US2840637A - System for converting telegraphic code into characters - Google Patents

Description

June 24, 1958 McNANEY ET AL SYSTEM FOR CONVERTING TELEGRAPHIC coma INTO CHARACTERS Filed. Feb. '28, 1955 3 Sheets-Sheet 1 V 7 6 EE 6 e m r mm 5 QMKTW/AU K L fw m ZCBPLFH E m mufiA N YXJ ?v PM 9 v "M o 4 2: 2 GNDEn s M FIGJ FIEJ

INPUT June 24, 1958 J, MCNANEY ETAL 2,840,637

SYSTEM FOR CONVERTING TELEGRAPHIO CODE INTO CHARACTERS Filed Feb. 28, 1955 3 Sheets-Sheet 2 MORSE TO BINARY CODE CHART NORMAL ELEMENT SPACE= DOT IIGTH. NORMAL CHARACTER n =3 TIMES n NORMAL WORD =6 TIMES NORMAL DASH LGTH= 3 TIMES NORMAL DOT LGTH AREA OF ACCEPTANCE AREA OF ACCEPTANCE NORMAL WORD SPACE LENGTH E T SHORT NORMAL H L NG H DOT LENGTH DOT LENGTH TOO LONG 4O 5O 6O WORDS PER MINUTE I N VEN TORS F uoszw ZMCNANEK emu/20 Q. T/CE:

WORDS PER MINUTE ATT ENEY June 24, 1958 J McNANEY ETAL 2,840,637

SYSTEM FOR CONVERTING TELEGRAPHIC CODE INTO CHARACTERS Filed Feb. 28, 1955 '3 Sheets-Sheet 3 T0 VERTICAL 466 SELECT/0N Pun:

T0 HOE/ZONTAL SELECT/0N PLATE INVENT OR.

JOSEPH T. MCNANEY.

BY Wflw AGENT.

United States Patent "ice SYSTEM FOR CONVERTING TELEGRAPHIC CDDE INTU- CHARACTERS Joseph T. McNaney, La Mesa, and Richard R. Ti'c e', Studio City, Calif., -assignors to General Dynamics Corporation, San Diego, Calif., a corporation of Delaware Application February 28, 1955, Serial No. 491,116 5 Claims. Cl. 178-15 This invention relates generally to a system for converting telegraphic codeinto charactersv and more particularly to such a system for substantially instantaneous visual display of characters corresponding to code signals.

Cathode ray tube display tubes in which an electron beam is shaped into desired character type information for direct reading visual presentation upon a screen of the display tube are known to the prior art. These tubes employ a matrix which is a stencil like presentation of desired character-shaped openings.

selected from the matrix and deflected on the screen to permit formation of words and sentences.

These display tubes then become important in permitting quick resolution of code into characters. Such codes form the bases forradio and landline communications, namely, Morse, Continental and like codes which are utilized in world-wide communications. In these codes the dot-dash signal system is used to interrupt, generally a continuous wave radio or-landline transmissicn, commonly referred to as C. W. code. This' code is changed into binary coding for presentation to proper circuitry which responds to apply the necessary display tube voltages to .produce the desired character display.

Messages may be received over a Wide range of speeds which are comparable to that of handeworked signals to the high speed transmission rates of modern telegraph systems. These operational rates, of presentyequipment, may vary from to .80 words per minute. The display tube and associated circuits are capable of speeds of several thousand words per minute.

The basic time measurement of sucha system is the dot signal. The dash is generally three times the length of the dot. All information sent'by'C. W. code-is coded into the dot-dash code; The individual letters, numerals, punctuation marks and the like, which are-coded, must be spaced properly to permit intelligent resolution upon reception. Further, grouping of characters or words is desired and therefor spacing is necessary :intermediate such groups to aid in resolution uponreception. With the dot as the basis of time measurement, the spaces separating successive impulses of a particular coded character are of one dot length. The spaces between characters or impulse groups are equal to three dots and the spaces between groups of characters or Words are equivalent to six dots. The particular parameters involved in converting code information for visual character presentation upon the display tube screen, are a The electron beam emitted by a cathode of the cathode ray tube is amass Patented June 24, 1958 2,. "5 minimum of a single dot length impulse and a maximum of six dot length impulses for information, character spacing or word spacing denotation. 7

The present invention utilizes the ,coded information receivedby an ordinary communications receiver or from a landline and presents this information to circuitry necessary to convert the dot-dash information into proper selection and deflection voltages for properly operating the cathode ray display tube and presenting a visual character display upon the screen of the display tube.

Morse, Continental and like codes, as previously explained, are sent in dot and dash pulses. Therefore, it is necessary to differentiate a dot from a dash. In addition, an element space (the spacing between consecutive dots or dashes), a character space (the spacing between groups of dots or dashes), and a word space (the spacing between groups of characters or words) must be sensed as such. I

-A dot-dash discriminator is provided for sensing the dot or dash and spacing. The discriminator circuit develops triggering pulses to a code converter. converter transforms the discriminator pulses into yesno information which is supplied to the display tube control circuit. The yes-no information received by the tube control circuit is converted to proper'horizontal and vertical selection voltages toselect the proper character from the display tube matrix for presentation upon the display tube screen. Additional circuitry is supplied to position the characters -inproper sequence uponrthe screen.

As this system lacks mechanical inertia,. very high speeds of code reception and resolution are possible.

It -is-an object of this invention to provide a system which converts telegraphic code into characters.- I

It is another object of thisinv ention to 'provide;.a ;-s'ystern capable of resolving code into characters with minimal inertia, I

It is another object of this temfor resolution of code into characters which system permits reasonable variations inspeeds of the transmittingoperators.

It is another object of this invention to provide a sys-' vtem for-resolution of, code i-nto characters which is capable. of adjusting itself to varying dot'and dash le'ngths witln' n reasonable ;li-mits.'

It is another object of tern capable of resolving equally well varying quality code transmissions into a visual character. presentation.

Other objects and advantages will hereinafter appear. For the purpose of illustrating our invention, an embodiment thereof is shown in the accompanying drawings,

. wherein:

, Figure l is a block diagram-of a system embodying the invention;

Figure 2 shows an illustrative Morse to binary code conversion chart;

Figure 3 is a perspective view partially in section of.

a cathode ray display tube diagrammatically shown in Figure 1;

Figure 4 is an enlarged view of a portion ofthe matrix of the cathode ray display tube of Figure 3;

figure 5 shows curves illustrating discrimination and tolerance limits of the embodiment of Figure 1;.

Figure 6 is a schematic circuit diagram of the gates and adder portions of the system. p

Referring more particularly to the drawings, Figure 1 is illustrative of an embodiment of the invention for Figure l is shown in block diagram form and includes an input v 10. Various codes such as Morse, Continental or the like, generally designated as telegraphic code may be The code.

invention to provide a sys-'- this invention to provide a sys presented to input 10. Telegraphic code 11 is shown nals 12, 13 actually becomes an aggregate of forming r diifering length square waves. These square waves, representing dot and dash signals 12,13, have a leading edge which generally indicates an abrupt rise in voltage and a trailing edge which generally indicatesan abrupt drop in voltage. edge and the trailing edge is varied in length to thereby indicate either the dot signal 12 or the dash signal 13. It should be appreciated, accordingly, that the invention utilizes as its basic' constituents devices which measure time and devices which respond substantially instantaneously to predetermined time measurement.

The dot signal 12 is utilized as the basic measure of time. As is shown in Figure 5, which figure will be examined in greater detail further on, the normal dash signal lenth is three times the length of the dot signal.

The normal element space, that is, the space between dot or-dash signals, is equivalent to a normal dot signal length;- that of a normal character space, that is, the

'space intermediate a group of dot and dash signals signifying a character, is equivalent to three times 'a normal dot signal length; and that of a normal word space,

that is, groups of characters, is equivalent to six times the length of a normal dot signal length.

When the dot or dash signal 12, 13 is impressed upon input 10,'a first means 15, is needed, which is responsive to the code 11 or dot and dash signals 12, 13 for sensing and discriminating between the dot and dash signals. A second means 16 which is also responsive to the code 11 impressed upon input 10, is provided for The portion intermediate the leading sensing spacing of the dot and dash signals 12, 13 and 'of the character and word spacings or of the groups of signals 12, 13. The dot and dash signals having been identified and proper spacing being supplied, it is now necessary to convert this information into a binary code 17, illustrated in Figure 2. The numeral 1 shown in binary code 17 represents yes information, and the numeral 0 shown in binary code 17 represents no information. The binary code 17, therefore, is merely a yes and no information which results as output from a third means 18. I a

Third means 18 is responsive-t0 the code 11 impressed upon input 10, to first means 15 and to second means 16 for selectively converting output of the first means 15 and the second means 16 into yes and no information. A fourth means 19 is responsive to second means 16 and utilizes the yes and no information of third means 18 for presenting the code 11 as characters 14. In addition, a coincidence means 29, which may be grouped with first means 15, is shown as an And gate, as is well known in the prior art as shown in Figure 10.16, page 379 of Waveforms, editedby Chance et al., published by McGraw-Hill Book Company, Inc., New York, 1949, and is responsive to the remainder of the first means 15 for selective operation of the second means 16 through coincidence means '29- to cause responses in the third means 18.

The broad overall aspect of the present invention having been described, a more detailed description to further the understanding of the instant embodiment-follows. The embodiment as shown in block diagram in Figure l, utilizes a new and novel combination of known elements, namely; And gates, designated as G in the drawing and which may be constructed pursuant to the teachings of Chance et al. in the book entitled Waveforms, published by McGraw-Hill Book Company, Inc., New York, 1949, page 379, Figure 10.16, shown in'the drawings as various gates, namely, gates 23, 29, 38

through 43 and 84 through 89, which gates respond to a pulse of energy to open the gate and to pass a second information pulse through the gate, each gate having two inputs and a single information pulse output; sawtooth generators constructed in accordance with the teachings of Samuel Seely in his book entitled Electron-Tube Circuits, published by McGraw-Hill Book Company, Inc., New York, 1950, page 449, utilize either the circuits of Figures 20-l7 or 20-18, or, the preferred circuit as shown in the figure of problem 20-7 on page 458, in the sawtooth generators 24 and 30, for time measure ment of signals 12, 13 and space lengths, in which the amplitude of the sawtooth function is substantially directly proportional to the length of the input function utilized. For example, as the dash signal 13 is three times the length of the dot signal 12, the sawtooth amplitude for dash signal 13 will be three times that for -dot signal 12. The sawtooth generators are followed by amplitude-sensing trigger circuits, such as an Evans trigger circuit as illustrated by O. S. Puckle on page of his book Time Bases, published by John Wiley &

Sons, Inc., New York, ll, and used in the circuits 25, 31'and 32. These trigger circuits will trigger only when the sawtooth amplitude reaches a predetermined amplitude. The general curves of response for these trigger circuitsare shown in Figure 5 as for example for the areas of acceptance for dashes and word spaces. In addition, flip-flop circuits, of well known circuitry as is shown by Seely in his book entitled Electron-Tube Circuits," McGraw-Hill Book Company, Inc., New York, 1950, pages 419 through 422, preferably utilizing the Eccles-Jordan circuit shown in Figures 19-14, and designated as RF. in the drawing and numbered as 28, 35, 37, 47 through 52, are employedas yes and no or on" and oif switches. These flip-flop circuits mere- Electronic Digital Counters, published in the April 1949 issueof Electrical Engineering, page 309, vol. 68, No. 4, to convert telegraphic code 11 into binary code 17 which is convertedinto characters 14.

First means 15 is adaptedto receive either dot signal 12 or dash signal 13 and includes a dot gate 23 and a dot-dash sawtooth generator 24. Dot gate 23 passes the leading edge of code pulses, whether dot or dash. This leading edge pulse passes on to means 18, energizing one of the gates 38 through 43. Dot gate 23 also initiates a pulse in response to the trailing edge of the received code pulse. This initiated pulse'also passes to means 18, through the energized gate of gates 38 through 43 'to a corresponding one of flip-flop switches 38 through 52. Should gate 23 be turned ofi' middle way through a dash pulse, the trailing edge of the dash pulse will not pass through gate 23 and-no produced pulse will pass from dot gate 23 to gates 38 through 43 and in turn, to the flip-flop'switches. The leading edge of either signal 12 or 13 starts the dot-dash sawtooth generator operating to build up a sawtooth amplitude. A dash trigger 25 responds to a predetermined sawtoothamplitude equivalent to the dash signal length and triggers when that amplitude is reached, thereby furnishing an output which closes the dot gate 23 and at the same time turns on a dot-dash flip-flop sensor 28. Since dot gate 23 is capable of passing the trailing edge of either a dot 0r dash pulse in its open position, should gate 23 not 5., P s. the. t ai ing, e geof a pu s tt gnal- .mustb dash signal 13 and is sensed as such, and passed through dot-dash sensor 28 to open a coincidence means or gate 29. Coincidence gate 29 remains in an open condition until dot-dash sensor 28 is turned off by a subsequent dot pulse.

When dot signal 12 is received by first means-15, the leading edge thereofis passed through dot gate 23 and at the same time starts the dot-dash sawtooth, generator 24. The length of dot signal 12 does not permit sufficient sawtooth amplitude to permit dash trigger25 to operate, therefore dot gate 23 remains in an open position and turns off thedot-dash sensor 28, if it was in the on position also closes coincidence gate 29.

The second means. 16 furnishes the spacing, function. An element space causes no action by second means in, however, character and Word spaces cause second means 16. to generate an output. Included in second means 16 is a space sawtooth generator 30 which' begins its sawtooth amplitude generation upon receipt of=the trailing edge of dot or dashsignal 12 or 13. Connected in parallel, and to the output of space generator 30, area character space trigger 31 and a word space trigger 32 The output of character trigger 31 is connected to a space flip-flop switch 35 which is turned on .in response to trigger 31. A multivibrator 36, constructed in accordance with Figure 18-2, page 396, of Seely, Electronic-Tube Circuits, McGraw-Hill Book Company, Inc., New York, 1950, is responsive to the character and word triggers 31, 32 throughthe on position of space switch 35. Multivibrator 36 furnishes pulses to the third means 13 and to the coincidence gate; 29, which gate 29 being in an open position following dashsignal 13, will pass pulse therethrough from multiyibrator 36 to the third means 18.

Third-means 18 includes a plurality of binary counters 37, each of which maybe constructed as shown in-Figure 19-15, page 420, of Seely Electronic-Tube-Circuits, published by McGraw-Hill Book Company, Inc., New York, 1950, or maybe constructed as. desired in accordance with the aforementioned Eccles-Jordan circuit, which furnish six outputs for siX converter gates 38 through 43; which in turn furnish six outputs for six converter flip-flop switches-47 through 52,whose output in turn is utilized by the fourth means 19-. Assuming the first code 11 received at input is dot signal 12, the leading edge of dot signal-12 is also conducted directly to binary counters 37, which are thereby advanced one count. The binary counter 37 therefore opens converter gate 38 which gate '38 is now ready to receive and pass therethrough a second or information pulse. The information pulseis the trailing edge of dot signal 12 which has passed through dot. gate 23 and is presented to all of the converter gates 38 to 43. As converter gate 38.is the only open gate, the trailing edge'of dot signal 12 passes therethrough and turns converter switch 47 to an on or yesT position. Should the second signal be dash signal 13, which together with dot signal 12 is code 11 for the character A, then as previously explained, dash trigger responds to dot-dash sawtooth generator 24-toclose dot gate '23 andat the same time turn on dot-dash sensor 28' which in turn opens coincidence gate 29. The leading edge of dash'signal 13 has-advanced binarycounters 37 one additional countand has opened converterr'gate 39. However, as .the dot gate 23 is closed, the trailing edge of dash signal 13 cannot pass to converter gate 39, converter gate 39 passes no information-to converter switch 48 leaving it in a no information position. This cycle can be repeated for a maximum total of six'dot and dash signals.

When the final signal 12:. orv 13.has been received, assuming it tobe dash signal.13 as illustrated above and completing. the character A, the space generator begins generation at the receipt of trailing edge of signal 13 and generates a; sawtooth offsutficient amplitude to cause character trigger 31 to operate. Trigger 31 energy pulses from multivibrator 36function to set up yes information in those converter switches 47 through 52 not acted upon by the incoming code. In either of its functions, multivibrator 36 serves to fill out a complete 6 -uni t binary code for each character. Coincidence ate219ihas remained in an open position followingdash signal 13. Binary counters 37 are new advanced in response to multivibrator 36 which sends its pulses through coincidence gate 29 to converter gates40, 41, 42 and .3 which: are opened and presented with multiyibrator output thereby turning converter switches 49, 50, 51 andQSZ on or in a yes information position. When converter gate 43. hasbecn opened, the binary counter 37 output is fed back, to space switch 35 turning it off and stopping multivibrator 36. Should the last code information of a character have resulted in dot signal 12, coincidence gate 29 will remain closed and no outputwould reach the remaining convertergates and the converter switches remaining would indicate no information. Thus, .whether the remaining converter switcheswill indicate yes or no information depends upon whether the last element of code information for a respective character was a dash of a dot. Upon completionof character 14, a delay circuit 55, of any well known type such as is shown in Figure 19-8, page 418, ofv Seely Electronic Tube Circuitsjpublished by Me- Graw-Hill Book Company, Inc., New York, 1950, which receives its responses from space switch 35, initiates at a predetermined delay time a resetpulseto reset converter-switches 47. to 52m their normal off or no in-. formation position in readiness for the ncxtcode 11 to be presented to input-10.

The yes? and no information, contained by converter switches 47 to 52 at the end of.-a character, is utilized by fourth means 19. Fourth means 19 utilizes as the heart thereof acathode ray display tube 56, diagrammatically shown in Figure 1 and structurally shown in Figure 3. The display tube 56,.which is .known in the art, employs a cathode 57 which emitsa stream of electrons. A grid58, along with anodes 59., 6t) and 61 control the emitted electronsand shape them into an electron beam positioned along the axis of. display tube 56'. Vertical selection plates 64 and horizontalsel'ection plates 65 are positioned about the tube .axis for electrostatically defiectingtheheam in response to a predetere mined voltage pattern to illuminate a particular matrix character, 66 in matrix- 67. Matrix 67., shownin detailin Figure 4,-is preferably made of a metallic mediuminto which character-shaped openings are'made. Thesecharacter-shaped openings or matrix characters cause the electron beamjto be shaped in accordance with the char.- acter selected by the selection plates 64, 65.

The character-shaped beam'then is deflected to a predetermined position upon display tube screen 70by vertical'and horizontal deflection coils 71, 72. Additional anodes 74; 75 maybe provided to accelerate the beam toward screen 70. Proper predetermined: voltages are supplied'from power supply 76 to cathode S7 and anode 60. Grid 58 receives its control voltage from grid unblanking amplifier 77, ofknown construction. Amplifier 77 also receives its voltages from supply 76 and is triggered in response to delaycircuit- 55 thereby providing display tube 56 unblanking. Anodes 74, 75-receive their power frompower supply 78. Vertical andhorizontal deflection circuits 80,-81 are ofawell known construction and are responsive to output of?- character and word triggers 31, 32 to-present proper voltages .to. coils r "7, 71, 72 to etfect'screen position advance, either character or word space advance, as indicated.

The operation of display tube 56, as described, utilizes predetermined voltages applied to the selection plate 64, 65 in response to the yes and no information of converter switches 47 to 52 from third means 18.

Fourth means 19 includes three vertical selection gates 84, 85 and 86 which are controlled by converter switches 47, 48 and 49, respectively for utilizing third means 18 output. Three horizontal selection gates 87, 88 and 89 are controlled by converter switches 50, 51 and 52, respectively. The information signals or voltages to be passed by the selection gates when in an open position are first, second and third predetermined fixed voltages 90, 91 and 92, respectively. These three voltages are the fixed input for gates 84, 85 and 86, in that order, and likewise, for gates 87, 88 and 89, in that order.

The output of gates 84, 85 and 86 is received by a vertical selection voltage adder 93, of any well known construction, and likewise, the output of gates 87, 88 and 89 is received by a horizontal selection voltage adder 94. The output of vertical selection voltage adder 93 being applied to vertical selection plates 64, and the ouput of horizontal selection voltage adder 94 being applied to horizontal selection plates 65, thereby positioning the beam to illuminate a character corresponding to the code 11 received at input 10.

Assuming the conditions of converter switches 47 through 52 to be in the yes, no, yes, yes, yes, yes condition, respectively, in response to the character 14 A, converter switch 47 will open vertical selection gate 84 and first voltage 90 will be presented to adder 93; switch 48 being no, gate 85 will remain closed; switch 49 being yes, gate 86 will be opened and third voltage 92 will be added to first voltage 90 in vertical selection voltage adder 93 to determine the vertical selection plates 64 voltage. Converter switch 50 will be in a yes position and therefore open horizontal selection gate 87 and first voltage 90 will pass to the horizontal selection voltage adder 94; switch 51 is yes, so gate 88 is open to pass second voltage 91 to adder 94 to be added to first voltage 90; switch 52 is yes, so gate 89 is open to pass third voltage to adder 94 to be added to first and second voltages 90, 91 resulting in the voltage to be applied to the horizontal selection plates 65. Plates 64, 65, having these voltages impressed upon them will set up the electrostatic field to position the electron beam to illuminate the matrix character A, which character is subsequently presented in visual display on the screen 70 by impingement of the electron beam thereupon.

Illustrated in Figure 6 is a circuit embodiment of the vertical and horizontal selection gates 84 through 89, vertical selection voltage adder 93 and horizontal selection voltage adder 94, all of which comprise the pertinent part of Figure in application Serial No. 340,245, filed March 4, 1953, and assigned to the common assignee hereof. Inclined herein is explanatory matter material to Figure 6, taken from pages 49 through 54 of the aforesaid application, Serial No. 340,245. The adder unit serves to transform a parallel representation of the code group, as developed by the six converter flipflop switches 47 through 52 into two uni-directional potentials. Each of the gating circuits 84 through 89, is functionally and physically similar and includes an electron tube 450, which has an anode 451, a screen grid 452, second control grid 454, first control grid 453 and a cathode 455. Corresponding components of each circuit are assigned the same reference numerals. Anode potential is afforded tube 450 by a potential source (not shown), which is connected to the anode 451 through primary winding 456 of a transformer 457. The primary winding employed in each of the gating circuits are functionally similar and preferably have an equal number of turns. The control grid 453 of each circuit is both returned to ground through a grid return resistor 458 and connected by lead 459 to an oscillator (not shown), which may be of a conventional design and well known to those skilled in the art. The second control grid 454 of each of gating circuits 84 through 89 is inter-connected with the memory flip-flop switches 47 through 52, shown in Figure l, by coupling said control grids 454 to the leads 333, 259, 261', 263, 265 and267, respectively, which carry high orlow voltages appearing in the output of the flip-flop switches. The leads 333, 259, 261, 263, 265 and 267 are at low potential conditions in the no condition and at a high potential when a yes code element appears in the associated channel.

The sinusoidal output generated by the oscillator is continuously applied inparallel over the lead 459 to the first control grids 453 of the six gating tubes. The unidirectional potentials which appear at the output of the flip-flop switches in Figure 1 in the presence of a no condition of the particular code element, and which are impressed upon the second control grids 454 of the associated gating tubes, are insuflicient to'allow conduction of the tube 450 even though sinusoidal oscillator voltage is applied to the first control grid 453. A yes condition of the particular code element will cause a high potential positive pulse at the output of the associated flip-flop switch and upon its being transferred to the second control grid by one of the leads 333, 259, 261, 263, 265 or 267, will cause the second control grid 454 to be driven positively. This allows tube 450 to become conductive and an alternating voltage, as the result of the oscillator voltage being applied to the first control grid 453, appears across the primary winding 456 of the transformer 457 These alternating currents, which flow through the primary windings 456, induce voltages in either of the two accumulator networks 93 or 94. Accumulator network 93 comprises secondary windings 462, 463, 464 and a rectifying element 465, which includes a cathode 466 and an anode 467. Network 94 comprises secondary windings 468, 469 and 470 and a rectifying element 471 which also includes a cathode 472 and an anode 473. A step-up factor ofthe windings 464, 463 and 462 and windings 468, 469, and 470 arein the relationship of 4, 2 and 1, respectively, thus, establishing predetermined voltages in the relationship of 4, 2 and 1 in the presence of yes conditions for the respective code elements. The windings 462, 463 and 464 are serially connected in a manner to be series aiding such that the individual voltages which appear across each winding are additive. Windings 468, 469 and 470 of the accumulator network 94 are similarly interconnected to be series aiding and also providing additive potentials. Thus, the individual voltages which appear across each winding of the two networks are additive. The winding 464 and windings 468 are separately connected to anodes 467 and 473 of the rectifiers 465 and 471, respectively. The cathodes 466 and 472 are connected in any suitable manner to the vertical and horizontal deflection plates 64 and 65, respectively.

In operation, when the six converter flip-flop switches have been cleared by the reset pulse, all of the switches are in the no condition and the low potentials appearing at leads 333, 259, 261, 263, 265 and 267 are of insuflicient magnitude to allow conduction of the gating tubes. Hence, the voltages induced to the adder networks 93 and 94 are zero and no deflection voltage is supplied to the display tube. Upon one of the switches 47 through 52 being placed in the yes condition, an output voltage is impressed on one of the gating tubes grids 454 of sulficient potential magnitude to effectuate triggering of the respective gatingtube and with the oscillator voltage applied in parallel to the first control grid 453, an alternat- 7 ing voltage appears across one of the associated primary windings 456. Considering initially the selection of the correct row of openings within the matrix 67 wherein code elements afford the required information, the additive" voltages induced in accumulator networks93 and 94have; as aresultofthe individualstep-upiactors, a voltagepotential output which, whenapplied to the'vertical -andhorizontal selection plates establishes therequired electrostatic field for positioningtheelectron beam upon th'e'correct characterof matrix 67. V

Figure shows one setof curves illustrating the areas of acceptance for dots and'dashes; and another-set o'f curves-illustrating the areas-o1 acceptance for word spaces, characterspacesand element'spacesz- The discriminating ability of the system disclosed, herein, regarding the length-of dots, dashes and spaces is shown to be more than adequate over ,therangeshown, from to 80 words per minute by, these performance curves. For-example, at 60W;P. M..thetime of a dot signal may vary between 3 and;23'milliseconds; a dashsignal between 24 milliseconds andinfinity; an element space, between 2 and 23 milliseconds; a character space, between 24 and 73 milliseconds;, and a; word space between'74 and infinity.

Although the" indicated speeds are" based on normal time lengths of elements and spaces, the system iscapable ofadjusting itself to substantiallyinstantaneous changes in speed. For example, if Ma 60- W. P'. M. rate the time of a dash is increased from 47 to 57 milliseconds, the average rate becomes less than 60,W. P. M. and the systern adjusts itself substantially instantaneously to the new speed, while retaining at theisame time its discriminating between different length code elements and difterentlength spacesof codell: The wide limits between the curvesbeing the acceptable'limitswhich may-not be exceeded.

The particular emb'odimentsof the invention illustrated anddescribed herein'is,illustrativeonly, and the inventionincludes-such other modifications and equivalents as ode Taydisplay tube 'having'a matrix;therein, comprising;

first means responsive to said code for-sensing anddiscriminating betweenr saiddot and dash signals, second means responsiveto, said code for sensingand effecting spacing of said signals and-groups of saidsignals, coincideuce .means responsive-to .said.first' means for selective operation .ofsaidsecond.meanstherethrough, thirdmeans responsive-to: said .code, .said.first means: and said coincideuce means" for selectively. converting. outputof said first means and saidsecond means into yes and no information, said second means having means supplying energy pulses to said third means for-completing the-output of said first means in said third means to the same number of elements of said yes and no information regardless of the number of dots or dashes in the code character received, fourth means responsive to said second means and said third means for presenting predetermined selection and deflection voltages to said display tube whereby a selected character of said matrix is positioned at a predetermined display position on said display tube, and means responsive to said second means for restoring said third means and said fourth means to their respective predetermined original conditions.

2. A system for converting telegraphic code into a visual presentation of characters including a source of code, said code comprising selectively presented dot signal and dash signal, each signal having a leading edge and a trailing edge, and a cathode ray display tube having a matrix therewithin, said tube being capable of selectively displaying said characters, said system comprising an input for receiving said leading edge and said trailing edge, a plurality of binary counters and a dotdash sawtooth generator, both being responsive to said leading edge, a space sawtooth generator responsive to said trailing edge, a dash trigger selectively responsive to said dot-dash sawtooth" generator;,,,a dot" gate selectively responsive. to said dash trigger, said dot gate being adapted to pass'said' trailing edge of said dot signaLsaid dot'gate closing in response to said dash'trigger,---a dotdash sensor-responsivetosaid dot gate outputand said dash trigger for oft'and'on position, respectively; a coincidence gatefresponsive' to-said dot-dash sensor, acharacter trigger anda word trigger each being-selectively responsive to said. space sawtoothgenerator, a space flip-flop switch sel'ectively responsiveto said character trigger, a multivibrator responsive to' said character trigger through said space switch, said binary counters b'eing 'responsiye to said multivibrator, a pluralityof converter gates, .said converter gates .being selectivelyresponsive to said'multivibrator through said-coincidence gate, said space switchbeingresponsive; to' the last of.

said converter gates, a plurality of converter flip-flop switches matching. and being responsive tooneonlyyof eachof; said converter gates, said converter flip-.flop switches selectivelyiproducing fyes. andn'o intorrna' tion, fjourth means for presenting said code as characters upon saiddisplay 'tube, vsaid fourth means being responsive to said"yes. and no information of said converter flip-fiop-switches, said fourthmeans being further selectively'responsive to saidcharacter' triggerand said word trigger. V

3'. *A" system for converting telegraphic. code into a 1 said, trailing edge, a dash trigger selectively responsive to said dot-dash sawtooth"generator; a. dot gate selectively responsive to saididash'trigger, said dotgate'being adaptedto pass said'trailin gi edge of said dot'signal, said dotjgateicl'osingi in response to said dash trigger," a'dot= dash sensouresponsive. to saidf'dot gate output and said dash triggerfbr -ofi and 'on' position, respectively, acoin cidence gate responsive to said'fdot dash sensor, a character'triggerand a word. trigger. each being selectively responsiveito said spacesawtooth generator, a space flip=flop switchwelectivelyresponsive to said character trigger, amultivibrator responsive to vsaid character trigger through said" space" switch, said binary. counters being responsive" to said' multivibrator, a plurality of converter gates; said converter gates being selectively responsive to said multivibrator through said coincidence gate, said space switch being responsive to the last of said converter gates, a plurality of converter flip-flop switches matching and being responsive to one only of each of said converter gates, said converter flip-flop switches selectively producing yes and no information, fourth means for presenting said code as characters upon said display tube, said fourth means being responsive to said yes and no information of said converter I ,flip-flop switches, said fourth means being further selec- I tively responsive to said character trigger and said word and a trailing edge, and a cathode ray display tube having a matrix therewithin, said tube being capable of selectively displaying said characters, said system coma sent 11 prising an input for receiving said leading edge and said trailing edge, a plurality of binary counters and a dotdash sawtooth generator, both being responsive to said leading edge, a space sawtooth generator responsive to said trailing edge, a dash trigger selectively responsive to said dot-dash sawtooth generator, a dot gate selectively responsive to said dash trigger, said dot gate being adapted to pass said trailing edge of said dot signal, said dot gate closing in response to said dash trigger, a dot-dash sensor responsive to said dot gate output and said dash trigger for OE and on position, respectively, a coincidence gate responsive to said dot-dash sensor, a character trigger and a word trigger each being selectively responsive to said space sawtooth generator, a space flip-flop switch selectively responsive to said character trigger, a multivibrator responsive to said character trigger through said space switch, said binary counters being responsive to said multivibrator, a plu rality of converter gates, said converter gates being selectively responsive to saidtmultivibrator through said coincidence gate, said space switch being responsive to the last of said converter gates, a plurality of converter flip-flop switches matching and being responsive to one only of each of said converter gates, said converter flipflop switches selectively producing yes and no information, fourth means for presenting said code as characters upon said display tube, said fourth means including selection means and deflection means for presenting predeterminedselection anddeflection voltages to said display tube, said selection means being responsive to said yes and no" information of said converter flipflop switches, and said deflection means being selectively responsive to said character trigger and said word trigger, and means selectively responsive to said character trigger through said space switch for restoring at a predetermined time said converter flip-flop switches and said fourth means to their respective predetermined conditions.

5. A system for converting telegraphic code into a visual presentation of characters including a source of code, saidcode comprising selectively presented dot signal and dash signal, each signal having a leading edge and a trailing edge, and a cathode ray display tube having a matrix therewithin, said tube being capable of selectively displaying said characters, said system comprising an input for receiving said leading edge and said trailing edge, a plurality of binary counters and a dotdash sawtooth generator, both being responsive to said leading edge, a space sawtooth generator responsive tosaid trailing edge, a dash trigger selectively responsive to said dot-dash sawtooth generator, a dot gate selectively responsive to said dash trigger, said dot gate being adapted to pass said trailing edge of said dot signal, said dot gate closing in response to said dash trigger, a dot-dash sensor responsive to said dot gate output and said dash trigger for off and on position, respectively, a coincidence gate responsive to said dot-dash sensor, a character trigger and a 'word trigger each being selectively responsive to said space sawtooth generator, 21 space flip-flop switch selectively responsive to said character trigger, a multivibrator responsive to said character trigger through said space switch, said binary counters being responsive to said multivibrator, a plurality of converter gates, said converter gates being selectively responsive to said multivibrator through said coincidence gate, said space switch being responsive to the last of saidconverter gates, a plurality of converter flipflop switches matching and being responsive to one only of each of said converter gates, said converter flip-flop switches selectively producing yes and no information, fourth means for presenting said code as characters upon said display tube, said fourth means including three horizontal selection gates and three vertical selection gates, a plurality of predetermined voltage sources one of said voltage sources being associated with each of said gates, a vertical selection voltage adder and a horizontal voltage adder both being responsive to their respective sets of selection gates, horizontal, and vertical selection plates presented by said display tube, said vertical selection plates being responsive to said vertical selection voltages adder and said horizontal selection plates being responsive'to said horizontal selection voltage adder, said vertical selection gates and said horizontal selection gates being responsive to said yes and fno information of said converter flip-flop switches whereby said characters are selected from said matrix for display ,upon said display tube in response to said code impressed upon said input,'said fourth means being further selectively responsive to said character trigger and said word trigger, and means selectively responsive to said character trigger through said space switch for restoring at a predetermined time said converter flipflop switches and said fourth means to their respective predetermined conditions.

References Cited in the file of this patent V UNITED STATES PATENTS 2,458,030 Rea Jan 4, 1949 2,534,387 Thomas Dec. 19, 1950 2,621,250 Apencer Dec. 9, 1952 2,736,770 McNaney Feb. 28, 1956 FOREIGN PATENTS 156,861 Australia Jan. 17, 1952

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