US3037566A - Telegraphic code character generation - Google Patents

Description

June 5, 1962 R. J. PAsco TELEGRAPHIC CODE CHARACTER GENERATION Filed March 16, 1961 INVENTOR.

RICHARD J. PASCO ATTORNEY June 5, 1962 R. J. PASCO 3,037,566

TELEGRAPHIC CODE CHARACTER GENERATION Filed March 1e, 1961 2 Sheets'sheet 2 2O MILLISEC AT 65 W.P.M.

www U U U U I I 'LI LV OUTPUT OF LETTER U oo- RESET PU LSES V lf' V FIG.2

INVENTOR. RICHARD J. PASCO ATTORNEY Unite States Patent 3 037 566 TELEGRAPHIC coDE crrRAcTER GENERATION Richard J. Pasco, South Williamsport, Pa., assigner to Sylvania Electric Products Inc., a corporation of Deia- Wll Filed Mar. 16, 1961, Ser. No. 96,284 9 Claims. (Cl. 178-82) This invention relates generally to apparatus for shaping and counting pulses, and more particularly to an irnproved circuit for generating telegraphic code characters, commonly known as CW keying.

In the development of the now very old art of telegraphy, many devices have been proposed for forming the code characters, the dots and dashes and spaces therebetween, beginning with the manually operated telegraphic key with which the lengths of the dots, dashes, and spaces were controlled by the time the key was depressed or released. Being under human control, this type of keying resulted in variations, from operator to operator, in the lengths of the code characters, and a variety of keying rhythms. The speed of generation of telegraphic code characters was increased somewhat by the introduction of a device known as a bug, a semi-automatic keying device which automatically forms a series of dots, ybut requires that the dashes be formed manually. When the key is moved in one direction, say to the right, a vibrating reed is set in motion to form a string of dots, possibly thirty to forty, before the oscillations of the reed are damped out. Thus, the duration of the dots and the spaces therebetween are determined by the characteristics of the reed, but the duration of the dashes is determined by the time the key is held to the left. The bug permitted generation of better code characters, but still being dependent on the manual dexterity of the operator, there was still a lack of uniformity from operator to operator.

More recently, a number of electronic devices have been proposed for eliminating some of the variations in the generated code characters due to the human element which have utilized timing circuits of various kinds to establish the rhythm of character generation and to maintain a predetermined mark-to-space ratio between dot-tospace and dash-to-space. Circuits of this type with which applicant is familiar are quite complicated and expensive, and have the disadvantages that the operators key must be kept depressed throughout the period of a dot or dash, which, in turn, may, under certain conditions, atfect the mark-to-space ratio.

It is a general object of the present invention to provide a circuit for adding and/or subtracting pulses in an input pulse train to generate pulses differing from the input pulses but in timed relationship therewith.

Another general object of the invention is to provide an improved keying circuit for generating telegraphc code characters.

Another object of the invention is to provide a keyer which insures perfect mark-to-space ratio of both dot-tospace and dash-to-space in a telegraphic code character.

Still another object of the invention is to provide a keyer which insures perfect spacing of dots and dashes throughout the speed range of the operator of the keyer.

A further object of the invention is to provide a keying circuit for generating telegraphic code characters which establishes the rhythm of character generation so as to eliminate variations in this important characteristic of the resulting code due to the operator.

Another object of the invention is to provide a keying circuit having the foregoing properties which requires a minimum of components and accordingly is relatively compact and inexpensive.

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Broadly, the circuit according to the invention features a novel tri-stable gating circuit, controllable by the operator when employed in a telegraphic code generator, for selectively controlling the application of pulses from a time base generator to a counter tube, which may be of the glow discharge transfer type. When in one of its stable states the gating circuit inhibits the transfer of pulses to the counter tube, and when in either of the other stable states produces in response to the input pulses two overlapping drive pulses for the counter tube which step the glow discharge in the counter in one direction when in the second stable state and in the other direction when in the third stable state. Circuitry associated with the counter tube causes the glow discharge to rest on a selected one of the cathodes preparatory to receiivng driving pulses, and produces output pulses of lengths which are selected multiples of the repetition period of the input pulses by transferring the glow discharge in one direction or the other a selected number of steps. When used in a keyer, for example, transferring the glow discharge two steps in one direction from the rest cathode produces an output pulse equal in duration to the repetition period of the input pulse, and counting four steps in the opposite direction from the rest cathode produces an output pulse of a length three times the length of the repetition period of the input pulses, the accepted dot-to-dash ratio in telegraphic code characters. A reset pulse is generated at the completion of an output pulse which transfers the glow discharge back to the rest cathode and resets the gating circuit to prevent the generation of another output pulse until conclusion of a space interval at least as long as the repetition period of the input pulses.

This tri-stable circuit is particularly useful in the generation of telegraphic code characters to determine the rhythm of character generation and the mark-to-space ratio. The time base circuit, which may be a free-ruuning blocking oscillator, produces a train of pulses of selected duration and repetition frequency which is coupled to the gating circuit, the opening of which is initiated by the operator by activating a key. The pulses passed by the gating circuit are shaped and applied to a multi-cathode glow transfer counting tube to cause the glow to move from one cathode to the next. Selected ones of the cathodes are connected to a circuit for controlling the current in the keying relay, and other cathodes of the tube are connected to a pulse generator which generates a pulse which closes the gating circuit upon completion of the code character originally initiated by the operator. The gating circuit is arranged to apply pulses from the blocking oscillator to the counter tube in one phase when the operators key is depressed in one direction and in opposite phase when the key is depressed in the other direction whereby the glow discharge in the counter tube moves in one direction for one position of the key and in the opposite direction for the other position of the key. The gating circuit, counter tube and reset pulse generator are so arranged that when the key is depressed in one direction, the pulses passed by the opened gating circuit and applied to the counter tube cause the glow to be transferred in one direction a predetermined number of counts, for example, two counts for a dot, whereupon the pulse from the reset pulse closes the gating circuit and resets the glow discharge in the ycounter to the selected rest cathode. When the operators key is depressed in the other direction, the blocking oscillator pulses passing through the gating circuit are applied in opposite phase to the counter tube causing the glow to be transferred in the other direction. The circuit is arranged to count four pulses (three repetition periods), to generate a dash, before the reset pulse is generated to close the gating circuit and reset the counter tube. The tube controlling the current in the keying relay remains conducting for one or three repetition periods of the blocking oscillator, thereby maintaining a fixed ratio between the lengths of the dots and "dashes. The reset pulses being generated at the termination of a particular character, the spacing between characters is maintained at a value equal to the repetition period of the blocking oscillator pulses, provided the key is actuated at a rate at least as great as the repetition rate of the blocking oscillator. The gating circuit features a novel lockout characteristic which prevents the formation of a new dash or dot until the space following the last dash or dot is completed, regardless whether the key has been actuated in the meantime. It is necessary only to momentarily close the key to initiate a code character, the gating circuit including a memory circuit to complete the character and the following space, a feature usually referred to as self-completion.

Other objects, features, and advantages of the invention will be apparent as the invention becomes better understood by reference to the following description, taken in conjunction with the accompanying drawings, in which:

FIG. l is a schematic circuit diagram of a keying circuit embodying the invention; and

FIG. 2 is a timing diagram illustrating the wave forms which occur in various portions of the circuit during generation of code characters representing the letter U in the Morse code.

Referring now to the drawings, timing pulses for the keying circuit are conveniently generated by a free-running blocking oscillator including, by way of example, a triode whose anode is coupled to its control grid through a suitable pulse transformer 14. The repetition rate of the blocking oscillator is determined by the RC combination of capacitor .1.6 and the combined resistances of resistor 1S and potentiometer 20, the latter affording adjustment of the repetition frequency of the oscillator. Positive going pulses are developed across the cathode resistor 22 having, for example, a duration of approximately 30 microseconds and an amplitude of 40 volts. As is well known in the art, the duration of the pulses is largely determined by the characteristics of the coupling transformer 14, and the amplitude is determined by the potential of the energizing source, represented by terminal 24, and the value of cathode resistor 22. The repetition rate of the blocking oscillator is selected to afford a reasonable period between pulses for keying, and is thus related to the keying proficiency of the operator. For an operator capable of transmitting 65 words per minute, a repetition period of approximately milliseconds is satisfactory. If the operator is slower than this, the repetition rate of the blocking oscillator may be correspondingly lowered to provide a longer period between pulses for the operator to actuate the manual key. In FIG. 2, the duration of the pulses has been shown exaggerated for clarity, it being understood that the pulse duration is much smaller, as compared with the repetition period, than is illustrated.

The train of regularly recurring pulses from the blocking oscillator (see FIG. 2) is coupled via capacitor 26 to a combination gating and driver circuit 28, the function of which is to control the transmission of pulses from the blocking oscillator to the counter tube. The gating circuit includes a pair of pentodes, preferably contained in a common envelope 30, such as a 6BU8, in which the first control grid and the screen grid are common to both halves of the tube. The anodes of the tube are respectively connected through load resistors 32 and 34 to a source of positive potential, indicated by terminal 24, and the common cathode is connected to ground as shown. The screen grid is connected to a suitable source of positive potential, represented by terminal 36, and the cornmon control grid is connected to a suitable source of negative biasing potential, represented by terminal 38, through grid resistor 4t). The secondary control grids of the two sections of the tube are separately connected to a source of negative biasing potential, indicated by terminals 42 and 42 through resistors 44 and 46, respectively. A pair of cold cathode trigger tubes 48 and 50, such as an NE77, are connected in series between the two secondary control grids, with the cathodes of the trigger tubes connected to a respective secondary grid and the anodes of the two trigger tubes connected together and through a common load resistor 52 to a source of positive potential, represented by terminal 54. The trigger electrodes of tubes 48 and S0 are respectively connected to the left and right hand contacts 56 and 58 of the operators key 60. As will be more fully explained hereinafter, the direction in which the key 60 is depressed determines which sides of tube 3) conducts, which, in turn, controls the direction in which the glow discharge in the counter tube is stepped. Suice it to say for the present that when one side of tube 30 is conducting, negative pulses appear on the plate of the conducting half of the tube in time coincidence with the pulses from the blocking oscillator, The timing of the output of the gating circuit is illustrated in the second trace of FlG. 2. As is indicated in FIG. l, the gating circuit amplies the input pulses somewhat so as to provide negative pulses of an amplitude of approximately volts for application to the counter tube.

The dot-to-space and dash-to-space ratio of the code characters is determined by a glow transfer counting tube 64 which may be a Sylvania 6910, commonly termed a decade counter. The counting tube includes a disc-shaped anode 66 surrounded by slim rod-like cathodic elements arranged in a circle about the anode. In a decade counter, which has 30 such elements, each third electrode is designated as a main or count-indicating cathode, identitied in the drawing as 1, 2, 3 9, 0. The remaining cathodic electrodes are divided into two groups, all of the members of each group being connected together to form two sets of lguide or transfer electrodes, these electrodes in the interest of clarity, being schematically illustrated as only two electrodes designated G1 and G2. One guide electrode in each of the groups is mounted adjacent each main cathode. In other words, between successive main cathodes, between 4 and 5 for example, are positioned two guide electrodes, one associated with group G1 and the other associated with group G2. It is the function of the guide electrodes, when properly energized, to transfer a glow discharge existing between the anode and a particular cathode to the next adjacent main cathode.

This stepping action is accomplished by lowering the potential of one set of guide electrodes to a point where the glow will leave its position on a main cathode and transfer to the nearest guide electrode of that set. The potential of the second set of guide electrodes is then lowered while the potential of the rst set is allowed to return to its normal value. When the potential on the second set is suciently lower than that on the first set, the glow will transfer from its position on the rst guide elecrode to the adjacent guide electrode of the second set. The potential of the second set of guide electrodes is then allowed to return to its normal value. The normal potentials on the second set of guide electrodes and on the main cathodes are such that the glow will then move from the second guide electrode to the next adjacent main cathode, whereby the glow is moved in a predetermined direction from one main cathode via two guide electrodes to the next main cathode. The successive lowering of the potential of the two sets of guide electrodes is normally accomplished by forming in response to a single negative pulse to be counted two pulses of substantially the same duration and amplitude, with one delayed relative to the other.

In the present circuit this is accomplished by a high irnpedance delay line consisting of a choke coil 68 connected between the two anodes of tubes 30 and a pair of capacitors 70 and 72 connected from respective ones of the anodes to ground. As was noted earlier, when the key 60 is closed, one side of tube 30 conducts causing a negative pulse to appear on `the anode of the conducting section. Assuming for the moment that the right-hand section is conducting, the negative pulse appearing on the anode is coupled via capacitor 74, undelayed, to the guide electrodes G1 of the counter tube. At the same time, since the left-hand section of tube 30 is not conducting, the pulse appearing at the anode of the right-hand section is coupled through the choke coil 68 and thence through coupling capacitor 76 to the other set of guide electrodes, G2. In a circuit which has been satisfactorily operated, a value of 1 henry for the choke coil 68 and a capacitance of 330 micromicrofarads for capacitors 70 and 72 (chosen so as not to load down the negative pulse appearing at the anodes), a 3() microsecond pulse is delayed approximately l5 microseconds with a negligible loss in pulse amplitude, -because of the low D.C. resistance of the choke. Although the drive pulses are not ideal in the respect of the leading edge of the delayed pulse coinciding with the trailing edge of the undelayed pulse, they are considerably wider than the 4 microsecond minimum speciiied by the manufacturer for satisfactory operation of the type 6910 counter tube. Because of the pulse duration of 30 microseconds and the delay of 15 microseconds, each set of guide electrodes are aiorded approximately microseconds of transfer time, more than adequate to insure `good transfer. To insure reliable operation of the counter tube, guide electrodes G1 and G2 are respectively connected through diodes 78 and 80 to a source of biasing potential derived from a voltage divider consisting of resistors S2 and 84 connected in series between a source of positive potential, represented by terminal 86, and ground.

It is signiicant to here note that when the right-hand section of -tube 30 is conducting the pulse applied to guide electrodes G1 leads the pulse applied to guide electrodes G2, which causes the glow discharge in the counter tube to be moved in one direction. say in the direction of descending cathode number. However, when the left-hand section of tube 30 is conducting, the undelayed pulse is applied to guide electrodes G2, with the delayed pulse applied to guide electrodes G1, with the result that the glow discharge is stepped in the opposite direction. Thus, the gating circuit 28 not only controls the passage of pulses from the blocking oscillator to the counter tube, but also determines the direction of transfer of the glow discharge in the counter tube.

Again turning attention to the counter tube, its anode 66 is connected through a suitable load resistor 86 to a source of positive potential represented by terminal 88, which may be of the order of 450 volts. As will be seen, only seven of the ten main cathodes of the counter tube are necessary in the present application; accordingly, the cathodes designated 1, 2 and 0 are grounded and serve no active function. The cathodes designated 3 and 9 are connected together and to ground through a load resistor 90. Cathodes 4, 6, 7 and 8 are connected together and through a common load resistor 92 to a source of negative potential, indicated by terminal 93; thus, an output signal is developed across resistor 92 regardless of on which of cathodes 4, 6, 7, or 8 the glow discharge may be invested. Cathode 5, as will appear from the discussion to follow, is the home base for the glow discharge between counting sequences, and is connected to ground through load resistor 94.

For reasons which will be more apparent later, cathodes 3 and 9 of the counter tube are coupled through capacitor 96 to a reset pulse generator 9-8 which functions to terminate either a dot or a dash after the number of pulses required to form a particular character have been counter. The reset pulse generator may consist of a gas-filled tetrode, such as a 2D2l, with its second grid and cathode connected together and grounded, and its anode connected through a plate load resistor 102 to a source of positive potential, represented by terminal 1014.

The control grid is negatively biased through grid resistor from a negative voltage source, represented by terminal 106, of a value such that the tube is normally cut off. When the tube is triggered into conduction, which occurs when the glow discharge is invested at either of cathodes 3 or 9, a negative voltage spike of approximately 150 volts amplitude is produced at its plate. This voltage spike is stretched somewhat by the action of capacitor 108 and resistor 109 and applied through the key 60 (which, of course, is insulated from the electrical conductor) to the anodes of trigger tubes 48 and 50i. The negative spike is also coupled via capacitor 110 to cathode 5 of the counter tube to reset the glow back to this cathode preparatory to the formation of another code character.

The output pulses, telegraphic code characters for example, are developed across resistor 92 which is common to cathodes 4, 6, 7 and 8. The pulses produced at this point may be utilized directly to key an oscillator, or may be used to actuate a keying relay, such as is shown at 112. The generated pulses are direct coupled through resistor 114 to the control grid of tube 116 connected in series with a relay coil 118 and current limiting resistor 120 to a source of positive potential, represented by terminal 122. In the absence of output pulses across resistor 92, tube 116 is cut off by the negative potential applied at terminal 93. When a positive voltage developed across resistor 92 is coupled to the grid of the tube, the relay is pulled in to key an external circuit (now shown), the tube 116 continuing to conduct for the period of a dot or dash as the case may be.

The various components of the system having been described, and, in a general way the coaction between them, the manner in which a dot is generated will now be described. In the quiescent condition of the circuit, with the key 60 in the illustrated neutral position, the glow discharge in counter tube 64 is on cathode 5, and both sections of the gating-driver circuit 28 are cut off by the negative biasing potential applied to both of the secondary control grids of tube 30. The blocking oscillator 10 is producing a train of regularly occurring positive pulses, but since the gating circuit is closed they are not transferred to the counter tube. To initiate the generation of a dot, the key 60 is moved to the right into engagement with contact 58 thereby connecting the positive voltage source 54 to the trigger electrode of trigger tube 50, the source 54 having a potential of approximately volts, sutiicent to ionize tube 50 and to cause it to conduct. This has the effect of connecting resistors 52 and 46 in series as a voltage divider between potential sources 54 and 42 which results in raising the voltage on the secondary control grid of the right-hand section of tube 30 to a sulciently positive value to allow the 30 microsecond pulses from the blocking oscillator to be passed by the right-hand section of the tube. The common load resistor 52 for trigger tubes 48 and 50 provides a unique lock-out feature for the system in that i-t allows conduction in only one of the trigger tubes at any one time. The +150 volts applied to the trigger electrode of one of the trigger tubes is suticient to initiate conduction therein, but because of lthe large startto-drop ratio of trigger tubes of this type, the trigger tube, once ionized, will continue to conduct a substantially constant current even though the key is released from the trigger electrode. This property of the trigger tube insures the completion ot' a particular code character should the key be released before the character is completed.

The pulses from the blocking oscillator are inverted by the right-hand section of tube 30 and are amplied to Ia suitable level to actuate the counter tube. The negative pulse appearing at the `anode of the right-hand section is coupled directly to the guide electrodes G1 and after a delay introduced by the choke coil 68 and capacitor 70 is applied to guide electrodes G2. Application of this pair of overlapping pulses to the guide electrodes in this sequence causes the glow to be transferred from cathode 5, where it was initially invested, to cathode 4, the glow current flowing through cathode load resistor 92 to enerate a positive voltage which is direct-coupled to the control grid of a relay control tube. This voltage signal, in the present circuit of a magnitude of approximately 30 volts, causes the relay to pull in to start the dot This voltage is maintained as long as the glow is invested on cathode 4 whereby relay M8 is held closed until another pulse has arrived from the blocking oscillator. The next pulse applied to the gating circuit 2S (which is still open because of the action of trigger tube 50) transfers the glow from cathode 4 to cathode 3, whereupon a voltage no longer is developed across resistor 92, causing relay tube 116 to be cut olf and the dot to be terminated. Thus, the length of the dot is equal to the repetition period of the blocking oscillator, as shown in the third Waveform of FIG. 2, all dots being of the same length regardless of the length of time key 60 is depressed.

Simultaneous with the removal of the voltage signal from the relay tube, the transfer of the glow to cathode 3 causes .a signal to be developed across load resistor 90 of a magnitude sufficient to overcome the bias on the reset tube 100. The plate excursions of this tube produce a negative going spike pulse of a magnitude, in the present embodiment of the circuit or approximately 150 volts amplitude and 30 microseconds duration, which is coupled via capacitor 108 to the anodes of the cold cathode trigger tubes 48 and 50. This negative pulse counteracts the positive potential from source 54, by reducing the potential across trigger tube 50 to a level which extinguishes the tube. With trigger tube S eX- tinguished, the negative bias from source 42 is again applied to the secondary control grid of the right-hand section of tube 30, thus closing the gating circuit 28.

At the same time, the negative voltage spike appearing at the plate of reset tube 100 is coupled via capacitor 110 to cathode 5 of the counter tube, which lowers its potential sutciently below the potential of cathode 3 at which the glow was invested, to reset the glow back to cathode 5 to ready the counter tube for generation of another code character. If the key 60 is held to the right, trigger tube 50 will break down again and allow the sequence just described to be repeated to generate another dot, as shown in FIG. 2, it being impossible, however, for the second dot to be started before the occurrence of the next following blocking oscillator pulse. That is, the space between dots is also equal to repetition period of the blocking oscillator and is maintained at this length. As has been noted earlier, momentary closure of the key is all that is necessary to initiate the generation of a complete character, the trigger tubes serving as memory devices which are cleared only upon occurrence of a reset pulse from the reset pulse generator. Since only one of the trigger tubes can be broken down at a time, it is impossible to form a new character unless the previous character and its following space have been completed. When the repetition rate of the blocking oscillator is geared to the sending speed of a particular operator, `and the operator gets into the rhythm of the key, automatic letter spacing is achieved by allowing one blocking oscillator pulse to pass during the space between two letters, giving a two-space period between letters, which is conventional practice.

The circuit functions in a similar manner to generate a dash, except that provision is made to insure that the dash is three times as long as the dotf Remembering that the glow was returned to cathode 5 of the counter tube at the completion of a character, and the gating circuit 28 closed, the formation of a dash is initiated by moving the key 6() to the left, into engage ment with contact 56, causing ionization of trigger tube 48 to remove the negative bias from the secondary con- 3 trol grid of the left-hand section of tube 30. The blocking oscillator pulses now passed by the left-hand section are inverted and coupled undelayed to guide electrodes G2, and after a predetermined delay to guide electrodes G1. Thus, the driving pulses for the counter tube are of opposite phase to what occurs when the right-hand section of tube 30 is conducting. The first pulse passed by the gating circuit 28 causes the glow to be transferred from cathode 5 to cathode 6, the glow current flowing in cathode resistor 92 developing a voltage suicient to cause conduction of the series relay tube 116 to start the dash Tube 16 continues to conduct so long as the glow is at cathode 6, and upon arrival of a second pulse from the blocking oscillator, the glow is transferred from cathode 6 to cathode 7. Since load resistor 92 is common to cathodes 6 and 7 the voltage on the grid of tube 116 is maintained during the transition since the short time required for the transfer does not cause the voltage developed across resistor 92 to drop enough to cause tube 116 to be cut off. The next pulse to arrive from the blocking oscillator transfers the glow to cathode 8, and the fourth pulse, which occurs three repetition periods of the blocking oscillator after the pulse which initiated the dash, transfers the glow to cathode 9. This removes the potential from the grid of tube 116 causing relay 118 to drop out to terminate the dash and also causes a voltage to be developed across load resistor to trigger reset pulse generator 98 into conduction. The resulting negative spike at the plate of tube extinguishes trigger tube 43, and also transfers the glow in the counter tube from cathode 9 back to cathode 5. As shown in FIG. 2, the resulting dash is three times as long as a dot, and three times as long as the space between characters. Thus, the dot-to-dash ratio, and the length of the spaces between code characters are accurately maintained by the repetition frequency of the blocking oscillator. It will be noted from the fourth trace in FIG. 2, that reset pulses are generated only at the termination or conclusion of a code character.

If the key 60 is held to the left, trigger tube 48 will break down again after the reset pulse terminating the dash character has decayed and allow the just-described sequence to be repeated to generate another dash, it being impossible for the second dash to be started before the completion of the space following the first dash Thus, if the key is held to the left, a series of dashes will be generated for as long as the key is held, and as was indicated earlier, holding of the key to the right produces a series of dots Appropriate manipulation of the key to the left or right produces the desired code consisting, in general, of a series, including one, of dots and a series, also including one, of dashes From the foregoing description it will have been seen that the present keying circuit insures self-completion of a character, once initiated, and a perfect mark-to-space ratio of both dotto-space and dash-to-space. Perfect spacing of the characters is automatically maintained, and perfect rhythm is established, by the repetition rate of the free-running time base generator. The circuit also has the advantage of precluding the formation of a new dash or dot until the space following a dash or dot is completed. The circuit employs a minimum of components which may be packaged in a relatively small volume to provide an inexpensive and compact unit.

In a circuit which has been satisfactorily operated with a Sylvania 6910 counter tube, the values of the circuit components were as follows:

Tube 12 1/26U8 Tube 30 6BU8 Tube 116 1/36BN8 Tube 100 2D2l Diodes 78 and 80 1N38 Trigger tubes 48 and 50 NE77 9 Resistor 18 33K Potentiometer Ztl 100K Resistor 22 ohms..- 270 Resistors 32, 34- and 52 56K Resistors 44 and 46 10K Capacitors 70 and 72 micromicrofarads 330 Resistor 82 100K Resistor 84 22K Resistor 86 220K Resistors 90, 92 and 94, and 120 47K Resistor 114 megohms l Resistors 102 and 105 470K Potential source 24 volts +25() Potentials 33, 42, 42', 93, and' 106 do -14 Potential sources 36 and 54 do +150 Potential source 88 do +450 It is to be understood, however, that the invention is not limited to these specific components and circuit values since many variations are possible with other available components. Likewise, the time base generator may utilize blocking oscillators of configurations different from that illustrated, and indeed may be vany free-running time base generator of which many examples are known to the art. Similarly, the reset pulse generator fmay employ a variety of circuit configurations, and other means may be employed to obtain the requisite delay between the pulses applied to the guide electrodes Gl and G2. And, although a series relay tube is illustrated as one way of utilizing the code character output of the counter tube, it will be apparent to those skilled in the art that many different means are available for utilizing the output pulses. For example, the output of the counter tube may be applied to the screen grid electrode of a pentode connected las an audio tone generator to directly key the tone generator, in which case resistor 92 may be connected to ground instead of to source 93 of negative potential.

Although the sub-system consisting of the gating circuit 28 and the counter tube have unique application in the present keying circuit, it will be appreciated that this sub-system may have general application as an addsubtract circuit for input pulses, or as a generator of output pulses differently related than the dot and dash For example, input pulses from a source may be applied to the common first control grid of the tube 30, these pulses being added or subtracted by the counter tube under control of appropriate keying signals applied to the trigger electrodes of tubes 4S and 50. In essence, the gating circuit 28 with its associ-ated delay network and trigger tubes is a tri-stable circuit capable of controlling the direction of transfer of the glow in the counter tube in response to the selective breakdown of the trigger tubes 4S and Sti.

Thus, although a preferred embodiment of the invention has been described as applied to a gating circuit for generating telegraphic code characters, the invention is not limited to the specific details illustrated and described nor to this specific application, inasmuch as various omissions and substitutions in the form and details of the circuit and its oper-ation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, that the invention be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In combination, ,a source of regularly recurring pulses having a predetermined repetition period, a counter tube having a plurality of cathodes between which a discharge is stepped in one direction or the other in response to the applica-tion of a pair of drive pulses, one delayed relative to the other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by whether corresponding drive pulses applied to the first group of switching electrodes leads or lags the drive pulses applied to the second group of switching electrodes, and va gating circuit having first and second output terminals respectively connected to the first and second groups of said switching electrodes and -an input terminal to which said regularly recurring pulses are applied, said gating circuit being operative when in a first stable condition to inhibit the transfer of pulses from said source to said counter tube and operative when in either of second 0r third stable conditions to generate in response to one of said regularly recurring pulses a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of switching electrodes leading the pulse applied to the second group of electrodes when said gating circuit is in the said second stable condition, and vice versa when said gating circuit is in the said third stable condition.

2. A circuit for adding or subtracting pulses in a train of input pulses comprising, in combination, a counter tube having a plurali-ty of cathodes between which a discharge is stepped in response to the application of drive pulses, delayed relative to each other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by Whether the drive pulse applied to the first group of switching electrodes leads or lags the drive pulse applied to the second group of switching electrodes, -a source of input pulses, a gating circuit connected to the switching electrodes of said counter tube and to which said input pulses are applied, said gating circuit being operative when in a first stable condition to inhibit the transfer of input pulses Kfrom said source to said counter tube and operative when in either of second or third stable conditions to generate in response to an input pulse a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of switching electrodes leading the pulses applied to the second group of switching electrodes when said gating circuit is in the said second stable condition, and vice versa when said gating ci-rcuit is in the said third stable condition.

3. A circuit for adding or subtracting pulses in a train of input pulses comprising, in combination, a counter tube having a plurality of cathodes between which a discharge is stepped in response to the application of drive pulses, delayed relative to each other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being deter-mined bfy whether corresponding drive pulses applied to the first group of switching electrodes leads or lags the drive pulse applied to the second group of switching electrodes, a source of input pulses, a gating circuit having a pair of output terminals respectively connected to the first and second groups of switching electrodes of said counter tube and -an input terminal to which said input pulses are applied, said gating circuit being operative when in a first stable condition to inhibit the transfer of input pulses from said source to said counter tube and operative when in either of second or third stable conditions to generate in response to an input pulse a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of swi-tching electrodes leading the drive pulse applied to the second group of switching electrodes when said gating circuit is in the said second E stable condition, and vice versa when said gating circuit is in the said third stable condition, and circuit means connected from selected ones of the cathodes of said counter tube to said gating circuit for switching said gating circuit from the second or third stable condition to 'the Afirst stable condition after the discharge in the counter tube has been stepped a selected number of steps in one direction or the other, respectively, in response to successive input pulses.

4. A circuit for generating output pulses of duration bearing a fixed relationship to the repetition period of a train of input pulses comprising, in combination, a counter tube having a plurality of cathodes between which a discharge is stepped in response to the application of drive pulses, delayed relative to each other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by whether corresponding drive pulses applied to the first group of switching electrodes leads or lags the drive pulses applied to the second group of switching electrodes, a source of input pulses having a predetermined repetition period, a gating circuit having a pair of output terminals respectively connected to the first and second groups of switching electrodes of said counter tube and an input terminal to which said input pulses are applied, said gating circuit being operative when in a first stable condition to inhibit the transfer of input pulses from said source to said counter tube and operative when in either of second or third stable conditions to generate in response to an input pulse a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of switching electrodes leading the drive pulse applied to the second group of switching electrodes when said gating circuit is in the said second stable condition, and vice versa when said gating circuit is in the said third stable condition, circuit means connected from selected ones of the cathodes of said counter tube to said gating circuit for switching said gating circuit from the second or third stable condition to the first stable condition after the discharge in the counter tube has been stepped a selected number of steps in one direction or the other, respectively, in response to successive input pulses, and circuit means connected to other selected ones of the cathodes of said counter tube for deriving output pulses of durations respectively equal to the number of repetition periods rbetween the input pulses necessary to step the discharge said selected number of steps in one direction or the other.

5. A circuit for generating telegraphic code dot pulses of a first duration and dash pulses of a duration which is a selected multiple of the dot pulse separated by spaces of a duration which is a multiple of the dot pulse, said circuit comprising, in combination, a source of regularly recurring pulses having a repetition period equal to a submultiple, including one, of the desired duration of said dot pulses, a counter tube having `a plurality of cathodes between which a discharge `is stepped in one direction or the other in response to the application of drive pulses, delayed relative to each other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined lby whether corresponding drive pulses applied to the first group of switching electrodes leads or lags the drive pulses applied to the second group of switching electrodes, a gating circuit having first and second output terminals respectively connected to the lfirst and second groups of said switching electrodes and an input terminal to which said regularly recurring pulses are applied, said gating circuit being adapted for switching by an operator from a first stable condition, in which transfer of input pulses to the counter tube is inhibited, to either of second or third stable conditions, said gating circuit being operative when in either said second or third stable conditions to generate in response to a pulse applied to said input terminal a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of switching electrodes of the counter tube leading the pulse applied to the second group of switching electrodes when the gating circuit is in the said second stable condition, and vice versa when said gating circuit is in said third stable condition, a first load resistor connected to a selected first cathode of said counter tube, a second load resistor connected in common with second and third other cathodes of said counter tube respectively displaced in either direction from said first selected cathode by a number one greater than the multiple of input pulse repetition periods desired for the durations of the dot and dash pulses, a third load resistor connected in common with all of the cathodes between said second and third other cathodes, except said first cathode, means operative in response to the transfer of the discharge in the counter tube to either of said second and third other cathodes to generate a reset pulse, means for applying said reset pulse to said gating circuit to switch it from said second or third stable conditions toits first stable condition, and means for also simultaneously applying said reset pulse to said selected rst cathode to return the discharge to said first cathode, the output dot and dash pulses being developed across said third load resistor.

6. A circuit for generating telegraphic code dot pulses of a first duration and dash pulses of a duration which is a selected multiple of the dot pulse, separated by spaces of a duration which is a multiple of the dot pulse, said circuit comprising, in combination, a source of regularly recurring pulses having a repetition period equal to a submultiple, including one, of the desired duration of said dot pulses, a counter tube having a plurality of cathodes between which a discharge is stepped in one direction or the other in response to the application of drive pulses, delayed relative to each other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by whether corresponding drive pulses applied to the first group or" switching electrodes leads or lags the drive pulses `applied to the second group of switching electrodes, a gating circuit having first and second output terminals respectively connected to the first and second groups of said switching electrodes and an input terminal to which said regularly recurring pulses are applied, said gating circuit being adapted for switching by an operator from a first stable condition, in which transfer of input pulses to the counter tube is inhibited, to either of second or third stable conditions, said gating circuit including means for maintaining the circuit in said second or third stable conditions, once switched thereto until application of a reset pulse thereto, said gating circuit including a delay circuit connected between said first and second output terminals and being operative when in either said second or third stable conditions to generate in response to a pulse applied to said input terminal a pair of drive pulses delayed relative to each other, the drive pulse applied to the first group of switching electrodes of the counter tube leading the pulse applied to the second group of switching electrodes when the gating circuit is in said second stable condition, and vice versa when said gating circuit is in said third stable condition, a first load resistor connected to a selected first cathode of said counter tube, a second load resistor connected in common with second and third other cathodes of said counter tube respectively displaced in either direction from said first selected cathode by a number one greater than the multiple of input pulse repetition periods desired for the durations of the dot and dash pulses, la third load resistor connected in common with all of the cathodes between said second and third other cathodes, except said first cathode, means operative in response to the transfer of the discharge in the counter tube to either of said second and third other cathodes to generate a reset pulse, means for applying said reset pulse to said gating circuit to switch it from said second or third stable conditions to its first stable condition, and means for also simultaneously applying said reset pulse to said selected first cathode to return the discharge to said first cathode, the output dot and dash pulses being developed across said third load resistor.

7. A circuit adapted to generate telegraphic code characters in which the dash is three times the duration of a dot and the space has a duration equal to that of the dot, said circuit comprising, in combination, a source of regularly recurring pulses having a repetition period equal to the desired duration of a dot puise, a counter tube having ten cathodes between which a discharge is stepped in one direction or the other in response to the application of a pair of drive pulses, one delayed relative to the other, to rst and second groups of switching electrodes associated with the cathodes, -the direction of stepping being determined by whether the drive pulse applied to the `first group of switching electrodes leads or lags the drive pulse applied Ato the second group of switching electrodes, a gating circuit having irst and second output terminals respectively connected to the tirst and second groups of said switching electrodes and an input terminal to which said regularly recurring pulses are applied, said gating circuit being arranged to be switched from a rst stable condition in which it inhibits the transfer of input pulses Ito the counter tube to either of second or third stable conditions, said gating circuit being operative when in either said second or third stable conditions to gencrate in response to a pulse applied to said input terminal a pair of drive pulses delayed relative tc each other, the drive pulses applied to the iirst group of switching electrodes of the counter tube leading the pulses applied to the second group of switching electrodes when the gating circuit is in said second stable condition, and vice versa when said gating circuit is in said third stable condition, a iirst load resistor connected to a selected rst cathode of said counter tube, a second load resistor connected in common with second and third other cathodes respectively displaced in opposite directions from said first selected cathode by two and four cathodes7 a third load resistor connected in common with all of the cathodes between said second and third other cathodes, except said iirst cathode, means operative in response to the transfer of the discharge in the counter tube to either of said second and third other cathodes to generate a reset pulse, means -for applying said reset pulse to said gating circuit, to switch it trom said second or third stable conditions to said first stable condition, and rneans for also simultaneously applying said reset pulse to said selected lirst cathode to return the discharge to said rst cathode, the output code characters being developed across said third load resistor.

8. A circuit adapted to generate telegraphic code characters in which the dash is three times the duration of a dot and the space has a duration equal to that of the dot, said circuit comprising, in combination, a source of regularly recurring pulses having a repetition period equal to the desired duration of a dot pulse, a counter tube having ten cathodes between which a discharge is stepped in one direction or the other in response to the application of a pair of drive pulses, one delayed relative to the other, to iirst and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by whether the drive pulse applied to the rst group of switching electrodes leads or lags the drive pulse applied to the second group of switching electrodes, a gating circuit having first and second output terminals respectively connected to the irst and second groups of said switching electrodes and an input terminal to which said regularly recurring pulses are applied, said gating circuit being arranged to be switched Ifrom a first stable condition in which it inhibits the transfer of input pulses to the counter tube to either of second or third stable conditions, said gating circuit including a pair of cold-cathode trigger tubes arranged to maintain the gating circuit in either said second or third stable condition after being switched thereto until a reset pulse is applied thereto to return the circuit to its iirst stable condition, said gating circuit being operative when in either said second or third stable conditions to generate in response to a pulse applied to said input terminal a pair of drive pulses delayed relative to each other, the ldrive pulses applied to the rst group of switching electrodes of the counter tube leading the pulses applied to the second group of switching electrodes when the gating circuit is in said second stable condition, and vice versa when said gating circuit is in said third stable condition, a ii-rst load resistor connected to a selected iirst cathode of said counter tube, a second load resistor connected in common with second and third other cathodes respectively displaced in opposite directions from said first selected cathode by two and four cathodes, a third load resistor connected in common with all of the cathodes between said second and third other cathodes, except said iirst cathode, means operative in response to the transfer of the discharge in the counter tube to either of said second and third other cathodes to generate a reset pulse, means for applying said reset pulse to said cold-cathode trigger tubes to switch said gating circuit from said second or third stable conditions to said iirst stable condition, and means for also simultaneously applying said reset pulse to said selected iirst cathode to return the discharge to said first cathode, lthe output code characters being developed across said third load resistor.

9. A circuit adapted to generate telegraphic code characters in which the dash is three times the duration of a dot and the space has a duration equal to that of the dot, said circuit comprising, in combination, a source of regularly recurring pulses having a repetition period equal to the desired duration of a dot pulse, a counter tube having ten cathodes between which a discharge is stepped in one direction or the other in response to the application of a pair of drive pulses, one delayed relative to the other, to first and second groups of switching electrodes associated with the cathodes, the direction of stepping being determined by whether the drive pulse applied to the -iirst group of switching electrodes leads or lags the drive pulse applied to the second group of switching electrodes, a gating circuit having lirst and second output terminals respectively connected to the irst and second groups of said swtiching electrodes and an input terminal to which said regularly recurring pulses are applied, said gating circuit being arranged to be switched from a rst stable condition in which it inhibits the transof input pulses to the counter tube to either of second or third sta-ble conditions, said gating circuit including a pair ot cold-cathode trigger tubes arranged to maintain the gating circuit in either said second or third stable condition after being switched thereto until a reset pulse is applied thereto to return the circuit to its irst stable condition, said gating circuit being operative when in either said second or third stable conditions to generate in response to a pulse applied to said input terminal a pair of drive pulses delayed relative to each other, the drive pulses applied to the irst group of switching electrodes of the counter tube leading the pulses applied to the second group of switching electrodes when the gating circuit is in said second stable condition, -and vice versa when said gating circuit is in said third stable condition, a first load resistor connected to the iifth cathode of said counter tube, a second load resistor connected in common with the third and ninth cathodes of said counter tube, a third load resistor connected in common with the fourth, sixth, seventh and eighth cathodes of said counter tube, means operative in response to the transfer of the discharge in the counter tube to either of said third or ninth cathodes to generate a reset pulse, means for applying said reset pulse to said cold-cathode trigger tubes to switch said gating circuit from said second or third stable condition to its rst stable condition, and means for also simultaneously applying said reset pulse to said fth cathode to return the discharge to said iifth cathode, the output code character pulses being developed across said third load resistor.

No references cited.

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