US2183147A - Printing telegraph system - Google Patents

Description

Dec. 12, 1939.

J. B. MOORE ET AL 2,183,147

PRINTING TELEGRAPH SYSTEM Original Filed May '7, 1936 2 SheeiS-Shet 1 INVENTORS JOHN B.- MOORE 6' RICH D E. MATHES ATTORNEY 12, 1939. J MOORE r AL 2,183,147

PRINTING TELEGRAPH SYSTEM Original Filed May 7, 1936 2 Sheets-Sheet 2 INVENTORS JOHN B. MOORE 61 BY RIC R E. MATH ES v l I e,

ATTORNEY Patented Dec. 12, 1939 REISSUED NOV 23 1943 UNITED STATES PRINTING TELEGRAPH SYSTEM we 1 7 17 Claims.

This invention relates to printing telegraph systems and more particularly to a system in which the circuits are subject to static interference and fading conditions.

Printing telegraph apparatus of the more generally used types employ five time elements for coding the signals representing each character to be printed. If these signals are sent over a radio channel or a carrier wave conductor channel they are very much subject to distortion and fading or to mutilation due to the presence 01' static impulses. The code signals, therefore, are liable to be received in an unintelligible form.

Accordingly, it is an object of our invention to provide a new method of code signaling for operation of printing telegraph equipment. It is a further object of our invention to provide the means for so actuating a printer in response to code signals that the correct characters will be 29 printed so long as the signals are not mutilated,

ware but that when a signal is mutilated by static or fading, then a misprint will be prevented.

It is a further object of our invention to provide means for causing the printer to produce an error indication if any character signal becomes unduly distorted or mutilated.

In carrying out our invention we propose to utilize a signaling code which in all cases comprises a uniform number of marking impulses.

Thus, if fewer or more than the correct number of impulses for character selection is received, the master selector device at the receiver will lock out the printing mechanism and thereby prevent the printing of an incorrect character.

In place of the character that would be incorrectly printed we can operate the master selector so as to cause an error indicating type bar to be actuated.

If instead of a five-unit code, we adopt a sevenunit code, taking either three or four of the seven elements at a time as marking pulses, it is possible to obtain thirty-five combinations. By the use of eight time elements, taking four at a time as marking pulses for each combination, there is available a total of seventy combinations. By

taking only three at a time of the eight time elements a total of fifty-six combinations is available.

Our invention will be described in more detail upon. reference to the accompanying drawings, in which Figures 1 and 2 are code charts showing a specific arrangement of marking and spacing time elements suitable for selecting the type bars of a printing telegraph receiver to be actuated.

Application May 7, 1936, Serial No. 78,348 Renewed April 19, 1939 John B. Moore, Riverhead, N. Y., and Richard E. Mathes, Fanwood, N. J assignors to Radio Corporation of America, a corporation of Dela- Fig. 3 shows in perspective certain details of a printer including the master selector bars and a few of the type bar selectors of which one is a selector for an error indicating type bar. Means are also shown for causing the printing mechanism to be locked out and the error indicating type bar to be selected when more or less than the proper number of marking impulses is received; and

Fig. 4 shows a circuit diagram ,of a modification of our invention wherein relays are used in place of step-by-step mechanical apparatus for obtaining the selection of the error indicating type bar when needed.

The Baudot code which is in general use in printing telegraph systems is composed of five permutational time elements in any one of which a-marking or spacing impulse may be transmitted. The character significance of each code signal is determined by the order of sequence of the marking and spacing impulses. In synchronous systems a continuous succession of five-unit code signals is transmitted. In the so-called startstop systems, however, a spacing impulse of fixed duration is utilized to start the printer in operation for selecting each transmitted character to be printed. This spacing impulse is immediately followed by the five-unit code signal and then comes a stop-impulse of indefinite duration to arrest the printer operation until another type key on the keyboard is depressed. In the description to follow it will be understood that the marking and spacing impulses required for character selection are the only ones to be herein considered since the use of additional impulses for operation of a printer by the start-stop method is op-' tional and our invention may be applied to a start-stop system as well as to a synchronous system. There are thirty-two possible combinations of marking and spacing impulses in the fiveunit code arrangement. That code makes maximum use of the circuit time and of the frequency band of a radio communications channel. It is, however, only suitable for use on a circuit which is free from interference. Fading or noise of any kind results in errors in the received copy. Its use on radio circuits is, therefore, relatively limited. Another disadvantage of the five-unit code is that the number of combinations available is not suflicient to print all of the characters desired including letters, figures, punctuation marks, etc. Accordingly, it is the practice to employ a shift mechanism. It can easily happen that static impulses will produce such a code signal as to improperly actuate the shift mechanism at the receiving end when the transmitting machine is still unshifted. The intelligence thus becomes garbled even without the knowledge of the transmitting operator.

The arrangement of marking and spacing impulses as shown in Fig. 1 may be considered from the standpoint that it is suitable either for a seven-unit code or for a portion of an eightunit code. For a seven-unit code the marking and spacing units may be according to the'showing in the first seven columns. For an eight-unit code, the marking and spacing units may be as designated in the eight columns of both Fig. 1 and Fig. 2. In this case it would usually be unnecessary to employ any code signals for shift and unshift as shown in Fig. 1.

It will be noted that in the embodiment of our invention suggested by Figs. 1 and 2 every signal is composed of three marking impulses but these marking impulses are differently arranged with spacing impulses interspersed. It is equally possible that four marking impulses might be used with the remaining portion of each equal length code signal filled in by spacing impulses. It is also equally possible that a signalling code might be adopted in which each signal is composed of four marking and four spacing impulses arranged in different combinations.

Referring now to Fig. 3, we show one embodiment of the receiving apparatus which is suitable for use with code systems having a fixed number of marking units in each character signal. Only those portions of a printing telegraph instrument are shown which relate to the invention.

The master selector includes the conventional code selector bars 5 over which are the type character selector bars 6. During the reception of a code signal any three of the bars 5 may be moved longitudinally to the left so as to bring into alignment certain notches 1 into which a selected cross bar 6 may drop. Only when the proper number of impulses is received during the time taken up by a seven-unit code signal will a type bar selector 6 be permitted to drop into these aligned notches. If more or fewer than three impulses are received, the cross bars 6 will, all of them, be held up by the raised portions of the selector bars 5.

In order to actuate an error indicating type bar, we have provided a counting device to be controlled by the successive actuations of the master selector code bars 5. This counting device includes an escapement wheel 8 mounted on a shaft 9 and permitted to rotate step-bystep when released by the escapement pawl mechanism H) which is pivoted on the rock-shaft II and is caused to oscillate by virtue of a cross bar l2 which engages with raised teeth l3 on the code selector bars 5.

A coiled spring H5 tends to unwind and to rotate the escapement wheel 8 in a counter clockwise direction with each release of one of its teeth from engagement with the escapement pawl Ill. The escapement wheel is prevented from over-riding successive steps by the downward movement of the pawl member l5 into the gaps between the escapement wheel teeth. After each movement of one of the code selector bars 5 the escapement pawls l0 and [5 are returned to their normal position under the tension of the spring I6,

The various parts illustrated in Fig. 3 have been shown in the position which they would occupy after three of the code bars 5 have been actuated for selecting a character to be typed. The escapement wheel 8 has, therefore, rotated three steps from its initial position. It must be understood, however, that these three steps will be taken regardless of which particular code bars 5 are actuated, although in the illustration it is shown that the' first three of these code bars viewed from the front of the device have been actuated. During the rotation of the escapement wheel 8 a cam ll has been rotated through a like are so that a notch [8 in the face of this cam has come into alignment with a rider member I9 mounted on the end of the error indicating selector bar 20. This bar 20 has accordingly been pulled slightly to the left under the traction of the spring 2|. In this position the selector bar 22 corresponding with the error indicating type bar has been restrained from dropping into the guide notches 23 of the code selector bars 5 by virtue of a raised portion 24 adjacent the notch N on the error selecting bar 20. In the code bars 5 the notches 23 are purposely made wider than some of the other notches in these bars in order that the selection of the cross bar 22 may be effected solely in response to the actuation of the error bar 20.

One of the type bar selectors 6a has been shown in the figure as having been lowered into the notches of the code bars 5 where these notches were brought into alignment by the actuation of the first three of these bars and by not actuating the remaining four bars. If one of these four remaining bars had been actuated the escapement wheel would have taken a fourth step. None of the type bars for the printing of intelligence could be actuated in this case but in order to distinguish between the ommission of a character due to a faulty signal and a normal space between words, the error indicating type bar is preferably actuated by the mechanism shown. This actuation can take place either in response to a deficiency or an excess in the number of marking impulses in the code. Assume, for example, that the number of impulses was only two instead of three. In this case the notch I8 in the cam I! would not be in alignment with the rider member l9 and, therefore, the notch N would be exactly under the bar 22 permitting it to be lowered the same as for the selection of any normal printing character.

In order to restore the escapement wheel 8 to its normal position upon completion of any printing operation, we preferably provide a rack and pinion mechanism connected in any suitable manner with the driving mechanism for the printer. The rack bar 25 has been shown in the drawings as in its normal position, ready to make a restoring movement. This movement is longitudinal of the bar and during its stroke to the left it engages with the pinion 22 rotating the same clockwise so as to wind up the spring I4. The pinion 22 is loosely mounted upon the shaft 9 in order that its rotative movements may always be through the same are regardless of the number of steps by which the escapement wheel 8 has been released. If an error has been detected by the reception of four or more impulses when three impulses were normal, then the pinion 22 and the shaft 9 will be rotated through a like are in response to the full stroke of the restoring bar 25. If, however, the escapement wheel 8 has taken fewer than four steps, then while the pinion 22 is rotated through its full are for a restoring operation, it will first bring arcane:

held by the escapement pawl l9, and with the pin 21 resting against a stop 29; Further rotation of the pinion 22 will result in winding up the spiral spring 25 which is stiffer than the spring I4. Uponcompletion of the stroke of the restoring bar 25' a pin 29 which has ridden over the top of the guide member 38 is now depressed into a channel'below this guide member 38 under control of a spring M. This disengages the rack from the pinion 22 and if the spring 25 is under tension it will immediately unwind so as to reposition the pinion22 in n'ormalrelation to the shaft 9; that is, with the two stop pins 32 and 33 pressing one against the other. is mounted on the shaft 9 while thepin 33 is mounted on the pinion 22. The normal engagement of these pins one with the other is maintained under tension of the spring 25.

Upon completing the return stroke of the restoring bar 25, the pin 29 mounted thereon is lifted out of the channel beneath the guide member 38 by virtue of a resilient spring 34. This actuation of the restoring bar 25 will be understood to take place coincidently with the printthat at least four impulses are received during the transmission of a'code ignal, then further operations of the escapement member Ill-l5 will have no effect in releasing the escapement wheel 8 because after four steps the shaft 9 will be arrested from further rotation due to the engagement of its pin 21 with the abutment member 35. The number of teeth in the rack bar 25 is, therefore, limited to what are necessary for rotating the pinion 22, the shaft 9 and the escapement wheel 8 through the arc subtended by four teeth on the escapement wheel.

In certain instances it may be found preferable to employ a counting mechanism which comprises a system of relays as a substitute for the escapement wheel and escapement pawl mechanism shown in Fig. 3. Reference will, therefore, be now made to Fig. 4 in which such an electrical relay system has been shown diagrammatically.

In Figs. 3 and 4 corresponding parts, or parts possessing substantially the same functions, have been given like reference characters. In Fig. 4, for example, the code selector bars 5 have been similarly shown with teeth l3 and with notches 1 for selecting the type selecting cross bars 5. In this case, however, instead of actuating escapem'ent pawls like those, Ill, l5, shown in Fig. 3, the teeth I3 are caused to lift a lever 35 against the-pressure of a spring 31. This action takes place with each successive. movement of the code bars 5. Contact is therebymade between the contact springs 38 so as to momentarilyclose' contact 4| of relay 44, and thence through relay The pin 32 tacts 45, relay 44, contacts 43, relay 49, and

thence to ground. Current flows through this circuit immediately upon the opening of contacts 39, but not before, because during the operation of impulsing, which takes place when the lever 35 rides over a tooth l3, both terminals of the relay 44 are at .the same potential. When relay 44 is energized the contacts 43 cause relay 48 to be locked up. Also the armature 42 of relay 44 is pulled away from the back contact 4| and into engagement with the front contact 49. This prepares'relay 41 for actuation in response to the second impulse. The second impulse may, there- 38, armature 42, contact 45, armature 59, contact 49, relay 41 and thence to ground. Upon the completion of this impulse and the opening of contacts 38, relay 41 locks up 'due to the closing of its contacts 5i and the establishement o a locking circuit from battery 39 through conta ts 45 and relay 52. Upon the pulling up of the armature 50, a circuit is now prepared through the front contact 53 and thence to the armature 54 of relay 55. The third impulse initiated at contacts 38 may then be further traced through back contact 59 of relay 55 and relay 5'! to ground. When relay 55 is actuated in response to the opening of the contacts 38 and the closing of the locking contacts 58 a circuit is established from battery 39 through circuit breaking contacts 45 and the serially connected relays 55 and 51.

Relay 55 has two armatures 54 and 53 both of which are pulled up simultaneously upon the breaking of the impulsing circuit at the contacts '38. Armature 54 upon contacting with the front circuit breaking contacts 45, contacts 6.4 and 58' and thence through a magnet 52 to ground. The function of magnet 52 is to pull up its armature lever 55 to which is connected the error bar 29; In the embodiment of our invention shown in Fig. 4, the error bar 28 is normally held in position for selecting the type bar 22 having an error indicating character thereon. It is .only when a character selection consists of three markingimpulses, no more and no less, that the magnet 52 is actuated. The notch 25 is at that time withdrawn from beneath the bar 22 and prevents its selection. Any one of the type bars 5 may, however, be selected according to the code combination set up in the code bars 5.

Assuming now that a fourth code bar were to be actuated by a static impulse so as to mutilate the code signal, then the impulse pro-- contact 45, armature 58, front contact 53, armature 54, front contact Ii and thence to the relay 51 which is grounded. This relay immediately locks up through the closing of contacts 12 and simultaneously it breaks connection between the contacts 58 which are disposed in the energizing circuit for the magnet 52. Now although all of the relays. 48, 44, 41, 52, 51, 55 and 51 are-locked up, magnet 52 becomes de-energized and permits of the selection of the error indicating type bar 22, the same as when only one or two impulses of the seven-unit code signal had been received.

Simultaneously with the printing of a character the restoring bar 25 is mechanically actuated. The mechanism for doing this has not been shown because it is well within the scope of an ordinary mechanic to provide it. The circuit breaking tion. The relay system is thus prepared for counting the impulses of a succeeding code signal.

We claim:

1. In a printing telegraph system, means responsive to character representing signals all of which signals are of equal length and possess a fixed ratio other than one-to-one between the number of marking and spacing units thereof, means to de-code said signals, and actuating mechanism responsive to the operation of said de-coding means to print a designated character only when a signal is received the marking and spacing units of which are in conformity with said fixed ratio.

2. In a printing telegraph system a plurality of type bar selectors, means including a plurality of decoding elements cooperative with said selectors for making character selections only when a predetermined invariable number of said elements has been caused to respond to the controlling impulses of a code signal, an errorindicating device, and means controlled solely by the integration of said controlling impulses and operative in response to the reception of an excess or deficiency thereof within the time interval allotted to said code signal for actuating said error-indicating device.

3. A printing telegraph apparatus having a plurality of de-coding members each actuable in response to the reception of a marking element of a code signal, and type selecting elements each selectable only upon the actuation of a fixed normal number of said de-coding members other than one-half the total number thereof.

4. In a printing telegraph system, receiving apparatus having a plurality of decoding members each actuable in response to the reception of a marking element of a code signal, type selecting elements each selectable only upon the actuation of a fixed normal number of said decoding members, means including an additional type selecting element for indicating the reception of a mutilated signal and means rendered effective upon receipt of an abnormal number of marking impulses within a fixed time interval allotted to a code signal for then actuating said additional type-selecting element to cause an error-designating character to be printed in place of such character as would correspond to the signal before mutilation thereof.

5. In a telegraph system, code signal receiving apparatus, a receiving printer having character selecting elements, de-coding means operable in response to signals having a permutational arrangement of marking and spacing units, the number of said marking units being in fixed ratio to the spacing units, for determining the sequence of operation of the character selecting elements, and. means operable in sole dependence upon a departure from said fixed ratio for causing said printer to print an error-designating character.

6. A system in accordance with claim 5 and having an impulse counting device mechanically associated with said decoding means and fully controlled thereby for determining instances when mutilated signals are received.

7. A system in accordance with claim 5 and having a relay network operable under the full control of said de-coding means for effecting an error-key selection upon receipt of a mutilated signal.

8. In a device of the class described, printing mechanism operable in response to the receipt of code signals having a uniform number of marking elements and a uniform number of spacing elements, an error-designating key, and means for actuating said key solely in response to the receipt of a signal which lacks conformity with the usual number of marking and spacing elements.

9. A device in accordance with claim 8 and having an escapement mechanism operable stepby-step upon receipt of each marking element of a code signal and means operable by said escapement mechanism to select for actuation the error-designating key when the number of marking impulses received during a time interval allotted to a code signal is either excessive or deficient.

10. A device in accordance with claim 8 and having a relay system operable to count the number of marking elements of a code signal and to make selection of the error key when the number of marking impulses received during the fixed time interval allotted to a code signal is either excessive or deficient.

11. The method of indicating the reception of a mutilated character code signal over a ,telegraph system by signal elements having selecting and non-selecting functions which comprises allotting an invariable time interval to each code signal, employing a code in which each signal possesses an invariable ratio between the elements having selecting and non -selecting functions, counting the selecting elements in each said time interval and causing an indication to be made when there is an excess or deficiency in.said selecting elements.

12. In a telegraph receiving system, recording means responsive to code signals having a uniform number of elements of a certain characteristic plus elements of a different characteristic, an error indicating device, and means responsive to the receipt of a code signal having an abnormal number of elements of said certain characteristic for actuating said error indicating device, said means comprising a first series of impulse-responsive devices and a recond series of devices each responsive upon the cessation of an impulse through an associated one of said impulse-responsive devices, and circuits interconnecting the devices of the two series in such manner that they act as impulse counting relays for preventing the operation of said error indicating device upon reception of a correct code signal.

13. In a printing telegraph system, means responsive to character representing signals of equal length, means to decode such of said signals as possess a normally fixed ratio between the number of marking and spacing units thereof, actuating mechanism responsive to the operation of said decoding means to print a designated code signal contains an excess or deficiency of marking elements with respect to said normally fixed number for preventing the selection of said type selecting elements.

"15. A printing telegraph apparatus having a plurality of de-coding members each actuable in response to the reception of a marking element of a code signal, type selecting elements each selectable by an appropriate combination or a normally fixed number of said de-coding members, an error indicating device, and means effective whenever a received code signal contains an excess or deficiency of marking elements with respect to said normally fixed number for actuating said error indicating device.

16. In a printing telegraph system, a plurality of type bar selectors, means including a plurality of decoding elements cooperative with said selectors for making character selections in response to the reception of any one of a number of different code signals all of which are characterized by an invariable number of controlling units, and means controlled solely by the integration of said controlling units and operative'in response to the reception of an excess or deflciency thereof within the time interval allotted to a single code signal for preventing the operation of the first said means.

17. A telegraph receiving system comprising means responsive to character representing signals of equal length, means to decode such of said signals aspossess a normally fixed ratio between the number of marking and spacing units thereof, apparatus under control of said decoding means for recording the characters represented by said signals. and a utilization device operable in response to the reception of a signal wherein the marking-to-spacing unit ratio is other than the one normally fixed.

JOHN B. MOORE.

RICHARD E. MATHES.

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