US2203609A - Telegraph system with repetition of the signals - Google Patents

Description

, June 4, 1940. A' BAKKER ET AL 2,203,609

H REPETITION DF THE SIGNALS TELEGRAPH SYSTEIM WIT Filed June '7, 1952 4 Sheets-Sheet 1 Il lllllllifJ-r-Illl- L IL v w 2 s, .Q4 QU. sA t VSS RR www n um C n GN mm 0 P n n NM 2. n n n n \m\ EN 2 .t 2 l NE w m WQ lm A h A N s V m 4 2 n n s .ww 1% m ml T m N n Q x Emu S Gamm 0 )l L N 2 MN A o w il il 1J n 1 u N N n n f 2 Mmwzv man. nm m Il R m m h b WQWN@ o M1 l Am ..1 -w|m Y AAI m S m m iii. G I E m AOL T H E 9 v l l, ill` 4 m N1 .J r *IJ D Y N A E www C/uh/m K WML N 4 Sheets-Sheet 25 v A. BAKKER ET AL TELEGRAPH SYSTEM WITH REPETITION CF THE SIGNALS Filed June 7, 1932 June '4, 1940.

ARJEN BAKKER AND HENDRIK C1A. VAN DUUREN BY n Q ATTORNEY June 4, yA. Er AL TELEGRAPH SYSTEM WITH REPETITION OF THE SIGNALS Filed Ju-ne 7, 1932 4 Sheets-.Sheet 4 Patented June 4, 1940 'UNITED STATES PATENT OFFICE TELEGRAPH SYSTEM WITH ItEPETITION F THE SIGNALS Arjen Bakker, The Hague, and Hendrik Cornelis `Antoniel van Duuren, Noordwijkerhout, Netherlands, assignors to Radio Corporationof America, a corporation of Delaware Application June 7, 1932, Serial No. 615,896

In the Netherlands June 11, 1931 16 claims. (01.250-8) y The invention relates to a telegraph system tional marking currentv at the receiver, and by provided with means for effecting repetition or missing current impulses are to be understood reiterati-ion `of the signals. Systems of this type disturbancesfwhich result in the non-appearance are known and their purpose is to render harmof the marking or spacing current (that is to less,` for the greater part, disturbances of any Say, iadingphenomena). 5

' origin but of the same character, for example, If a repeating system be imagined which has disturbances Whichonly cause additional current for itssole object to nullify the effect of addiimpulses. tional marking current impulses, then each Our system is particularly adapted to printing marking current impulse that drops out, due to telegraphtransmission `and reception .via radio fading, will lead to the printing of anY incorrect 10 channels wherethe usual five-unit code is emoharacter. Conversely, inl a repeating system ployed. This code, as is well known, is made which is adapted merely to supply missing'mark-` up `of different.` permutations of elemental siging current impulses, an incorrect character p nals commonly termed marking and spacing will` be printed `by eaclaadditional current iml elements.` There are 32 `possible combinations pulse which `results fromstatic or other disturb- 15 of such elements in a live-unit code. The inances. In this connection,` it is immaterial vention is adapted also `for `use with other sig- Whether .the missing currentimpulse or the addinalingcodes. Thusgenerally speaking, if each tional current impulse occurs inthe first signal character` signal consists `of 11-units then the transmitted or in one of the repetitions. Repev number of possible permutations equals 2n. tition systems areV hence more sensitive to dis- 20 lIn order that signalscomprising ve-unit code turbances Whose influence snot rendered harmelements may` bel accurately received and deless than systemswithout signal repetition, i. e. coded despite mutilation by atmospheric disturbrepetition increases the possibility of the occurances and fading, We have found that a continurence of such disturbances.

ous repetition` of the `signals is essential. Our The systems described hereinbefore cannot 25 apparatus is, therefore, designed to `cause their therefore be used. for communications in Which transmitter to repeat `or reiterate the signals, disturbances of both characters (i. e. both addiwhile the receiver is caused to `store `the signals tional signals and missingsignals) `may occur.` for certain iixed intervals of time. The stored An example of such a communication is a shorteffects of the repeated signals are then combined Wave radio communication. 30

l and caused to control the operation of there- The system according to the invention proceiving printer so as to print the characters of vides the possibility of` rendering harmless to a` a message without repetition. great extent both the influence of the additional It `is within the scope of our invention to procurrent impulses and that ofthe missing current `vide transmitting and receiving apparatus suitimpulses. This is attained by making the inable iorlrepeating the signals either once or sevuence of the missing current impulses on the eral times. The periodicity of repetition being receiver equal to that of the additional current xedpthere is very small likelihood that a disimpulses. turbing impulse would also be repeated with the In order to more clearly set forth the present ce l 4,0 same periodicity. l invention,.it will be described in connection with 40 There are two possible methods of carrying the accompanying drawings in which: out our invention. By one method the receiving Figurel is a diagrammatic showing of a transprinter `is caused to print in .accordance with mitting circuit corresponding to the present insignals `whose marking elements are each revention.

`peated the proper number of times.` By the Fig. `2 isa diagrammaticshowing of a, receiv- 45 other method the receiving printer is caused to ing circuit adapted to` cooperate With the transfunction in response to the reception of signals mitting circuit shown in Fig. 1.

whose spacing `elements are each repeated the Fig. 3 isa diagrammaticshowing of a modified correct number of times. form of transmitting circuit. 3. With the system described in the foregoing, it Fig. `4 isa diagrammatic showing oi a receiving 5o is therefore` possible to render harmless `either circuit adapted to cooperate `with the circuit of additional current rimpulses or missing current Fig. `3, and l impulses, Fig. 5 shows both transmitting` and receiving 4 By additional current impulsesV are to be unfeatures of a signal reiterating system as used yderstood disturbances which produce an addi-` in simplextelegraphy.

receiver 46 by means of" a nrst detector.

Referring to'l'igures 1 and 2 of the accompanying drawings, a method according to the invention will be described by way of example, wherein both types of disturbances exert the same inuence on the receiving reiterating system. l

In Figure l we show a conventional code transmitter'for a printing telegraph system. A code unit repeating system is placed under control of the code transmitter. This repeating system is here shown diagrammatically and will be hereinafter described upon reference to Fig. 3. Output signals from the repeating system are fed to a transmitting relay 9 having an armature 44, a marking contact 49 and a spacing contact 42.

The contact 40 is connected to a tone-frequency generator 4|'which produces a tone of a certain frequency indicative of a marking impulse. Contact 42 is likewise connected to a tone frequency generator 43 which produces a different frequency indicative of a spacing impulse. The armature 44 connects through the primary of a transformer 45 to ground. The secondary of the transformer 45 may be connected to a modulator at which carrier frequency energy is combined with the tone frequencies. Thence the signals are passed through an amplifier of any suitable description to a transmitting radio an- 'tenna Fig. 2 shows apparatus at a receiving station for utilizing such signals as may be transmitted from the system shown inl Fig. 1. The tone frequency currents arederived from ythe radio These currents are then filtered separately through two nlters 41 and 54. Filter 41 is tuned to pass the marking tone frequency vas generated at 4| (Fig. l), while filter 54 passes both marking and spacing tone frequencies. The output from filter f 41 is then fed to a rectifier 48, while the output of the filter `54 is fed to rectifier 55.

Amplifier stages 48 and 55 are respectively connected to the rectifiers 48 and 55.l The connections are such that when signaling energy is passed through either one of the rectifiers it causes its associated amplifier to block. The normal current now through the amplifier 48'@ which occurs inA the absence of a signal energizes the relay winding 49 so as to hold its armature 5| against the contact 52. Likewise in the pres- The operation of the system shown in Fig. 2

may be understoodA from the description immediately following.

When a marking impulse is received the rectifier 4B passes the signal to its associated amplifier 48', causing this `amplifier to block. The normal now of current through the tubes 48' is interrupted and the coil 49 de-energized. The armature 5| is then attracted by the biasing coil 50 and contacts with the negative Contact 53, thereby impressing a marking impulse on the repeating and translating system shown in detail in Fig. 4. Y .Since the Wide band filter 54 also passes the same signal through the rectifier 55, the amplifiers 55 are also caused to block and the relay coil 56 de-energized. The armature 58 is then drawn up against the positive contact 59 by the biasing coil 51. There is, however, no transfer of energy through the armature 58 at this time because the circuit thereof is dead-ended at the the armature 58 so as to pass positive current through the closed contacts 59, 58, 52 and 5I to the signal repeating system of Fig. 4.

An incoming impulse produced by an atmospheric disturbance would normally influence both rectifiers 48 and 55. The result obtained is, therefore, the same as though a marking impulse were received, but such a disturbance being of a casual nature would not be likely to be repeated with the same effective periodicity that is provided for the signal impulses. Therefore, the disturbing impulse itself will be nullied by the operation of the signal repeating and translating system presently to be described. 4

When fading occurs there will be a normal flow of current through both ampliers 48 and 55', thereby causing relay coils 49 and 56 to become simultaneously energized. In this case the signal repeating and translating-system Will be fed with a negative marking impulse, irrespective of whether a marking or a spacing signal was sent. This effect is produced by the passage of current from the negative contact 60 through armature 58, contact 52 and armature 5I.

It will thus be seen that the repeating system receives negative markingl current not onlyin response to the marking signals and to atmospheric disturbances, but also in response to fading phenomena.

The relays 49 and 56 `(Figs. 2 and 4) are each provided with a biasing Winding 50 or 51, through which direct current of adjustable intensity is always flowing, and the purpose of which is tov put the tongues 5| and 58 against the contacts 53 and 59 when the windings 49 and 55 are not energised. Of course this result may be attained by other means, for example springs, or by means of the spacing current.

In Figures l and 2. it has been assumed that the carrier" frequency is modulated alternately with two audio-frequencies. The arrangement of the circuits may also be so designed, however, that under the influence of the transmitting relay 9 high frequency marking and spacing waves are alternately transmitted by the radio` transmitter.

The method described in the foregoing for reversing the influence of the missing current impulses in a repeating system may likewise be employed if, according to the invention, several channels of transmission are formed simultaneously through one radio-transmitter, that is to say, if several messages are transmitted simultaneously through one radio-transmitter. Such transmission is of particular importance in the use of repeating systems on account of the considerably smaller transmission capacity. If the normal transmission, in which one ormore freis obviated by means of a circuit arrangement `in Y which only one frequency is employed at any moment for the simultaneous transmission` of several messages through one radio-transmitter.

With such a construction, only one reversing device is employed for all the channels, While there is also the important advantage that the entire power of the transmitter is available for each channel at any time;

The `circuit arrangement according to the invention will be described by way of example with reference to Figures 3 and 4. Figure 3 represents the transmitter end and Figure 4 the receiverend. At the transmitter end there are twotelegraph systems I and II. For these two telegraph systems working independently of each other there are now four different possibilities, viz:

` 1.` System I gives marking current, system II gives spacing current. a

2. System I gives marking current, system II gives marking current.

3: System I` gives spacing` current, system II gives marking current.

4. System I gives spacing current, system` II gives spacing current. i

'As `shown in Figure 3, each system is provided with two transmitting relays El, (i2` and 63, 64

` respectively connected either in series or in parallel. The marking contact 85 of the relay 6I is connected throughthe output transformer of `an audio-frequency generator 66 to the spacing contact 61 of the relay 63. The spacing contact l q generator 12 to the spacing Contactin; of the y relay 64.

The tongues of the relays 6 I and 62 are connected together and to one terminal of a transformer Tl. This transformer is `connected `to the line leading to the radio-transmitter. The other terminal of the transformer ll is connected to the two tongues of the relays 63 and 64. Since` the relays work in pairs simultaneously, it follows frorrrFigure 3` that there is always one, but never more than one, audiofrequency generator connected to the line leading to the radio-transmitter.

i By tracing the connections through contacts of relays 6l, 62, 83 and 64, it will be seen that the different tone frequencies from the generators 66, 69, 'l2 and l5, may be utilized to represent different combinations of marking and spacing signals simultaneously transmitted via thetwo channels I and II as follows:

Channels Contacts 'lge Gener- I H closed quency ator Mark Space 65 67 m 66 Mark Mark 7l 73 m 75 Space Mark 68 70 m G9 Space Space 74 76 n4 72 the repeaters of both channels.

At the receiver end (Figure 4) are provided two radio-receivers lll5 and |86. Each receiver receives one side band of the incoming modulated carrier wave and feeds the telegraph signals to the corresponding low-frequency part of the circuit. In the drawings, the two low-frequency parts are shown adjacent each other. They are exactly alike and also cooperate in the same `through a transformer I 0l to three low frequency filters 38 and one filter 54. The filters 38 are designed to pass respectively the frequencies 121,`

nz, andina, each corresponding to one of the pos`` sible combinations of signals (except the fourth) sent via channels I and II. Filter 54 passes all four of the signaling frequencies.

Five separate rectiiiers 19a and 19D, 88a., 80D and 8| are preferably provided for receiving the output energy from the respective filters. These rectifiers may be similar to the rectifiers 48 and `55 as shown in Fig. 2 and they are caused to control three blocking ampliers `82, 83 and 84 so as to operate the relays 49a, 48h and 56. Fig. 4 shows the interconnections from the filters through the rectifiers and amplifiers to the relays as follows:

` Derived signal signi" Rectifier` Am phiior Relay frequency channel channel I II nl 79a 82 49a Mark Space n 79h 82 49a Mark i 80a 83 4911 Mark n; 80h 83 49h Space Mark n4 81 84 56 Space Space Since filter 54 passes all four frequencies, the l associated amplifier 84 will normally remain continuously blocked and the relay 5B will remain de-energized. It will become energized only on the occurrence of fading. Hence the relay armature 58 remains normally in contact with the positive (spacing) contact 59so as to feed a positiveimpulse through either or both of the armatures 5| to the repeating systems of channels I and II according to the respective energizations of relays 49a and 49D. The Aspacing signal is,

therefore, normally produced on channel I if both frequencies n1 and u2 are absent, and on channel II if both frequencies n2 and 113 are absent. In the event of a fading condition relays 49a 49h and 5E will become energized simultaneously,

thereby delivering negative marking impulses to v On the occurrence of atmospheric disturbances or static impulses amplifiers 82 and 83 will both become blocked and the relay armatures 5l will be drawn against the negative (marking) contacts 53 by the biasing coils 50, thus delivering marking cur- Of v synchronism is maintained between the automatic devices for the signal repetition at the transmitter and receiver ends of the com munication. v

In reiterating devices employed in combination with means which render the influence of the missing current impulses equal to that of the additional current impulses, yspecial measures are` necessary, however, for maintaining synchronism, because fading generally lasts kconsiderably longer than a disturbance which causes an additional current impulse.

Our transmitting system for automatically repeating the signals is illustrated in Fig. 3.4 The cooperating system for storing the received signals and combining the repetitions thereof is` illustrated in Fig. 4. The synchronization be-` tween the transmitter and receiver isobtained by well known methods as used, say, in multiplex systems having rotary distributors. In Figs. 3 and 4 the invention is illustrated in respect to a diplex printing telegraph system, that is to say, where two communications channels .are provided for simultaneous transmission of signals in one direction. From the description to follow `it will be obvious, however, that simplex transmission and reception would be available by merely utilizing sufficient apparatus to accommodate a single communications channel, as shown in Figs. 1 and 2.

Figure 3 shows the transmitting ring of the distributor of a multiplex telegraph system.

, This ring, in the present example, is sub-divided gized with spacing current.

of which each signal is composed. 'Ihe device works as follows:

If the contact device kii of the signal trans-g mitter is connected to the positive terminal of 1 the battery, as shown in the drawings, and hence' spacing current is sent, then when the brush 6 on its first revolution passes over the corresponding contact segment 7, the corresponding polarized relay 8 in series with the transmitting `relays (il and B2 will be energized The tongue of the relay 8 will thereby be connected to the positive or spacing contact. second revolution, passes over the contact segment I I of the sector 3, the relay I2 will be energized, `whereby its tongue I3 will be connected to the positive or spacing contact or will remain there if it was already in contact with the said contact. In this case, the transmitting relays 6| and 52 will again be energized. On the third revolution of the brush ii, on passing over the contact segment i4, the relay I5 will be energized and its tongue I6 will be connected to its positive or spacing contact. Now the transmitting relays 6| and 62 again receive spacing current. Finally, on the fourth revolution of the brush and on contacting the contact segment |l'|,`the transmission relays 6| and 62 will again be enermitting relays 6| and 62, onthe revolution of the brush 6, will receive in succession all the current impulses which have been established at the individual contact segments of the distributor by the signal transmitter in co-operation with the tongues of the repeating relays.

The receiving system shown in Fig. 4 comprises apparatus for the simultaneous reception of sig- When the brush 6 on the Hence the transp nals on two channels I and II. f In the description to follow, however, it will suflice to explain one unit .of the repeating system since this unit is duplicated for as many channels as wouldy be provided. Fig. 4, therefore, kcomplements vthe showing of Fig. 2 insofar as a simplex system would require a simplex repeating device. for storing the signals before translating thesame. On the other hand, Fig. 4 illustrates a diplex receiving system adapted to cooperate with thl diplex transmitter of Fig. 3. f

There are two receivingrelays |81 and |811 either of which may be supplied with marking or spacing current according to the reception of marking and spacing signals pertaining to each of the channels I and II; Further reference, therefore, to the relays |81 and |311 will be made with respect to either relay alone as relay I3. One of these relays will follow the movements of the transmitting relays Iii and 62 (Fig. 3) which, it was noted, are operated conjointly. The other of the relays IIB operates in accordance with the transmitter relays E3 and 64, also operating conjointly. The purpose of the relays |8 is to supply marking or spacing current tothe repeating relays which are associated with the receiving ring of the distributor. The segments of this distributor are shown in developed diagram. The ring is subdivided intofour sectors, each sector' containing five segments corresponding to the five units of a code signal. Each of the Contact segments of the ring, as in the ordinary multiplex telegraph apparatus, is perferably made somewhat shorter than the corresponding contact segments of the transmitter ring. That is to say, the intervening insulation segments are made somewhat longer.'A The purpose of this is to render the. reception immune to slight deviations from synchronism between the transmitter and receiver. kThe segment |02,

' however, is made to comprehend an arc approximately equal to the sum of the segments |00 and ||l| of the transmitter. Segment |02 is used for synchronizing and controls a correction `device in conventional manner.

In ltheposition shown in the drawings,v the tongue of the receiving relay I8 is connected to the spacing contact As soon as the brush I9, which rotates synchronously with the brush 6 at the 'transmitting station, passes over thereceiver segment 2|) corresponding to thel transmitter segment 1, the repeating relay 2i is energised so that its tongue 22 is connected to the spacing contact (-l-). the brush I9 on contacting the contact segment 23, will energise the relay 24 through the tongue 22, the tongue 25 being thereby connected to its spacing contact As soon as, on the third revolution, the brush I9 comes into contact with the contact segment 26 the relay 27 will be energized and the tongue 28 will be connected to its spacing contact. Finally, on the fourth revolution, when the brush I9 is passing over the contact segment 29, the output relay 36 will be energized and the tongue 3| of this relay Iwill be connected to its spacing contact, whereby a signal element will be supplied to the receiving apparatus. It follows from the foregoing that when, at the receiver end, one of the repeating relays has once had spacing current, the operation of the succeeding repeating relays is completely independent of the receiving relayv I8, since each of the further repeating relays receives current directly from the spacing contact of the' tongue of the preceding repeating relay.

On the next revolutiorn.

If, however, the receiving relay I8 receives marking current, so that its tongue isconnected to the contact marked minus ),.the repeating relays receive marking current one .after the other, but

now through the marking contact of the receiving n relay I8.

The result hereby attained is that atmospheric `disturbances no longerlcause mutilation ofthe received signals.

.i In the foregoing description of Figs.` 3 and 4 the novel features of our invention have been explained whenapplied to one particular embodi- `ment `of our apparatus wherein `two separate the receivingend, one of the receiving filters,`

however, being adapted to pass all four tone frequencies. In a more simpleapplication of the reiterating systems either of two tone frequencies `may be employed as shown in Fig. 1, and the system may be operated as a simplex reiterating system as shown in Fig. 5. Furthermore, the reiterating system may be employed where the carrier wave is simply keyed on and oil and where `the employment of any tonefrequency may be immaterial; Fig. 5, therefore, furnishes a comprehensive picture of the reiterating system as a whole, and the operationboth at thetransmitting end and at the receiving end may be readily understood from the foregoing description which isinore particularly directed to Figs. 3 and 4. Theoperation is still further described in respect to either of the Figs. 4 or 5 as follows:

According to the foregoing description itwill be understood that when `signals are mutilated by atmospheric disturbances the receiving apparatus is `caused to apply negative marking impulses to the repeating apparatus additional to those of the signal itself. Also the dropping out of any of the original marking impulses due to fading is compensated by the introduction of marking impulses at the receiver. In all probability, however, the mutilations of a given signal would not be repeated. Hence, the repeating system is designed to control the receiving printer according to the exact repetitions of marking signals and only when each of these repetitions takes place the full number of times. l

Let it be assumed by way of illustration that each signal is to be repeated four times. Take one signal, for example, which is composed of the following elements: Marking, Spacing, Spacing, Marking, Marking. In the following tabulation the elements will be `designated as follows: M=Marking, S==Spacing, A=Atrnospherics. In the four repetitions of the signal originally transmitted asMSSMM, mutilated signals may appear at the receiver as follows:

First transmission MASMM Second transmission MAAMM Third transmission MASMM Fourth transmission MSAMM paratus will so function that the successive transmissions of signals will be stored as follows:

First transmission MMSMM Second transmission MMMMM Third transmission MMSMM Fourth transmission MSMMM Since in the second and third positions there are no instances of four repetitions of the marking signal, spacing signals will be applied to the printer. The marking signals being repeated four times, will also be applied to the first, fourth and fifth positions. Hence, the correct signal as originally transmitted will be applied to the printer'. f l

An advantage of the described system resides in the fact thata transmitter repeating system and a receiver repeating system can be easily coupled to a common driving member. Moreover, by providing more than one disc several complete repeating systems may be` operated. The distributors may for instance be provided with sixfold distributor discs, so that three channels maybe operated per disc, each with one repetition, or two channels each with two repetitions. When employing fourfold distributor discs two channels may be operated each with one repetition or, as described in connection with Fig. 3, one channel with three repetitions. It Willbe readily understood by 'those skilled in the art that the methods employed as herein described are applicable not only to synchronous multiplex systems, but also to so-called start-stop telegraph systems.` In other words, it is immaterial whether the distributors as shown, for

example, in Figs. 3, 4 and 5 `are caused to rotate continuously or intermittently. The principles involved in the operation of the reiteratingsystern are the same in either case.

Various modifications of our invention will suggest themselves to those skilled in the art in view of the foregoing description.` The invention, therefore, is to `be considered ashaving all the breadth which is permitted by the scope of the claims.

What We claiml is: .n l

`1. A multiple unit code telegraph system comprising means for producing marking signals` of one frequency, means for producing spacing signals` of a. .different frequency, repeating means for controlling the operation of the signal producing means to effect repeated transmission oi the signals, means for receiving said signals, repeating means associated with the receiver for singly printing the received repeatedly transmitted signals, relays associated with the receiver repeating means adapted to supply. marking or spacing current thereto, means operable uponre- `ception of marking signals and upon reception of external disturbances of marking signal frequency for operating the relays to supply marking current tothe receiver repeating`means, means operable upon undisturbed reception of signals of a frequency exclusive of. that of the marking signals foroperating said relays to supply spacing current to the `receiver `repeating `means, and means operable upon the failure to receive signals for setting the armatures of said relaysto a position to supply only marking current to the receiver repeating means.

2. A multiple unit code telegraph system comprising means for producing marking signals of one frequency, means for producing spacing signals of a different frequency, reiterating means for controlling the operation of. the signal pro- .ducing means to eiiectrepeated transmission of the signals, means for receiving saidsignals, reiterating means associated with the receiver for singly printing the received reiterated signals, means associated with the receiver reiterating means for supplying, spacing current thereto upon thejreception of spacing signals and means for supplying only marking current to said receiver reiterating vmeans uponV the reception of marking signals, external disturbances and upon the Vfailure to receive any signals.

' 3. A multiple unit code telegraph system for simultaneously transmitting several messages through different channels by means of a single Wireless transmitter, comprising means for producing a plurality of marking signals of different frequencies'means for producing a plurality of(` spacing signals of still different frequencies, re-

peating vmeans for controlling the operation of the signal producing means to eiect repeated transmission of the signals, means for receiving said signals, repeating meansA associated with the receiver for singly printing the, received repeatedly transmitted signals, relays associated with :the receiver repeating means adapted to supply marking or spacing current'thereto, means operable upon reception of marking signals and upon reception of external disturbances of marking f signal frequency for oper-ating the relays -to supply marking current to thereceiver repeating means, means operable upon undisturbed reception of signals of frequencies exclusive ofthose of the marking signals for operating said relays to supply spacing current to the receiver repeatingfmeans, and means for moving said relays to a position to supply only marking current to the receiver repeating means upon the failure' to receive signals.

4. A multiple unit code telegraph system yfor simultaneously transmitting several messages through different channels by means'of a single wireless transmitter, comprising means for producing a plurality of marking signalsof different frequencies,y means for producing a plurality of `spacing signals of still different frequencies,

transmitting means for controlling the signal frequency producing means of allchannels to )effectV the transmission by the Wireless transmitter at any one moment of signals of one frequency only, repeating means for controlling theroperation of the signal producing .means to effect repeated transmission of the signals, means .for receiving vsaid signals, repeating means associated with the Ving means, and means forfmoving said relays to la-position to supply marking current to the receiver repeating means upon the failure to receive signals. :I v

5. A multiple unit code telegraph system comprising means for producing marking signals or one frequency, means for producing spacing signals of a different frequency, lrepeating means for lcontrolling the operation-of the signal producing means to eiect repeated transmission'of'r the signals, means for receiving saidsignals, repeating means associated with the receiver for singly printing the received repeatedly transmitted signals, relays associated with the receiver repeating means adapted to supply marking or spacing lcurrent thereto,` means operable 'upon reception of marking signals and upon reception of, external disturbances `of marking signal 'frequency for operating the relaysto'supply marking current tothe receiver repeating means, means operable upon undisturbed reception of signals of a frequency exclusive of that-of the marking signals for operating said relays to supply spacing current to the-receiver repeating meansjmeans'for moving said relays to a position to supply marking current to the receiver repeating means upon the failure to receive signals,foutput relays associated With the receiver repeating means, andv a lprinter connected to and rendered operable by the actuation of said output relays.

6. A multiple unit code 'telegraph system according to claim 2, in which the repeating system at the transmitter comprises' a series of contact segments sub-divided into a number of sectors equal to the number rof times each signal is to be transmitted, each sector containing a numberlof contact segments equal to the number of elements of Which each signal is composed, and a movable contact member adapted to pass over the Contact segments and to successively connect them to a signal transmitting relay, whereby of each group of correspondingcontact segments in the different sectors, vconsidered in a direction opposite to the direction of, motion of the contact member, the 'first contact segment is connected through the Winding of arelay to a contact ofthe signal transmitter, each of the following contact segments are connected throughthe Winding of a relay'with the tongue of the relay of the preceding contact segment, and the last contact segment is directly connected to the tongue of the relay of the next to the lastv contact segment, the tongues of the relays of all Contact segments beingk connected to alocal source of current oflone polarity in one position andA to a local source ,of current of Yopposite polarity inthe other position.

7. A multiple unit code telegraph system according to claim 2, in which` the. repeating sys-j vided into a numberof sectors equal tothe number of times each signal is received, eachr sector containing a. number cfcontact segments equal to the number of elements of which each signal is composed, and a movable contact member adapted to pass over the contact segments and to successively connect `them in a current cir.- cuit, whereby ofv each. group of corresponding contact segments in the differentv sectors, considered in a direction yopposite, to the direction of motion of the contact, member, the first con-l tact segment is connectedthrough the winding of a relay to the tongue of the signal receiving relay, and each of the following contact segments are connected through the Winding of a relay to the tongue of the relay of the preceding contact segment, the tonguesof the relays ofall contact segments but'the last being connected tothe tongue of the signal receiving relay in one position andto a localsource' of current in the other position, and the tongue of the last relay being connected to the receiving-apparatus.

8. In artelegraph system, means for transmitting marking and spacing signals, means for receivingthe marking and spacing signals, a signaltranslating device, means controlled by said Sti til

signal receiving-meanslupon the Vreception of cuirentfimpulses due to external disturbances forlsupplying onlymarking currents to `said translatingdevice, means differentially responsive to the reception of spacing signals and to ,fading effects and means operable. uponfading of the transmitted signals for causing the differentially responsive means to supply marking signals to said translating device.` i r 9.In a` telegraph system, means for transmitting marking and spacing signals, means for receiving the marking and spacing signals, a signal translating device, controlling means comprising a relay operable upon reception-of signals of `one `character for supplying equivalent signals to said translating device, complementary meansvcomprising a` second relay operable on the` reception'of signals ofthe other character for supplying corresponding signals to said translating device, one of said relays having means in cooperation therewith operable upon `reception of external impulses to supply signals of one characteronly, thetwo said relays being jointly operable onthe reception of no signals and con-` stituting means `for supplying to said translating devicesignals of thesame character aslthe signals produced upon reception of external impulses; i

10.` In a telegraph system, means for receiving i marking signals of onefreque'ncy and spacing signals of a different? frequency, a signal transl lating device, `al` pairof relays having armatures movable between two contacts `and normally engaging one contact, the armature of the rst relay being connected to said signal translating device and the armature of the second relay being connected to the normally engaged contact of the first relay, the other contact of the first relay and the normally engaged contact of the second relay being connected to a source of marking current, the other contact of the second relay being connected to a source of spacing current, means controlled by said receiving means for operating the first relay in response only to marking signals and interfering signals, and means controlled by said receiving means for operating the second relay in response to spacing, marking and interfering signals.

11. A multiple unit code telegraph system, for simultaneously transmitting several messages through different channels by means of a single wireless transmitter, comprising means for producing a plurality of marking signals of different frequencies, means for producing a plurality of spacing signals of still different frequencies, means for receiving said signals, a signal translating device, relays associated with the translating device adapted to supply marking or spacing current thereto, means operable upon reception of marking signals and upon reception of external disturbances of marking signal frequency for operating the relays to supply marking current to the translating device, means operable upon undisturbed reception of signals of frequencies exclusive of those of the marking signals for operating said relays to supply spacing current to the translating device, and means for moving said relays to a position to supply marking current to the translating device upon the failure to receive signals.

12. In a multiplex telegraph system, the combination of a pair of signal circuits for transmitting independent messages, each consisting of marking and spacing currents, an outgoing channel, means controlled jointly by said signal la circuitsfor supplying to said channelv signaling current of one frequency upon receipt of marking current in the first circuit and spacing current in the secondcircuit, for supplying signaling current of al' second frequency to the channel upon receipt of marking current over both circuits, for supplying signaling current of a third frequency upon receipt of spacing current in the rst circuitandl marking current in| the second circuit, and forsupplying signaling current of a fourth `frequency upon receipt of spacing current in both circuits, means at a distant station for receiving the signal `currents transmitted over said channel, a pair of signal translating circuits, and relays for controlling said translating circuits,v andmeans `responsive to said received signaling currents for controlling said relays so that received currents of the first `frequency im,- press marking current on the rst translating circuit` and spacing current on the second, received currents of the second frequency impress markingcurrents on both translating circuits, receivedcurrents of the third frequency impress spacing current l on the first translating circuit and marking current on the second, and received currents ofthe fourth frequency impress spacing current on both translatingcircuits.

13. `In a multiplex telegraph system, the combination of a pair of signal circuits for transmitting independent messages, each consisting of marking and spacing currents, an outgoing channel,imeans-`controlled jointly by said signal circuits for supplying to said channel signaling `current of one frequency upon receipt of marking current in the first circuit and spacing current in the second circuit, for supplying signaling current of a second frequency to the channel upon receipt,` of marking current over both circuits, for supplying signaling current of a third frequency upon receipt of spacing current in the rst circuit and marking current in the second circuit, and for supplying signaling current of a fourth frequency upon receipt of spacing current in both circuits, means at a distant station for receiving the signal currents transmitted over said channel, a pair of signal translating circuits, a pair of relays having armatures movable between two contacts and normally engaging one contact, the tongue of one of said relays being connected to energize one of said translating circuits and the tongue of the other relay being connected to energize the second translating circuit, a third relay'having an armature movable between two contacts and normally engaging one contact, the armature of the third relay being connected to the normally engaged contacts of the rst and second relays, a source of marking current connected to the normally engaged contact of the third relay and the normally open contacts of the rst and second relays, a source of spacing current connected to the normally open contact of the third relay, means responsive to received signals of the rst and second frequencies singly or jointly for operating the rst relay, means responsive to signaling currents of the second and third frequencies singly or jointly for operating the second relay, and means responsive to signaling currents of any of said four frequencies for operating the third relay.

14. A multiplex telegraph system comprising means for transmitting carrier wave energy, means for impressing upon said energy modulations consisting of frequencies from any one of four different'tone sources, said means including two keying devices for sending marking and spacing signals, means for causing said keying devices when actuated independently to se-lect a single tone frequency which represents a given one of the four possible combinations of simultaneous marking, and/or spacing signals appropriate to the two different communications channels, a receiver having four tone frequency lters of which one is a multi-frequency filter adapted to passall of the signaling tone frequencies and the remaining lters are each adapted to pass a different frequency exclusively, means including signal responsive devices for translating the signals into separate pieces of intelligence as separately keyed at the transmitting end, and means operable under control of the all-frequency filter When it passes no signals for producing a marking signal response in each of the signal responsive devicesy for thediierent communications channels.

15. A telegraph system comprising means at a transmitting station for simultaneous keying of signals appropriate to separate .communications channels, means for reiterating the transmission of each signal with others of said signals intervening, and means at a receiving stationv for translating the reiterated signals into a non-reiterated record of intelligence, the last said means including a device responsive alike to static impulses and to fading conditions for supplying the equivalent of a marking signal to the translating'means.

16. In a telegraph system, means for transmitting marking and spacing signals, said marking and spacing signals being" characterized as'different modulation frequencies impressed upon a carrier frequency, a reiterating system associated with said transmitting means, a receiver adapted to accept said marking and spacingsignals, a filter system selectively responsive to said marking and spacing signals, a pair of relays connected to the output side of said filter system, one of said relays being adapted to respond to signals of marking frequency and the other of said relays being adapted to respond to signals of marking and spacing frequencies, a re' iterating system under control of said relays, means including circuit arrangements interconnesting the contacts of said relays with sources of operating potential for causing said marking signals to be applied to said reterating system both in accordance with the marking signals as transmitted and also in accordance with the reception ofA current impulses due to disturbing influences and further in response to fading conditions and further means including circuit arrangements interconnecting said sources of potential through contacts of said relay system to said reiterating system for causing spacing signals as such to be impressed upon said reiterating system.

ARJ EN BAKKER. v HENDRIK CORNELIS ANTONIE VAN DUUREN.

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