US3548407A - Keying apparatus for use with beacon markers or the like - Google Patents

Description

Dec. 15, 1970 A. G. BLACKWELL 7 3,548,407

KEYING APPARATUS FOR USE WITH BEACON MARKERS OR THE! LIKE Filed May 22, 1967 2 Sheets-Sheet 1 Ado h G.B1QQKWH INVENTOR.

1970 A. G. BLACKWELL 3,548,407

K EYING APPARATUS FOR USE WITH BEACON MARKERS OR THE LTKI J Filed May 22, 196'? 2 Sheets-Sheet 2 as I United States Patent 3,548,407 KEYING APPARATUS FOR USE WITH BEACON MARKERS OR THE LIKE Adolph G. Blackwell, Beaumont, Tex., assignor to Southern Avionics Company, a corporation of Texas Filed May 22, 1967, Ser. No. 640,082 Int. Cl. G061: 9/06 US. Cl. 340353 11 Claims ABSTRACT OF THE DISCLOSURE For the identification of transmitting facilities and the like, a solid state keyer, preferably having a symbol board of plug-in construction for each symbol, including up to eight time determining circuits sequentially connected'for forming dots, dashes and spaces as needed, said symbol forming units being adapted to be connected in sequence with recycling means for restarting the first after a time interval.

SUMMARY OF PROBLEM AND INVENTION tended to be left in operation for indefinite periods of I time without maintenance or inspection. The requirements of keying devices have been recognized by the present invention within the apparatus summarized as preferably including a code symbol plug-in unit adapted to form appropriate dots and dashes for the Morse code representation of the symbol, means for sequentially operating a predetermined number of code symbol forming units as a code group and means for recycling operation whereby the code group is formed in a repetitive manner.

One object of the present invention is to provide a new and improved solid state keying unit for use with beacon markers and the like which has no relay contacts, breaker mechanisms or other mechanical apparatus which is prone to failure, requires extensive maintenance and is usually inflexible.

Another object of the present invention is to provide a new and improved means electronically forming an indefinitely expandable code group in order which is recycled from the last symbol to the first without regard to the length of the code group.

A further object of the present invention is to provide a new and improved keyer unit having a symbol forming plug-in unit with four identical portions thereof for forming appropriate dots or dashes, wherein the only differences needed are change of values in RC timing circuit means to form both dots and dashes.

Yet another object of the present invention is to provide a new and improved keyer apparatus gated at a consistent rate determined in all stages of the apparatus.

A noteworthy object of the present invention is to provide a relatively inexpensive and reliable keying means which adds or deletes code symbols to a code group in an easily facilitated manner.

Other objects and advantages of the present invention will become readily apparent from a consideration of the specification and drawings, wherein: I

FIG. 1 is an overall schematic block diagram of the present invention showing sequential arrangement of an indefinite number of code symbols;

FIG. 2 is a detailed wiring schematic of the circuitry for forming a code symbol;

FIG. 3 is a detailed wiring schematic of means for recycling operation of the keying apparatus of the present invention; and

FIGS. 3A and 3B illustrate alternative interface means for use with the present invention.

In the drawings, attention is first directed to FIG. 1 which illustrates the keying means 10 of the present invention. The means 10 incorporates a plurality of code symbol generating means 12 such as those labeled at A, B, C and Z, it being appreciated that an indefinite number of code symbol units 12 can be sequentially connected. The code symbol forming units 12 are identical to one another with the exception that a minimal number of circuit elements are changed to form dots or dashes to comprise Morse code letters. As shown in FIG. 1, the circuit also includes a recycle delay means 14 communicated by way of a conductor 15 to the first of the code symbol forming units 12. After means 12A operates, it triggers operations of the second means 12B, which then triggers operation of the third unit, and so on. On operation of the last unit in the sequential arrangement, a conductor 16 returns a signal to the recycle delay means, which re-starts operation after an appropriate time delay. An output is derived from all of the units 12 in the form of a signal on a conductor 18. It will be appreciated that a sequentially operated, repetitive triggered means is provided by the present invention.

Considering the invention more in detail, it is appropriate to first detail construction of the symbol forming means 12 which is illustrated in FIG. 2. As will be noted in alphabetic telegraphic symbols, four units (dots or dashes) encode all alphabetic characters. Of course, those having fewer than four symbols are generated by the symbol forming means 12 of the present invention without utilizing the entirety of the circuits provided therefor. Alphabetic characters having four units also include four spaces to separate the various dots and dashes. Therefore, the symbol forming means 12 shown in FIG. 2 preferably includes eight similar or even identical timing circuits which cooperatively form the required dots and dashes with spaces therebetween for the entire alphabet, it being appreciated that shorter characters are derived from an abbreviated version of the repetitive circuit means 12 shown in FIG. 2.. Since the circuit means 12 preferably includes eight identical stages in the complete embodiment, several (four) stages have been omitted from the drawings for clarity because they are identical to the circuitry shown in the drawings.

Considering the input to the .circuit means 12, a trigger input signal is providedftom a source to be described on the conductor 15 which communicates with a series capacitor and resistor. A pulse is provided on the conductor 15 to initiate operation of the first portion of the circuit means 12. The first portion of circuitry which is associated with the first symbolic unit, a dot or dash, is encompassed by the bracket 20 to indicate the entirety of means forming the first dot and dash and the delay interval preceding the next dot or dash. The NPN transistor 22 is biased on by a base resistor 23 communicated with the B[ supply 24 which is connected to a collector load resistor 25. The collector load resistor 25 maintains adequate current flow in the transistor 22 with the emitter grounded to a bus 26. An input pulse on the conductor 15 is communicated with a relatively large storage capacitor 27 and a series resistor 28. In the quiescent condition, the transistor is normally turned on since the base is connected with a positive bias source. The continued current flow through the transistor establishes a voltage potential on the plates of the capacitor 27 after an interval of time which maintains the quiescent condition. On occurrence of a negative going pulse to the capacitor 27, the base potential is driven negative with respect to the emitter and the transistor is cut off. The change in base voltage is reflected at the collector where the voltage rises substantially to the supply voltage, and is maintained for an interval of time. The negative charge communicated to the plates of the capacitor 27 is slowly reduced because the bias resistor connected to the supply line 24 restores the capacitor voltage to a positive value which permits the transistor to reconduct. The interval during which the transistor is cut off is determined primarily by the RC time constant of the circuit which includes the capacitor 27 and the series resistors 23 and 28. While the transistor is cut oft for a controlled interval of time, a pulse from the collector is transferred in the manner noted below.

The transistor 22 co-operates with the collector load resistor 25 wherein the output signal derived from the collector is communicated to a coupling capacitor 30. The capacitor 30 is not only a coupling capacitor to the next transistor 33, but is similar to capacitor 27 in functioning as part of an RC timing circuit for operation of the transistor 33. More will be noted concerning this stage hereinafter.

The output from the collector of transistor 22 is also serially communicated through a resistor 37 and then to a conductor 38. As was previously noted, the symbol forming unit 12 preferably forms up to four dots and dashes as needed. The conductor 38 is connected to each of the four stages which forms the dots and dashes for the code symbol. A maximum of four resistors is connected to the conductor 38 for conveying up to four dots or dashes, and of course, fewer resistors 38 are used with symbols having less than four dots and dashes. However, further attention will be devoted to details con cerning the circuit arrangement hereinafter.

Returning again to the output signal from the transistor 22, it was noted above that the capacitor 30 couples signals to the transistor 33. The circuitry associated with the transistor 33 is similar to that of the transistor 22 More particularly, an input series resistor 32 communicates the signals to the base of the transistor which is biased on by a resistor 34. A collector resistor 35 communicates with the supply conductor 24. The emitter of the transistor is grounded. In the quiescent state, the transistor 33 is normally biased on and continues to conduct for an indefinite period of time. When the circuitry associated with the transistor 22 forms a positive going pulse at its collector, the positive going pulse is communicated to the base of the transistor 33. Since the transistor is already on, the positive going pulse has no elfect on operation of the transistor 33 except to increase the degree of saturation. The change in bias is essentially ineffective on output voltage. At the trailing edge of the positive pulse formed at the collector of transistor 22, the signal is negative going which change is coupled through capacitor 30 to the base to drive the transistor 33 to cutotf to thereby form the leading edge of the positive pulse its collector. The pulse from the transistor 33 is similar to the pulse formed by the transistor 22, but is delayed by an interval of time.

It will be appreciated that the connection of eight similar or even identical transistor circuits in sequence in the manner above noted will provide eight sequential pulses with the leading edge of each pulse coinciding with the trailing edge of the pulse formed by the preceding stage. The chain reaction progresses through the circuitry to the last transistor as will be described in detail hereinafter.

In the foregoing, it was noted that the eight consecutive stages form time pulses between dots and dashes. An output (dot or dash) is derived from altern t ve stages including the first, third, fifth and seventh transistors. These alternating stages in the chain form pulses coupled through the resistors 37 to the bus 38. Also, the second, fourth, sixth and eighth transistor circuits form the spaces for intervals between dots and dashes, and, of course, have no output save the serial connection with other stages shown in FIG. 2.

As was previously noted, the symbol forming means 12 forms up to four dots and dashes. As a generalization, dashes are preferably three times as long as dots. In the present embodiment, a dot is preferably on the order of 0.13 second long, while a dash is approximately 0.39 second long. The timed interval between dots and dashes is determined by the time constant of the RC circuit including the capacitor 30 and series resistors 32 and 34. This interval is preferably about 50% longer than the interval of one dot, and is therefore approximately .20 second long. This is preferably consistent for the time constant of all space determining circuits connected between means for forming the dots and dashes of each code symbol, and in the example of FIG. 2, describes the second, fourth, sixth and eighth transistors.

As previously noted, the dots and dashes formed in each of the unit means 12 are output through resistors such as the resistor 37 shown in FIG. 2. Since all the circuitry of FIG. 2 is preferably placed on one circuit board, the bus wire 38 then communicates with an output diode 39 as the output of the circuit board. The diode 39 communicates with the conductor 18 forming a keyed output in co-operation with other circuit means as will be described in greater detail. The dots and dashes are, so to speak, delivered in sequence as a result of their parallel connection to the conductor 38. The conductor 38 is normally maintained at a relatively low potential since it is connected at a number of parallel collectors of transistors/which are conducting and which therefore have low voltage. However, the formation of a positive pulse at any of the collectors is communicated to the conductor 38 and through the diode 39 to the conductor means 18. The passage of several pulses to the conductor 18 forms the sequential units comprising the various symbols formed by the present invention.

Attention is directed to the conductor 16 at the right hand portion of FIG. 2 which carries a trigger output from the circuit means 12A which forms the first symbol in code group. The trigger starts formation of the second symbol in the means 12B. Referring again to FIG. 1 by way of illustration, means 12A and 12B are serially connected. As will be recalled by those familiar with code, the symbol for A is comprised of a dot and dash, while B is a dash and three dots. To relate the circuit means shown in FIG. 2 and its symbol A and the formation of B, the conductor 16 communicates with the input of the circuit means 12B comprising the second means in sequence. Because of the need for the timed interval between adjacent letters in a code representation, the conductor 16 is connected to the fourth transistor in the means 12A while the third transistor stage forms the dash of the letter A. It will be appreciated that a timed interval is needed between letters; the timed interval is provided by the fourth stage to which the conductor 16 1s connected. Of course, the circuit means 12B likewise needs a trigger output to the means 12C forming the symbol C. The connective arrangement is repeated throughout the apparatus to form the code group repeated by the means of the present invention.

Attention is next directed to the circuitry shown in FIG. 3 which illustrates the circuit details of the recycle delay means 14. More particularly, the circuit means shown in FIG. 3 incorporates a circuit which forms a trigger pulse for application over the'conductor 15 to initiate operation of the symbol forming means 12A. Operation of the circuit means 14 shown in FIG. 3 is withheld by the circuit means indicated generally at 48 in FIG. 3 so long as the various means 12A, 12B, and so on are operative to form the dots and dashes comprising the code group. For instance, if the five symbol forming means 12 are connected in sequence, when the operation of the last of the fi=ve units is completed, an interval of time is permitted to pass. During this interval of time, the absence of dots or dashes input to the circuit means 48 terminates its withholding action to permit the recycle delay means 14 to form the pulse on the conductor 15 which restarts the sequential operation of the means 12. As was noted, a positive pulse is formed on the conductor 18 shown in FIG. 2. The positive pulse withholds action of the recycle delay means 14 for the predetermined interval of time between code groups.

For consideration of details of the circuitry shown in FIG. 3, attention is first directed to the input conductor 18 which is connected with an emitter follower transistor 49'. Transistor 49 is input to the base of transistor 50 with both the transistors provided with B+ potential through collector resistors 51 and 52, respectively. The emitter follower arrangement shown in FIG. 3 provides current amplification to avoid heavy loading on the signals on the conductor 18. The pulse input is communicated to the transistor 50 and the amplified output is derived from the collector over the conductor 53. An adequate positive potential is provided to transistors 49 and 50 through a supply conductor 54.

When a positive potential (dot 0r dash) is applied to the base of the transistor 50, the collector voltage of the transistor 50 drops substantially and is communicated over the conductor 53. This drop is communicated through a series resistor 56 to lower the potential at a nodal point 57 connected to the input terminal of a unijunction transistor 58. Low potential at the input of the unijunction transistor 58 withholds its trigger action which is dependent on input potential exceeding a predetermined level. An additional series resistor 59 and parallel diode 60 permit dropping of the input potential at node 57 rapidly in response to reduced voltage caused by each pulse formed in the conductor 18.

Circuit means connected to the unijunction transistor 58 normally accumulate a charge level whereby the transistor 58 forms a pulse. This is provided by a storage capacitor 63 which accumulate the charge. A charging path is provided for the capacitor 63 through series resistors 52, 56 and 59. This presupposes that the transistor 50 is essentially cut off with the collector maintained at a relatively high voltage as is the case when no input pulses are applied to the transistor 50.

A voltage drop on the conductor 53 is communicated through a capacitor 64 and series resistor 65 to cut oif a transistor 66. The transistor 66 is normally biased on by a base resistor 67 which communicates with the B+ voltage. The transistor has a conventional collector resistor 68 communicated with the B+ supply, and a current source for the unijunction transistor 58 includes a resistor 69 connected with the supply.

In operation, the recycle delay means of the present invention forms a pulse of the unijunction transistor 58 when the voltage at the node 57 rises to a predetermined level. When the level is reached, a pulse is communicated to the transistor 66. Since the transistor 66 is normally biased on, and the pulse from the unijunction transistor is negative going, the transistor is cut oil. Since the conductor 15 is connected to the collector of the transistor 66, the collector pulse is on, the conductor 15 is applied to the means 12 comprising the code group forming means. Thereafter, the additional means 12 are operated to form pulses returned to the means 48 which withholds operation of the recycle delay means 14 for the duration of the code group formed by the means 12.

The time delay of the recycle delay means 14 is subject to variation, but is preferably similar to the delay between words of telegraphic operators transmitting at a speed of perhaps eight to ten words per minute. The delay, of course, is subject to some variation, but is determined primarily by the value of the capacitor 63 and the resistance of the serial resistors 52, 56 and 59.

FIG. 3 incorporates an interface means indicated generally at 70 for supplying the output of the present invention to cooperative circuitry (not shown) selected by those needing application of the present invention. A voltage divider including resistors 71 and 72 is supplied with the pulsed signals on the conductor 53. It should be recalled that the conductor 53 communicates from the circuit means 48. The mid-point of the voltage divider is connected with a base of a transistor 74 whereupon the occurrence of a pulse on conductor 53 provides a synchronized signal to the transistor 74 turning it off and on as the case may be. An output conductor 75 is connected with the collector of the transistor 74 to communicate the output signal to connective apparatus for use with the present invention. It will be appreciated that the operation characteristics of the transistor 74 are subject to a wide range of variation dependent on the transistor selection.

Attention is next directed to FIG. 3A of the drawings of the present invention which illustrates an oscillator circuit means indicated generally by the numeral 76. The means 76 is keyed off and on by the signal on the conductor 53, and is adapted to form an output in a conductor 77 which is an audio tone synchro nized with the pulses from the means 12A, 12B and so on. In the main, the means 76 includes an RC phase shift network connected between the base and the collector. The circuitry includes phase shift capacitors and resistors indicated by the numerals 78, 79, 80, and 81. The base signal is provided through a coupling capacitor 82 to series resistor 83. The transistor is biased on by the connection of a base resistor 85 to the collector. The collector load resistor 84 is connected to supply line 54. The pulse output tone is derived from the collector by a coupling capacitor 86.

On provision of a low voltage signal on the conductor 53 (coincident with a pulse) adequate phase shift is provided between the collector signal through the RC phase shifting network to the base to cause positive feedback and oscillations into the circuit. The oscillations are supplied to the conductor 77 for application to a selected output device responsive to the tone formed by the audio oscillator means 76. During the absence of a pulse indicative of information. The conductor 53 becomes a high voltage conductor, and is approximately equal to the voltage found on the conductor 54. This inhibits operation of the RC phase shifting network and prevents positive feedback to terminate oscillations in the oscillator means 76.

Attention is last directed to FIG. 3B of the drawings which also shows means connected with the conductors 53 and 54 as an output means. A reed relay 88 is connected between conductors 53 and 54. On low voltage on the conductor 53, adequate current flows through the reed relay 88 to cause closure of the contacts coincident with the pulses. On the other hand, high voltage in the conductor 53 provides a minimal current flow through the reed relay 88 inadequate to close the relay contacts which are then opened.

While the foregoing has described the details of the present invention specifically, it should be noted that the present invention is subject to a range of variation understood by those skilled in the art. More particular, the device described has been constructed with the view of maintaining a relatively inexpensive circuit which is particularly adapted for use in unmanned beacons and markers for continued operation for an extended period of time. The timing means of the present invention is RC circuitry used to bias off sequentially arranged transistor stages. However, more elaborate means may be adapted such as multivibrators. If the apparatus of the present invention is to be subjected to wide temperature extremes, it may be wise to provide a heater or other temperature stabilizing apparatus to maintain the RC timing circuits at generally constant temperatures whereby operation of the apparatus is neither speeded up or impeded. Of course, thermistors and temperature stabilizing circuit elements may be used.

While the foregoing describes the preferred embodiment of the present invention, it will be appreciated that variations in application may be adopted. For instance, the foregoing illustrates in FIG. 1 the application of four code symbol forming means 12. The sequential arrangement wherein completion of operation of the first unit triggers operation of the second is useful without practical limitation on the number of sequentially connected units. As noted above, this arrangement permits the invention to sequentially and repetitively transmit a code group of any predetermined length. For ease and convenience, each of the means 12 is preferably formed on a separate printed circuit board co-operative with plug-in apparatus to permit the code group to be changed in a relatively easy manner. In a typical installation, sockets may be sequentially wired for perhaps eight or ten symbols in a code group. The ground and voltage connections are provided to all of the sockets as needed, and of course, appropriate wires in the harness are included to accommodate the conductors 16 shown in FIG. 1. The first aliphatic representation is selected for the first socket, and an appropriate printed circuit board is placed therein. The additional printed circuit boards are selected for the additional sockets in order and all are connected in sequence to form the code group. The above arrangement requires no special means to terminate the code group other than to place the printed board representing the last alphabetic symbol in the apparatus and to rely on operation of the recycle delay means to restart the code group. A degree of flexibility heretofore never achieved is provided by the present invention, and by these means, a solid state device is provided which operates over an extended period of time. As was previously noted, each of the plug-in boards in the above example are preferably identical, save for alteration of the resistance of the resistor 23 to provide dots or dashes as needed, and further to omit unneeded stages of the means shown in FIG. 2.

What is claimed is:

1. Code forming apparatus providing a repetitive code group of selected symbols, comprising:

(a) first electronic circuit means for forming the first of the selected symbols;

(b) additional electronic circuit means for forming additional selected symbols;

() connective means extending from said first circuit means to the next of said circuit means for providing thereto a signal starting formation of the symbol from said circuit means;

((1) additional connective means between the several circuit means operative to sequentially start operation of said several units;

(e) there being a common output conductor means provided with signals from said several circuits means; and,

(f) re-cycle circuit means connected to said several circuit means and provided with signals therefrom which suppress operation of said re-cycle circuit means, said re-cycle circuit means forming a re-cycle signal applied to said first circuit means after passage of an interval of time indicative of completion of one cycle of operation of said several circuit means, said recycle signal beginning operation of said first circuit means.

2. The invention of claim 1 wherein said first circuit means includes up to four unit forming means connected for sequentially forming the symbol thereof.

3. The invention of claim 2 wherein said sequentially connected unit forming means form code symbols having less than four units thereto.

4. The invention of claim 1 wherein the code symbols are formed of code units of two time lengths determined by RC timing circuit means which are similar configurations providing the dilferent time lengths on change of component values.

5. The invention of claim 1 wherein said first circuit means is adapted to form dots and dashes associated with Morse code and said first means forms dots having a duration of approximately 0.13 second as determined by RC timing circuit means.

6. The invention of claim 5 wherein the dashes are approximately three times the time duration of the dots.

7. The invention of claim 1 wherein the code symbols are formed of dots and dashes and wherein the time between symbols is approximately the time of one dash.

8. The invention of claim 1 wherein said last named means provides a predetermined interval approximately equal to three times the interval of one dash.

9. The invention of claim 1 wherein said last named means incorporates a unijunction transistor triggered at a rate determined at least partially by an RC circuit means.

10. The invention of claim 9 wherein said unijunction transistor is triggered in relation to the last code unit of the last selected symbols.

11. The invention of claim 1 wherein said first circuit means incorporates:

(a) a normally conducting transistor;

(b) a bias resistor connected to the base of said conducting transistor; and

(c) a capacitor for driving said transistor to cut-off on receiving a pulse from said last named means of claim 1.

References Cited UNITED STATES PATENTS Re. 26,079 9/1966 Cooper 340348 2,771,600 11/1956 Wright et al 340-365 3,021,516 2/1962 Spitz et al. 340353 3,206,743 9/1965 Nielsen 340353 THOMAS A. ROBINSON, Primary Examiner US. Cl. X.R. 17826

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