US3103658A

US3103658A - Character generation system

Info

Publication number: US3103658A
Application number: US708556A
Authority: US
Inventors: Franklin C Chiang
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1958-01-13
Filing date: 1958-01-13
Publication date: 1963-09-10
Anticipated expiration: 1980-09-10

Description

FRANKLIN c. cHlANG 3,103,658

CHARACTER GENERATION SYSTEM Sept. 1963 4 Sheets-Sheet 1 Filed Jan. 13, 1958 lllljlll-lu sept. 1o, 1963 Filed Jan. 13, 1958 FRANKLIN c. cl-uANG 3,103,658

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Sept 10, 1963 FRANKLIN c. cHlANG 3,103,658

CHARACTER GENERATION SYSTEM 4 Sheets-Sheet 4 Filed Jan. 15, 1958 inve/vir.;

United States Patent O 3,103,658 CHARACTER GENERA'HON SYSTEM Franklin C. Chiang, Palo Alto, Calif., assigner to International Business Machines Corporation, New Yorlr, N .Y., a corporation of New York Filed Jan. 13, 1958, Ser. No. 708,556 2 Claims. (Cl. 340-324) This invention relates to electrical signalling, and more particularly to a system of character generation for graphically reproducing and displaying selected characters responsive to electric signals representing said characters.

The principal object of this invention is to provide a system for generation and displaying selected characters in ia signal-responsive device such as a cathode-ray tube from fa remote point by transmitting a relatively small number of electric pulses.

It is a further object of this invention to provide a plurality oi character-identification generators such that each generator permanently identities a particular character and only a single signal isrequired to .trigger the generation of a selected character to be graphically reproduced. Also, depending upon the individual requirements of the character reproductions, each character can be generated for a time interval as short as 25 microseconds, `or as long as many seconds, and can be repeated as many times as desired to aid visual perception.

-Another object of this invention is to provide a system of character generation wherein, in the case of long distance transmission, only one identification code is required for each character.

The above and other objects may be attained by employing this invention which provides among its features a system in which a selected character is reproduced graphically upon the repetitively scanned screen of a cathode-ray tube by means of a pulse train generated in time relation with the raster of the cathode-nay tube. Diiferent pulse trains for reproducing the different characters are generated by means of a plurality of character-generators-a separate character generator being provided for each character that is to be graphically reproduced. 'Ilhe system also includes means for selecting any desired one of the character generators, and means ior connecting the selected character-generator to the cathode-ray tube.

Other objects `and advantages will become apparent from a consideration of the following detailed description :taken -in conjunction with the 'accompanying drawings, wherein:

FIG. 1 is a schematic circuit diagram of an exemplary embodiment of this invention, ia plurality of charactergenerators being shown therein represented by blocks 1011 through 109;

FIG. 2 is a schematic circuit diagram of a typical charcoter-generator 10A;

FIG. 3 is a schematic view showing the construction of a delay line employed in character-generator 10A;

FIG. 4 is a representation of several of the characters which may be reproduced and displayed; and

FIG. 5 is a schematic circuit diagram of another exemplary embodiment.

The embodiment illustrated in FIG. 1 comprises a plurality of character-generators A through 10', connected in parallel with each generator identifying a particular Character, such las a letter of the alphabet or a numeral. The subscript identities the character which that generator reproduce. As is best shown in FIGS. 2 and 3, each character-generator (10A for example) includes a delay line 111 and a plurality of pick-up units 121 through 127 in axially spaced relation to each other along the delay ence numerals 1321 through 1325; etc. Selected windings of each unit are connected in parallel with corresponding windings of other units and to respective output lines 151 through 1155 to provide a pulse train which gencrate a selected character, as hereinafter explained. In the generator 10A shown in FIG. 2, the windings are interconnected so as to define a matrix coded to generate the character A. Isolation resistors 14 are connected in series with the respective windings to prevent undesirable interactions therebetween.

In the specific embodiments herein illustrated and described, dellection circuitsof the cathode-ray tubes I19 and i19 are arranged to Yprovide `a scanning raster composed of live approximately vertical scanning lines. In other words, horizontal sweep generator 21 operates with a period live times as long as that of the vertical sweep generator 231. Each of delay lines 11 has a delay time equal `to the scanning time of one vertical line of the raster of the cathode-ray tube. Approximately at the beginning of eadh vertical scanning line an electric pulse is supplied by a pulse generator 219 through lines 11 to the input end of each delay line 11 of the character generators. As each such pulse travels down a delay line 11, voltage pulses are induced rst in the live windings of pick-up unit 121, then in the ve windings of pick-up unit 122, etc., so that seven sets of live pulses each are successively produced within each character-generator during each vertical scanning line. In a manner hereinafter explained, each of the five output lines 151 through `1511 of a selected character-generator is connected in succession to the cathode-ray tube 1-9 during each scanning frame of five lines, so that pulses from thirty live windings may be transmitted to the cathode-ray tube at the thirty live different points in the scanning cycle, respectively. 'Ilhe delay line 11 is terminated with a resistor 16 equal to the characteristic impedance of theline to prevent reflections from the lower end of the line.

As will be noticed in FIG. 3, the seven pick-up units 121 through 127 are annular and extend around delay line 11. Each pick-up unit may be adjusted in position along the length of line 11 to adjust the timing of the pulses induced in its windings. may be of conventional construction; la helix -or the like of insulated wires wound about an insulating form 1-7 and one or more metal foil grounding strips 18. This construction provides a fairly large distributed inductance or capacitance, whereby appreciable time delays (e.g., up to several hundred microseconds) are readily obtained. y

The thirty ve windings 11311 through 137i,- are arranged as shown in FIG. 2, to define a rectangular matrix in which corresponding windings ott' the seven units represent seven horizontal rows of the matrix and the ve windings of each unit represent live vertical columns of the matrix. Each intersection of a matrix row with a matrix column represents a point on the screen of the cathode-ray tube. lf the coil at such `an intersection is connected into a circuit, a visible spot will be generated at the corresponding point on the screen, by means hereinafter described. l-Ience, to obtain a coded interconnection of the windings to identify a specific character, selected windings in each'ventical matrix column are connected in-parallel, so that when successive electric pulses are transmitted down the delay line 11, and the ve columns of the matrix are connected in succession to the cathode-ray tube, a pulse train is supplied to the control electrode of the cathode-nay tube in timed relation with The delay line proper 3 the scanning raster to cause a graphic reproduction of the character defined by the coded matrix ofthe selected character generator.

The conventional cathode-ray tube 19 has an electron gun at the base of the neck, including a cathode 24 and a control electrode 25, to produce a beam fof electrons which is acted upon by horizontal and vertical deflection means 20 and 22 to produce a scanning raster upon the screen 26. A raster may be defined as a pre-determined pattern of scanninglines Iwhich provide substantial uniform coverage of an area. An electrical circuit 13 inciudes horizontal and vertical sweep-

generators

21 and 23 which are connected to the deflection means 20 and 22 respectively of the cathode-ray tube 19. Each of the two sweep generators produces a sawtooth waveform scanning signal `for deflecting the electron beam of the cathode-ray tube repetitively back and fort-h and up and down lthe screen 26. The period of the horizontal sweep generator is five times as long as the period of vertical sweep generator 23, so that, in this case, the scanning lines are approximately vertical and there are live -vertical lines in each scanning frame.

Electric circuit 18 also includes a pulse generator `29. Pulse generator 29 and vertical sweep generator 23 are synchronized by any suitable means (ifor example, by using the pulses generated by generator 29 as synchronizing pulses fior generator 23) so that generator 29 supplies a pulse to each input line 11' of the character generators approximately at the beginning of each vertical scanning line. Horizontal sweep gen-erator 21 is synchronized with another pulse generator 30 which supplies a pulse substantially concurrently with each fifth pulse supplied by generator 29.

The cathode-ray tube 19 is biased to cut-off by any suitable means, such as the positive voltage supply 27 connected to the cathode 24. Therefore, no light appears at the screen 26` except at points in the scanning cycle when pulses are supplied to the control grid 25. rIihus, each pulse supplied to grid 25 produces a visible spot on screen 26, at a point in the screen that depends upon the timing of the pulse relative to the scanning cycle. It is evident that any desired character can be displayed on the screen 26 by supplying a properly timed train of pulses to grid 2S during each scanning cycle. Accelerating voltage ror the electron beam of the cathoderay tubeis provided by a voltage supply 28.

Means are provided for selectively connecting one of the character 'generators to the cathode-ray tube and in this instance comprises a selector switch 31 having a plurality of input leads 321 through 325 adapted toi be connected 4to the output leads 151 through 155 of a selected character generator. Switch 31 may be manually or automatically operated, and in practice may be a highspeed electronic or electromagnetic switching network responsive to coded signals received from an electrical communications system, or the dike. However, the specic construction of the switch is of no concern to this invention. yFor present purposes, switch 31 can be considered to be a simple, manually operated, mechanical contact, electrical switch.

Assume that the input leads 321 to 325 have been connected to the output leads 151 through 155 respectively of the character generator A, which has been coded to have a matrix identifying the character A. ,It be observed that leads 321 through 325 are connected to respective ones of the iive normally-closed or non-conductive :gates 331 through 335. Thus, each pulse appears at one of the output leads 151` through 155 .for the selected character generator and passes through switch 31 to a respective one of the .gates 331 through 335.

Each of the gates is connected by an output lead 34 into the control electrode 25 of the cathode-ray tube 119. 'Ilhese gates are Well-known circuits that transmit electric pulses from an input lead to an output lead only when the gate is opened, or made conductive, by voltages supplied to anotherinput lead.`

ln this case, the gates 331 through 335 have their second or control input leads connected to respective taps 351 through 355 of a master delay line 36. Thus, an electric pulse traveling yfrom lett to right along delay line 36 will open each of the gates 331 through 335 in succession. Delay line 36 is terminated by resistor 31 equal to the characteristic impedance of the line, to prevent undesirable reections from the right end of the delay line.

`Pulse `generator 30 provides a pulse approximately at the begin-ning of each scanning frame. 'l'ihese pulses are amplified by an amplifier 38, and are supplied to the left end of the master delay line 36. The duration of each pulse so supplied to line 36 is made approximately equal to the lduration of one vertical scanning line, which is oneiifth of the duration of the scanning frame. Therefore, Agate 331 is open during the scanning time of the first vertical line of each frame. It is closed during the scanning of the other `four lines of each frame.

Delay lli-ne 36 -is constructed to provide between each of its taps and the next tap a ltime delay approximately .equal to the time interval between vertical scanning lines. Thus, :gate 332 is open during the second vertical scanning rline of each frame, gate 333 is open dur-ing the third vertical lline of each frame, etc.

Considering the period of the pulses provided by the generator 29 to be Tn, then the second pulse generator 30 and the circuit 18 is arranged so` as to provide to the master delay line 36 pulses having a period of 5Tn, and a duration of Tn. Thus, as each of the pulses supplied to the master delay line 36 travels from one end to the other en'd thereof, each of the gates 331 through 335 in succession is opened for a time interval Tn. Since the total delay of lines 11 in the character generator is Tn, the complete train of pulses appears in each of the lines 151 through 155 during each interval Tn. Therefore, each gate in succession transmits a complete train of pulses yfrom one output line of the `selected character generator to control grid 25 of the cathode-ray tube. This permits a complete sequence of the pulses received from the selected character generator output leads 151 through 155 to pass sequentially into the leads 34. In turn, the control electrode 25 of the cathode-ray tube gun is driven more positive by each pulse allowing the electron beam to pass through the deiiection means 20, 22 and produce Iupon the cathode-ray tube 19 a pattern of dots thus forming the character selected for display. Thus, the matrix connecti'ons of the selected character generator are displayed on a screen 26, to provide a graphical display of lthe se- `lected character. When switch 31 is connected to generator 10A, a pattern of dots Iforms the characterA on screen 26. i

Considering once again the character generator 10A representative of the character A (FIG. 2), it .will be seen that the matrix is so arranged that if the` generator y29 drives the delay line 11 by imparting a train` of pulses thereto, one such pulse is` supplied to the upper end of line 11 approximately at the beginning orf each vertical scanning Ili-ne. During the tirst scanning line ot the frame, line 151 is connected to cathode-ray tube 19 through open gate 331, while the remaining lines 152` through 155flead to closed gates. Hence, considering only the tirst matrix, from the iirst scanning line at a time T1, the windings 1371 and 13-15 of the tirst pick-up unit 121 will receive a pulse which is transmitted through switch 31 and gate 331 to the control electrode v25 of the cathode-ray tube, Similarly, at time T2 the

windings

1351 and 1355 of the unit 122 receive a pulse; at time T2 the

windings

1351 and 1355 of the unit 123 receive a pulse; at time T1 the windings 1311 through 13.15 of the units `121 each receive a pulse; while at a time T5 and T5 windings 1332through 1331 and 1322 through 132,l respectively each receive a pulse; and at a time T.,

windings

1312 and 1315 and 1314 each receive a pulse. All of the pulses are sequentially transmitted through -output leads 151 through 155 as a pulse trainand then through respective gates 331 through 1 5 t 335 to the contnol electrode 25 by action of the delay li-ne 36.

In the manner hereinbefore indicated, these pulses'will be I.transmitted through switch 31" to respective ones of the gates 331 through 335 which will be actuated sequentially'to produce these pulses in the same sequenceupon the control electrode 25 of the cathode-ray tube to -reect the sequence prearranged and coded into the matrix of the selected character generator. At the Sametime, since rangement and function is similar to 4the embodiment of FIGS. 1-4, except for the arrangement of the means whereby the train of pulses from a selected character generator 19'), through 109 is selectively switched intro connection with the electric circuit 18 and the cathode-ray tube 19. The selector switch 31', similar to the selector switch 31, is now connected into lead 4l) from pulse generator 29 so that a Iselected character generator can be connected through its input line 11. On each :of the output lines 151 through 155 of each character generator, there is provided diodes 421 through 425 respectively to prevent feedback through character generators other than die one selectively connected into switch 31.

Corresponding output lines of each character generator 16A through 199 are connected into respective common lines 441 through 445, which are in turn connected to delay line 36, through respective leads 461 through 465, at spaced locations therealong. Thus, for instance, line 441 connects all of the output leads 151 of character generators A-1il5 to the right end of master delay line 36 (as viewed in FIG. 5). Corresponding leads 152, '5 and 154 of the other generators are connected into delay line 36 at selected points intermediate its ends l while all of the output'leads, corresponding to 155 of character generator IWA, connect into delay line 36 at its left end as viewed in FIG. 5 Delay line 36 acts to sequentially store the pulses transmitted thereto by the output leads 151 through 155 and deliver these pulses sequentially at its right end, as viewed in FIG. 5. The train of pulses appearing at lthe right end of delay line A36 Will be supplied to the grid 25' of cathode-ray t-ube 19' to function in t-he same manner as described in connection with the embodiment of FIGS. 1-4. The horizontal and

vertical sweep generators

21 and 23 are, in the form of the invention of FIG. 5, connected into electromagnetic deflection means 48 and 50 (in place of the electrostatic deflection means 20, 212 of FIGS. 1 4) respectively acting upon the electron beam of the cathoderay tube 19 to produce a scanning raster on the screen 26 of the tube.

Sweep generators 21 and `23 are synchronized, by suitable means, with the pulses delivered by generator 29 to the character generators IWA `through 10's. As previously indicated, 4horizontal sweep generator 21 operates with a period live times as long as that of the vertical sweep generator. Therefore, the pulse train of a selected character generator, such as 10A, will be fed into the master delay line 36 in sequence, stored in the delay line by being sequentially transmitted thereto, and appear sequentially at the control electrode 25 of the cathoderay tube from the end of master delay line 36', thus the character represented by the selected pulse train will be graphically reproduced on the screen of the cathode-ray ytube in the same manner as explained in connection with the embodiment of FIGS. 1 4.

Essentially then, the modification of FIG. 5 eliminates (l) the need for a switch for each one of the output leads on each character generator, (2)' the requirement for a plurality of gates in connection with the means for selectively connecting a character generator to the cathoderay tube, and (3) the necessity for a separate pulse generator and a gating amplifier `in its electrical circuit 18 'connecting the character generators to the sweep generators of the cathode-ray tube, when compared to the embodiment of the character generation system of FIGS. 1 4.

iFrom the foregoing, it will be seen that a desired character dened by a character generator may be selectively switched into the system and be graphically portrayed by actuation from an external source, which source may be remote from the system, by employing in each character generator a plurality of pick-up units having separate windings which are interconnected in a prearranged manner defining a matrix, and said coils being excited by a delay line to produce a pulse or signal train corresponding to the matrix selectively switchedv by means 31 or k31 into connection, through a master delay line, in timed relation with the raster of a cathode-ray tube upon the screen of which the character delined by the matrix will be visually displayed, the horizontal and vertical sweep generators being synchronized with the pulse or signal train generated in a selected character generator.

Although the present illustration shows the coils arranged in rows in the matrix and the cor-responding windings of the coils connected to represent columns of the matrix, this relationship of rows and columns can be reversed without departing from the concept of the invention by employing conventional techniques well known to those skilled in the art. Also the delay lines 11 employed in the character generators may be provided with taps in place of the inductively coupled pick-up units and as such would be similar in construction

t0 delay lines

36 and 36.

It will be understood that this invention is not limited to specific embodiments herein illustrated and described, and that the following claims are intended to cover all changes and modications which fall within the true spirit and scope of the invention.

What is claimed is:

1. A system of character generation, comprising in combination, a cathode-ray tube and deilection means therefor producing a scanning raster, a plurality of chairacter generators, each of said generators including a delay line and a plurality of coils spaced axially along said delay line, each of said coils having a plurality of separate windings thereon, said windings being interconnected to dene a matrix representing a selected character with certain corresponding windings of said coils being connected in parallel representing alinement of the matrix in a first direction and the windings on each coil itself representing alinement of the matrix in a second direction, an output lead for each of said corresponding windings so that when said delay line is excited a sequential signal train can be applied to the cathode-ray tube in timed relation with the raster thereof, an electric circuit synchronously connected to said cathode-ray tube deection means for driving the deflection means and connected to said plurality of character generators to drive said delay line in timed relation to said raster, and rneans for selectively connecting one of said character generators to said circuit and to said cathode-ray tube in response to a received signal froman external actuation source, said means being connected to the control electrode of said cathode-ray tube and synchronized with said electrical circuit whereby said sequential signal train will allow a beam of electrons to strike the screen of the cathode-ray tube under the control of said deflection means and produce a raster in timed relation with said circuit whereby the character determined by the matrix of the selected character generator will be Visually reproduced.

2. The combination according to claim 1 wherein said means comprises a switch selectively connectable to said output leads, a plurality of gates arrangedv in sequence and connected to said switch and to the control electrode of the cathode-ray tube to -be thus connected sequentially to said output leads, and a master delay line synchronously connected to said circuit and to said gates to have the gates function sequentially -in response to the sequential Isignal train transmitted from the matrix of the selected character generator through said output leads and said gate, whereby the control electrode of said cathode-ray tube will be driven in response to said signal train.

UNITED STATES PATENTS' Gloess Sept. 19, 1950 Wheeler Feb. 6, 1951 Baker May `15, `1951 Baker June 12, 195,1 Eckert Jr. ..-i Aug. 10, 1954 Toulon Oct. ,5,` 1954 Sheftelman Oct. 9, 1956 Young Mar.5, 1957 McNaney et al. June 24,` `1958 Gordon et al. Jan. 5, 1960 Triest Mar, 29, 1960

Claims

1. A SYSTEM OF CHARACTER GENERATION, COMPRISING IN COMBINATION, A CATHODE-RAY TUBE AND DEFLECTION MEANS THEREFOR PRODUCING A SCANNING RASTER, A PLURALITY OF CHARACTER GENERATORS, EACH OF SAID GENERATORS INCLUDING A DELAY LINE AND A PLURALITY OF COILS SPACED AXIALLY ALONG SAID DELAY LINE, EACH OF SAID COILS HAVING A PLURALITY OF SEPARATE WINDINGS THEREON, SAID WINDINGS BEING INTERCONNECTED TO DEFINE A MATRIX REPRESENTING A SELECTED CHARACTER WITH CERTAIN CORRESPONDING WINDINGS OF SAID COILS BEING CONNECTED IN PARALLEL REPRESENTING ALINEMENT OF THE MATRIX IN A FIRST DIRECTION AND THE WINDINGS ON EACH COIL ITSELF REPRESENTING ALINEMENT OF THE MATRIX IN A SECOND DIRECTION, AN OUTPUT LEAD FOR EACH OF SAID CORRESPONDING WINDINGS SO THAT WHEN SAID DELAY LINE IS EXCITED A SEQUENTIAL SIGNAL TRAIN CAN BE APPLIED TO THE CATHODE-RAY TUBE IN TIMED RELATION WITH THE RASTER THEREOF, AN ELECTRIC CIRCUIT SYNCHRONOUSLY CONNECTED TO SAID CATHODE-RAY TUBE DEFLECTION MEANS FOR DRIVING THE DEFLECTION MEANS AND CONNECTED TO SAID PLURALITY OF CHARACTER GENERATORS TO DRIVE SAID DELAY LINE IN TIMED RELATION TO SAID RASTER, AND MEANS FOR SELECTIVELY CONNECTING ONE OF SAID CHARACTER GENERATORS TO SAID CIRCUIT AND TO SAID CATHODE-RAY TUBE IN RESPONSE TO A RECEIVED SIGNAL FROM AN EXTERNAL ACTUATION SOURCE, SAID MEANS BEING CONNECTED TO THE CONTROL ELECTRODE OF SAID CATHODE-RAY TUBE AND SYNCHRONIZED WITH SAID ELECTRICAL CIRCUIT WHEREBY SAID SEQUENTIAL SIGNAL TRAIN WILL ALLOW A BEAM OF ELECTRONS TO STRIKE THE SCREEN OF THE CATHODE-RAY TUBE UNDER THE CONTROL OF SAID DEFLECTION MEANS AND PRODUCE A RASTER IN TIMED RELATION WITH SAID CIRCUIT WHEREBY THE CHARACTER DETERMINED BY THE MATRIX OF THE SELECTED CHARACTER GENERATOR WILL BE VISUALLY REPRODUCED.