multivibrator. The grid of triode section 102b of the multivibrator is connected to a voltage divider formed by a trace position control potentiometer 103 (controlled by screws 22 of Fig. 1) connected across a source of positive voltage indicated as 13+, by a series combination of

resistors

104 and 105. Resistor 105 is shunted by a capacitor 106. The geophone output voltage corresponding to the first geophone channel is developed across capacitor 106 and therefore combined with a bias voltage of magnitude determined by the position of the trace position potentiometer 103. The combination of the bias voltage and the geophone signal voltage is a composite voltage, which is compared with the high speed sawtooth voltage by comparator 101.

As indicated in Fig. 4, each of voltage comparators 49 is provided with a geophone input from a difierent demodulator. For each of these comparators, the trace position potentiometer is adjusted differently, so that a different bias voltage is added to the geophone signal voltage for the different trace channels.

Multivibrator 101 will flip from its normal condition whenever the instantaneous vertical sawtooth voltage is approximately equal to the composite voltage formed by the geophone output voltage and the bias voltage. When this flipping action takes place, a pulse of voltage will be supplied from the plate circuit of triode section 102b to a trigger tube 107. The output of the trigger tu'be controls a blocking oscillator 48 which is of conventional design. The output of the blocking oscillator 48 of this first channel is combined with the outputs of all the other blocking oscillators 48 and developed across a resistor 108 connected in the cathode Thus, each time that one of the composite voltages formed by the combination of the bias voltages and the geophone signal voltages is approximately equal to the instantaneous high speed sawtooth voltage, a pulse of voltage is developed across resistor 108. The train of these pulses of voltage is supplied to the video amplifier.

Horizontal sawtooth generator bination of a capacitor 112 and

series resistors

113 and 114 to a source of negative voltage indicated as B"- as B+ and is also connected through the shunt combi nation of? aresistor I16 anda capacitor 11-7 t'oitl-ief sup.-= pressor grid of the pentode. In' order toincrease the: speed of recovery of the phantastron action, the pla'te of' the pent'ode is connected to the control grid of a triode 118 which hasits cathode connected to the junctionbetween capacitor 11 2and resistor' 113-and its plate connected'to'B The phantastron. circuit so far described is conven-' tional' in design and yieltis a sawtooth wave-of voltage-f in-its plate circuit which isdnitiated bya positive-goingsynohronizingpulse applied to its suppressor grid, the sawtooth voltage being developed across resistors" 113 and 1143 g As indicated above; the initiation of the horizontal sweep is controlled by asweep-trigger volta'ge developed" in the sweep and window sync source 58 through the time break pulse prov-ided frornxhead 55. This sweep trigger voltage is connected to a polarity selection: cir-- cuit 120- of Fig. Shaving-a switch 121 for selecting-the sweep trigger of'appropriatepolarityto drive" a Schmitt' trigger circuit- 122'. The sweep trigger voltage is compared with a-volt'age*devel'oped by a-t'riggersync poten-- ti'ometer 123' connected in a series circuit: between B+ and B through

resistors

124 and 125. The slider of the potentiometer is connected tothegrid oftriode section 12Gb of the: polarity selection circuit; while the sweep: trigger. is connected to the grid oftriode section 12612::

The Schmitt triggencircuit isiof conventional design and supplies its output as: a positive: pulse to' the grid of w cathode. follower 130 including a= triode 131. Triode lBl is" normally 'b'ias'ed to: cut ofii through a resistor 1321 connecte'dto' Bandito the; grid ofthe triode. A positive'pulse-fr'om theischmitfitrigger circuit cuts triode 131 on, and the resultantpulseof voltage developed across the cathode resistor 133 is supplied to the suppressor. grid" of. the phantastron pentod'e 111' to trigger the' swe'cp voltage;

The-sawtooth voltage developed across resistor 114 is supplied' to the grid of. triode section 135a of a circuit 186'. designed"v to. convert the. single-ended sawtooth voltage to a push-pull voltage for driving the horizontal deflection coil; Triode section: 135a has its' cathode connectedthrough' a resistor 137"to-B' and is" connected" through a; potentiometer 138; whose position controls the: length of the horizontal sweep, to the cathode of triode section. 135b: The: grid of section 1351: is connected. to. the? slider of a potentiometer 134 whose posi-- tion controls theiposition of the horiiontal' sweep and which" isconnected' between Bf and B The plates of the. twcr-tnode sections are connected through resistors 139aand 13%, respectively; toB+. tion 135a. is. connected to the: grid of a triode driver section. 140a,. while. the plate of triode section 13515 is connected'ito theigridioffdriver triodesection140b; The push-pull output' from the driver including sections 140a and. 1405 is cathodezcoupled to thehorizontal deflection coillzil: Flybackxblankingandfly baclc pulses are also developedacross' thisicoil .andusedto control the cathode ray tube grid:.circuit"46- to turn the beam oif during flyback and to supplyiaireset voltage-for thecontrol circuit 57, respectively.

The speed of the horizontal sawtooth sweep is controlled: by: the control portion of the window multivibrator and control 61, the control circuit including a resistor 1'45 and' apair of'parallel-

connected triodes

146 and 1 1-7 having: their plates connected to B+. The'side ofiresistor 145-:remote-from' thie'cathodes of the'triodes' is connected to the junction between the control grid" of phantastron' pentod'elll and capacitor 112; As will be' obvious, the charging current for the -capacitorpasses" through one' orrboth.of-thetrids; so'th'atith'e plate current of" thetriodes" determinesthe magnitude of the charging current; and hence-the slope of'thei. sawtooth voltage; Triode"l4'6 isnormallyconducting"to an extent The plate of sec-- adjustable by control of' a sweep speed potentiometer. Shaving-"it's slider (controlledbyknob 27" Of FIg. l connected to'the' grid of'the triode1'46, the=potentiom-- eter being connected between B and ground. T-riode" 147- is normally' biased to 'cut off, but'-' it may becut on to increase the" capacitorch'arging current through a multivibrator lstl includingtriodes' 1 5-1 a-nd' IS2i Mul tivib'rator 156- is of conventional design having triode section-1 51 normally conducting and adapted to be flipped by a ne'gativei pul's'e applied to the" grid of the triode 151, tosuppl'y apositivepulse of'voltage at the output= ofitriode IST. The width ofthe positive pulse so supplied i'sl cont-rolled {by 'a window width potentiometer 153*(controlled by-knob -Z6"'of Fig: l)'--which-is' connected i'nthe"grid eircuit of'triode 1522 p The trigger; pulse for multivibrator' 159 to control the time when-a the window of the sweep is" initiated may be supplied from an external source, or may begenerat'ed" within window comparator60. A- switch lst'r's'elects the external window'- trigger or the local" window comparatorcircuit. The window'comparat'or circuit includes aimultivibrator' 1 56' which is of conventional design and has the grid of its triode section 157 supplied with thehori zontal sawtooth voltage from across resistors 1'13 and 114% The grid of triode section 158" i's" provided with" a controllablehias-voltage through a potentiometer 159" (-controlled by'k-noh 2; of Fig. l)' which controls'thc" position of the window in the-horizontal sweep. When switch is in its lower position connecting the-windowcomparator tothe window multivibrator 1'50, triode section- 158 is normally conducting and the multivibrator" 1"56'-fiips'to a condition such that triode" section 157' is conducting when the horizontal sweep voltage on the grid of triode 157; is: lowenough to. permit triode 157 to conduct.

Beam: intensify control: circuits Referring'now to'Fig': 6; the intensity controllingcircuitsof the cathode ray tube. and the" circuits which provide. voltages therefor will n'owib'e' described. As indicated in conjunction with Fig; 4; the train of pulses from acrossresistor. 108 is. supplied to a video amplifier 47...

Amplifier'47 includes a pair of pentodes 1'65 and 166;, with the pulse train from the blocking oscillators being: supplied" to the control grid ofthe-i first. pentode,. and. the plate thereof being transformer-coupled to the con? trol grid of the second pentode. The plate-.oflthe. second pentode is connected'through a pair. of resi'stors..16.7 and 168 to B+.. The junction between these resistors. is capacity-coupled to. the cathode of. the. cathode ray tube 40. and the amplifiedpulses from thevi deo ampli her are developed acrossresistor 169;.connected between. the. cathode and. ground. A. circuit including potenti' ometer 170 (controlled-by knob. 31- of- Fig. 1). connected between the cathode of the cathode ray tube and. 13+ determines the over-all intensity of the cathoderay beam.

As indicated lII-CDDjllIlCtiOIlwith. Fig. 3,.the. grid circuit 460i thecathode ray'tube is supplied. with voltage from an intensity gate 67. Thisintensity gate includesa cascodecircuitincludingethe seriescombinationof a triode 170 withthe shunt combination of: a=resistor 17-1 and three diodes-172474; and a'- cathode resiston'175; The-control grid of the. cathode ray tube isconnectedthrougha pair ofresistors 176*and 177 to the" junction between the cathodes of. triodes. 172-174 and. resistor 1 75,so that avoltage determined by; the current flow-- ing. through: the four triodesis: developed between. the control grid and t cathode. of the cathodeiraytube.

'lrheplate currentof triode 170' is controlled in part; by a resistor. 180-. connected between. the? gridthereof! and'B so,that the tube i's.nor-mal1y conducting,butrthe: grid. issupplied. with. a flybaclc. blankingpulseiatv theend. offevery. h'oriiont'al sweep to. cut ofhthertube-andlthereby. cut ofithe cathode ray, beam..

The gridoft'r'iode 172 has its voltage controlled from a circuit including a pair of

triodes

181 and 182 which form a differential amplifier. The grid of triode 181 is connected to the grid of triode 147 of the window multivibrator and control circuit, to receive a pulse of voltage each time the window is generated. The triode 182 has a controllable bias adjustable through a potentiometer 183 (controlled by knob 30 of Fig. 1) connected in the grid to cathode circuit of the triode.

The plate current through each of

triodes

173 and 174 of the intensity gate circuit is controlled through timing line generator 66. This generator is intended to place timing lines on the face of the cathode ray tube for every one-tenth and one-hundredth of a secondof the horizontal sweep. To accomplish this function, a pair of

multivibrators

185 and 186 is used, one being controlled by the one-tenth second timing line sync voltage, and the other being controlled by the one-hundredth of a second timing line sync voltage. The first multivibrator controls the bias of triode 173 while the second controls the bias of triode 174. The static bias of the grid circuits of each of these tubes is controlled through

triode circuits

187 and 188, respectively, each having potentiometers in their grid circuits to control the normal conduction level of

triodes

173 and 174. Potentiometer 189 (controlled by knob 29 of Fig. 1) in the grid circuit of triode 187 controls the intensity of the tenth of a second timing lines, while potentiometer 190 (controlled by knob 28 of Fig. 1) in the grid circuit of triode 188 controls the intensity of the onehundredth of a second timing lines.

The control circuit of Fig. 6 also includes a so called anti-blossoming" circuit to prevent the beam from being unduly intensified when a timing line is being placed on the face of the cathode ray tube and a pulse from the blocking oscillators simultaneously tends to turn the beam on. When these two conditions occur simultaneously, the tendency would be for the beam to be intensified to such an extent that some of the information on the face of the cathode ray tube would be obscured. In order to prevent this, the grid of the cathode ray tube is connected to ground through a diode 195 and a resistor 196 connected in series, while the plate of pentode 166 is connected to ground through the series combination of a resistor 197 shunted by capacitor 198 and resistor 196. The action of this circuit is such as to decrease the amplitude of the pulse supplied by pentode 166 to the cathode of the cathode ray tube when a timing line is being generated.

Synchronizing and control circuits Referring now to Fig. 7, the control circuit 57 of Fig. 3 will be described in more detail. The control circuit includes a source of internal standard frequency 200 which may be, for instance, 1 kc. The output of the standard 200' is supplied to an amplifier and shaper 201 when a switch 202 isin the appropriate position. The switch 202 may also be used to supply the amplifier with an externally-generated standard frequency. The output of the amplifier is connected to a gate 203 and is passed by the gate only when the gate is turned on by a pulse supplied from a main latch circuit 204. As indicated, the main latch circuit includes a bi-stable multivibrator which is flipped to condition such as to open thegate by the time break input.

When gate 203 is opened it supplies a sweep trigger voltage to the low speed sawtooth generator of Fig. 3. After the gate is opened, and until it is closed again, the gate transmit pulses from the amplifier and shaper 201 to a series of decade counters 205 through 208. Decade counters 205 and 206 areconnected in series and each has the function of providing an output pulse for every tenth pulse supplied to its input. The counters are of conventional design and are readily. available on the market, so that they will notbe more particularly described. Counter 205 divides the one kc. internal standard by ten 10 and supplies one-hundredth of a second pulses to mnlti vibrator 186 of the timing line'generator, while counter 206 divides the output of counter 205 by ten and supplies one-tenth of a second pulses to multivibrator of the timing line generator.

The third and fourth decade counters have the characteristic of supplying an output pulse for every n input pulses, with n being manually selectable. The result is that counters 207 and 208 provide pulses for a number of tenths of a second and for a number of seconds after the time break, respectively, to the delay latch trigger circuit 210. The output of the delay latch trigger circuit is supplied to the delay latch 211 which, as indicated, is a bi-stable multivibrator, and the delay latch, when in open position, supplies a window trigger pulse to the window multivibrator 150. As indicated in Fig. 7, the main latch andthe delay latch are reset to their proper positions at the end of every sweep by a reset voltage, and the main latch, when reset, supplies a reset pulse to reset stage 212. Reset stage 212 supplies controlling voltages to decade counters 205208 to reset the counters to zero at the end of every horizontal sweep.

Referring now to Fig. 8, the control circuit of Fig. 7 will be described in more detail. The one kc. internal standard is supplied by an oscillator 215 which provides a sine Wave voltage to amplifier and shaper circuit 201. This circuit consists of a triode amplifier 216 and a Schmitt trigger circuit 217 which shapes the input sine wave into a series of pulses of voltage of frequency corresponding to that of the oscillator 215. the trigger circuit 217 is supplied to gate 203 through capacity coupling to one triode section 218a of the gate. The other triode section 218b of the gate is normally conducting, so that section 218a is normally turned oif, but

in positive sense to the trigger triode 221 to cause plate.

current to flow therein and furnish a negative pulse of voltage at the output of the trigger. This negative pulse is applied to the grid of triode section 218b of. gate 203 to open the gate, so that pulses from the amplifier and shaper 201 pass through the gate to the decade counters.

The trigger time break pulse from trigger 221 also flips a multivibrator circuit including triode sections 2230 and 223b, the trigger output being supplied to the plate of section 223a. section 223a is conducting, While section 2231: is cut ofi. The main latch is also controlled by a reset trigger circuit including triode 224, the reset trigger tube also being normally cut off through a circuit including a resistor 225 connected between its grid and B. The grid of triode 224 receives the reset input furnished by the flyback pulse of the horizontal deflection coil, and, when this positive-going pulse is supplied to the reset trigger, a negative pulse is applied from the trigger to cut off triode section 2230 of the gate and cut on triode section 223b. The positive pulse of voltage from triode section 223a caused by the reset trigger operation is then coupled to reset stage 212, including a triode cathodecoupled amplifier 226.

The reset action accomplished with the output of triode 226 will be described hereinafter.

When gate 203 has been opened by arrival of the time break trigger pulse, the shaped pulses from the oscillator- 215 drivedecade counter 205. As described in conjunc- One output of the decade counter 205 is supplied to the A The output of After the arrival of the trigger pulse, triode secrete 1 1 input of like decade counter 206, while the other output is provided to a shaper circuit including a triode 230l The shaper'circuit supplies one-hundredth of a second "tim ing' 'line sync pulses to the timing generator tid ofFig'. 6'.

Decade counter 206 also provides two outputs, with one pulse for every ten pulses provided its input, and one output of the decade counter drives ashaper circuit, including triode 231. The output of the shaper circuit provides one tenth of asecond timing line sync pulses to the timing line generator.

The other output of decade counter 206 drives decade counter 207 which, like counter 208, is of somewhat difierent design than

counters

205 and 206. Counter 207 has one output which represents a division of the input of the counter by ten, while the other output of the counter provides one pulse for every n pulses at its input. The number n is selected by push-buttons such as shown at 235 on the block'of the decade counter. Thus, with the one kc. oscillatr215 and the two decade coun ters ahead of it in the chain, the second output of decade counter 207 provides a pulse a number of tenths of a second after the time break determined by the pushbutton- 235 depressed. This pulse is provided to a delay latch trigger circuit'210 through a resistor 236 connected to the grid of a triode 237.

Decade counter 208 is identical with counter 207 and provides an output pulse delayed a number of seconds after the time break determined by which of pushbuttons 235 is depressed. This pulse is supplied to the delay latch trigger circuit through a resistor 238 likewise connected to the grid'of triode 237.

The delay latch trigger circuit controls a bi-stable multivibrator of delay latch 211 including triode sections 240a and 24%. When the trigger is operated by pulses supplied from both the decade counters ,207 and 208, triode section 240b is turned on to supply a negative pulse in its plate circuit as a window trigger voltage for the window multivibrator 61 of Fig. 5. Despite any action of the

counters

207 and 208, no window trigger will be supplied until the delay latch is reset. The reset input is connected to the delay latch through the combination of a capacitor 241 and a rectifier 242 connected to the grid of triode section 24011. When the horizontal deflection coil supplies itsfiyback pulse as this reset inputtotriode section 240a of the delay latch, section. 240a is turned on and section 24012 is turned off to prepare thelatch for its next operation to provide a window trig ger'.

Reset stage212 provides its output across the cathode resistor of triode 226' to the reset input of the decade counters 205208, to reset all of the counters to zero at the end of a horizontal sweep.

Operation.

In operation of the apparatus described above, the recorder' drive 51 of Fig. 3 is operated to start the magnetic recorder drum 50 rotating. Head 55 picks up the time break pulse, which operates the main latch circuit and opens gate 203. The time break pulse is simultaneously applied as a sweep trigger pulse to the low speed' sawtooth generator to begin the horizontal sweep. The vertical sweep of the cathode ray tube beam also begins through operation of the usual power switch (not shown) so that the beam begins its trace back and forth across the vertical dimension of the cathode ray tube target, while being deflected slowly along the horizontal dimension of the target. The vertical sawtooth voltage is compared in the circuits of Fig. 4 with the composite voltages formed by the bias voltages selected by potenti'ometers'103 and the signal voltages obtained from magnetic heads 52' of the recorder. As" each composite. voltage approximately coincides with the vertical sweep voltage, the appropriate blocking oscillator 48 provides a pulse of voltage to the video amplifier 47, and that puiseis supplied to the cathode of-the cathode ray tube- V 12 toturn the beam on instantaneously; This last-detailed action repeats' automatically during" each vertical sweep of the cathode ray beannWith'the positions of the visible spot in each trace being determined by the instantaneous" magnitudes of the signal voltages at the relative times with respect to the time break. Every one hundredth of a second and every tenth of a second after the time break, decade counters 205' and I 206- provide pulses to

multivib'rators

185 and 186, which in turn provide pulses to the grid of the cathode ray tube to turn the beam on for a period of time appropriately coinciding with the length of one vertical sweep of the beam. Thereby, one-tenth of a second and one hundredth of a second timing lines are generated on the face of the cathode ray tube.

After an interval of time from the time break determined by the setting of the pushbuttons. of counters 20.7 and 208', or by the setting of the window position potentiometer 1 59', depending upon which position switch 155 is in, the multivibrator 150 of Fig. 5 generates a positive pulse which turns on triode 147 to increase the voltage across cathode resistor and thereby increase the speed of charge" of the phantastron" capacitor 112. The slope of the horizontal sawtooth is thereby increased, to increase the speed of the horizontal sweep for a portion of the-horizontal sweep time determined by the setting of the window width potentiometer 153. This window expands the corresponding portions of the geophone voltages on the faceof the'cathode ray tube.

After the multivibrator 150 returns to its normal condition to cut off triode 147, the horizontal sawtooth returns to its normal slope and completes the horizontal trace of the cathode ray beam. When the horizontal trace is completed, the horizontal deflection coil. 141 supplies a flyback' blanking pulse to the intensity gate 67 to turn ofi the beam, and the same coil supplies a fiyback pulse to the control circuit of Fig. 8 to reset the delay latch, reset the main latch, return gate 203 to its closed condition, and reset the decade counters. When the magnetic recorder drum again reaches a position in which the recorded time break pulse isopposite pick up head 55, the above-described sequence of operations is repeated.

For the normal five second recording tape of the geophone outputs, the horizontal sweep time may be selected to be of the order of three to five seconds, while the vertical sweep time may be of the order of 200 microseconds. The fluorescent material of the target of the cathode ray tube is preferably selected to be of the high persistence type that will show the information presented thereon'for a period of the order of the horizontal sweep time.

Modified: synchronizer It: is not necessary that. the horizontal sweep be initiated by the time: break pulse, or that the window be synchronized: by output pulses from. decade counters. The apparatus of Fig; 9 is designedto accomplish both of. these functions. That apparatus includes a commutator generally indicated1at250 which has a rotatable con-' tact member 251 driven by: themagnctic recorder drum drive-51'. A plurality of arcuately-spaced stationary conislets-252 are positio'ned inthe path of the rotatable contact member and are each connected to one side of each of. a

pain ofswitches'v

253 and 254'.- The other sides of switches 253 are connected together to a common circuit 255' which. may be connected to the sweep trigger circuit, such as shown in Fig. 5. i

The other sides of switches 254 are connected together to a common circuit 256'which maybe connected to. the Window trigger circuit, such as the multivibrator 1'50 ef Fig. 51

The rotatable contactme'mber 251 is connected to any appropriate source of voltage 257.

The operation of the apparatus of Fig". 9" is as folassesses lows. When recorder drum drive 51 is operated to begin rotation of the recorder drum, the rotatable contact member 251 rotates in synchronism with the drum. The operator may depress any one of each of

switches

253 and 254, thereby selecting when the horizontal sweep is initiated, and when the window of that sweep is initiated. When the rotatable contact member touches the stationarycontact corresponding to the

closed switch

253 or 254, a pulse of voltage is supplied to the trigger circuit 255 or 256 to initiate the appropriate operation. The apparatus of the present invention has been described in conjunction with preferred embodiments thereof. It Will be obvious that many minor changes could be made in this apparatus without departing from the scope of the invention. Therefore, the invention is not to be considered limited to the apparatus specifically described herein, but only by the scope of the appended claims.

We claim:

1. In a cathode ray tube viewing device for exhibiting a plurality of signal voltages on a fluorescent target and including means for generating a beam of electrons and directing it at the target, means for controlling the intensity of the beam to turn it on and off and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said one dimension of the target, respectively, means for generating a first sawtooth wave of high frequency and applying it to said first deflecting means, means for generating a second sawtooth wave of low frequency and applying it to said second deflecting means, means for adding a diflerent bias voltage to each of said signal voltages to produce a plurality of composite voltages, means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at different points along the first sawtooth determined by the bias voltages and by the magnitudes of the signal voltages, said last-named means being connected to said intensity-controlling means to turn the bearn on each time said last-named means provides a pulse of voltage, said second sawtooth being linear and normally of a pre-determined slope, and means for changing the slope of the second sawtooth along a portion of its extent to change the speed of sweep of the beam along a portion of said other dimension.

.2. The apparatus of claim 1 in which said means for generating the second sawtooth includes a capacitor and a charging circuit therefore, and in which said slopechanging means includes means for changing the impedance of said charging circuit.

3. The apparatus of claim 2 in which said charging circuit includes a pair of parallel-connected discharge tubes eachvhaving a control electrode, one of said tubes being normally cut ofi and the other tube conducting the capacitor charge current, and said impedance-changing means includes means for supplying a pulse of voltage to the control electrode circuit of said one tube to cause it to conduct.

4. The apparatus of claim 3 in which said supplying means includes a monostable multivibrator, and means for triggering said multivibrator to supply said pulse of voltage.

5. In a cathode ray tube viewing device for exhibiting a plurality of signal voltages on a fluorescent target and including means for generating a beam of electrons and directing it at the target, means for controlling the intensity of the beam to turn it on and off and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said one dimension of the target, respectively, means for generating a first sawtooth wave of high frequency and applying it to said first deflecting means, means for generating a second sawtooth wave of low frequency {1nd applying it to said second deflecting means, said last-named means including a capacitor and a charging circuit normally operable to charge the capacitor at a predetermined rate to produce a linear sawtooth of predetermined slope but operable in-resp'onse to a controlling voltage to charge the capacitor at a faster rate to increase the slope and thus the speed of sweep of the beam along a portion of said other dimension, means operable to supply said controlling voltage to said charging circuit for a portion'of the charging operation, means for adding a different bias voltage to each of said signal voltages to produce a plurality of composite voltages, and means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at difierent points along the first sawtooth determined by the bias voltages and by the magnitudes of the signal voltages, said last-named means being connected to said intensity-controllingmeans to turn the beam on each time said last-named means provides a pulse of voltage.

6. The apparatus of claim 5 including means for initiating the operation of said means for generating said second sawtooth wave, and in which said means operable to supply said controlling voltage is controllable to supply said controlling voltage a desired time interval after generation of the second sawtooth wave is initiated.

7. The apparatus of claim 6 including means for generating a train of equally time-spaced pulses of voltage, and means for controlling said last-named means to supply an output pulse of voltage a controllable interval of time after generation of the second sawtooth wave is initiated, said output pulse of voltage being operable to control said means operable to supply said controlling voltage.

8. The apparatus of claim 5 including means responsive to increase in the rate of charge of said capacitor operable to increase the voltage supplied to said intensitycontrolling means whenever a pulse of voltage is supplied thereto to compensate for the apparent decrease in beam intensity caused by the higher sweep speed.

9. In a cathode ray tube viewing device for exhibiting a plurality ofsignal voltages on a fluorescent target and including means for generating a beam of electrons and directing it at the target, means for controlling the intensity of the beam to turn it on and off and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said one dimension of the target, respectively, meansfor generating a first sawtooth wave of high frequency and applying it to said first deflecting means, means for adding a different bias voltage to each of said signal voltages to produce a plurality of composite voltages, means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at different points along the first sawtooth determined by the bias voltages and by the magnitudes of the signal voltages, said lastnamed means being connected to said intensity-controlling means to turn the beam on each time said last-named means provides a pulse of voltage, means for generating a second sawtooth wave of low frequency and applying it to said second deflecting means, means for initiating the operation of said last-named means to start sweep of the beam along said other dimension of the target, means for generating a train of equally time-spaced pulses of voltage, counting means operable to supply an output pulse of voltage in response to arrival of a predetermined number of pulses from said train generating means, said counting means and said train generating means being effectively disconnected normally but connected together when the beam sweep along said other dimension of the target is initiated, said means for generating a second sawtooth including a capacitor and a charging circuit therefor, said charging circuit being normally operable to charge said capacitor at a predetermined rate to sweep said beam along said other dimension at a predetermined. speed but being operable in response to arrival of a 601k agas 1'5 trolling voltage to. charge the capacitor at a faster rate to increase the speed of sweep, and means. connected to said counting means operable to supply said controlling voltage to said charging circuit in response to generation of' said output pulse of voltage.

10. The apparatus of claim 9 in which said means for generating a second sawtooth includes a phantastron having said capacitor connected therein, said charging circuit including at leastone resistor, a source of voltage and a pair of parallel-connected discharge tubes, each of said tubes having a grid-cathode circuit, oneof said tubes being normally conducting to carry the normal charging current of the capacitor and the other tube being normally cut ofl, saidmeans for supplying said controlling voltage being connected to the grid-cathode circuit of said other tube to cause it to conduct for a portion of the sweep to allow the capacitor to charge at a faster rate.

11. The apparatus of claim 10 includinga main latch circuit, a gate circuit, a delay latch circuit, and" a reset circuit supplied with a flyback pulse from the second'deflecting means operable in response thereto to furnish a reset pulse, said gate being connected between said countingmeans and said train generating means and operative in response to initiation of said sweep along said other dimension to permit the train of pulses to reach the counting means when the gate is in its normal condition, said main latch circuit being operable to switch said gate circuit to an abnormal condition immediately after said sweep is initiated, said means connected to said. counting means including said delay latch circuit, said delay latch circuit being operable when in its normal condition to permit said output'pulse of voltage to cause said controlling voltage to be connected to the grid-cathode circuit of said other discharge tube, said delay latch circuit being switched to anabnormal condition immediately after said output pulse of voltage reaches it, and said reset circuit being connected to said main latch and said delay latch and operable to reset them. to their normal conditions when said flyback pulse is received.

12. In'a cathode ray tube viewing device for exhibiting a plurality of signal voltages on a fluorescent target and including means for generating a beam of electrons and dire'cting'it at the target, means for controlling the in tensity of the beam to turn it on and oif and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said'one dimension of theltarget, respectively, means for generating a: first sawtooth wave of high frequency and applying it to said first deflecting means, means for generating a second sawtooth wave of low frequency and applying it to said seconddeflecting means, means for adding a differentbias voltage to each of said signal voltages to produce a plurality of composite voltages, means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at different points along the first sawtooth determined by the bias voltages and by the magnitudes of the signal voltages, said last-named means being connected to said intensitycontrolling means to turn the beam on each time said last-named means provides a pulse of voltage, means for generating a train of equally time-spaced pulses of voltages spaced aparta time intervalmuch. smaller. than the sweep time along saidother dimension, and. means for supplying said train of pulsesto said-.intensity-controlling means to turn the beam on and provide time indications on the target.

13. The apparatus; of: claim 12 in which said. one dimension is horizontal and said other dimension vertical, said first sawtooth: occupies so much less time than said second sawtooth that: the beamsweepsup and down in the vertical directionmanytimes during one sweep in the-horizontaldirection; so that the vertical sweep is substantiaiy' perpendicular to the horizontal dimension of the target, and said supplw'ng means turns the beam on for 16 substantially. one complete vertical trace each time a pulse of voltage, reaches it;

14. The apparatus of claim 12 including means connected to said comparing means and said supplying means operative when a pulse from each reaches the intensity-controlling means simultaneously to prevent the beam intensity from being as great as the sum of the pulses would otherwise direct.

15. In a cathode ray tube viewing device for exhibiting a plurality of signal voltages on a fluorescent target and including meansfor generating a beam of electrons and directing it at the target, means for controlling the intensity of the. beam to turn it on and off and first and second means for deflecting the beam along one dimension and. another dimension substantially perpendicular to said one dimension of the target, respectively, means for generating a first sawtooth wave of high frequency and applying it to said first deflecting means, means for generating a second sawtooth wave of low frequency and applying it to said second deflecting means, means. for supplying a synchronizing voltage, means for initiating operation of said means for generating a second sawtooth in response to arrival of said synchronizing voltage, means for adding a different bias voltage to each of said signal voltages to produce a plurality of composite voltages, means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at diflerent points along the first sawtooth determined by the bias voltages and by the magnitudes of the signal voltages, said last-named means being connected to said intensity-controlling means to turn the beam on each time said last-named means provides a pulse of voltage, said second sawtooth being normally'of a predetermined slope to sweep the beam. at a predetermined speed along said other dimension of the target, a source of a train of pulses of voltage equallyspaced in time, first counting means operable to supply one pulse for every 11 pulses reaching it, second' counting means operable to supply one pulse for every n pulses reaching it and controllable to vary the value of n, a gate circuit connected-between said source and said first and second counting means opened by arrival of said synchronizing voltage, means connected between said first counting means and said intensity controlling means operable to turn said beam on every time said first counting means supplies a pulse, means connected to said second counting means operable in response to arrival of a pulse therefrom to increase the slope of said second sawtooth to increase the speed of sweep of the beam along said other dimension for a portion of a sweep, means for increasing the intensity of the beam above the normal amount directed by a pulse from the comparing means when the sweep speed along said other dimension is increased, andv means responsive to simultaneous arrival of a pulse from said comparing means and a pulse from said first counting means at said intensity-controlling means operable to prevent the beam intensity from being as great as the sum of the pulses would otherwise direct.

16. In a cathode ray tube viewing device for exhibiting a plurality of geophone output signals simultaneously on a fluorescent target and including means for generating a beam. of electrons and directing it at the target, means for controlling the intensity of the beam to turn iton and off and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said one dimension of the target, respectively,,means for generating a first sawtooth volt-age of high frequency and supplying it to said first deflecting means to sweep the beam rapidly along said one dimension, means for generating a second sawtooth voltage of low frequency and supplying it to said second deflecting means to sweep the beam slowly along said other dimension, said sweep speeds being of such rela tive values that the beam sweeps along said one dimenaseaese sion many times during one sweep along said other dimensicn, means for increasing the slope of said second sawtooth voltage to increase the speed of sweep along said other dimension of the target for a portion of said sweep, means for initiating the second sweep voltage and for controlling the time the speed thereof is increased, means for adding a different bias voltage to each of said signals to produce a plurality of composite voltages, and means for comparing the composite voltages individually with the first sawtooth voltage operable to produce a pulse of voltage every time the magnitude of a composite voltage substantially coincides with the magnitude of the first sawtooth voltage, said comparing means being connected to said intensity-controlling means to turn the beam on each time the comparing means provides a pulse of voltage.

17. The apparatus of claim 16 in which said geophone signals are recorded and played back from a rotatable drum, said initiating and controlling means includes a commutator comprising a rotatable contact member rotating with the drum and a plurality of arcuately-spaced stationary contacts positioned in the path of movement of the contact member, a source of voltage connected to the rotatable contact member, said fixed contacts being each connected to a switch and the other sides of the switches being connected together.

18. The apparatus of claim 16 in which a time break signal is supplied along with the geophone output signals and said initiating and controlling means includes a control circuit supplied with said time break signal and supplying an output sweep trigger voltage to said means for generating a second sawtooth voltage to initiate the second sawtooth and also supplying a window trigger voltage delayed with respect to the sweep trigger voltage to said means for increasing the slope of the second sawtooth voltage.

19. In a cathode ray tube viewing device for exhibiting a plurality of signal voltages on a fluorescent target and including means for generating a beam of electrons and directing it at the target, means for controlling the intensity of the beam to turn it on and off and first and second means for deflecting the beam along one dimension and another dimension substantially perpendicular to said one dimension of the target, respectively, means for generating a first sawtooth wave of high frequency and applying it to said first deflecting means, means for generating a second sawtooth wave of low frequency and applying it to said second deflecting means, means for adding a different bias voltage to each of said signal voltages to produce a plurality of composite voltages, means for comparing the composite voltages individually with the first sawtooth operable to produce pulses of voltage at different points along the first sawtooth de- 18 termined by the bias voltages and by the magnitudes of the signal voltages, said last-named means being connected to said intensity-controlling means to turn the beam on each time said last-named means provides a pulse of voltage.

20. The apparatus of claim 19 in which said comparing means includes a plurality of monostable multivibrators each having said first sawtooth connected to one input circuit and one of said composite voltages connected to its other input circuit, a plurality of blocking oscillators each connected to one of said multivibrators and operable to develop a pulse of voltage when its multivibrator flips to its unstable condition, and means supplying the pulses from all of said blocking oscillators to said intensity-controlling means to turn the beam on each time a multivibrator flips to its unstable condition and causes its associated blocking oscillator to develop a pulse of voltage.

21. The apparatus of claim 20 in which said pulse supplying means includes a resistor common to the cathode circuits of all the blocking oscillators, and means for amplifying the voltage across said resistor.

22. The apparatus of claim 19 in which said means for generating the second sawtooth includes a capacitor and a charging circuit therefor, and in which said charging circuit includes a discharge tube and means for varying current flow through the discharge tube to change the speed of the second sawtooth.

23. The apparatus of claim 19 in which said second means for deflecting the beam includes first, second, third and fourth vacuum tubes each having at least a cathode, anode and control grid, means coupling said means for generating a second sawtooth between grid and cathode of the first tube, means biasing the second tube to a desired operating level, means directly connecting the anode of the first tube to the grid of the third tube and the anode of the second tube to the grid of the fourth tube, resistors in the cathode circuits of each of said third and fourth tubes, and a deflection coil connected between the cathodes of the third and fourth tubes.

24. The apparatus of claim 23 including a variable resistance connected between the cathodes of the first and second tubes adjustable to vary the length of the sweep along said other dimension, and means for varying the bias on said second tube to vary the position of said sweep.

References Cited in the file of this patent UNITED STATES PATENTS 2,453,711 Isbister Nov. 16, 1948 2,628,689 Rieber Feb. 17, 1953 2,688,126 Weller Aug. 31, 1954