US3041397A - Telegraphic keyer - Google Patents

Description

June 26, 1962 J. B. RICKS TELEGRAPHIC KEYER Filed April 22, 1960 United States Patent P 3,041,397 TELEGRAPHC KEYER James B. Ricks, Lake Forest, Ill., assignor to The Hallicrafters Co., a corporation of Delaware Filed Apr. 22, 1960, Ser. No. 24,000 14 Claims. (Cl. 178--82) 'Ihis invention is concerned with a keyer, as for a radio transmitter, and more particularly with an electronic keyer actuated by a mechanical key.

In code transmission, use is made of short periods of transmission, preferably of different length and referred to as dots and dashes or marks, separated by periods of non-transmission, referred to as spaces. In accordance with best practice, the dot and space should have the same time period and a dash should be formed by bridging the space between two dots, thus the dash is three times as long as a single dot.

A principal object of this invention is the provision of an improved 4automatic keyer which will provide uniform dots, dashes and spaces at a constant speed, and which is not dependent upon the skill or accuracy of the operator in forming the individual marks.

One feature of the invention is the provision in a keyer of a free-running multivibrator having a pulse output, first selectively operable control means for actuating the free-running multivibrator, a bi-stable pulse actuated multivibrator having a pulse output, second selectively operable control means yfor conditioning the bi-stable multivibrator for operation and for actuating the yfreerunning multivibrator, means for deriving a trigger pulse from the free-running multivibrator and applying it to the bi-stable multivibrator and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of the iirst and second control means.

Another feature is that the second or bi-stable multivibrator acts as a frequency divider to cooperate with the free-running multivibrator in the provision of dashes having a liXed time relation with the dots formed by the freerunning multivibrator.

A further feature is that each of the multivibrators is normally maintained in an inoperative condition and is rendered operative upon actuation by the control means of a control device connected therewith. Yet another feature is the provision of a feedback circuit between the multivibrators and the associated control device to effect completion of an initiated character regardless of the condition of the selectively operable control means.

Still a further feature is the provision of a control for varying a bias condition of each section of the free-running multivibrator to control the speed of formation of the characters. And another feature is the provision of a Variable control element to vary a time constant in the circuit of the free-running multivibrator to control the mark-to-space ratio.

Further features and advantages of the invention will readily be apparent from the following specification and from the single ligure of the drawing, lwhich is a schematic diagram of an embodiment of the invention.

Code transmission is widely used for certain types of communication and various automatic electromechanical keyers have been developed, primarily for high speed commercial circuits which employ automatic translating equipment at the receiver. They are not designed or readily usable `for amateur communication, for example. The

keyer of the present invention is intended for manual ice During the course of the following description of the embodiment of the invention illustrated in the drawing, the various circuit elements will be given specific values or type designations. It is to Ibe understood that this specilic disclosure is made for the purpose of describing an operative embodiment of the invention and that many changes will be apparent -to those skilled in the art.

The keyer operation is based on the' action of a freerunning multivibrator 10 which provides a series of positive pulses that are utilized to actuate a keying relay 11, through the operation of a relay control tube 12. The pulses from the free-running multivibrator alone form a series of dots, separated by spaces having a time duration preferably equal to that of the dots. A bi-stable pulse actuated multivibrator 13 is actuated by pulses derived from free-running multivibrator 10 and provides a pulse output to the relay control tube which elfectively bridges the space between succeeding dot pulses, for the formation of a dash.

Each of the multivibrators is biased in a manner rendering it inoperative, and operation is effected through the manipulation of a control means, as the two-position key 414.

The construction and operation of the keyer will now be described in more detail. The apparatus is energized from a suitable A.C.y source through power trans-former 15, having a high voltage secondary winding 16 connected with a voltage doubler power supply 17. Regulators 18 and 19, as type OA`2 and OBZ gas regulator tubes, respectively, are connected across the power supply 17 and a junction between them returned to a reference potential or ground 20. A positive potential of the order of +150 volts appears at terminal 21a of the power supply and a negative potential of the order of volts at terminal 2lb.

Free-running multivibrator '10 includes a first section 25 and a second section 26, each one-half of a dual triode 12AU7. The cathode of lirst section 25 -is returned directly to ground and the anode is connected through resistor 27, 100,000 ohms, with the volt positive source. The control grid is connected through one or the other of resistors 2S, 2.2 megohms or 29, 5.6 megohms, section 30a of switch 30, and a portion of potentiometer 31, 1 megohm, with the movable arm of potentiometer 32, 100,000 ohms, which is connected in series with resistor 33t, 10,000 ohms, across the 150 volt source.

The cathode of second multivibrator section 26 is connected with the anode of control tube 35, one-half of a 12'AU7, the cathode of which is returned to ground. The control grid of control tube 3S is connected with a voltage divider including resistors 36, 2.2 megohms, 37, 680,- 000 ohms, and 27, between t-he +150 volt and -105 volt supplies. This establishes a potential at the control grid of control tube 35 of the order of -10 volts, biasing the control tube below cutoff and rendering multivibrator '10 inoperative.

The anode of the second section 26 of multivibrator is connected through resistor 40, 100,000 ohms, with the y150 volt supply. 'lhe control grid is connected through one or the other of resistors 41, 2.2 megohms and 42, 5.6 megohms, as selected by section 306 of switch 30, with the end of potentiometer resistor 31 opposite the connection of the control grid of multivibrator section 25. Coupling capacitors l43 and 44, each 0.02 af, are connected from the anode of section 26 to the control grid of multivibrator section 25, and from the anode of multivibrator section 25 to the control grid of section 26, respectively, completing the multivibrator circuit.

The bi-stable, pulse actuated multivibrator 13 comprises two sections 50 and 51,each one-half of a 12AU7. The cathode of section 50 is returned directly to [ground and the anode is connected through resistor 52, '100,000 ohms, and resistor 53, 22,000 ohms, with the positive 150 volt supply. Thecontrol grid is connected with a voltage divider including resistor 53, resistor 54, 100,000 ohms, resistor 55, 470,000 ohms, resistor 456, 470,000 ohms', and a portion of potentiometer 57, 500,00 ohms, between the positive 150 volt supply and the negative 105 volt supply, the movable tap of potentiometer 57 being connected to the negative supply. As will appear below, the potentiometer 57 is so adjusted that the control grid of section 50 has essentially zero bias potential applied thereto and section 50 is normally conducting.

The cathode ofthe section 51 of multivibrator 13 is u connected with the anode of control tube 58, one-half of a 12AU7, the cathode of which is returned to ground and the control grid of which is provided with a negative cutoflpotential by a voltage divider including resistor 59, ,w 2.2 megohms, resistor 60, 680,000 ohms, and resistors 52 and Y53, connected between the negative 105 volt and positive 150 volt supplies. The anode of section 51 of multivibrator '13 is connected through resistors 54 and 53 with the positive 150 volt supply. The control grid of section l,

51 is connected with a voltage divider which includes resistors53, 52, `62, 470,000 ohms, 63, 470,000 ohms, and

a portion of potentiometer 57; This divider applies a negative potential to the control grid of multivibrator section 51, suicient to render it nonconducting, even Vwhen control tube 58 is not cut olf. The feedback circuit for multivibrator 13 Yincludes a capacitor 64, 0.001 nf., connected between the anode of section Si) of the multivibrator and control grid of section 51, shunting resistor 62,

and capacitor. 65, 0.001 uf., connected between the anode section 51 and the control grid of section 50, shunting resistor 55. t

Key lilincludes a key lever 14a spring biased to a position inten-mediate Va pair of contacts 14h and 14e,

connected with the ycontrol grids of control tubes 35 and l 58, respectively. The key 14a, which is returned to ground, Vand may be actuated manually to make contact with one or the other of contacts 146 and 14C. The key switch Vcontacts are shunted by capacitors 66 and 67, each 0.02. nf.

Dots are formed by the keyer upon actuation of key A lever 14a to the left, grounding contact 1-4b and thus the control grid of control tube 35. This renders free-running multivibrator section 26 conductive and initiates operation of the free-running multivibrator 10. So long as the key lever 14a is held to theY left, multivibrator 10 will continue to operate with first one section and then the other conducting. When the operation is initiated and section 26 vfor it'rendered conducting, the anode potential drops sharply and this sharp drop is coupled through capacitor 43 to the control grid of section 25, `cutting it oi. The plate voltage of'section'25 rises rapidly providing a positive pulse which is coupled through resistor 70, 2.2 megohms, to the control grid of relay control tube 12.

Relay control tube 12 is normally cut olf as its controlY grid is returned to` a' negative potentialV of the order of V--15 volts provided by a voltage divider including resistor 71, 2.2 megohms, anda' circuit including resistors 70 and '27 in onebranch and resistors 72, l megohm, 52, and 53 in the other branch, connected between the negative and positive terminals of the power supply. The positive pulse derived from section Y25 of free-running multivibrator 10 renders relay control tube 12 conducting, energizing relay coil 11a and reversing the connections of the contacts associated therewith; It will be noted that certain of the contacts are normally grounded while others are nor- Vmally isolated lfrom ground. The ground connection condition reversal upon actuation may be utilized by suitable connection of a transmitter keying circuit to output terminals 75.V

Dashes arey formed' by actuating key lever 14a to the right, grounding contact 14C connected with the control grid of control tube 5S. This in itself merely conditions section 51 of bi-stable multivibrator 13 for conduction but does not render it conductive as there is a negative potential of -the order of '12 volts on its control grid. A diode 76, lNl763, is connected between the control grids ofrcontrol devices 58 and 35 and phased to conduct when the control grid of control tube 58.is at a more positive potential than that of tube 35. Accordingly, when the grid of tube 58 is grounded, the control grid of control tube 35 is also grounded initiating operation of free-running multivibrator 10. The negative pulse appearing at the anode of section 26 of multivibrator 10' upon initiationof its operation, is coupled through a diterentiating circuit including capacitor 77, 0.001 nf. and resistor 53, to the anodes of the two sections 50 and 51 of bi-stable multivibrator 13. Conducting section 50 has an extremely low anode voltage because of the high resistance in the anodecircuit, and the negative pulse from the ditierentiator circuit serves to cut it off, whereupon section 51 begins to conduct. This condition remains for a full cycle of operation of free-running multivibrator 10 until section 26 is again rendered conducting whereupon a further trigger pulse is coupled t0 bi-stable multivibrator, this time rendering section 51 cut ot and permitting section 50 to conduct. The positive pulse appearing at the anode of section 50 of bi-stable multivibrator 13 when this section is rendered nonconducting, is coupled through resistor 72 to the control grid of relay control tube 12, and serves to bridge the gap between successive positive pulses provided by section 25 of `free-running multivibrator 10, keeping the relay control tube 12 conducting and providing a dash equal in time to two dots and the space between them.

Each of the multivibrators is provided with a feedback circuit connected with the associated control tube to insure the completion of a character once it is initiated, regardless of the operators handling of key lever 14a. In the free-running multivibrator 10, there is a connection between the anode of the first section 25 through resistor 37 with the control grid of control tube 35. When formation of a dot is initiated by grounding the control grid of the control tube 35, multivibrator section 25 is rendered nonconducting and the plate voltage jumps to B-lpotential. This positive potential changes the condition of the voltage divider to which the control grid of control tube 35 is connected, keeping it conducting until multivibrator 10 completes a cycle of operation. Similarly, in bi-stable multivibrator 13, there is a connection through resistor 60 between the anode of section 50 and the control grid of control tube 58. When a dash is initiated and section 50 of multivibrator 13 is rendered nonconducting, the increase in potential at the anode changes the condition in the biasing network for control tube 58 keeping it, and through diode 76, control tube 35, conducting until the character is completed.

Two controls are provided for the speed of free-run-` ning multivibrator 10. Switch 30, comprising switch sections 30a and 30h, provide for a selection of resistors in the grid circuits of the two sections 25 and 26 of the 'free-running multivibrator. A high speed range is provided with resistors 28 and 41 in the circuit, and a low speed range with resistors 29 and 42 in the circuit. A further control over the speed is provided by potentiorneter 32 which simultaneously varies the bias conditions in the grid circuit of the two sections of the multivibrator.

Variable resistor 31 controls the portion of the resistance 31 which is in each of the two grid circuits. If the other components of the circuit are properly matched and potentiometer 31 set at its mid-point, the two circuits are substantially identical and the mark-to-space ratio of the free-running multivibrator is unity. Adjustnient of potentiometer 31 increases or decreases the mark time as related to the spacetime.

Potentiometer 57 in the circuit of the control grid of the two sections of the bi-stable multivibrator is utilized to provide a balance in the bi-stable multivibrator to compensate for variations .in tube characteristics.

A visible indication of the operation of the keyer is provided by a neon lamp 78, NESl, connected in series with resistor 79, 100,000 ohms, between the anodes of sections 25 and 26 of free-running multivibrator 10. When the keyer is in operation and functioning properly, neon Ibulb 78 flashes continuously, once for each dot and twice for each dash. With a perfectly formed character, the rhythm of iiashes in uninterrupted.

An audible monitoring signal is provided by an audio relaxation oscillator utilizing a neon bulb 82, NEZ, shunted by capacitor 83, 0.001 pf. connected in series with resistor 84, 2.7 megohm, across the 150 volt positive portion of the supply. The oscillator operates continuously and its output in coupled through capacitor 85, 0.001 pf., to a volume con-trol potentiometer 86, 2*

megohms, connected in the grid circuit of an audio amplifier 87, one-half of a 12AU7. The output of the audio amplilier is coupled through transformer 88 and a contact associated with keying relay 11 to loud speaker 89. Whenever a character is formed and relay 11 actuated, the circuit t0 the loudspeaker is completed, provided an audible indication of the keyer operation.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modifications. Changes therefore, in the construction and arrangement may be made Without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In a keyer: a free-running multivibrator, having a pulse output; iirst selectively operable control means for actuating said free-running multivibrator; a bi-stable, pulse actuated multivibrator, havinga pulse output; second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of saidy first and second control means.

2. In a keyer: a free-running multivibrator, having a pulse output; rst selectively operable dot producing control means for actuating said free-running multivibrator; a frequency dividing, bi-stable, pulse actuated multivibrator having a pulse output; second selectively operable dash producing control means for conditioning said bistable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said pulse to said bi-stable multivibrator; and means combining the pulse outputs of both multivibrators to provide a series of dot and dash keying control pulses in accordance with the actuation of said first and second control means.

3. In a keyer: a free-running multivibrator, having a pulse output; first selectively operable control means for actuating said free-running multivibrator; a bi-stable, pulse actuated multivibrator, having a pulse output; second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; means operatively connected With each of said multivibrators for effecting completion of initiated pulses; and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of said first and second control means.

4. In a keyer: a free-running multivibrator having a normally conducting section and a normally nonconducting section, and having a pulse output; a first control device connected with said normally nonconducting section and biased to maintain such section in the nonconducting condition; first selectively operable control means connected with said first control device, operable to change the bias thereon to render said free-running multivibrator operative; a lbi-stable, pulse actuated multivibrator having a normally conducting section and a normally nonconducting section, and having a pulse output; a second control device connected with the normally nonconducting section of said bi-stable multivibrator for maintaining it nonconductive; second selectively operable control means connected with said second control device, operable to change the bias thereon to condition said bi-stable multivibrator for operation; means for deriving a trigger pulse from a free-running multivibrator and applying it to a bi-stable multivibrator; and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance With the operation of said first and second control means.

5. In a keyer: a free-running multivibrator having a normally conducting section and a normally nonconducting section, and having a pulse output; a first control device connected with said normally nonconducting section and biased to maintain such section in the nonconducting condition; first selectively operable control means connected with said first control device, operable to change the bias thereon to render said free-running multivibrator operative; a bi-stable, pulse actuated multivibrator having a normally conducting section and a normally nonconducting section, and having a pulse output; a second control device connected with the normally nonconducting section of said bi-stable multivibrator for maintaining it nonconductive; second selectively operable control means connected with said second control device, operable to change the bias thereon to condition said bistable multivibrator for operation; a diode connected b etween said control devices to couple a bias change of the second control device to the first control device; means for deriving a trigger pulse from vsaid free-running multivibrator and applying it to said bi-stable multivibrator; feedback circuits associated with each of said multivibrators for effecting completion of initiated pulses; and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the operation of said iirst and second control means.

6. In a keyer: a free-running multivibrator having a pulse output; first selectively operable control means for actuating said free-running multivibrator; a bi-stable, pulse actuated multivibrator, having a pulse output; second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; means for varying a bias condition of each of the sections of said free-running multivibrator for controlling the speed of the pulses; and means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of said first and second control means.

7. In a keyer: a free-running multivibrator having a pulse output; first selectively operable control means for actuating said free-running multivibrator; a bi-stable, pulse actuated multivibrator, having a pulse output, second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; means for varying a time constant in said free-running multivibrator for controlling the mark-to-space ratio of said pulses; means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of said first and second control means.

Y 8. In a keyer: a free-running multivibrator having a pulse output; tirst selectively operable control means for actuating said free-running multivibrator; a bi-stable, pulse actuated multivibrator, having a pulse output; second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means for deriving a trigger pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; means combining the pulse outputs of both multivibrators to provide a series of keying control pulses in accordance ,with the actuation of said irst and second control means;

and a visual indicator connected With said free-running multivibrator and responsive toV the pulses generated thereby.

9. In a keyer: a free-runnngvrnultivibrator having a pulse output; tirst selectively operable control means for actuating said tree-running multivibrator; a bistable, pulse actuated multivibrator, having a pulse output; second selectively operable control means for conditioning said bi-stable multivibrator for operation and for actuating said free-running multivibrator; means Ifor deriving a trigger .pulse from said free-running multivibrator and applying said trigger pulse to said bi-stable multivibrator; means combining the pulse outputs of both multivibrators to provide a series lof keying control Ipulses in accordance with `the actuation of said iirst and second control means; and

an audible monitor connected with said multivibrators and Aresponsive to the pulse outputs thereof.

10. In a keyer: a Ifree-running multivibrator having a deriving a trigger pulse from said free-running multivibra- .tor of xed time duration and having apredetermined time relationship to the pulse output of said tree-running multivibrator and for applying said trigger pulse to said bi-stable multivibrator; a second selectively operable control means for conditioning said lbi-stable multivibrator for operation upon receipt of a trigger pulse and for actuating said free-running multivibrator; and means for utilizing said pulse outputs of both multivibrators to provide a series of keying control pulses in accordance with the actuation of said tirst and second control means.

ll. In a keyer: ya free-running multivibrator having a pulse output and having two sections, one normally conducting and the other normally non-conducting; a

.control device connected with the normally noncon- -ducting section of said multivibrator and maintaining .it in the nonconducting condition, selectively operable control means connected with said control device for actuating the control device to condition the normally -nonconducting section of said multivibrator for operation; means including a feedback loop coupled between said norm-ally conductive section and said control device for maintaining said control device conducting for a predetermined length of time; land means for deriving keying control pulses from said multivibrator.

l2. In a keyer: a 4free-running multivibrator having a pulse output and having two sections, one normally conducting and the other "norm-ally nonconducting; a control device including 1an electron discharge device having anode, cathode, yand control electrodes, said anode and cathode connected to the said normally nonconducting section of said multivibrator and main-taining it in the nouconducting condition; selectively operable control means connected with said control electrode of said electron discharge device for actuating the control device to condition the norm-ally nonconducting section of said multivibrator for operation; and means for deriving keying pulses from said multivibrator.

13. In a keyer: a free-running multivibrator having a pulse output and having a iirst, normally conducting electron discharge device fand ya second, normally non- Aconducting electon discharge device; a control device including a third normally non-conducting electron discharge device coupled to said second device and maintaining said second device in the normally nonconducting state and including ya selectively operable control means cou-pled to said third electron discharge device for actuating said third electron discharge device to condition said second electron discharge device for operation; and means for deriving keying control pulses from said multivibrator.

14. In a keyer: a iirst switching device having input and output terminals in a normally closed position; a second switching device having input and output terminals in a normally open position; a rst feedback path connected between the input terminals of said second device and the output terminals of said irst device; a second feedback ,path connected between 'the input terminals of said iirst for utilizing the output pulse of said rst switching device.

References Cited in the iile of this patent UNITED STATES PATENTS Beecher Aug. 8, 1950 OTHER REFERENCES Publication: A Simple Electronic Key by I. D. Gallagher; in Radio-Electronics for April 1950; pages 68-71.

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