US1807368A - Method of and apparatus for operating cable telegraph systems - Google Patents

Description

l 2 Zfy'l CHAR/1cm? A May 26, 1931. H. ANGEL E'r AL. 1,807,363

METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS me@ March so. 1929 e sheets-sheet 1 Suvenfors:

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METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS H. ANGIEL ET AL 9 Sheets-Sheet 2 Filed March 30. 1929/4 Gttorneg May 26, 1931. H. ANGEL ET AL 1,807,368

METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed'march 5o. 1929 9 sheets-sheet 3 few eff Af/962 fom es ff'o mrow May 26, 1931.

METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSEIS H. ANGEL ET AL Filed March 30, 1929 9 sheetssheet 4 May 26, 1931. H. ANGEL ET AL 1,807,368

METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed March 30, 1929 9 Sheets-Sheet 5 ,ZV/fag. 6.

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METHOD 0F AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed March 50, 1929/ 9 Sheets-Sheet 6 May 26, 1931. H. ANGEL ET AL 1,807,368

METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed March 30, 1929 9 Sheets-Sheet 7 u :n P gin m Suncntor's g a Hem/wf Angez f/a/fzeo il( Fa/mmm gwm- @frm Gttorncg May 26, 1931. H. ANGEL ET AL y 1,807,368

METHOD OF.AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed March 30. 1929 9 Sheets-Sheet 8 BS Lvj f 722 ,y n ne CABLE' May 26, 1931. H. ANGEL ET AL METHD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPH SYSTEIS Filed March 30, 1929 9 Shee'tS-Sheet 9 if WMV 6 ee ,0m

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.Ulmlwmm Patented May 26, 1931 UNITED STATES PATENT orf-ICE HERBERT ANGEL AND JAMES W. ROBINSON, OF BROOKLYN, NEW YORK, ASSIGNOBS TO THE WESTERN UNION TELEGRAPH COMPANY, OF NEW YORK, N. Y., A CORPORA- TION 0F NEW YORK METHOD OF AND APPARATUS FOR OPERATING CABLE TELEGRAPHI SYSTEMS Application led March 30, 1929.

This invention relates to the operation of printing telegraph systems over ocean cables but it is also applicable to the operation over land lines and radio circuits. The purpose of the invention is to increase the output by reducing the original fundamental frequency of a standard uniform code, such as the fiveunit Baudot code, and transmitting it as a non-uniform or differential code. Our invention also makes it possible to detect errors caused by line failure, 'relay sticking and other causes.

p In order to operate duplexed submarine cables with the least amount of signal distortion, it is desirable to operate them with twocurrent signals and at the lowest possible rate of fundamental frequency. Cables are operated at present with three-current codes and with two-current codes. In the latter case, however, the received signals arrive as three-current signals owing to the fact that the two-currentcodes must be transmitted at a relatively high rate of speed in order to deliver an output equal to that obtained with the three-current code. For thisV reason the single elements or a series of single elements of a two-current code are attenuated to such an extent that they fail to arrive at the distant end and appear on thecable receiving apparatus as zero signals which must be filled in or interpolated into the original reversal elements b complicated rotary devices, vibrating for r devices or Gulstad relayl7 devices. Furthermore, on account of the igh frequency to which these two-current codes are transmitted, the cable balance is more dillicult to procure and to maintain and the zero signalsare subjected to more or less distortion by the unbalanced condition'of the cable.

We have found that the above mentioned defects in transmission can be overcome by changing the construction of the code signals before they enter the cable so that, in one case, the two-current code can be transmitted at a. lower rate of fundamental frequency than its original rate at a given output and also the two-current code can be transmitted at its original rate of fundamental frequency, so that the arrival or received zero and current waves may be repeated directly into the Serial No. 351,379.

standard multiplex receiving apparatus without requiring auxiliary rings or segments on the distributor or tu'ning forks or Gulstad relays for interpolating the zero waves or mpulses into their constituent reversal elements. For this purpose we have invented a telegraph system in which the standard two-current codes now used can be changed between the passing of the tape through the transmitter and the transmission of the signals into the cable by the transmitting relay, whereby the signal impulses can be transmitted into the cable at a lower rate of fundamental frequency than the original frequency of the code as indicated by the perforated transmitting tape and with an output equal to that obtained with the Cable-Morse code. Again, by means of our invention we are able ,to change the construction of a standard code as it enters the cable, so that said code may be transmitted at its original high rate of fundamentalfrequency over high speed cables, the missing attenuated signals which arrive as zeros being repeated directly into the standard multiplex printer receiving apparatus without requiring any of said interpolating devices which have heretofore been required to interpolate the zero signals into their constituent reversal elements.

Another important feature of this invention brought about by changing the construction of the code just as it enters the cable, is the means for automatically detecting any errors caused by electrical and mechanical troubles which are common in telegraph 0peration. With our system, if a signal arrives dierent from the original transmitted signal, the receiving apparatus is thrown out of synchronism, thereby making it apparent to the operator that an error has occurred.

In the following detailed description we shall refer to the accompanying drawings in which- Figure 1 illustrates diagrammatically how the uniform code is changed in construction to a non-uniform code.

Figure 2 shows another modification of the manner of changing the code.

Figure 3 is a diagrammatic illustration of apparatus for transmitting and receiving a 100 two-unit code in accordance with our invention.

Figure 3A illustrates a fragmentary por tion of transmitting tape.

Figure 3B, 3C,A 3D, 3F and 3G illustrate the effects produced by the change in the construction of the code. i

Figure 4 illustrates diagrammatically the manner of changing the standard Baudot uniform code into a non-uniform or differential code for the purposes of our invention.

Figure 5 is a diagrammatic illustration of an arrangement of apparatus for synchronizing the apparatus at the receiving station with the transmitter after an idle period in the cable. v

Figure 6 is a diagrammatic illustration of a brush-type constant speed continuously rotating transmitter for operation in accordance with our invention.

Figure 7 is a diagrammatic illustration of apparatus for permitting the interruption of a printing telegraph and the interjection of a request message, usually referred to as an RQ message which is received upon a separate printer after which the regular message proceeds as before. v

Figure 8 is a diagrammatic illustration showing ,specific examples of the manner of changing or reconstructing the standard uniform two-current code as now used for multiplex operation on ocean cables so that they may be transmittedand recorded exactly as they were transmitted.

Figure 9 is a diagrammatic illustration of a circuit arrangement for converting the signals in the manner illustrated in Fig. 8.

Figure l0 is a diagram of circuits showing a transmitting apparatus using the standard -multiplex tape, perforated with the uniform code and which electrically reconstructs the code by co-action of the transmitter, distributor and relaysl so that the marking or selecting elements of the code are transmitted as reversals and the non-selecting elements are of the same polarity as a preceding element, the reconstructed code being transmitted into the cable or line as a uniform code as distinguished from a non-uniform code disclosed in the preceding figures; and

Figure 1l is a diagrammatic illustration of an arrangement of circuits at the receiving station under the control of the receiving operator'for readily bringing the receiving distributor into synchronism with the transmitter at the distant sending station.

We will rst describe the method of transv mitting the standard code, such as the Baudot spacing of non-selecting elements may be one time unit or less in length. However, a onetime unit signal is never transmitted alone because a spacing element (or elements) are transmitted with the same polarity as the preceding marking or selecting element and hence there will never be less than three units transmitted for a two-unit selecting element code. It will'be clear, therefore, that for a given output in letters per minute, thefundamental frequency of this transformed code is lower than the frequency of the conventional two-current codes because no elements of onetime unit length are transmitted.

A novel feature of this code is that the rate of speed, that is, the number of letters per minute, may be increased without increasing the fundamental rate of transmission frequency. This is accomplished by increasing a selecting element to two, three, four or more time units in length while the non-selecting elements are made of one time unit or less in length. v

It will be obvious, therefore, that if the selecting elements are made to comprise three time units, the perforated tape may be passed through the transmitter at one and a half times as fast as the code in which the selecting elements are two time units in length. Or ifthe selecting elements are four time units in length, the tape may be passed through the transmitter at twice the rate 0f speed as a tape containing two-unit selecting elements,l while the fundamental frequency will be'exactly the same rate in cycles per second as the frequency transmitted by a tape containing selecting elements of two time units. The output in letters per minute, how ever, will be greater.

We give below an approximate comparison of the relative difference in outputs for two, three, four, five and six-unit length selecting elements.

A three-unit selecting element yields 12% more than atwo-unit.

A four-unit selecting element yields 20% more than a two-unit.

A five-unit selecting element yields 25% more than a two-unit.

A six-unit selecting element yields 28.8% more than a two-unit.

The fundamental operating frequency for codes having selecting elements three, four, five and six time units in length is the same as the two-unit selecting element code. This is graphically illustrated in Figure l which shows diagrammatically-(l) the letter A in the usual uniform length five-unit code; (2) the selecting elements each two-units in length, with the second element of reversed polarity, and the non-selecting elements each one unit in length; and then as this transformed code becomes when the speed of the tape is doubled; (3) the length of each selecting unit trebled and fthe transmission speed trebled; (4) the length of the selecting units and the speed of transmission quadrupled; (5) the length of the selecting units and the speed of'transmission increased five times; (6) and the selecting unitsv and speed of transmission increased six times. Figure 2 shows a modification 1n which the selecting elements may be two or more units in length of opposite polarity and the nonselecting elements of one unit length, each of opposite polarity to the preceding select- ,ing element and each non-selecting element of opposite polarity to its preceding non-selecting element. This construction is not so practicable for ocean cable operation .because it increases the fundamental frequency of the code and the result would be a three-current code received'at the end of the cable more orl less distorted by the unbalance caused by the transmissionof the high frequency code. It, however, provides the means for detecting the errors previously referred to.

It therefore becomes possible by means of this invention to operate a long ocean cable with a two-current code having a lower fun'- damental operating frequency than any other known code at a given rate of speed and whereby all of the transmitted signals are. received with equal amplitude at a rate of speed which can be obtained with a threecurrent code or with the existing two-current codes when all of the signal impulses of these codes are received.

Furthermore since itis possible to receive all of the transmitted signals, the well known cab-le relays, such as drum relays,which employ relatively widely separated contacts including a no-mans-land for recording vthe three-current signals may be dispensed withv and a faster or more eiiicient relay having two contacts separated by avery small gap may be employed. This obviously produces signals of clearer definition and allows of overriding fa lgreater amo-unt of duplex unbalance.

vAlso because of the automatic means. for detecting errors caused by mechanicalI and electrical troubles,4 the degree ofv .accuracy will be much greater with this system of printing telegraphy than is obtainable with those now used for ocean cable operation.

Before further describing the operationstated, the code when transmitted to the line is not a uniform five-unit code such as the Baudot code in lwhich each character is five equal units in length, but is a dierential live unit code in which the units are of unequal length. This is done for the purpose of shortening the time length of the Baudot or uniform code, which correspondingly reduces the transmission rate of fundamental-frequency and at the same time provides for the reception of all of the transmitted signals.

This is done to permit the tape to be passed through the transmitter twice as fast as a tape with uniform length elements. When the speed of the tape is thus increased, the 2l 4time units shown in group B occupy only the time of lOl/2 time units, as indicated in group C, a saving of 30% in time over the time required when the tape is prepared with uniform length elements. Although the tape is moved through the transmitter at double the normal speedpermitted for the code of uniform length elements, the selecting elements of the code will all be received at the distant en'd of the cable with the same amplitude and duration as the single unit signals of group A, because each selecting elem`ent in group B is two time units in length.

Figure 3 is a schematic diagram of apparatus embodying our invention for transmitting and receiving the two-unit code. The

transmitting apparatus includes a tape transi contacting'device RC, a synchronizing tuning fork F and relays R. A portion of perforated tape Ta is shown at Fig. 3A, containing one or more characters, the transmission of which will be described. The appara.-

tus at the receiving station includes the synchronizing-tuning fork F1, step-by-step rotating contacting device RC1, printer PR and relays R1.

resents a selecting element of the code and a sents a non-selecting element. As will appear, a hole in the tape will cause the contacting device RC to hold a contact closed for two time units and a corresponding imperforate portion for one time unit. Hence if the tape is rperforated with five holes, as shown at X in Fig. 3A the contacting device will be l 1'20 A hole or perforation in the tape Ta repv stepped around five teeth, each step being held two time units in length. If the tape contains no selecting holes as shownat X1, the step-by-step rotor RC is stepped around five teeth with one time unit length per tooth.

So that as the vtape Ta containing the charac-v second and third for one time unit each, to

l Morse code.

' are similar to those just described in refer- That'v its fourth and fifth for two time units each and so on; This mechanical sequence can be followed by imagining the rotor stepping around with short and long steps something like the sound of the vdots and dashes of the For example the group X in Ta would sound like five dashes of the Morse code shown at 3D. The character A would sound like two dashes and three dots and so on.

The sequence for the character B can be followed in a similar manner.

At the receiving end of the cable or circuit the transmitted signals shown at Fig. 3C are received with the same shape and are passed `mto the' receiving apparatus.

The sequence of events which happen at the receiving end ence to the sending end of the circuit. is to say a selecting signal, which is always a reversal, will cause the step-by-stepA receiving rotor RC1 to be stepped to a tooth for a two time unit length and a non-.selecting signal Vwill cause it to be stepped to a tooth or teeth for one time. unit each. To differentiate the non-selecting part of a received character from'the selecting part, the received signals are locally reshaped before they enter the printer apparatus. They are reshaped so that only the reversals or the selecting lelements are sent into the printer apparatus. So that the character A, as shown at 3F when locally reshaped appears as shown at leo has two selecting units, namely, the irst and secondindicated by the holes in the first and second positions. When a tape passes lthrough the .transmitter T certain tongues of the transmitter will be operated to the selecting or marking bar MB andothers to the non-selecting or spacing bar SB. The

tongues -operated to the marking bar will be the ones Corresp onding to the holes in the perthe non-selecting tongues 253, t2, t5 to the negav tive battery. As already stated aselecting signal operates the step-by-step rotor RC forv two time units and a non-selecting signal for one time unit.

In this case the sending cam rotor RC will step to its first position andA close contacts 01 for two time units, then it will step to its second position and close contacts c2 for two time units, 'following this it will step to its third, fourth and fifth positions and close contacts 03, 04, c5 for one time unit each'. 'The rotor cam shaft RC is moved stepby step] by the magnet 15 which actuates the ratchet wheel 16 by means of the dogs 17 and 18.

The shaft is providedwith a series of cam projections 20 which successively lift the pivoted levers 21 into engagement with the contacts 01, 02-05.

Themeans for bringing about the differentiallstepping of the cam rotor and consequently the differential transmission o'f the code is as follows :-The tuning fork F is vibrated in the well-known manner through a make and break contact 10 which alternately closes and opens the local circuit of the magnet 11. The contacts l2 and 13 of the fork,

control a train of relays R1, R2, R3 which in turn cause the rotor 'cam shaftyRC to be stepped up for two or for one time .unit per tooth.

For instance let it be assumed that when the contacts 14 were closed, they operated the magnet 23 of the transmitter T, which in turn moved the perforated tape in a position so that tongues t1 and t2 connected with the selecting bar MB and'tongues t3, t4 and t5 remained against bar SB.l Further let it be assumed that the tine ft of the fork F -swung outwards to contact 13. In this case negative battery at N flows into circuit L2 to` tongue 25, contact s of relay R2 into conductor 30, through resistance 31 .and the rotor magnet 15 to plus battery. This causes the cam shaftRC to be stepped, we lwill say, to its rst position, thus closing its contacts 01. At the same time the shunt circuit 32 operated relay R1 to its spacing contact s. Now thefork tine 'ft swings inward to contact 12 so that negative battery from Nflows into circuit L1 nthrough tongue and spacing contact s'of relay R1, conductor 35, winding W of relays R2V and R2, conductor36 to the common` cbnnector 40 of the cam rotor contacts, through the closed contacts @l to positive batte 'via the tongue t1 and selecting bar MB- o the transmitter T. yThis circuit causes relay R2 to be operated to its contact m which opens the circuit to the cam rotor magnet 15 and prevents the cam rotor from being iniiuenced upon the next outward stroke of the fork. This same circuit also operates relay R3 to its marking contact m, which in turn, by discharging condenser K, operates relay R, to its contact m, thereby transmitting the first selecting signal impulse of the character A as shown at Fig. 3B. i

As the fork tine ft now swings outward to engage contact 13, current from negative battery N flows into circuit L2 but cannot flow into conductor 30 because the tongue of relay R2 is on its Contact m. The rotor RC therefore will not be energized on this stroke of the fork and will be held for two time units or while the fork is making four half swings.

The circuit, therefore, through L2 is now diverted from conductor 3() to circuit L2 via the tongue and m contact of relay R2 into winding XV, of relay Rl. This circuit causes relay Rl to operate to its marking Contact m, thus preparing a path for restoring the relay R2 to its normal contact s upon the next inward swing of the fork. When the fork tine swings inward to contact 12, current from negative battery N iows through circuit L1, the tongue and contact m of relay R1, and winding W1 of relays R3 and R2 to positve bat-tery. This operates relays R3 and R2 to their normal contacts s. y

The train of relays are now restored to their normal s contacts and upon the next outward swing of the fork tines the cam rotor RC will be stepped to its second position. Hence because the tongue t, of the transmitter T was on the selecting bar MB of the transmitter T, the relay tra-in was energized and caused the cam rotor magnet 15 to be held or unoperate'd for two time units or the equivalent of four half swings of the fork.

Since tongue t2 of the transmitter T is also on the marking or selecting bar MB, the same sequence of events will happen when the fork swings outward and steps the cam rotor RC to its second position, thus closing its contacts c2. (It should be noted that the rotor contacts el open when contacts c2 close and the latter open when contacts c3 close, and so on.) Simultaneously with the operation of the cam rotor magnet 15, current through the shunt circuit 32, energizes the winding WY of relay R1 and restores its tongue or armature to its normal contact s. Now when the fork tine swings inward to Contact 12, current flows through circuit L1, energizing relay R3 and moving its tongue to its marking contact m, which causes. the condenser K to discharge through the winding of line relay R4. The tongue of relay R4 moves to its marking contact s and thereby sends current from the positive pole of the line battery over the line or cable to produce the second selecting signal impulse of the character A, as shown at Fig. 3B. The cam rotor RC is held for two time units, in this case in the same manner as previously described in sending the first selecting impulse of the character A".

Now because the third, fourth and fifth elements of the character A are non-selecting, indicated by the ,absence of holes in tape D, the tongues t3, t4 and t5 of the transmitter T are shownv on the spacing or non-selecting bar SB of the transmitter T. In this case no current will fiow in circuit Ll when the fork makes contact with contact 12 because the two sources of current, namely, battery N connected to the fork and the battery connected to bar SB of the transmitter T are' both of the same polarity and hence nothing will happen to the train of relays.v Therefore because relay R2 will not be operated to its marking contact for the third, fourth and iifth elements of the character A, the rotor magnet 15 will be stepped forward one tooth for one timek unit per tooth, for each outward swing of the fork.

The operation for any other character is brought .about in a similar manner. So for the character A perforated as shown at Fig. 3A, the actual signals transmitted to the line are as shown at Fig, 8B. It will be remembered that thecode may be constructed so that each selecting element may be two or more units in length and each nonselecting element one unit each in length, and that the non-selecting elements are transmitted with the same polarity as the preceding element. lHence in this case, the first selecting element of "character A is transmitted with two units of negative current, the second selecting element with two units of positive current, the third non-selecting element with one unit of positive current, followed by the fourth and fifth non-selecting one unit element-s.

Receiving circuit At the receiving end of the line or cable the transmitted signals arrive as shown at Fig. 3F.

The relays R5 and RG are operated by the cable relay, which operates in the usual manner and hence will not be described.` The remainder of the receiving apparatus functions practically the same as already described in connection with the operation of the transmitting apparatus. The receiving apparatus differs from the sending apparatus in that the relays R7, R8 and the printer PR take the place of the transmitter T of the sending apparatus. Y

The actual reception of the character A as shown at Fig. 3F is as follows The relays R5, RG operate to their marking contacts m for the rst negative selecting impulse of A.

The relay Rgi is for the purpose of vibrating the fork F. As the relay operates to its s and m contacts, it energizes the fork magnet lliwith sudden impulses from the condenser K and causes it to vibrate in synchronism with the fork F at the transmitting end. The relay. R6 and .condenser K2 are for the purpose of locally reshaping the received signals before they are sent into the actual receiving or translating apparatus.

The signals for the character A shown at Fig. 3F are reshaped by means of the condenser K2 so that they appear as indicated at Fig. 3G. The only signals actually set into the translating apparatus are ther selecting elements of the character. These selecting elements cause thereceiving apparatus to function in exactly the same 4manner as the transmitting apparatus was operated by the selecting elements from the transmitter T. In other words a selecting element received on either of the selecting relays R7 or R8 will 'cause the relay train R1, R2, R"3 to step up the receiving rotor RC for two time units per step and a non-selecting element or elements will cause it to be stepped up for one time unit per step.

The actual operation of the receiving circuit for the character A is as follows z-As the tine ft of the fork F swings to contact 13 the cam rotor magnet 15 is actuated by current from negative battery N over a circuit "from contact 13, through conductor 50,

tongue and s contact of relay R2, conductor 52, magnet l5 to positive battery. Simultaneously current through shunt circuit 53 caused relay R 1 to move its tongue to its normal or spacing contact s. In this case as-r sume that the cam rotor shaft RCe was stepped to its first position, thus closing its contacts 01. When the fork F swings to contact 12', the relays R3 and R"2 w'ill operate their tongues to their m contacts, because thev selecting relay R7 is closed by the reception of the first element of the character A The circuit may be traced from negative battery v N', contact 12 of the fork, conductor 56,

i ing magnet tongue and s contact of relay R7, conductor 57 windings W of relays R3 and Rz, conductor 58, tongue and contact m of selecting relay R7, conductor 59,v common connector 60, contacts c1 of the cam rotor RC', first selectp1 of the printer to positive battery.

The rotor c am shaft RC will remain in this position for two time units, or until the receiving relay R6 is reversed by the line signal. During this time the fork makes four half swings, which is the exact equivalent of a two-unit selecting signal.. When the fork swings to contact 13 during this period, the rotor magnet 15 is not energized because its circuit is open `at contact sof relay R2, its tongue being on its contact m. At this instant whenthe fork is on contact 13 the relay R1 is energized through its winding W, via

windings W1 .of relays R3 and Rz. Upon the fourth swing of the fork to contact 13', the rotorl will' be stepped to its second position and held there for two time units, because the next received signal is a selectingl signal which will close the selecting relay R8 and open the selecting relay R7. The relay R1 also operates to its normal contact s at this time. The same sequence of events are repeated as described for the first element of character A and the second selecting magnet p2 of the printer is energized.

Now for the third, fourth and fifth elements of character A, the two selecting relays R7 and R8 are operated to their spacing contacts by the biasing circuit BS, and remain on their spacing contacts s for the zero portion of the character A shown at Fig'. 3G. In this case no current can iiow through windings WW of relays R2, R"3 and these relays -remain on their normal spacing contacts for the zero portion of the character A Under this condition the rotor magnet 15 will be energized' and stepped around one tooth for each outward swing of the fork during the zero portion of the signal, and the contacts c3, 04 and c5 of the rotor will close successively. No current, however, will flow into the printer selecting magnets p3, p4 and p5 because the selecting relays R7 and Rs are on their spacing contacts, which open the circuit leading to these magnets, namely, conductor 59.

The two selecting elements of the character A operated two magnets of the printer, namely, the first and second and the character A was printed when the sixth rotor contact 14 closed the local circuit through the printing magnet pm.

Any other character is transmitted and received in a similar manner.

The relay R3 is employed to repeat into another line the regenerated signals which come from relay R6 and are timed by the fork to lcorrespond exactly with the length of the original selecting and non-selecting elements. As will be understood, the relay R3 will control another transmitting relay in the same manner as the relay R4 is controlled by the relay R3 at the transmitting end.

Automatz'csg/nchrom'sm When no message or intelligence signals are being transmitted over a line or cable, some means must be provided for keeping the sending and receiving apparatus in synchronism durin this interval, or means must be provided at t e receiving end for bringing the apparatus into synchronism when a message is started in case the cable has been idle. This is accomplished in the present invention in either of two methods. The first is accomplished when the tape runs out of the transmitter, and all of the transmitter pins naturally bear against the marking bar. According to our invention, continuous reversals will be transmitted until a new tape is inserted in the transmitter. In other systems special current switching devices and cam devices must be provided to bring aboutthe automatic synchronizing feature. In the present invention the means whereby each selecting impulse is transmitted with reversed polarity to its preceding impulse causes continuous reversals to be transmitted when the tape runs out.

The other method of synchronizing according to the present invention is brought about by providing an 4automatic synchronizing .means at the receivingre'nd of the circuit. For

this purpose a message is started with a repeated character containing one selecting element which, for example, may be the space character in which thel selecting element is y in' thel third position.

At the receiving end this repeated character will operate a selecting device which causes the step-by-step rotor to step around to its third osition, which is the synchron- .izing position for the repeated character.

The message can then follow along and will be received in proper synchronism. ItI is known, -of course, that the stop and start printing systems which use the equivalent of a seven or eight element code can be stopped and started in synchronism, but in the,case of continuoustransmission using a iive'element code it has not been possible heretofore to completely stop the' transmission and then be able to start up immediately with a message which will automatically arrive in synchronism at the distant end.

An arrangement for synchronizing at the receiving end of the line or cable is shown in Fig. 5. The series of repeated characters transmittedas indica-ted in Fig. 5 are received over the line and operate the three,

rela-ys R1, R2 and R3. Relay R1 controls the operation of the magnet 11 to keep the fork F in synchronism with the incoming signal impulses. Relay R2 controls the impulses sent into the printer magnets, and relay R3 controls the stepping of the cam rotor RG. These relays operate momentarily through the condenser K. rThe key KY is for the ypurpose of unlocking the relay R.l whenever the transmission stops. Then the key KY is momentarily depressed into the dotted line position and is immediately released to its upper full line position.

ssume now that the line has been idle and that a message is to be transmitted which is preceded by a series of the repeated cha-racters as shown at the right hand side of Fig. 5. This repeated character represents the space signal in which the third element is a selecting two-unit element. Let it further be assumed that when the transmission previously stopped, the receiving cam rotor was in its fourthposition. The rotor will therefore be ont of step when the transmission starts, for instance, with number one signal element. The rotor will be only stepped by the line signals until it is in proper synchronism. The signal impulse indicated at X1. in the first character will operate .relay R3 which will step the rotor via the circuit from positive battery, through the front contact and tongue of relay R3, conductor 67, back Contact and tongue of relay R4, conductor G8, rotor magnet 15, conductor 69, contact and tine of fork F to negative battery. Operation of magnet 15, steps the cam rotor from the fourth to the fifth position. The next signal reversal, indicated atfXQ, charges' the condenser K in the reverse direction and the condenser current operates the relays, thus causing the magnet 15 to step the cam rotor RC from the fifth position to the first position; likewise for the reversal X3 it will be stepped to its second position and for .the reversal X4 to its third position.

As the rotor RG is stepped to its third position during the transmission of the fourth repeated code character, current flows from positive battery through the tongue and front contact of relay R2, conductor 70, contact4 c3 of rotor RC, right-hand winding of relay R., printer magnet 3 to negative battery. Relay R4 is now continuously energized by a locking circuit from positive battery through key KY, conductor 71, tongue and left hand winding of relay R4 to negative battery. The rotor RC will thereafter be stepped in synchronism with the incoming signals by a circuit from positive battery through the front contact and right hand tongue of relay R4, conductor 68, magnet 15, conductor 69, contact and fork F to negative battery N. In this manner, by simply transmitting a given character a few times before starting the message, the receiving apparatus is automatically brought into synchronism with the transmitter at the sending end.

In the previous description of the operation of apparatus for carrying out our invention we have used for purposes of illustration, a code arrangement in which the selecting elements were two time units in length, and the relay train consists of three relays R1, VR2 and R3. The selecting elements may be made longer if desired by merely increasing the number of relays in. the train. For selecting elements equal in length to three time units, a train of four relays may be employed and so on for selecting elements of other lengths such as illustrated in Fig. 1.

We have illustrated in Fig. 11, another circuit arrangement at the receiving end of the cable for readily restoring the receiving apparatus to synchronism with the transmitter during the reception of a message in case the receiving distributor should fall out of step due to line failure or 4for any other reason.

` By introducing a key and relay in the distributor stepping circuit, the attendant or operator is enabled to control the stepping 10 operation, Ione step at a time until synchronism and proper phase relation is attained. The-operation of the apparatus at the receiving station illustrated diagrammatically in Fig. 11 will be readily understood. 15

.mains against its stop s so that a circuit is established for actuation of the stepping magnet 15 of the rotary cam distributor RC each time the tine ft of the fork F engages its outer contact 13 and hence the cam shaft of the distributor is moved the distance of one ratchet tooth for each signal impulse received by the cable relay.

If the operator observes that the characters coming from the printer are unintelligible, he depresses the key KY for an instant, thereby closing a circuit from negative battery N,

i fork tine f,'contact 12. winding W of relay R, conductor 96, key KY, condenser K to positive battery. The charging current of condenser K ener izes winding W and causes' the tongue of relay R to move to its contact m. Upon the next outward swing of the fork tine a circuit is closed from negative battery N through fork tine. ft', contact 13, conductor 97. tongue, contact fm, and winding W2 of relay R. resistances r1 and r2 to positive battery. The energization of winding W2 holds the relay tongue against its m Contact and the drop of potential across resistance 7'1 charges the condenser K1, .the current through winding W2 and the condenser charging current through winding W1 being in a direction to hold the tongue against contact m. As the fork tine moves from contact 13, condenser K1 discharges through vwinding W1 in a direction to return the tongue of relay R to its s contact, thereby restoring the receiving apparatus to normal condition/ The operation .just described caused the stepping magnet 15 to remain unenergized during the receptionv of one signal impulse so that the rotary contact cam shaft RC of the receiving distributor dropped back one impulse with respect to the sending distributor. If this was suiiicient to correct the phase relation to bring the receiving apparatus into synchronism, the characters now printed by -the printer will be correct. If, however, the printed characters are still unintelligible, the operator will again depress the key KY and repeat the phase correcting operation. It is obvious that a yfive-unit code willrequire a maximum of four correcting operations which will consume'only a fraction of a min- Normally the tongue of the relay R re-v ute. The circuits for transferring the signalv impulses from the receiving relays to the printer have not been shown in Fig. 11 as they have been fully described in connection with Fig. 3 and other figures.

We have described the invention applied to only one channel arrangement but it will be perfectly evident to engineers that it may be used in a multiple channel system. Several transmitters may be used and the rotor cam shaft of the sending distributor arranged with several groups of cams. Likewise the receiving distributor may be arranged with several groups of cams or segments connected to different printers.

It will be further understood from the description that the transmission is a continuous transmission. That is to say, no line time is required between the last element of the code and the first element for operating the transmitter magnet or printer magnet. This continuous transmission is illustrated in U. S. patent to Gr. R. Benjamin #1,447 ,748 and U. S. patent to G. R. Benjamin and H. Angel ,tt-1,57 9,999. In both of these patents overlap circuits are shown for making possible continuous transmission.

It will be further understood that the differential transmission of the uniform twocurrent code referred to, may be accomplished by using a Wheatstone type of transmitter or any type of a constant speed continuously rotating transmitter, such as thec brush type shown in the Figure 7. The perforator in this case would be a differential perforator which is well known to those familiar with the art.

Referring to Fig. 6, a selecting signal element in the longitudinally perforated tape consists of a perforation followed by a unit blank portion, so as to make the time length equal to two units, while a non-selecting signal element consists of a single blank portion. The perforations in the tape cause the current applied to the line to be reversed while a blank portion allows the current to remain unchanged.

When there is no perforation passing under the brush b of the transmitter there is no contact between the brush and drum D. and no current can iiow in the winding of relay RR. The tongue of relay RR rests on its contact s, and since the circuit to the winding of relay TR is broken at contact m of relay RR, the tongue of relay TR will remain on the contact to which it waslast operated. For example, assume that the tongue of relay TR rests on its contact s. Condenser K is charged with positive battery through'contact s and tongue of relay TR, conductor 71, contact sand tongue of relay RR, andcondenser K to ground.

When a perforation appears under brush b of the transmitter, contact is made with the drum D and the tongue of. relay RR is operated to its contact m. The circuit may be traced from positive battery through drum D and brush b of the transmitter, conductor 72, Winding of relay RR to negative battery. The tongue of relay RR causes the condenser K to discharge into the Winding of relay TR, operating the tongue of relay TR to its opposite contact. In this case condenser K discharges through the tongue and contact m of relay RR, winding of relay TR to ground. thus operating the tongue of relay TR to its contact m, and connecting battery of the opposite polarity to the line.

Thus for each perforation in the tape the line battery is reversed and for the absence of a perforation in the tape the line battery remains the same as it was for the preceding signal.

Sir/aching .sg/stem To those familiar with printing telegraph systems it Will be known that in using page printers, it lis undesirable to transmit any other signals than those Which go to make up the message. That is to say should it be necessary to transmit an RQmessage or What is known as a request, asking for a repetition or some other routine request, the page upon which the regular message is being received would be spoiled if the RQ were injected into this message.

lVe have overcome this undesirable feature with our signaling device by using a spare combination of the code which may not be used for other purposes but when transmitted over the line Will, by means of a selecting device at the receiving end` transfer the signals which follow this particular code combination into a separate printing or recording apparatus, conveniently located remote from the regular receiving printer or Where the RQ A`attendant is located.

vWith this kind of a signaling device it becomes practicable to operate printing telegraph circuits With page printers Without spoiling the copy When RQ signals are transmitted. It Will be further understood by those familiar Wit-h the printing codes that other characters than the Roman characters may be used for the RQ signals. For instance on the upper case of one type bar of the printer there is a period or dot and on another type bar there is a dash, so that Morse characters could be transmitted by using the code combination for a period, for the Morse dot, and the other combination for the Morse dash. i

The arrangement for the RQ signaling circuit is shown in Figure 7. In the perforated tape at the transmitting station the RQ message is preceded and followed by a signal of five non-selecting elements,-as shown at X, Xl in the specimen of tape. At the receiving station, the tongues of relays D, E and F normally rest on their s contacts. Condenser K is charged with positive battery through the contact s and tongue of relay E, conductor 73, contact s and tongue of relay Dand condenser K to ground.

rl'he printers A'and B are equipped with the usual cut-out contacts Z1 and Z2, Which are closed mechanically only when any one or more of the selecting magnets operate. When these contacts close they complete the circuit through the printing magnet of their respective printers.

Since the tongue of polar relay F rests on its s contact, the selecting magnets of printer A, only, will be actuated by the received signa-ls and contacts Zl will close, the circuit of printer B being open at the m contact of relay F.

When contacts c6 of the distributor close, current flows from positive battery through contacts c6, conductor 74 printing magnet 6, contacts Z1, conductor 75, contact and tongue of polar relay F to negative battery. A current also flows :from positive battery through contacts c6, conductor 76, Winding of relay D, and resistance R2 to negative battery, but R2 is a high resistance in comparison with the resistance of the printing magnet 6, so that this current is not of suiiicient strength to cause the tongue of relay D to operate against the tension of spring g.

When the signal of live non-selecting elements is received the selecting magnets are not actuated and contacts Z1 remain open and break the circuit through the printing magnet. Now when contacts es close, all of the current flows from positive battery through contacts ce, conductor 76, Winding of relay D, resista-nce R2 to negative battery, causing the tongue of relay D to move to its m con* tact. Condenser K discharges through the tongue and m contact of relay D', conductor 78 and windings of relays E and F to ground. The tongues of both relays E and F operate to their m contacts. The negative battery return is transferred by the tongue of relay F, from the magnets of printer A to those of printer B.

When the contacts c5 open, the current Will cease to flow in the Winding of relay D and the tension on spring g will cause the tongue iicient value to operate the tongue of relay A D aga-inst the tension of spring g. Printer B will continue to operate, the tongue of relay D will rest on its contact s, and the tongues of relays E and F will rest on their m contacts until a signal of five non-selecting elements is received.

, When this signal is received, at the end of the RQ signal, none of the selecting magnets 11, 12, 13, 14, 15 are operated and contacts Z2 remain open. Then when conta-cts c6 close, all of the current flows from positive battery through contacts c6, conductor 76, the winding of relay D, and resistance R2 to negative battery and the tongue of relay D operates to its m contact. Condenser K discharges through the tongue and m contact of relay D, conductor 78, and windings of relays E and F to ground. The tongues of relays E and F are operated to their s con-v tacts, which is their normal position. The negative battery return is transferred back from the magnets of printer B to those-of printer A by the tongue of relay When contacts c6 open, the circuit through the Winding of relay D is broken at c6 and the tongue of relay D returns to its s contact. Condenser K is charged with positive battery through the s contact and tongue of-relay E, conductor 73, contact s and tongue of relay D, and condenser K to ground. The tongues of relays D, E and F will remain on their s contacts, and printer A will continue to operate in the regular manner.

The circuits-from the distributor unit to the first and second selecting magnets of the printers are provided with the usual overlap relays, as disclosed in the patents above referred to.

Hence on printer A the word telegraph is printed withoutany mutilation between the letters R and A andthe RQ, stop and start again is printed on the printer B.

In the above -description we have shown that by changing the construction of the original two vcurrent code as it enters the v cable we are able to receive all of the transmitted signals when delivering an output equal to that of the cable Morse code.

The invention for changing the-construction of the code as it entersthecable is not limited to the above butin cases where it is desirable to transmit the two-current code into a high speed circuit and in which case the fundamental waves, that is to say, the vsingle reversal waves or a series of reversal waves are at-tenuated and arrive as vzero signals at the end of the cable, the reconstruction of the two-current vcode as it enters the cable causes the signals to arrive at the distant end in sucha manner that the zero signals and current signals may be repeated directly into the standard types of Baudot or multiplex receiving apparatus or Wheatstone receiving apparatus without requiring any interpo- .lating means for filling in the signals which failed to arrive.

A and B represent the uniform two-current .y

code as nowused for multiplex operation on ocean cables. The group A represents the transmitted signals which are transmitted at such a high rate of speed that they arrive as represented at B in which case the fundamental waves, that is, the single unit` waves or a series of single unit waves arrive as zero Waves and have to be filled in by rotating distributors, tuning forks or whatever may be used as illustrated in U. S. Patent #1,57 9,999 for interpolating the zero signals.

The groups C, D and E show the standard code characters at A transposed or reconstructed so that they are transmitted as at C, with each selecting element transmitted with reversed current and the non-selecting elements transmitted with the same polarity as the preceding selecting element.

VThe group D shows the arrival of these sigy nals with the fundamental waves missing as shown at the Zero portions. If ythen the zero portions of this group are considered as the selecting elements which, of course, they are, the local relay which goes back to its spacing contact upon the receipt of these zero signals and goes to its marking contact on the receipt of current signals, will transform the group Dinto group E, which is the exact reproduction of the uniform code for these characters shown at group A.

The circuitl arrangement for transposing the uniform code at the sending end is shown vin Figure 9 which is practically the same as shown in Figure, but more simple. It will be obvious, of course, that the arrangement of the code may be reversed both at the f Figure 9 is the circuit arrangement for showing the adaptation of our invention in relation to Figure 8 in which we convert the signals of a uniform two-current code before it enters the cable and transmit it with a new electrical construction and as a uniform code, and not as a non-uniformfcode as described for the low frequency transmission.

Only enough apparatus is shown to clearly describe this adaptation of the -invention which is to so change the electrical construction of the code'as it enters the cable that the attenuated or missing received signals do not have to be filled in or interpolated into their constituent reversal elements. In all prior systems the attenuated signals which 'arrive as zeros must be filled in -or interpolated into their constituent reversal elements.

The apparatus is controlled by the fork F,

- and the tape is stepped forward in the transmitter T. The five pins of the tape transmitter are shown in the position for the character A, that is with t, and t2 in contact with the selecting bar MB, and with t3, t, and t5 in contact with the non-selecting bar SB.

Assume that the tongue of relay R2 rests on its s` contact. The tonguerof relay R1 also rests on its s contact,due to the bias cirgo cuit BS through winding W1 and condenser K is charged with positive battery via circuit from positive battery through s contact and tongue of relay R2, conduc-tor 81, s contact and tongue of relay R1 land condenser to ground.

The fork tine ft swings outward, completing the circuit to the rotor magnet 15 from negative battery at N via the fork, contact 13, conductor 83, and rotor stepping magnet 15-to positive battery? The rotor contacts c1 close.

On the inward swing of the fork, contact 12 is closed, which completes a circuit from negative battery at N, through the fork, contact 12, conductor 84, winding W of relay R1, conductor 85, Contact c1 of cam rotor, pin t1 of the tape transmitter and selecting bar MB to positive battery. The current in winding W of relay R1 is greater than the biasing i o current in winding W1 and hence the tongue of relay R]L moves over to its m Contact. Condenser K discharges its positive charge into the winding of relay R2 and operates the tongue toits m contact.. This transmits negative battery to the line for the first element of the character A.

As the fork tine ft swings outward again closing the contact 13, the magnet 15 steps the rotor cam shaft RG to open the contact L'a 'c1 'and close contact c2. At this time the biasing current in winding W1 of relay R1 operates its tongue to the 8 contact so that Vcon- `denser K is charged fromnegative battery over a circuit from negative battery through 5 contact m and tongue of relay R2, conductor 81, contact s and tongue of relay R1 and condenser K to ground.

On the next inwardswing of the fork, tine ft makes contact at 12, completing acir- 19 cuit from negatiye battery at N through the fork and contact 12,1' conductor 84, w-indlng W of relay7 R1, conductor 85, contact c2 of cam rotor RC, in `t2 of the tape transmitter, and selecting lar MB to positive battery. 5 The tongueof relay R, is operated to its m f closing the rotor contacts c3, c4 and c5 succontact, and condenser K discharges its negative charge into the winding W of relay R2 in such a direction as to operate the ,tongue of relay R2 to its s contact. This transmits positive battery tothe line for the second element of the character A.7

Up to this point instead of transmitting the first two elements of the character A 'with the same polarity as is done with the standard transmission, shown at A in Figure 8, they are transmitted with opposite. polarity as shown at C in Figure 8. For the third, fourth and fifth elements of the character A, the rotor shaft is stepped' around each time the fork makes contact at 13, thus cessively.

However, each time the fork tine makes contact at 12, the circuit set up from negative battery at N returns through the nonselecting bar SB to negative battery and hence no current iows in winding W of relay R1. The tongue of relay R1 is held on its s contact by the bias circuit BS through winding W1, and the tongue of relay R2 remains' on its s contact for the duration of the third, fourth and fifth elements of the character A, thereby transmitting positive battery to the line for these three elements. S0 that the character A as shown at A, Figure 8 which is the standard form of transmission, has been converted and transmitted as shown at C, Figure 8.

Another modification for converting the uniform code is shown in Figure 10. In this 10o case referring to Figure 10 only the uniform code as perforated on the standard multipleX tape is referred to and is converted through the medium of the transmitter, distributor and relays so that the marking or selecting elements of the code are transmitted asreversals and the non-selecting elements with the same polarity as the preceding element. The reconstructed code, however, is transmitted as a uniform code and `110' not as a non-uniform c ode as described for the low frequency transmission. The operation of the arrangement shown in Fig. 10 is as follows: Any one contact pin t of the tape transmitter T operates a pair of relays R through the contacts of a relay included in the pair of relays operated by the preceding pin of the transmitter. That is to say, pin t2 for instance of the transmitter,

operates the pair of relays R2 through the 12a contacts s or m and tongues of they pair of relays R1, which are operated by contact pin t1 of the transmitter.

These relays are merely for the purpose of converting a series of selectingelements of l a character of one polarity into elements of reversed polarity. For example, the two tongues t1 and t2 being on the selecting bar MB of the transmitter represents the character A. These two elements of like sign 1&0'.

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