US2313980A - Printing telegraph systems - Google Patents

Description

March 16, 1943. H. c. A.-VAN DUUREN FRYINTING TELEGRAPB SYSTEMS Filed April 22, 1940 e Sheets-Sheet 1 March 16, 1943- H.'C. A. VAN DUUREN PRINTING TELEGRAPH SY STEMS Filed April 22, 1940 6 Sheets-Sheet 2 wmmw MNN March 16, 1943.

H. c. A. VAN DUUREN PRINTING TELEGRAPH SYSTEMS Filed April 22, 1940 6 Sheets-Sheet 5 M2 v w M!!! w o c o o xxoo XXXO XOOO gm o o o0 rdzlaw March 16,

1943- H. C(A. VAN buuREN I PRINTING TELEGRAPH SYSTEMS I Filed April 22,1940

5 L .L J.

6 Sheets-Sheet 4 TELETYPE me'r Patented Mar. 16, 1943 PRINTING TELEGRAPH SYSTEMS Hendrik C. A. van Duuren, Wassenaar, Netherlands, assignor to Kingdom of The Netherlands, Post Office Administration, The Hague, Netherlands Application April 22, 1940, Serial No. 330,959 In the Netherlands May 4, 1939 21 Claims.

The present invention relates to printing telegraph systems, and is concerned particularly with improvements over the embodiment of printing telegraph system disclosed in my prior application Serial No. 231,479, filed September 24, 1938.

In both applications, the invention is primarily concerned with the troubles arising in these systems from transmission disturbances. Transmission disturbances are particularly present in radio transmission where static and fading frequently mutilate the signals. For this reason, the invention has its primary field of utility in connection with radio transmission, but it will be understood that the invention can also be employed in wire transmission systems over land and cable lines for avoiding difiiculties arising from atmospheric disturbances, induction from adjacent power lines, etc.

The inventions disclosed in the present application and in my prior application provide a system in which the transmitted signal elements are made mutually protective by having them comprise impulses having different electrical values which are so chosen as to produce a constant ratio or constant total electrical value for each transmitted signal. Any deviation from this constant relationship in the signals received at the receiving station is an indication that the signal has been mutilated in transit from one station to the other, calling for a retransmission of that signal. In the preferred embodiment of the invention, the desired constant relationship is obtained by having the signals consist of a given number of positive and negative signal elements, which are transmitted in a combination characteristic of each signal. The mutually protective relation is preferably obtained by causing the proportion of positive and negative elements to be identical in each signal. The occurrence of a parasitic impulse or of fading during the transmission of the signal is detected through the deviation from normal of the proportion of positive and negative elements as determined at the receiver. Upon the reception of such a mutilated signal in the normal course of transmission from station A to station B, receiving station B emits a warning signal which is transmitted to transmitting station A for indicating that such mutilation of a signal has occurred. The warning is effected by the transmission of a number of warning signals not belonging to the group of normal communication signals. The reception of these warning signals at the transmitting station which has been transmitting the normal communication signals, sets into operation certain corrective apparatus at that transmitting station which performs certain corrective functions, such as stopping the keyer, then stepping back the perforated strip in the keyer, and finally restarting the transmitter after a predetermined time. This will be referred to in greater detail later,

If it were attempted to employ the normal five unit code, represented by the Baudot code, in the application of the above idea, a shortage of different combinations would result, because when operating upon the basis of a given proportion or ratio of positive and negative elements there would be several combinations of such five unit code which obviously could not satisfy the requirements relating to this proportion or ratio. It is therefore desirable to employ a code in which the signals are made up of a greater number than five units or elements.

In the preferred embodiments of the inventions disclosed in this application and in my prior application, I employ a code containing eight units or elements. The eight unit code is particularly suitable for the practice of the invention in that when the code is obtained by conversion from the five unit code which is usuallly employed in mechanical telegraphs or land lines, thirty of the thirty-two combinations of the five unit code may be changed into eight unit code signals by simply adding three elements, of which three, two, one, or none are marking units. Only those signals of the five unit code which have five identical units have to be transformed in a different manner.

The preferred embodiment of the invention, as it will be hereinafter described, uses a transmitter which transmits with an eight unit code, in response to received signals which are formed on the basis of a five unit code. The transmitter includes transforming apparatus for transforming the five unit signals into eight unit signals. Similarly, this embodiment utilizes a receiver which receives the eight unit code, and which receiver includes transforming apparatus which retransforms the received eight unit signals into five unit signals for controlling a printer. It will be clear that this transforming apparatus is not essential to the application of the funda mental of my invention. For example, in situations where messages originate directly at the transmitting station, or in situations where messages received over a land wire in a five unit code (such as the Baudot code) are printed at the transmitting station and are then manually recast into a code having a different number of units, there is no necessity of employing such transforming apparatus. However, in view of the fact that in most instances the large bulk of messages will be conveyed over land lines to the radio transmitting station, and in view of the fact that these land lines ar usually equipped to work with a five unit code, it is desirable to provide the aforesaid transforming apparatus to transform the five unit code into the eight unit code at the transmitting station, and to transform the eight unit code back into the five unit code at the receiving station. In this.re.-'

gard, it is to be understood that the description of an eight unit system is not to beinterpreted as a limitation of the invention, since seven units suffice for obtaining the required number of combinations; provided that in each signal four and three equal signal elements should always occur, in which case seven units provide 1-2-3-4-5-6-7 =35 combinations However, the use of eight units is more ad-- vantageous since it appears to simplify the apparatus considerably, as in this case all signals from the five unit code, except those having five equal elements, may be used in the eight unit code by merely'completing these signals to eight unit signals through the addition of three elements.

In the present application I have shown improved apparatus for converting or transforming the five unit signals into eight unit signals, and for reconverting or retransforming the eight unit signals back into five unit signals, such converting and transforming apparatus representing a substantial departure from the embodiments shown inmy prior application above referred to.

Referring now to th correcting apparatus or fault clearing apparatus which is set into operation whenever a transmitted signal is mutilated in its transmission from one station to another, such'apparatus is provided at each station and is arranged to respond to the reception of such a mutilated signal at the receiving station by immediately. bringing about the emission of warning or correcting signals from said receiving station, which signals are. transmitted back to the transmitting station foreifecting the necessary retransmission of the mutilated signal. The reception of the warning signal at'the transmitting station performs thecorrective functions of stopping the keyer, then stepping back the perforated strip in the keyer, and finally restarting the transmitter after. a predetermined time. Inasmuch as the: eight. unit code, when limited only to thezconditionthat eachsignal shall comprise,

four-positive andlfour'negative elements, affords seventy; distinct signal combinations, it will beevident that a largeznumber; of signals will be available for useiaswarning-signals. In the systemzof my invention, a limited number-of signals (i. e., two or three, depending on the transmission time) is repeated whenever. a disturbance occurs.

In the present application I have shown improved correcting apparatus or fault clearing apparatus which is a substantial departure from the embodiment of my prior application.

Summarizing the duties required to be performed at each station, it will be seen from the foregoing that in the transmission of normal communication signals from station A to station B, the transmitter at station A has to first take ill the five unit signals (which usually stand ready at the transmitting station in the form of a perforated paper tape) and convert or transform these signals into balanced eight unit signals, and to then transmit these balanced eight unit signals over the radio path. Furthermore, transmitter A must be capable of transmitting warning or correcting signals to station B for the purpose of warning transmitter B of disturbanceson the path B-A (i. e., whenever signals which have been transmitted back from transmitter B along the path B-A have been mutilated in transmission). With referenc to receiver B, this receivenhas to:convert the eight unit signals arriving on the radio path into five unit signals, which conversion or transformation consists in the simpleadmission of the first five of the elements of, the signal as received to a five unit printer, except in the cases in wh ch the original signal contained five identical elements, or where it was a signal for indicating a disturbance on the pathB-A. The particular requirements to be satisfied by-the transmitter A and receiver B will be better understood by referring to the ac-' companying drawings illustrating one preferred.

In these draw-- embodiment of my invention. ings:

Figure 1 is a circuit diagram of the transmitter. apparatus of each station;

Figure 2 is a circuit diagram of the receiver apparatus of each station;

Figure 3 is a circuit diagram of the correcting or fault clearing apparatus which is associated with the transmitting and receiving apparatus of each station;

Figure 4 is a chart illustrating different combinations available in the eight unit code;

Figure 5 is a timing diagram of a group ofrotary contactors which are driven by the timing shaft of the transmitter;

Figurefi is atiming diagram of a group of rotary contactors which are driven by the timing shaft of the receiver, and is also a timing diagram of the start-stopteletype connected thereto;

Figure 7 is a timing diagram of a group of rotary contactors which are driven by the timing shaft of the correcting apparatus;

Figures 8 to 11 are diagrams or charts representing four cases of disturbed reception, andshowing the timed relation at stations A and B between normal communication signals, mutilated communication signals, normal warning signals, mutilated Warning signals, etc., in these.

four representative cases; and

Figure. 12 .is a schematic diagram showing thesequence ofoperations exercised by the correcting apparatus over the transmitter under different situations of disturbed reception.

The. transmitter of Figure 1 can be regarded as the transmitter of station. A, or as the transmitter. of. station, E; and, similarly, the receiver of Figure 2 can be regarded as thereceiver of station B, or as they receiver ofstation A. It will be. noted that the-correcting apparatus of Figure 3 isv enclosed within a. dotted rectangle CA, and that by placing this rectangle approximately in registration with the fragmentary portions" thereof illustratedin Figures 1 and2, the elec-- trical connections between the correcting apparatus and the transmitter and receiver will be readily apparent.

Referring, now toFigure-i which shows different code. combinations in which the eight unit signal is made up, the transmitter A has to satisfy certain requirements with reference to creating these eight unit signals. For example, the five unit signals which are to be transmitted from transmitter A and which have four equal elements at most, have to be completed by the addition of three elements in such a manner that the resulting eight unit signal contains four positive and four negative elements. For accomplishing this relation, four combinations of the eight possible code combinations of the three added elements are required vlz., for the cases in which one, two, three, or four positive elements were present in the original signal. These four combinations have been shown in Figure 4 at the lines IIV. In this chart, the signal elements denoted by the circles or zeros may, for convenience of reference, be referred to as the spacing elements, and the signal elements denoted by the X marks may be referred to as the marking elements. For example, in the Baudot code the flat tops in the current waves are commonly referred to as marking elements and the valleys are commonly referred to as spacing elements. Correspondingly, in the present disclosure the X marks in Figure 4 may be regarded as the tops or marking elements, and the circles as the valleys or spacing elements, this arbitrary designation, however, being solely for convenience of reference. Referring more particularly to these socalled normal signals indicated in lines IIV, line I illustrates the three signal elements which are added when the original five unit signal contains only one marking element; line 11 the three signal elements which are added when the original signal contains two marking elements; line III the three signal elements which are added when the original signal contains three marking elements; and line IV the three signal elements which are added when the original signal contains four marking elements.

A further requirement of the transmitter is that if the original five unit signal has five equal elements, such signal must be transformed into a balanced eight unit signal comprising equal numbers of positive and. negative elements. There are two instances of such a five unit signal, one in which all five elements are positive (spacing elements U) and the other in which all five elements are negative (marking elements X). These two signals are shown in their transformed state in lines and V in Figure l, signal 0 being a transformation of the original signal having five spacing elements 8, and signal V being a transformation of the original signal having five marking elements X. In contradistinction to my aforementioned copending application, the last three elements of transformed signal V diifer from the last three elements of transformed signal 0 in the present disclosure. The sequence or order of the last three elements in each of these transformed signals difiers, moreover. from each of the other four sequences or groupings I, II, III and IV. As will be hereinafter described, when the receiver receives either one of the two transformed signals 0 or V it perceives that a transformation has taken place.

The four normal signals IIV and the two transformed signals 0 and V exhaust six combinations in all. Hence, of the eight possible three-element combinations, two yet remain, and these are used at the transmitter for the emission of warning signals under control of signaling relays, these signals being shown respectively in lines VI and VII in Figure 4. The receiver thus has the particular requirement to select between (1) normal signals, represented at IIV in Figure 4; (2) transformed signals indicated at 0 and V in which the first five elements have to undergo a retransformation opposed to the transformation experienced by these elements at the transmitter; and (3) warning signals indicated at VI--VII in Figure 4. Lastly, the receiver 13,

should be adapted to control its own. transmitter B for the emission of warning signals to A whenever a disturbance occurs on the path AB. Similarly, in this same regard, the reception of a warning signal at B has to occasion the repetition of the warning signal previously mutilated on the path BA. The converse of this situation is, of course, true when considering the message signals transmitted at B for reception at A.

Referring now to Figure 1, the transmitter comprises the five contact fingers or feeling tongues 2| to 25, inclusive, adapted to coact with the perforated paper tape in which the message is recorded in conventional five unit code, this part of the apparatus being commonly referred to as a keyer. When these contact fingers are in their upper positions, which is the case when the tongues register with perforations, they establish engagement with cooperating upper contacts, and when they are in their lower positions they establish engagement with cooperating lower contacts. Different polarities or potentials are imposed on these contacts to establish the marking or spacing elements of the first five unit portion of the complete eight unit signal. The perforated. paper tape is moved in a forward direction when the forward or start magnet S is energized over conductor M2, and the tape is moved in a rearward direction when the backward or reverse magnet T is energized over conductor I43. A common return conductor from both magnets connects through rotary contact 8 with battery midpoint, this rotary contact effecting the intermittent energization of the selected magnet. The two conductors M2 and I43 have connection with the correcting apparatus CA later described in connection with Figure 3. Throughout the circuit diagrams of Figures 1, 2, and 3, all ground connections will be considered as corresponding to a connection to battery midpoint.

The transmitter also comprises any known or preferred form of transmitting distributor TD comprising the eight contact segments 33 to 40, inclusive. The rotary elements of the distributor connect with the polarized sending relay [5, which in turn connects with any suitable radio transmitter RT which emits the radio wave in which the signal elements are defined in any well known manner. Each station having such radio transmitting apparatus RT also includes as a part of its equipment a suitable radio receiver RE, which will be described later in connection with Figure 2. It will be noted that the five contact fingers 2|, Z2, 23, 24 and 25 of the tape controlled keyer have permanent electrical connection with the first five distributor segments 33, 34, 35, 36, and 31 of the rotary distributor.

The apparatus for adding the three extra signal elements to make up the eight unit code comprises a bank of three supplementing relays 29, 3t, and 3|, it being noted that their respective armatures, 2E, 21, and 25, are connected with the last three segments 38, 39, and 4E! of the transmitting distributor TD. These relays are of the polarized type in which each armature remains in its actuated position after the cessation of the actuating current impulse and untila current impulse of opposite polarity traverses the relay winding for actuating the armature to the other position, these armatures remaining in rest positions (in engagement with their-lower contacts) when negative polarity is applied to the relay windings. When the armatures are in engagement with their lower contact they receive positive polarity, and when they are in engagement with their upper contact they receive negative polarity. The windings of said relays 29, 33, and 3| are connected with the rtary timing contacts 4, 5, and 6, respectively, and also with timing contact 3 and relay 53. The timing contacts to IT, inclusive, are all mounted on a common shaft V for synchronous operation, these contacts only being shown diagrammatically in Figure l but actually having the predetermined timing intervals illustrated in Figure 5. The shaft V rotates with and has the same speed as the rotary member of the transmitting distributor TD, and may be referred to as thetransmitter timing shaft.

Referring now to the manner in which the transformed signals (0 and V of Figure 4) are formed, the apparatus for transforming the signals which have five equal elements into signals havingfive non-equal elements, followed by three additional elements in the characteristic combinations illustrated at 0 or V, comprises a pair of polarized relays 4| and 42; which are adapted to be energized whenever all of the contact fingers or feeling tongues 2|25, inclusive, occupy similar positions. Relay 4| has a bias towards spacing position and relay .2 has a bias towards marking position. The movement of all of said contact fingers 2|25 to similar positions causes these fingers to have potentials of equal polarity. If then, shortly after the fixation of the five unit signals, all of the rotary timing contacts in the group 3 to |3 inclusive are closed, it will be evident that a current of corresponding direction will flow through the polarized relays 4|, 42. This current will be of one polarity if all of the contact fingers 2|25 are in their raised positions, and will be of the opposite polarity if all of said contact fingers are in their lowered positions. Accordingly, this current will energize the relays 4| and 42 and cause either one or the other of the armatures 45 or 45 to move to circuit closing positions, depending upon the polarity of the current to said relays. At the moment at which timing contacts 9|3 are closed, the timing contacts and 2 are open (see Figure 5), so that the spacing and marking contacts associated with the contact fingers 2|25 are connected to the voltage source through resistances- 43 and 44. It will thus be seen that the closure of timing contacts 9-43 does not result in a complete short circuit in the eventthat the contact fingers 2 do not all occupy similar positions. Insuch case, the transforming apparatus 4|, 42, 48, 49, 59, etc., should not function, and to this end the relays 4| and 42 do not carry current at this time, inasmuch as the contacts 9 to I3, as well as contact M, then have the potential of battery mid-point. When the relays 4| and 42 are energized in the operation of transforming a signal, they close holding or lock-up circuits: through their armature contacts 45 and 45, such holding circuits being opened upon the opening of timing contact !4. Therefore it will be seen that until the opening of timing contact l4, the point 41 has a potential corresponding,

in polarity to that of the similarly positioned contact fingers 2| to 25. This voltage, whether of one polarity or the other, now energizes the relay 48, which attracts its armatures 49, 50, 5|, and 52. The nature of the transformation resulting from this energization of the relay 48 will be first described in the situation where a five-space signal is being applied to the contact fingers 2| to 25, in which situation the contact fingers are all on their lower contacts in Figure 1, such corresponding to five successive circles according to the system of notation shown in Figure 4. After the armatures 49 and 53 have been attracted by the energization of the relay winding 48, contact finger 2| remains connected with positive (such being the spacing current or zeros of Figure 4) contact finger 22 is now connected to negative through the new position of armature 50; contact finger 23 remains connected to positive; contact finger 24 is now connected to negative through the new position of armature 50; and contact finger 25 remains connected to positive. Thus, the first five elements of signal 0 of Figure 4-. are formed. With reference to the last three elements of this signal formed through the supplementing relays 29, 30, and 3|, relay 3| is energized on time through timing contact 4. In the process of forming these last three signal elements, the winding of relay 25 is connected with positive polarity through armature 52 which has been moved to its actuated position by the energization of relay 48. The winding of relay 33 is connected with negative through armature 5|, which has also been moved to its actuated position by the energization of relay 48. The Winding of relay 3| is connected to positive if the original signal consisted of five spacing units (0), and is connected to negative polarity if the original signal consisted of five marking units (X). The choice between connecting the winding of relay 3| to positive polarity or to negative polarity is brought about by the action of a bridge circuit and a polarized relay 53 to be described in detail later, this bridge circuit and relay generally having the duty of making the total number of marking units in the final eight unit signal equal to the number of spacing units. When the windings of the three supplementing relays 29, 35, and 3| are thus connected with positive, negative and positive, respectively, as above described, the armatures of said relays are connected with negative, positive and negative, respectively, thereby producing the last three signal elements shown in signal 0 (Figure 4). When the first two supplementing relays 29 and 33 are energized in this same manner, but the winding of the last relay 3| is energized with negative polarity instead of positive, through the aforementioned bridge circuit and relay 53, then the armatures of the three relays produce the last three signal elements shown in signal V (Figure 4). The manner in which the five marking units of the original signal are transformed into the first five signal elements of signal V will be apparent from the description of the preceding transformation in the case of signal 0. It will be noted that in transforming the five marking unit signal into signal V, the contact fingers 2|-25 are all in their upper positions, and hence the shifting of relay armatures 49 and 5!) does not influence the polarity impressed on contact fingers 2|, 23, and 25.

Referring now to the manner in which the normal signals (IIV of Figure 3) are formed, the three control relays 4|, 42, and 48 remain at rest whenever asignal havingfcur identical elements or less than four identical elements is applied to the contact fingers 2 l25. The three signal supplementing relays 29, 30, and 3| return to rest position in engagement with their positive contacts when negative polarity is applied to the windings of these relays over the circuits closed by the rotary contacts 3, 4, 5, and 6. Under such conditions, these supplementing relays thus add spacing elements to the five units of the original signal. In this manner, a signal having four marking units and one spacing unit is converted into the eight unit signal IV of Figure 4. In the case of a signal in which the number of marking units is smaller than four, the polarized relay 53 is energized in a bridge connecting with the resistances 54-61 by way of the test conductor 32. This test conductor will not carry current when the eight unit signal is balanced, because such causes equal amounts of positive and negative currents to flow in the resistances 54-6l. In order to effect the conversion of the difierent normal signals, the five unit signal is tested three times by the action of timing contacts 4, 5, 6, and 1. If it is not balanced the first time, relay 30 is energized by way of rotary contact 5 and armature contact 62 of relay 53, the armature of relay 3!! being thereby moved to its upper position for transmitting a marking unit to the rotary distributor. If at the second test the signal is not yet balanced, the lower supplementing relay 3| is energized, thereby moving its armature into marking position. Finally, if the signal should not yet be balanced at the third test, the upper supplementing relay 29 is energized for moving its armature into marking position. In this manner, the signals III, II, and I of Figure 4 are consecutively formed respectively from original signals having three, two, or one marking units. In the above functioning of the timing contacts 4, 5, 6, and 1, it will be seen that for causing the aforementioned testing operations the rotary contact means I completes the circuit of the relay 53 three times, and during these closed circuit intervals the contacts 5, 4, and 6 successively energize the windings of relays 3D, 3i,.and 29 in that sequence.

Referring now to the manner in which the warning or correcting signals VI and VII of Figure 4 are formed, it will be seen that the signals ii to V, inclusive, utilize all groupings or sequences of the three added elements except those shown in these last two signals VI and VII. These last two signals are used as warning signals, but it is necessary that they be completed by five preceding elements of such polarity that a balanced eight unit signal results. Said warning signals are created by the energization of the relays S1 and S2, signal VI being created by the energization of relay S1, and signal VII being created by the energization of relay S2. The windings of these two relays are energized through conductors I44 and I45, which connect through timing contacts I6 and I! with the corrective apparatus CA, as will be later described in connection with Figure 3. The other ends of the two relay windings are connected through rotary contact I?) with battery midpoint. Upon energization, each relay S1 and S2 is adapted to be locked-up through an armature and a front contact connected with negative polarity, this locked-up relation being maintained until the opening of rotary contact l5.

Referring now to the manner in which the energization of relay S1 creates warning signal VI, it will be seen that the energization of this relay actuates armatures 64, 65, 68 and 69 toward the right or front contacts. This actuated position of armature 68 results in positive polarity being transmitted to the contact fingers 2| 23, and 25, irrespective of whether these fingers are in their upper or lower positions. Similarly, the actuated position of armature 69 results in negative polarity being transmitted to the contact fingers 22 and 24, irrespective of whether these fingers are in their upper or lower positions. Thus, the first five units of warning signal VI are created. Inasmuch as two of these first five elements of signal VI are marking units (X), the supplementing relays 28, 39, and 3| must be operated to add two marking units and one spacing unit. This same proportion of marking to spacing units is also found in the last three elements of signal II, but the last three elements of Warning signal VI are made to distinguish therefrom by interchanging the 6th and 8th elements, as shown in Figure 4. This interchange of the 6th and 8th elements is due to the crossing of the current supply leads to relays 29 and 3|, such being efiected by the shifting of armatures 64 and 65 of warning signal relay S1. The energization of warning signal relay S1 and the resulting emission of warning signal VI from the transmitter of a particular station is an indication to the receiver of the other station that there has been an atmospheric disturbance or fault in the signals emitted by the transmitter of that other station, the warning signal serving to indicate and to bring about the repetition of the mutilated signal. The manner in which the receiver responds to this warning signal and influences its own transmitter will be described later on in connection with the description of the receiver.

Referring now to the formulation of the other warning signal VII (Figure 4), attention should first be called to the fact that in normal operation the first warning signal VI is first emitted from the transmitter, and following this a series of second warning signals VII are then emitted from the transmitter. The energization of warning signal relay S2 actuates armatures 10, 'll, 12, and 13, and thereby formulates the second warning signal. Movement of armature 10 to its right hand position results in positive polarity being place-d on contact fingers 22 and 24, irrespective of whether these fingers are in their upper or lower positions. Movement of armature ll into its right hand position results in negative polarity being placed upon contact fingers 2|, 23, and 25, irrespective of whether these fingers are in their upper or lower positions. The movement of armatures l2 and 73 into their right hand positions eiiects a transposition with respect to the supplementing relays 30 and 3| so that the last three elements of Warning signal VII consists of two spacing elements and a marking element, in that order. When these second warning signals VII are received at a particular station, they exert a control influence on the correcting apparatus CA of that station similar to the influence exerted by the reception of a mutilated signal. This will be described more in detail later in connection with Figure 3.

Referring now to the receiving apparatus illustrated in Figure 2, it will be noted that this apparatus comprises any suitable radio receiver RR which communicates the received signals to a polarized receiving relay Hi. As previously de scribed, each station having such radio receiving apparatus RR also includes as a part of its equipment a suitable radio transmitting apparatus RT, illustrated in Figure 1. Such radio receivers and transmitters are not shown in detail as they may be of any conventional, well known design. The receiving relay I6 energizes the rotary receiving distributor RD with different polarities corresponding to the positions consecutively occupied by the armature of the polarized sending relay '15 (Figure 1). The receiving apparatus also comprises a multiplicity of rotating timing contacts 9| to 168, inclusive, all mounted on a rotating shaft V Said shaft V rotates with and has the same speed as the rotary member of the receiving distributor RD, and the timed relation of these several contacts is illustrated in Figure 6. Figure 6 also arIords a timing diagram of the star-stop teletype connected with the receiver. The receiving distributor RD is shown with sixteen contact segments, the first thirteen of which connect with the windings of the polarized relays l? to 89, inclusive. fhe fourteenth, fifteenth, and sixteenth segments are connected back to the windings of relays 82, 83, and 84. The first eight relays I! to 84, inclusive, are energized in conformity with a received eight unit signal (which, for clarity of description, may be referred to as the first received signal). The last five relays 85 to 89, inclusive, together with the last three relays 82, 83, and 8d of the first group of eight, serve for the reception of the next eight unit signal (which may be referred to as the second or next signal to be received). The relays iL-SQ are of the polarized type in which, after the cessation of current flow through the relay windings, the armatures remain in the positions last assumed. Thirty of the utilized thirty-five combinations of the eight unit code (excluding signals 0, V, VI, and VII of Figure 4) are received in the following manner. Upon the arrival of one of these thirty combinations, the first five elements of the first-mentioned signal are received by the relays I! to SI, and are directed to the printer without any modification. This is effected at suitable moments through timing contacts 52-4 to 98, and occurs for all signals except those in which the three element combination received on the last three relays 82, 83 and 8 of the first group correspond to the last three elements of signals 0, V, VI, and VII. When the signal terminates with the last three elements of the latter combinations, the armatures of relays $2, 83 and 84, and consequently the armatures II'.'I2I of relays Iii, H2, and H3 are caused to occupy such positions that one of the relays I I4, I 95 or I I6 is energized via circuit connections established through armatures II?I2I. Relay I24 is energized on the arrival of signal 0, the resulting actuation of the armature of said relay interrupting the printer start circuit which extends through rotary timing contact IM and through said relay armature, and thence by way of conductor HA to the correcting apparatus CA. Relays I I5 and I I6 are energized upon the arrival of a, combination corresponding to signal V. Relay IIE actuates armature I22 which is efiective to impress negative polarity on all of the lower contacts of the second series of five relays 85--89. Relay I I6 actuates an armature 123, which is likewise eifective to impress negative polarity on all of the lower contacts of the first group of five relays i l-8i. These two transforming relays H5 and H6 are each provided with lock-up armatures which are connected to negative polarities through the rotary timing contact I95.

After the operation and locking of relays H5 asiaoso and I I6, relays 82-84 and their connected tolays HIII3 are again free to be controlled anew by the next signal, which is done when the first five elements of this next signal have been registered on the relays 3589. To this end, it will be noted that the armatures of the relays 85-89 are periodically connected to the printer by way of the rotary timing contacts 99I03.. The rotary timing contacts I05 and I01, which are interposed in the circuits of the transforming relays H5 and H5, are so timed that the first mentioned signal which is registered on relays TI to 8I is adapted to influence relay H5, while the next received signal registered on re-- lays 85 to 89 is adapted to influence the otherrelay H6. Upon the energization of relay II5 and the resulting actuation of armature I22, negative polarity is transmitted to the marking, and spacing contacts of relays 8589 so that the first five elements of the transformed signal registered on these relays undergo a conversion or retransformation opposite to that which has been applied to them at the transmitter. Relay H6 is energized in corresponding manner by the first mentioned signal received on the relays 'II-8I, and the actuation of the armature I23 of this relay also transmits negative polarity in such manner that the marking and spacing contacts of these relays 'II 3I receive negative polarity, whereby the first five elements registered on these relays undergo a conversion or retransformation opposite to that has been ap plied to them at the transmitter.

Upon the reception of warning signal VI negative polarity is applied to conductor I24 through relays IIIH3 and their associated armatures I I'I-I 2 I. Similarly, upon the reception of warning signals VII, negative polarity is impressed upon conductor I25 from these same relays and their associated armatures. The conductors I24, I25 are connected to initiate the operation of the correcting apparatus CA, as will be later described in connection with Figure 3.

I shall now describe that portion of the receiving apparatus which detects the signals which have been mutilated by atmospheric disturbances. or otherwise. The aforementioned first received signal is effective to energize relays IL-84, and the armatures of these relays are then connected in circuit with the testing relay ST by way of timing contacts 92 and 93 through the resistors I25I33. The upper and lower contacts of relays 'I'I-89 are connected either to marking voltage (negative battery) or to ground (battery midpoint), and accordingly, the other extremity of the winding of relay ST is connected to a point I39 which has a potential equal to half the said voltage. If the signal which has arrived contains equal numbers of positive and negative elements, the detecting relay ST will not be energized. In any other instance, i. .e., whenever the signal is a mutilated one, relay ST is momentarily energized. This causes the armature I 45 of said relay to be moved out of engagement with its back contact and into engagement with its front contact, such operation of the armature interrupts the supply of negative polarity through rotary timing contact I08, in consequence of which no current is transmitted through the armatures IIII2I, thereby preventing operation of the relays H4, H5, and H5, and also preventing the energization of conductors I24 and I25 leading to the correcting apparatus. This motion of the testing relay armature I40 also performs the additional function of applying negative polarity to conductor 52 which joins with conductor 125 and extends to the correcting apparatus.

Referring now to the details of this correcting apparatus illustrated in Figure 3, it will be seen that it comprises a multiplicity of rotary timing contacts 201--212 inclusive, which are mounted on the corrector timing shaft 218. This shaft 218 turns at one-sixth /6) of the speed of the transmitter distributor shaft. The aforementioned timing contacts 201-412 on this shaft are opened and closed according to the timing diagram illustrated in Figure '7, in which time progresses from top to bottom. The left hand line in this diagram is divided into six parts, indicating six consecutive revolutions of the transmitter shafts. The corrector shaft 218 normally stands inert, and is only set into motion upon the energization of start magnet 211, Whereupon this shaft is started and stopped in predetermined synchronous relation to the motion of the transmitter distributor shaft, but only rotates at one-sixth the speed of this latter shaft, as above mentioned. The start magnet 21'! is energized whenever negative polarity is impressed upon conductor 124, or upon the joined conductors 125, 52. Thus, whenever the receiving apparatus of Figure 2 receives warning signal VI, the resulting energization of conductor 124 is operative to energize start magnet 21'! and initiate the motion of the corrector shaft 218. Similarly, whenever the receiving app-aratus receives the Warning signals VII, with the resulting energization of conductor 125, or whenever the receiving apparatus receives a signal which is mutilated, with the resulting energization of conductor 52, the start magnet 21'! is energized, or is maintained in an energized condition, for either starting or maintaining the motion of the shaft 218.

The correcting apparatus also comprises a plurality of relays 213, 214, 215 and 216, the armatures or armature contacts of which are all connected with negative polarity through conductor 230 which is controlled by rotary timing contact 29!. The armature 220 of relay 213 receives this negative polarity from conductor 239 during the time that the shaft 218 is rotating. When the relay is deenergized, the armature 22D transmits this negative polarity through its back contact to the timing contacts 204 and 205. It will be noted that these timing contacts connect with conductors M4 and 145 respectively, which serve to energize the warning signal relays S2 and S1, respectively, for causing the emission of warning signals from the transmitter. However, so long as the correcting apparatus is inert, with the shaft 218 in its normal rest position, the timing contacts 264 and 205 are open (see Figure 7), and hence the conductors 144 and 145 are not energized. Upon the energization of selecting relay 2l3, movement of the armature 220 to its attracted position transmits negative polarity through a front contact to the rotary timing contact 2%. In addition, the movement of the armature to this position transmits negative polarity over conductor 231 to the energized terminal of the relay winding 213 for locking up this relay until timing contact 291 interrupts the supply of negative polarity. It will be noted that timing contact 285 is connected with conductor 143 which leads to the reverse or back-stepping magnet T of the transmitter (Figure 1). Hence, during the intervalthat the relay 213 is energized and the contact 206 is in its closed circuit position, negative polarity, is transmitted over conductor 143 for causing backward movement of the perforated tape in the keyer. It will be noted from Figure 7 that the timing contact 2&5 has a span equal to approximately three revolutions of the transmitting distributor, and hence the perforated tape is stepped back three steps in each undisturbed or normal cycling of the correcting apparatus CA. As hereinafter described, the number of backward steps imparted to the perforated tape is reduced in situations of mutual disturbance between the two stations. When timing contact 206 is closed, negative polarity is also transmitted over branch path 232 to the three timing contacts 201, 208 and 208. As shown in Figure '7, the timed relation of these contacts is such as to energize the relay windings 2:4, 215 and 216 in staggered sequence. When relay 214 is energized, its armature 214' receives negative polarity from conductor 230 and the front contact of said armature. This negative polarity locks up the relay 214, and is also transmitted to timing contact 210. In like manner, when relay 215 is energized, the engagement of its armature 215 against the front contact locks up this relay and also transmits negative polarity to timing contact 21 l. Similarly, the energization of relay 2i5 results in the armature 2% of that relay completing a lock-up circuit for the relay and also transmitting negative polarity to timing contact 2%2. As shown in Figure '7, the closing of the contacts 218, 2i 1, and 212 occurs in staggered sequence, each separated from the other by one revolution of the transmitter distributor. iChe other terminals of these three timing contacts are all connected together and to the conductor 142 which extends to the start or forward advance magnet S, which feeds the perforated tape in a forward direction through the keyer. It will be noted that negative polarity is also transmitted to this conductor 122 through timing contact 203 while the shaft 2E8 of the cor recting apparatus is standing inert. The timing contact 222 also maintains negative polarity on conductor 141 leading to the printer, this contact being closed while the shaft 2i8 is inert, but being opened upon motion of said shaft. The winding of selecting relay 213 is connected through conductor 233 with conductor G24 leading from the receiving apparatus. Suitable resistances are associated with these latter conductors whereby the relay 218 is not energized by current fiow over warning signal conductor 125, 52, but is energized by current flow over warning signal conductor In order to clearly describe the action of the circuits of Figure 3, a preliminary discussion of Figures 8, 9, l0, and 11 is desirable, these showing four cases of disturbed reception of one or more signals. In these charts or time diagrams, the two left hand lines correspond to one station, such as station A, and the two right hand lines correspond to another station, such as station B. Of the two left hand lines, line AT represents the transmitter and line AR represents the receiver of station A; and, similarly, of the two right hand lines, line BR represents the receiver and line BT represents the transmitter of station B. In these diagrams, time progresses from top to bottom. It has been supposed that the propagation time on the radio path amounts to about four signal elements, and that on both transmitters the alphabet is emitted (indicated by the letters a, b, 0, etc., A, B, C, etc, respectively).

In Figure 8 the letter a is suposed to have been disturbance.

correctly received, but the letter b has been disturbed, this fact having given rise at the re-- ceiver BR to the operation of detecting relay ST,

the energization of which relay applies a nega tive polarity to conductor 52, as previously de scribed. The inclined dotted line in Figure 8 indicates the transmission of letter Z), which has been disturbed or mutilated, and the solid continuation of this line indicates that the receiver BR warns its transmitter ST of the received This warning is effected by means of the correcting apparatus of Figure 3, which functions in such manner that the transmitter- BT transmits to the receiver AR one emission of warning signal VI, and thereafter five emis sions of warning signal VII.

The warning of the transmitter ET by its receiver ER is performed by the operation of testing relay ST at the receiver BR, by which relay contact I48 is closed and working potentialis applied to conductor 52. Referring to Figure 3, the application of working potential to conductor 52 results in the energization of the start magnet 2I'I, which sets the shaft 2l3 into operation. Upon the starting of shaft 2H2, timing contacts ZEII and 2% are closed (Figure '7), and as a result, working potential is transmitted up through relay armature 2'20 and contact 285 to conductor I 15 which extends up to warning signal relay S1. Hence, warning signal VI is emitted by the transmitter ET. This occurs during the first; revolution of transmitter ET after the reception of a disturbance in receiver BR has been signalled. It is to be observed that this signalling function does not occur before a time interval belonging to the element of the vertical line BR (Figure 8) following on that, in which. this line intersects the inclined dotted line, is being traversed.

At timing contact 282, the transmission of working potential to conductor MI is interrupted during the time that the shaft 2I8 is rotating, the contact 262 being opened when the shaft starts rotating and not being closed until the shaft is again at rest. Interrupting the supply of working potential to the conductor I4! prevents the printer from starting or operating during the time that the shaft U8 is rotating. The opening of contact 2&3 at this same time interrupts the supply of working potential to conductor I42 so that the supply circuit for the start or advancing magnet S is deenergized at the same time that the supply circuit for the printer is deenergized. By reason of the above described closing of timing contact 295, warning signal VI is emitted once, this occurring during that part of the motion of shaft 2i8 corresponding to the first revolution of the transmitting distributor (Figure 7). Upon the opening of contact 255 at the end of this time interval, con tact 204 is closed, and this latter contact remains closed during the next succeeding five revolutions of the transmitter shaft or distributor. The closing of said contact 204 applies working potential to conductor I44 leading to warning signal relay S2, so that during these five revolutions of the transmitter shaft, five emissions of warning signal VII are transmitted from transmitter BT to receiver AR.

Figure 8 illustrates the emission of first warning signal VI from transmitter ET, and the reception of this warning signal at receiver AR. I shall now explain what action this first warning signal has on the receiver AR and transmitter AT. The reception of this warning signal on' Cal . ductors when energized. The contact 286 is closed tial to the conductor I24whi'ch leads to the correcting apparatus of 'stationA. As shown'in Figure 3, the energization of conductor I24 energizes startmagnet-ZI I and starts the operation of 'corrector shaft 2I8 of station A. At the same time that start'magnet 2| 1 is energized over conductor'IZA, selecting relay 2I3'is also energized. The energization of relay'2l3 and the successive energization of relays 2I4, 2| 5, and 2| 6 resulting therefrom, causes the transmitter AT to first make three steps in a backward direction and then three-steps in a forward direction.

This operating sequence is illustratedgraphically in Figure 12". In this figure the first column shows-the series of warning signals emitted by the transmitter of any station on the arrival of a mutilated signal at the'receiver of that station. The succeedingcolumns show the same, but modified by the supposition that'the transmitter referred to has already been emitting a series of warning signals V'Land VII in response to a received'disturbance. The second column in this figure illustrates the above described operating relation, wherein the transmitter AT is first caused to step the perforated tape three steps in a backward direction and then three steps in a forward direction. The third column of 'Figure 12 represents the operating relation wherein warning signal VI arrives from station Ben the second revolution of this emission from the distributor of station A. The succeeding columns in this figure presume that warning signal VI arrives every time one revolution later.

Referringagain to Figure 8, the above described operation of stepping transmitter AT in a backward direction through three steps, and then in a forward direction through three steps, results in the repetition of the signal which has been received in a disturbed condition. That is to say, the letter I) is again emitted on the 6th step after that in which the mutilated letter had been emitted. The manner in which the correcting apparatus of 'FigureS controls the automatic keyer to make the equired steps after the application of working voltage tolead I24 will now be described. -'On the application of negative potential to lead I24, relay 2I3 and start magnet 2 are energized. The relay actuates its armature 220, and the start magnet starts the shaft 2| 8. By'the actuation of armature 225), working potential is taken from con- I44 and I45, and this potential is applied by way of contact 206 to conductor I43. This conductor energizes the reverse or backward stepping magnet T, which steps back the keyer during three revolutions of the transmitter shaft, and hence the automatic keyer is stepped back over three steps. During the first revolution of the transmitter shaft, the timing contact 201 of 'corrector shaft 2I8 closes a circuit for relay 2| 4,

which is energized and which armature 2I4' connecting in series with timing contact 20L Negative potential is transmitted by way of this armature 2I4 to the rotary timing contact 2"), which now applies this negative potential to conductor I42 during the fourth, fifth and sixth revolutions of the transmitter shaft (Figure '7), thereby energizing the for ward advance magnet S and advancing the keyer by three steps.

If warning signal VI has been received during locks itself up at the second revolution of the transmitter shaft after the start of corrector shaft 2l8 at transmitter A by the arrival of a disturbance, then the keyer will have to go back two steps, and will thereafter have to advance two steps, as indicated in the third column of Figure 12. In between such forward and backward movements, one revolution remains free during which the keyer should be at rest. During this revolution the letter which is before the keyer is emitted, but this emission does not have any result as the receiver BR has interrupted its printer start circuit due to the rotation of its corrector shaft 2 i ii. If-the signal VI arrives on the third revolution, the keyer will have to go back a single step and afterwards advance a single step. In between such backward and forward motions, two revolutions remain free during which the keyer will be at rest. In both latter cases relays 215 and 216 are operated together with the above described circuits for controlling the required steps. If warning signal VI from transmitter B'I arrives on the fourth revolution, then relay 2l3 only is operated, this relay interrupting in the manner previously described the emission of signal VII by transmitter AT, so that this transmitter now emits the letter in the keyer during the ultimate three revolutions. Of these, only the last is active at receiver BR.

In all other cases of mutual and/ or simultaneous disturbance than those examined more in detail, the circuit described yields the correct results as may be easily concluded by referring to the examples given. Synchronism between transmitter shaft A and receiver shaft B, as well as between transmitter shaft B and receiver shaft A, is maintained in a known manner.

While I have illustrated and described what I regard to be the preferred embodiment of my invention, nevertheless it will be understood that such .is merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention.

I I claim:

,1. In a radio telegraph system, the combination of a radio transmitter comprising means for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, means for transmitting said signals by radio over a single radio channel in such manner that said positive and negative impulses produce the same fixed ratio of different components in each radio signal corresponding to said positive and negative impulses, a radio receiver associated with I to be set into motion in response to, said testing means for causing said radio transmitter to emit a signal indicating that the associated receiver has received a mutilated signal.

In a radio telegraph system, the combination of a plurality of stations each comprising a radio transmitter and a radio receiver, signaling means in each transmitter by which the signals are formulated in a code of elements ofdifferent nature and in which said elements of different nature occur in a mutually constant ratio in each signal, each receiver comprising testing means for testing each received signal to determine if said elements of different nature in that signal are in said mutually constant ratio, and a correcting device at each station adapted to respond to the testing device of that station when the latter indicates the reception of a signal mutilated by atmospheric conditions, said correcting device including means for causing the signaling means of each transmitter to be set back successive times until the atmospheric disturbance has cleared sufficiently to allow the transmission of a non-mutilated signal.

3. In a radio telegraph system, the combination of a plurality of stations each comprising a radio transmitter and a radio receiver, signaling means in each station for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, said transmitters transmitting said signals by radio in such manner that said positive and negative impulses produce the same fixed ratio of different components in each radio signal corresponding to said positive and negative impulses, each radio receiver comprising means for converting such components of the radio signals back into corresponding positive and negativeimpulses, and including testing means operative to test the signals for said fixed ratio of positive and negative impulses, and a repetition device at each station adapted to respond to the testing means of that station when the latter indicates the reception of a signal mutilated by atmospheric conditions, said repetition device including means for causing the signaling means of each transmitter to be set back successive times until the atmospheric disturbance has cleared sufficiently to permit the transmission of a non-mutilated signal.

4. In a radio telegraph system, the combination of first and second stations each comprising a radio transmitter and a radio receiver, each station comprising means for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, each transmitter comprising means for transmitting said signals by radio in such manner that said positive and nega tive impulses produce the same fixed ratio of different components in each radio signal corresponding to said positive and negative impulses, each receiver comprising means for converting such components of the radio signals back into corresponding positive and negative impulses, and also comprising testing means operative to test the converted signals for said fixed ratio of positive and negative impulses, and correcting apparatus at each station normally inert but set into operation upon the reception of a mutilated signal at the receiver of that station for causing the transmitter of said latterstation to emit a warning signal to the other station.

5. In a radio telegraph system, the combination of a plurality of stations each comprising a radio transmitter and a radio receiver, signaling means in each station for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, said transmitters transmitting said signals by radio in such manner that said positive and negative impulses produce the same fixed ratio of different components in each radio signal corresponding to said positive and negative impulses, each radio receiver comprising means for converting such components of the radio signals back into corresponding positive and negative impulses, and including testing means of positive and negative impulses, each transmitter including means for transmitting a warning signal to the receiver of the other station, and correcting apparatus at each station which is caused to function when the receiver of that station receives either a mutilated signal or a warning signal transmitted from the other station, said correcting apparatus comprising means responding to the reception of a mutilated signal for causing its transmitter to emit a warnin signal, and comprising means responding to the reception of a warning signal for causing the signaling means of its own transmitter to be set back for effecting a repetition of the mutilated signal.

6. In a radio telegraph system, the combination of a plurality of stations each comprising a radio transmitter and a radio receiver, signaling means in each station for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, said transmitters trans mitting said signals by radio in such manner that said positive and negative impulses produce the same fixed ratio of diiferent components in each radio signal corresponding to said positive and negative impulses, each radio receiver comprising means for converting such components of the radio signals back into corresponding positive and negative impulses, and including testing means operative to test the signals for said fixed ratio oi positive and negative impulses, each transmitter comprising warning signal emitting means, and correcting apparatus at each station comprising a normally inert shaft and a selecting relay means responsive to the reception of a mutilated signal for causing said shaft to be set into motion, means responsive to the reception of a warning signal for causing said shaft to be set into motion and said relay to be energized, and contacts responsive to said shaft and to said selecting relay for governing said warning signal emitting means and the backward and forward stepping of said signaling means.

7. In a radio telegraph system, the combination of a plurality of stations each comprising a radio transmitter and a radio receiver, signaling means in each station for establishing signals characterized by a fixed ratio of positive and negative impulses in each signal, said transmitters transmitting said signals by radio in such manner that said positive and negative impulses produce the same fixed ratio of different components in each radio signal corresponding to said positive and negative impulses, each radio receiver comprising means for converting such components of the radio signals back into corresponding positive and negative impulses, and including testing means operative to test the signals for said fixed ratio of positive and negative impulses, each transmitter comprising means for emitting a warning signal, correcting apparatus at each station having a predetermined operating cycle. means responsive to the reception of a mutilated signal at that station for initiating said operating cycle, means responsive to the reception of a warning signal at that station for initiating said operating cycle, and means operating with said correcting apparatus for setting said signaling means back successive steps upon the reception of a warning signal, the number of which steps is dependent upon whether the warning signal initiated the operation of said correcting apparatus or whether'said warning signal was not received until after the operation of said correcting apparatus had been initiated by the reception of a previous inn-- tilated or warning signal.

8. In a telegraph system, the combination of a plurality of stations each comprising a transmitter and a receiver, each transmitter comprising signaling means transmitting code combination signals each composed of elements having different electrical values so chosen that they bear a constant numerical relationship to each other in each transmitted combination, each receiver comprising testing means operative to test the received signals for this constant numerical relationship, and a repetition device at each station adapted to respond to the testing means of that station when the latter indicates the reception of a signal mutilated by atmospheric conditions, said repetition devices including means for causing the signaling means of each transmitter to be set back successive times until the atmospheric disturbance has cleared sufficiently to permit the transmission of a non-mutilated signal.

9. In a radio printing telegraph system, the combination of a plurality of stations each comprising a radio transmitter, a radio receiver and a printer, said transmitter comprising means for transmitting signals each composed of elements having different electrical values so chosen that they bear a constant relationship to each other in each transmitted signal, said receiver comprising means for differentiating between signals which have this constant relationship and other signals which have been mutilated, and correcting apparatus at each station comprising a plurality of timing contacts adapted who set into operation when said difierentiating means at the receiver detects a signal which has been mutilated, said timing contacts governing control circuits extending to said transmitter. said receiver and said printer, and relay means responsive to the receiver for selectively controlling the energization of a plurality of said control circuits.

10. In a radio printing telegraph system, the combination of a plurality of stations each comprising a radio transmitter, a radio receiver and a printer, said transmitter comprising means for transmitting signals each composed of elements having diflerent electrical values so chosen that they bear a constant relationship to each other in each transmitted signal, said receiver comprising means for differentiating between signals which have this constant relationship and other signals which have been mutilated, and correcting apparatus at each station comprising means for causing the transmitter to emit warning signals when the receiver receives a mutilated signal, and including counting relays for predetermining the number of times said warning signals are emitted under difierent operating conditions.

11.,In a telegraph system, the combination of stations A and B each comprising a transmitter and a receiver, each transmitter comprising means transmitting signals composed of elements having different electrical values so chosen that they bear a constant relationship to each other in each transmitted signal, each receiver comprising testing means for distinguishing between signals which have this constant relationship and other signals which have been mutilated, means at each station for causing the transmitter to emit a warning signal when the testing means of that station indicates the reception of a mutilated signal. means at each station operating in response to the reception of such a warning signal at that station for setting the transmitter of said station back to repeat the'emission of the mutilated signal, and means for causing said two last-named means to con-- make up an eight unit code, a transmitting distributor having eight distributor segments permanently connected to said five contact fingers and to the armatures of said three supplementing relays, and means coacting with said contact fingers and relays for transforming a perforated tape signal of five marking elements into an eight unit signal wherein the three elements established by said relays have one grouping, and for transforming a perforated tape signal of five spacing elements into an eight unit signal where-.

in the three elements established by said relays have a separate grouping.

13. In a radio telegraph system, the combination of a plurality of stations each comprising a transmitter having a transmitting distributor and a receiver having a receiving distributor, and correcting apparatus at each station for causing the transmitter of that station to emit a warning signal when the receiver of that station receives a mutilated signal, said correcting apparatus comprising a control shaft which rotates at a speed one-sixth of that of one of said distributors and which actuates control contacts governing said transmitter and receiver.

14. In a printing radio telegraph system, the combination of a transmitter comprising a transmitting distributor and signal formulating means for applying signals thereto each composed of signal elements having different electrical values so chosen that they bear a constant relationship to. each other in each transmitted signal, a single control shaft for said transmitter rotating at the speed of said transmitting distributor and actuating contacts governing said signal formulating means, a receiver comprising a receiving distributor and signal testing means for distinguishing between signals which have this constant relationship and other signals which have been mutilated, a single control shaft for said receiver rotating at the speed of said receiving distributor and actuating contacts governing said signal testing means, correcting apparatus for causing said transmitter to emit a warning signal when said receiver receives a signal which has been mutilated, and a single control shaft for said correcting apparatus rotating at one-sixth the speed of said other control shafts and actuating contacts governing said transmitter and receiver.

15. In a telegraph system, the combination of a plurality of stations each comprising a transmitter and a receiver, each transmitter comprising signaling means transmitting code combination signals each composed of elements having different electrical values so chosen that they bear a constant numerical relationship to each other in each transmitted combination, each receiver comprising testing means operative to test the received signals for this constant numerical relationship, and correcting apparatus at each station normally inert but set into operation receiver of its respective station for causing the transmitter of said latter station to emit a warning signal to the other station.

16. In a telegraph'system, the combination of a plurality of stations each comprising a transmitter and a receiver, each transmitter comprising signaling means transmitting code combination signals each composed of elements having different electrical values so chosen that they bear a constant numerical relationship to each other in each transmitted combination, each receiver comprising testing means operative to test the received signals for this constant numerical relationship, each transmitter including means for transmitting a warning signal to the receiver of the other station, and correcting apparatus at each station which is caused to function when the receiver of that station receives either a mutilated signal or a warning signal transmitted from the other station, said correcting apparatus comprising means responding to the reception of a mutilated signal for causing its transmitter to emit a warning signal, and comprising means responding to the reception of a warning signal for causing the signaling means of its own transmitter to ,be set back for effecting a repetition of the mutilated signal.

1'7. In a telegraph system, the combination of a plurality of stations each comprising a transmitter and a receiver, each transmitter comprising signaling means transmitting code combination signals each composed of elements having different electrical values so chosen that they bear a constant. numerical relationship to each other in each transmitted combination, each receiver comprising testing means operative to test the received signals for this constant numerical relationship, each transmitter comprising warning signal emitting means and correcting apparatus at each station comprising a normallyinert shaft and a selecting relay, means responsive to the reception of a mutilated signal for causing said shaft to be set into motion, means responsive to the reception of a warning signal for causing said shaft to be set into motion and said relay to be energized, and contacts responsive to said shaft and to said selecting relay for governing said" warning signal emitting means and the backward and forward stepping of said signaling means.

18. In a telegraph system, the combination of a plurality of stations each comprising a transmitter and a receiver, each transmitter comprising signaling means transmitting code combination signals each composed of elements having diiferent electrical values so chosen that they bear a constant numerical relationship to each other in each transmitted combination, each receiver comprising testing means operative to test the received signals for this constant numerical relationship, each transmitter comprising means for emitting a warning signal, correcting apparatus at each station having a predetermined operating cycle, means responsive to the reception of a mutilated signal at that station for initiating said operating cycle, means responsive to the reception of a warning signal at that station for initiating said operating cycle, and means operating with said correcting apparatus for setting said signaling means back successive steps upon the reception of a warning signal, the number of which steps is dependent upon whether the warning signal initiated the oper- 'upon the reception of a mutilated signal at the ation of said correcting apparatus or whether said warning signal was not received until after the operation of said correcting apparatus had been initiated by the reception of a previous mutilated or warning signal.

19. In a printing telegraph system for wireless transmission, the combination of a radio transmitter comprising means for transmitting a sig nal consisting of code groups of impulses of different nature wherein the impulses of one nature are in a predetermined ratio to impulses of another nature, and a receiver comprising an impulse receiving device, a signal printer, decoding means between said device and said printer for transmitting a signal to the printer to actuate the same only when the received impulses have the predetermined ratio of impulses of one nature to the impulses of another nature, and return signal means controlled by said decoding means for emitting a series of wireless impulses constituting a warning signal to the transmitter, said return signal means operating to stop the printer pending repetition of a prior imperfect signal, and means at the transmitter for receiving said return warning signal and for causing repetition of the next preceding code group of impulses from the transmitter.

20. In printing telegraphy, the method of signalling which comprises converting signals from a conventional five unit code into signals of a second code by the addition of signal elements in such manner that the components of each converted signal are maintained in a constant numerical ratio, transmitting such signals in this second code from a transmitting station to a receiving station, utilizing this constant ratio characteristic at the receiving station to differentiate between mutilated and unmutilated signals, converting the unmu'tilated signals back into conventional five unit code for printing, and utilizing the mutilated signals to set the signalling means of the transmitter back successive times until the atmospheric disturbance has cleared sufficiently to allow the transmission of an unmutilated signal,

21. In an electrical system of communication, the methodof signalling which comprises transmitting code combination signals from a transmitting station over a single channel, a plurality of said signals being composed of two kinds of elements having difierent electrical values so coded as to bear a constant relationship to each other in each of said code combination signals, receiving said signals at a receiving station, distinguishing at said receiving station between coded signals having this constant relationship and mutilated signals which do not, transmitting a warning signal from said receiving station back to said transmitting station upon the reception of such mutilated signal at said receiving station, and responding to the reception of such warning signal at the transmitting station through correcting, apparatus which causes the signalling means of its own transmitter to be set back successive steps for effecting a repetition of the mutilated signal, the number of which steps is dependent upon whether the warning signal initiated the operation of said correcting apparatus or Whether said warning signal was not received until after the operation of said correcting apparatus had been initiated by the reception of a previous mutilated or warning signal.

HENDRIK C. A. VAN DUUREN.

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