US2405570A - Cryptographic telegraph system - Google Patents

Description

Aug. 13, 1946. J. w. DEHN CRYBTOGRAPHIC TELEGRAPH SYSTEM 7 Sheets-Sheet 1 Filed oct. 12, 1942 /N VEN TOR J. W DE HN B59 9 A T'TORNE Y J. Aw. DEHN CRYPTOGRAPHIG TELEGRAPH SYSTEMv Aug. 13, 1946..

7 Sheets-Sheet 2 yFiled Oct. 12. 1942 /NVENTOR BYJ. W DEHN Cf? ATTO NEV J. w. DEHN 2,405,570

Filedpct. 12, 1942 7' sheets-sheet s /NVENroR J. W DE HN Aug. 13, 1946.

J. w. DEHN CRYPTOGRAPHIC TELEGRAPH SYSTEM ,Filed 061'.. 12, 1942 7 Sheets-Sheet 4 Hin /NVENTOR BYJ. W. DEH/V 0862.

Afro Ev J.`W. DEHN CRYPTOGRAPHIC TELEGRAPH SYSTEM 7 Sheets-Sheet 6 Filed Oct. 12, 1942 ATOR E Y Filed oct. 12, 1942 -7 sheets-sheet 7 /Nl/ENTOR J. I4. DE HN 5v ATTO@ EY Patented Aug. 13, 1946 UNITED STATES PATENT OFFICE Bell Telephone Laboratories,

Incorporated, n

New York, N. Y., a corporation of New York Application October 12, 1942, Serial No. 461,731

34 Claims.

This invenftion relates to cryptographic telegraph systems and methods and particularly to apparatus for generating cipher codes to be used in ciphering text codes to be transmitted and in deciphering received codes to derive message text codes therefrom.

An object of fthe invention is to generate a random sequence of codes for ciphering and deciphering transmitted and received code signals.

Another object of the invention is to determine the character of each impulse of a cipher code combination in accordance with the operation of a plurality of selectively operable instrumentalities.

Another object of the invention is to control the operation of the selectively operable instrumentalities from multiple bank switching devices.

Another object of the invention is to control the operation of the switching devices from certain of the selectively operable instrumentalities.

Another object of the invention is to provide other switching devices for variously rearranging the operative relation between said certain selectively operable instrumentalities and the switching device operating means.

Another object of the invention is to control the operation of at least one of said other switching devices according to a predetermined ch'aracteristic of certain ones of the message text codes.

Another object of the invention is to provide means for quickly and easily rearranging the selective control of the selectively operable instrumentalities by their respective switching devices.

Another object of the invention is to provide means for adjusting the switching devices to any desired position to serve as starting points.

Another object of the invention '1s to provide a relay distributor for timing the generation of ciphered and deciph'ered signals.

The invention features a multiple contact jack or socket associated with the contacts of each bank of the multiple bank switching devices in different connective arrangements from each other bank and multiple contact jack or socket, and a plurality of multiple prong plugs having different combinations of prongs interconnected, any such plug being usable in any one of the jacks.

The invention also features a plurality of jacks and patching cords which' in cooperation with selectively operable keys establish variable starting points for the switching devices.

In accordance with the preferred embodiment of the invention, an input relay receives plain 55 text signals to be ciphered and transmitted or alternately receives ciphered signals to be deciphered and impressedupon a receiving printer.

An output relay generates the ciphered signals to be transmitted or alternatively generates the deciphered signals to be recorded. Th'e operating circuit of the output relay, which is polar, is completed from the marking or spacing contacts of the input relay, which have battery connections of opposite polarity, over either of two paths and through the segments of a transmitting distributor or through' counting and distributing relays of a relay distributor. The operation of the output relay to its marking or spacing position will be dependent upon which of the .two paths is completed to eiect the energization of the relay, the paths entering the operating winding from opposite sides of the relay, and which of the two contacts the armature of the input relay engages at the time that the path is completed.

The completion of one or the other of the two paths is determined by a plurality of setsof cipher coding relays, there being a set for each selecting impulse of a permutation code signal combination. The armatures of the cipher coding relays control various chain circuits for completing connections' from either of the output relayoperating path conductors to the segments of the distributor or to the counting and distributing relays. Each of the cipher coding relays is controlled from a switch bank which has approximately one half of its contacts connected to the associated relay through a multiple contact jack or socket and associated plug. There is a full set of connections from each switch bank to its jack and the selective extension of paths from about one half of the switch bank contacts to the relay is determined by the electrical interconnection of about h'alf ofthe prongs of the plugs. Plugs having various arrangements of interconnection of their prongs are employed so that the selective control of the coding relay from its bank may be varied by the substitution of plugs.

The switch banks which control the cipher coding relays comprise multiple bank stepping switches so arranged that each switch has one contact bank assigned to control a relay in each of the sets of cipher coding relays, from which it follows that each of the relays in a set is controlled from a diierent stepping switch.

In addition to determining which of the two paths will be completed for operation of the output relay, certain of the cipher coding relays also selectively provide ground connections for a number of conductors equal to the number of f 9,405,976 j j 3 stepping switches which control the cipher coding relays. These conductors extend to the contact brushes associated with an equal number of contact banks of another stepping switch. The conductive paths to the contact brushes of the last-mentioned stepping switch are completed through a mixing jack with which several different plugs may be employed for varying the connections between the conductors and the brushes. The contacts of the banks of the lastmentioned stepping switch are connected in various combinations to five conductors which extend to the brushes of still anotherstepping switch. The contacts of the banks of this stepping switch are connected in different combinations to five conductors which extend to the normally released armatures of a timing relay. From the front contacts of the timing relayn `conductors extend through another mixing jack and plug combination tothe lstepping magnets of the stepping switches which control the cipher coding relays, so'` that the operation of the stepping magnets forV theV Ystepping Vswitches which control the ciphercoding relays will depend upon the selective application of ground to the conductors extending to the brushes of the first transposing stepping switch and the manner in which the twotranspcsing stepping switches transpose the conductive paths to the several stepping magnets.

One of the transposing steppingv switches is advanced one step for each signal combination transmitted or received. The advancement of theother transposing stepping switchv is dependentupon two factors. One is theV preparation of a ground connection for the stepping magnet of the second transposing stepping switch through a chain circuit controlled bycertain of the cipher coding relays. The'other condition is the appearance .of marking as the'nature of aparticular one of the impulses of the plain text codes. When these two conditions appear concurrently,

v the second transposing second switch is advanced one step.

The `appearance of the marking-condition forY a particular impulse of the text code signals isY detected'by a' relay Which'iscontrolled directly bytheinptrelay in the case of signal transmission, because the plain text codes are impressed directly upon the input relay under those circumstances, and is controlled in accordance with the operation of the output relay in the case of the received signals since the input relay is then responding to ciphered signals and the output relay operates in accordance with the deciphered plain text signals. Y i

'Each ofv the. stepping switches which control the cipher coding relays has one more bank of contacts than the number of sets of coding relays and leach of the two transposing stepping relays has an extra contact bank. By means of a sys-` rupter or buzzer action. When'each stepping switch reaches the contact to which a conductive path for energizing the steppinggmagnet has been extended, the stepping magnet will be held energizedY over a path in shunt relation to the path through the interrupter contacts whereby the 4 automatic advancement of the stepping switch will be discontinued. When all of the switches have come to rest, the manually controlled relay may be released whereby the energizing circuit for the stepping magnet will be interrupted and the brushes of the stepping'switches will be in starting positions as selected in accordance with thefpositions of the patching cords relative to the jacks and in accordance with the particular manually operable keys which had been op- Y erated.

For a complete understanding of the invention reference may be had to the following detailed description to be interpreted in the light of the accompanying drawings wherein: i

Figs. 1 'to 6, inclusive, are diagrammatic views showing parts of a cryptographic telegraph system in accordance with the present invention;

Fig. 7`is a diagrammatic view showing how Figs. 1 to 6, inclusive, are to be arranged to represent a complete telegraph station capable of ciphering and deciphering telegraph messages; and

Fig. Sis a diagrammatic view showing an alternative embodiment of the portion of the system shown in Fig. 1.

Fig. 1 is largely similar to Fig. 1 of the patent concurrently granted on copending application, Serial No. 435,178, led March 18, 1942, by K. E.

. Fitch et al. Fig. 2 of Fitch'et al. discloses a special repeater which cooperates with the apparatus of Fig. 1 of that application and arepeater identical withkthat shown in Fig. 2 of the copending application is intended to cooperate s similarly with Fig. 1 accompanying the presentY specication. For the purpose of simplifying the present specification and avoiding duplication of disclosure, the drawings accompanying the present specication do not include the repeater, nor does the specification contain detailed description of such repeater. In View of this the disclosure of the copending application and particularly Fig. 2 and the descriptive material pertaining thereto of the copending application is incorporated herein by reference as part ofthe present specification. 7

Referring now to the drawings and particularlyrto Fig. 1 the apparatus Vcontainedwithin the broken 1ine rectanglel II represents a combined receiving telegraph printer and keyboard transmitter which may be of the type `shown in'V Patent 1,904,164, granted April 18, 1933, Vto S.;

Morton et al. The disclosure `of kthe Morton patent is incorporated herein by reference as part of the present specification; In Fig. 1 the printer is indicated symbolically by the selector magnet I2 and the keyboard transmitter for transmitting start-stop permutation code signals is represented by the transmitting contacts I3. The selector magnet I2 is connected to the sleeve terminals of a double plug I4 andthe transmitting contacts I3 are connected to the tipterminals of the -double plug I 4. The double plugld is adapted to be inserted into either of two pairs of jacks associated with the repeater circuit shown 'in Fig, v2 of the copending application, depending upon whether it is desired to transmit straight unciphered message text signals or ciphered signals.

A ciphering and deciphering relay shown -in the lower right-hand portion of Fig. 1 comprising relays I6 and yI'I. Relay I6 is adapted t0 receive signals from the repeater circuit,

' (not shown) and has one terminal of its upper or system is which extends into the repeater circuit and the other terminal of the 'operating winding is connected through resistor I9 to ground and through resistor 2| to the negative terminal of battery 22, the resistors I9 and 2| forming a potential divider. In the repeater, conductor I8 receives negative battery connection in the idle condition Which causes current to flow in the operating Winding of relay I6 in a direction to hold the armature on the marking contact, which has a negative battery connection. When the repeater receives a spacing signal either from the local transmitting contacts I3, which generate straight text signals, or from a remote station, a ground connection on conductor I8 is substituted for the connections as will be described later. From the negative battery connection, which causes current to flow in the opposite direction through the operating winding of relay I6 and drives its armature to spacing which has ground connection. Relay I6 has a holding or locking winding, one terminal of which is connected through resistor 26 to ground and through resistor 21 to negative battery 23, the resistors 26 and 21 cornprising a potential divider, and the other terminal of the holding winding of relay I6 is connected over conductor 29 to the collector ring of a cipher code generating distributor 3| which will be described later.

The transmitting relay I1 has its armature connected to a conductor 32 Which extends into the repeater, its marking Contact connected to negative battery and its spacing contact connected to ground. When the armature of relay I1 is on the marking contact a marking signal is transmitted into ythe repeater and when the armature of relay |1 moves to the spacing contact a spacing signal is transmitted into the repeater. Relay I1 is operable under the joint control of receiving relay I6 and cipher code generating distributor 3|. When relay I6 responds to a plain text code generated by transmitting contacts I3 and causes the operation of relay I1, the signal transmitted by relay I1 is a ciphered signal and is repeated by the repeater into a line extending to a remote station. When relay I6 responds to a ciphered code received from a remote station, the operation of relay I1 in response thereto is to decipher the code and the signal transmitted by relay I'I into the repeater is repeated to the selector magnet I2 of the receiving printer. The armature of relay I'I is also connected to one terminal of the holding or locking Winding of that relay, the other terminal of which is connected through resistor 33 to ground and through resistor 34 to negative battery 36. The holding winding thus may be traversed by current in either direction from the marking and spacing contacts of relay I1 and serves to hold the armature in the position to which it is operated by the operating winding until the operating winding, which is paramount to the holding Winding operates the armature to the opposite position.

The armature of input relay I6 is connected by conductor 31 to one corner 38 off a triangular bridge network which comprises one side or arm containing resistor 39, a second side or arm containing resistor 4I, and a third side or arm containing the operating Winding of output relay I1 and resistor 42 in series therewith, From the point of interconnection of the operating winding of relay I1 and resistor 4|, designated as the bridge corner 43, conductor 44 extends to the stop segment 46 and to the start segment 41 of distributor 3| and into Fig. 2 where it has various point of interconnection of resistors 39 and 42, designated as bridge corner 48, conductor 43 extends into Fig. 2 and has various connections in that gure. From the bridge corner 38 conductor 5I extends to the rest segment 52 in the outer ring of distributor 3|.

The distributor 3| is somewhat similar to a tape controlled transmitter distributor disclosed in Patent 2,055,567 granted September 29, 1936, to E. F. Watson, and the disclosure of the Watson patent is incorporated herein by reference as part of the present specication. However, the distributor has a considerably diierent arrangement of signal generating segments and there are no tape-controlled contacts, the segments receiving their potentials from other sources as will be described hereinafter.

The distributor 3| has a brush arm 53 which is carried by a rotatable shaft 54 to which rotation is imparted from motor 56 through friction clutch 51 and gears 58. to shaft 54 and is arranged to be arrested by the armature lever 6I of electromagnet 62 when the magnet is deenergized. Upon the energization of magnet 62 the end of armature lever 6| presented toward cam 59 is rocked out of. blocking relation to the cam whereby shaft 54 is released for rotation. Brush arm 53 carries two electrically interconnected brushes which bridge outer and inner segmented rings.

The inner ring of the distributor is electrically continuous except for a short conductive segment 63 insulated from the main body of the ring, and the inner brush carried by brush arm 53 is in engagement with the segment 63 when brush arm 53 is held at rest, the outer brush then engaging rest segment 52 which subtends the same angle as the segment 53. The stop segment 4E is traversed by the outer brush of arm 53 just before reaching rest segment 52 and the start segment 41 is traversed by the outer brush immediately after leaving segment 52. The remainder of the outer ring contains five uniformly spaced short conductive segments Which correspond to the five code impulses of a permutation code combination and these segments are connected to conductors 66, 61, 68, 69 and II ywhich extend into Fig. 2. The inner ring of the distributor, exclusive of the rest segment 63, has one end in registry with the beginning of start segment 41 and the other end in registry with the end of stop segment 46 and thus is arranged to complete conductive paths from the start segment, the five code segments and the stop segment over conductor 29 to the locking Winding of input relay I6.

With distributor brush 53 in the rest position the two rest segments 52 and 63 are bridged by the brushes as previously stated and a circuit may -be traced from ground on the positive terminal of a battery 12 through the battery, resistor I3, Winding of start magnet 62, conductor 14, inner rest segment 63, brushes carried by distributor arm 53, outer rest segment 52, conductors 5| and 31, armature of input relay I6, and marking contact of that relay to negative battery, the positive terminal of which is connected to ground. The negative battery connected to the marking Contact of relay I6 opposes the negative battery connected to start magnet 62 so that the magnet is deenergized. When input relay I6 goes to spacing in response to the 'start impulse of a signal combination received over conductor I6 the opposing negative battery connection on the marking contact of relay I6 is removed from the A stop cam 59 is secured circuit of start magnet B2 and a ground connection on the spacing contact is substituted so that the magnet becomes energized and retracts armature lever 6I from blocking relation to start cam 59 thus permitting distributor shaft 54 and brush arm 53 to be rotated.

Referring now to Figs. 2 and 3 the apparatus for setting up cipher codes will be described. It may be stated generally that this involves selective determination of the completion of conductive paths over conductors 44 or 49 which extend from the bridge network corners i3 or d8 and thus from the opposite ends of the winding of output relay I1, to the five code segments of distributor 3|. In the lower portion of Fig. 3 are shown the stepping magnets Sl, 82, 83, 84 and'B 'of ve stepping switches each of which has six banks of contacts. The Contact bank-s associated with the stepping switch operated by stepping magnet 8| are designated 3 IA to 8 IF, inclusive. Similarly, the banks of contacts associated with the stepping switches controlled by the stepping magnets 82 to 85, inclusive, are designated 82A to B5F, inclusive.

Associated with the stepping switch banks SIA to 8IJE are individual relays 8 IAR to BIER. Similarly, the stepping switch banks 82A to 82E have relays SZAR to SEER, respectively, the switch banks 83A to 83E have the individual relays 83AR to BSER, the banks 84A to 84E have relays MAR -to MER, and the switch banks 85A to 85E have the relays BSAR to BEER. The switch banks bearing designations A to E, inclusive, include uniform numbers of contacts, such as 22, and the brush associated with each of these banks is connected to ground. The association of a relay with its switch bank is 'shown in full detail in the case of bank 85E land relay MER in Fig. 3. The

twenty-two contacts of 'switch bank 85E are connected to individual single contact'spring jack elements of a multiple jack SSEJ which has a minimum of twenty-three individual jack spring elements. Successive contacts of lbank 85E are not connected to successive jack spring elements of the multiple jack 85EJ but are scrambled or connected in purely random fashion. The uppermost jack spring element of jack 85EJ is connected to one terminal of relay EEER the other terminal of which is connected to grounded vbattery. There is provided for cooperation with jack B5EJ a multiple plug 85EP having a minimum of twenty-three independent contact prongs. The uppermost prong is connected by conductive straps to about one half of the other twenty-two prongs, selected at random. With the plug 85E? inserted into jack 85EJ, when the brush associated with switch bank 85E co-mes into engagement with contacts of the bank from which conductive paths extend through springs of jack 85EJ to prongs of plug 85EP that are connected to the uppermost prong, the circuit of relay 85ER. will be completed and the relay will be energized. With the specific arrangement of connections between switch bank 'E and jack 35EJ, and with the specific strapping of prongs of plug 85E? to the uppermost prong the circuit of relay 85ER will be completed Iwhen the stepping switch brush engages the rst, fifth, sixth, eighth, ninth, eleventh, fourteenth, twentieth, twenty-first and twenty-second contacts of the bank,

Fragments of other multiple jack and multiple plug arrangements are indicated 85D] and DP, respectively, in Fig. 3 and in Fig. 2 in association with switch bank SiC by the reference numerals 8ICJ and 8|CP, respectively, and in association 8 with the switch bank 83C by the reference numerals 83CJ and 83CP, respectively. Each of the twenty-ve stepping switch vbanks which controls a relay has a set of connections from its twentytwo contacts to twenty-two jack springs of its multiple jack which differs from the arrangement of connections between the remaining twentyfour switch banks and their multiple jacks, and each of the multiple plugs of which thereis a minimum .of twenty-ve has a different combination of strappings from the uppermost prong to about one half of the remaining twenty-two prongs of the plug. Any one of the plugs may be used in any one of the jacks to establish selectively variable paths for the energization of the relays. The multiple plugs, the number of which may considerably exceed twenty-ve, because a large number of different strapping combinations may be made, may be marked with distinctive identifying symbols so that they may be placed in conductive association with the multiple jacks in predetermined arrangement according to charts or other instructions.

Each of the relays controlled by the stepping switch bank has a sufficient number of armatures and contacts to provide two normal paths and two off-normal paths, the normal paths being those that are established through back contacts and the oir-normal paths being those that are established through front contacts. `In the majority cf instances this could be accomplished by providing relays having two armatures each operable between a back contact and a front contact. However, in Figs. 2 and 3 the relays have been shown as being provided with four armatures two of which cooperate only with a back contact and the other two of which cooperate only with a front contact. In some instances only one back contact is used and, accordingly, one of the armatures is not used. However, in systems of this type it is desirable to use similar relays throughout where they perform similar functions even though some of the armatures and contacts may not actually be used. The reason for this is that it may be desirable to rearrange some of the permanent connections from time to time and if all of the relays have full complements of armatures and contacts the rewiring may be done without the necessity of removing and substituting relays.

As previously stated the conductors 44 and 49 connected to the opposite ends of the winding of output relay I7 extend into Fig. 2. In branching relation to conductors 44 and 49 the conductors 44A and 49A extend to armatures of relays BIAR and BSAR. VConductor 44A is connected to armatures l and 4 of both relays, which have off-normal and normal relation respectively to their contacts. Conductor 49A extends to the armatures 2 and 3 of both relays 8|AR and 83AR. Of these armatures the armature 2 has normal relation to its contact and the armature 3 has offnormal relation to its contact. The contacts'of the armatures l and 2 of relay BIAR are connected to the armature l of relay 82AR. The contacts of the armatures 3 and 4 of relay HAR are connected to the armature 2 of relay BZAR. The contacts associated with the armatures I and 2 of relay 82AR are connected to the armature I of relay BSAR. The contacts associated with the armatures l and 2 of relay 83AR are connected to the armature I of relay MAR and the two contacts associated with the armatures 3 and 4 of relay 83AR are connected to the armature 2 of relay 84AR. The two contacts associated with the armatures I and 2 of relay 84AR are connected to the armature 2 of relay BEAR. The contacts associated with the armatures I and 2 of relay 85AR are connected over conductor 66 to the No. l code segment of distributor 3|.

With relay armature and contact connections as described above, there are two chain circuits, one comprising the armatures and contacts of relay 8|AR and the upper two armatures and contacts of relay 82AR and the other comprising the armatures and contacts of relay B3AR and the upper two armatures and contacts of the relay 84AR, these two chains leading into the upper two armatures of relay BEAR. Conductors 44A and 49A enter both of these chain circuits. When relay 85AR is deenergized the chain circuit cornprising relays 83AR and 84AR will be effective to control connections from conductors 44A and 49A to conductor 66. With both of the relays 83AR and 84AR energized Or both deenergized, conductor 44A will be connected t0 conductor 66. With either of these relays energized and the other deenergized conductor 49A will be connected to conductor 69. When relay 85AR is energized the chain circuit controlled by relays 8|AR and 82AR will be eiective. With both of these relays energized or both deenergized, conductor 44A will be connected to conductor 66 and with either of these relays energized and the other deenergized, conductor 49A will be connected to conductor 66. As the ve relays are selectively operated singly or in combinations, they cooperate in sets of three, namely, SIAR, BZAR and BEAR, or 83AR, 84AR and 85AR to determine which of the two conductors 44A and 49A shall be connected to conductor 66. The chain circuits are so arranged that it is not possible for both of the conductors 44A and 49A to be connected to conductor 66 simultaneously.

The relays BIBR, 82BR, 83BR, 84BR. and 85BR control chain circuits identical with those controlled by the relays BIAR to BSAR. It is not necessary that these two chain circuit systems be the same, as there are many ways in which the chain circuits may be arranged, and other sets of relays controlled by the stepping switches control diferent arrangements of chain circuits, as will be described later. The conductors entering the two chain circuits at the armatures of relays `BIBR and 83BR have been designated by the reference numerals 44B and 49B. The conductors 44B and 49B do not connect directly to conductors 44 and 49, respectively, as do the conductors 44A and 49A, respectively, but connect instead to the outer left-hand armature and to the right-hand armature, respectively, of a relay 9I. The back contact of the outer left-hand armature of relay 9| is connected through the second winding, counting from the top, of a relay 92 to conductor 44. Similarly, the back contact of the right-hand armature of relay 9| is connected through the third winding of relay 92 to conductor 49. The front contact of the outer left-hand armature of relay 9| is connected directly to conductor 44 and the front contact of the right-hand armature of relay 9| is connected directly to conductor 49. Thus when relay 9| is deenergized conductors 44 and 44B are interconnected through a winding f relay 92 and conductors 49 and 49B are interconnected through another winding of relay 92 whereas when relay 9| is energized conductors 44 and 44B are interconnected directly and conductors 49 and 49B are interconnected directly, the two windings of relay 92 being open.

. Conductor 61B extending from the contacts of the armatures l and 2 of relay SEBR extends to the back contact of the inner left-hand armature of relay 9| and to one terminal of the uppermost winding of relay 92, the other terminal of which is connected to the front contact associated with the same armature. The armature is connected to conductor 61 which extends to the No. 2 code segment of distributor 3|. When relay 9| is deenergized, conductors 61 and 91B are interconnected directly and the circuit of the uppermost winding of relay 92 is open. When relay 9| is energized, conductors B'I and 61B are interconnected through the uppermost winding of relay 92.

The operation of relay 9| is controlled by contacts I93` shown in Fig.` 1. Contacts 99 are normally open but are closed'by the operation of a locking bail arm 94 which is rocked in counterclockwise direction by a spring 96 under the control of a cam 91 associated with the cam assemf bly which controls the operation of transmitting contact |3. Cam l9'! is shown in the rest position and is rotated one revolution for each code Combination generated by transmitting contacts |3. This feature is more fully disclosed in Patent 2,018,368 granted October 22, 1935, to R. A. Lake and particularly` in Fig. 5 'oi' that patent. The disclosure of the Lake patent is incorporated herein by reference as part of the present speciiication. One of the contacts 93 is connected to ground and from the other contact a conductor 98 extends into the repeater circuit (not shown) for effecting a control fully disclosed in the copending application. A branching conductor 99 extends from conductor 98 toone terminal of relay 9| (Fig. 2) the other terminal of which is connected to grounded battery of the same polarity as the battery connected to conductor 98 in the repeater circuit, so that when contacts 93 are closed, relay 9| will be energized and when contacts 93 are open no energizing circuit for relay 9| will be completed through conductor 99 into the repeater circuit. From the foregoing it will be apparent that relay 9| will be energized only during the transmission of signals generated by transmitting contacts lf3. When signals are being received from a distant station over conductor I9 the local transmitter will not be operated, contacts 93 will remain open and relay 9| will remain released.

Before proceeding with the description of further features and elements of the apparatus, the operation of the apparatus heretofore described in ciphering signals to vbe transmitted to a distant station and in deciphering signals received from a distant station, will be described. The ciphering of a signal to be transmitted will iirst be considered. Upon the operation of transmitting contacts I3 to transmit a signal, the first impulse is the start signal which is of spacing nature and this causes the relay 6 to go to spacing, thus completing the energizing circuit for start magnet 62 over a circuit previously traced. The start magnet permits brush arm 53 to be driven and the brushes iirst encounter start segment 41. This segment is connected to conductor `44 so that conductor 44 becomes connected to conductor 29 through the brushes of the distributor while the outer brush is traversing the start segment 41. Conductor 49 has no direct connection to any segment of the distributor 3| but extends directly to the cipher coding relay system in Figs. 2 and 3, the return leads of which are to the code segments of the distributor, so

that no circuits can .be completed over conductor 49 while the brushes are .traversing the start segment. Accordingly, a circuit is traced from ground .on the spacing contactof relay `I 6 through .the armature of the relay .and conductor 3.1 to the bridge corner l38. At this point the cond-uctive .path divides, part of the current flowing over resistor 4I to the bridge corner E3 and the .remainder flowing through resistors 39, 4'2 and operating winding of .relay I1 from right to left to the bridge corner 4.3. r.he path reunites at the bridge corner 4'3 and .continues over conductor 44 tothe start segment 4 1 then Vto the inner ring of Ythe distributor, conductor 29 locking Winding of relay I6 and the resistor 21 through battery 28.to ground. Output relay I] is polar and with ground .on the armature of relay I6 and the circuit .of the operating Winding of relay I1 extended -over conductor .44, current flows through the .operating Winding of relay I1 in the direction to drive the armature of that relay to spacing. The current through the locking winding of relay IS is Vin the direction to 4hold relay 6 .in thespacing condition even though the start impulse of spacing nature received over conductor l8should cease and a marking impulse should lbe substituted before the .brushes have left .start segment 41.. From this it vfollows that .the locking windingof relay 'I 6 is paramount to the oper.. ating Winding. With relay condition a spacing impulse is transmitted over conductor 32 to the repeaterJ wherein it is repeated to the Aline extending to the distant station, and current is .supplied from the spacing contact of relay I1 through .the locking winding of that relay in the direction to hold the relay in the spacing condition. As soon as the brushes leave vthe .start .segment y4'! the circuit through the operating winding of output relay I1 and through 'the flocking Winding of input 'relay 16 is interrupted but the circuit through the locking winding of .relay I1 remains. Relay I 6 is noW free 'to be operated in response to the first code impulse of the signal but the locking Winding of relay I1 assures .that the start signal shall endure until a circuit through the operating Winding of relay l1 is again completed, which cannot occur until the brushes reach the No. 1 code segment ofthe distributor. The .operating `Winding of relay I1 is paramount to .the locking Winding and can move the armature of the relay Whenever .the operating winding becomes energized, although the locking Winding is seeking to hold the armature in Vthe position to yWhich it had last been moved.

Assume that the first code impulse of the signal generated by contacts I3 'is of marking nature, as a result vof which a marking signal will be received b y .relay I6 over conductor I8 and the armature will .be restored to the marking position. Assume alsothat the relays SIAR to BEAR are lenergized in such combination that 'a conductive path will be extended over conductors M and 44A to conductor 66. For this .condition there 'are four possibilities. vIf relay 85AR is deenergized the connection will be established with both of the relays BSAR and .84AR also deenergized or with both of 'the relays BSARv and MAR energized, the relays '8,IAR and 82AR having no effeet. If, on the kother hand the relay SSA'R is energized, the connection will be established with both of the 'relays BIAR and 82AR alsofenergized or With the relays 8IAR 4and BEAR both deenergized, the relays .BBAR and MAR having no effect. The .circuit is traced from ground through I1 in the spacing l the battery on the-,marking .contact of relay IB through the armature of that relay, conductor .31 through the branching paths of the bridge net- Work including the operating winding of relay I1 then through conductors 44 and 44A, armatures and contacts of relays BIAR to BSAR, conductor 6B, the N o. 1 contact of distributor 3|, the brushes and inner ring of that distributor, conductor 29, locking winding of relay I S'and resistor Z yto ground. Except for the .addition of conductor 44A, contacts and .armatures `of relays BIAR to 8 5AR and conductor B6, this ,is .the same ,path that was traced inconnection with the transmission of -,the start signal. However., `the polarities have been reversed because the armature A of relay l' now receives battery .connection instead of ground connection. Thereversal of polarity on the bridge ,network and through .the operating winding -of .relay l1 causes the armature of that relay to ,be moved to its markingcontact to effect the transmission ojf a marking signal overcomductor 32 and to com-plete a circuit .from 4the marking contact through the locking winding of relay I1 to hold the armature on themarking contact. If the first impulse of the code .combination had been spacing the polarity applied to the bridge circuit network would have been the same .as that applied in response to .the ,start signal and with the circuit completed to conductor .29 over conductor M the armature of relay I1 would have remained on the spacing contact,

Assume now that the No. 1 impulse of the code combinationis marking, Which Was the condition originally assumed, but that the relays BIAR. to BSAR are energized in such combination that they complete va conductivepath to conductor 6 6 over conductor 49A from conductor 49. There are four conditions of the relays under which this can occur. If relay 85AR is deenergized the connection will be made if either Iof the relays BSAR or 84AR is energized and the other is .deenergized the relays lARand BZAR having no effect. On the other hand, if the relay BSAR is energized, the circuit will be completed if either of the relays SIAR or 82AR is energized and the other is deenergized, the relays 83AR and BIIAR having no effect. The circuit is traced from .ground through the battery on 'the lmarking contact of relay IS through the armature andconductor 31 tothe bridge'corner 38. The .current now .divides in a different manner, one path being traced through resistor 39 ,to bridge corner 48 and the l other being traced through resistor 4I, operating Winding of relay I1 from leftto right and resistor 42 t'o'bridge corner 45. From this `point the cirarmatures and contacts of relays MARIO 85AR, conductor 66, the No. 1 code segment, brushes and inner ring of distributor 3|, conductor 29 locking winding of relay I6 and resistor 26 to ground. With the circuit completed from bridge corner v118 instead of bridge corner 43 the current through the operating Winding of relay I1 is in the `reverse of the direction in which it ilowed when with the armature of relay I6 on .the marking contact the circuit was completed through conductor `MLso that the armature .of relay I1 .is driven to the spacing contact to transmit a spacing signal over conductor 32 and the current through the locking winding-of relay I 1 holds the armaturev on the spacing contact. There has been no reversal of the direction of current through the locking Winding of .relay |76 so that its .armature remains on the marking con-tact. If instead of being of marking nature the first vcode impulse generated by transmitting contacts I3 had been of spacing nature, with the path to the locking winding of relay I6 extended over conductor' 49 as just described there would have been a reversal of the polarity on the operating winding of relay Il which over the same conductive path would have caused the armature of the relay to assume the marking position.

By Way of recapitulation there are four possible conditions of signal transmission. When relay I6 responds to a spacing signal and the circuit is completed over conductor 44 a spacing signal will be transmitted over conductor 32. When relay I6 responds to a marking signal and the circuit is completed over conductor 49, a spacing signal will be transmitted over conductor 32. When relay IB responds to'a's'p'acing signal and the'c'ircuit is completed over conductor 49 relay I1 will be operated to marking to cause the transmission of a marking signal over conductor 32. When relay I5 responds to a marking signal and the circuit is extended over conductor 44, relay I1 will be operated to marking and a marking signal will be transmitted over conductor 32. The further summarizing statement may be made that relay Il. operates in correspondence with relay I6 when the circuit is completed over conductor 44, and operates in reverse relation to relay I6 when the circuit is completed over conductor 49.

After the brushes have traversed the ve code segments and the ciphered impulses have been transmitted, the brushes traverse the stop segment 4t. At this time the relay IG receives the stop pulse, of marking nature, generated by contacts I3. 'I'he circuit is completed from the marking contact of relay IE through the bridge network including the operating winding of relay I'I, over conductor 44, stop segment 4S, inner ring of the distributor, and conductor 29 to the locking Winding of relay IS. This corresponds to the fourth condition recited in the preceding paragraph of recapitulation and relay I'I will be operated to the marking condition to transmit a marking signal, which is the true stop impulse.

It is to be noted that the cipher coding relays SIAR to 85ER in Figs. 2 and 3 have no effect upon the transmission of the start and stop signals. The circuit through the operating winding of relay Il is completed through conductor 44 in both cases, but relay IE is spacing for the start signal and marking for the stop signal, and relay I'I is correspondingly driven spacing for the start signal and marking for the stop signal.

After the brushes leave the stop segment they encounter the rest segments and are arrested, since the start magnet 62 was released when the brushes left the rest segment and presumably the relay I6 will still be responding to the stop signal when the brushes reach the rest segments, so that the start magnet will remain released. When the relay IB responds to the start signal of the next code combination, magnet 62 will again be energized and Will release the shaft 54 for another cycle of rotation.

There will now be described the operation of deciphering received code combinations. The code combinations are transmitted from a distant station having ciphering apparatus of the same type as that disclosed in the drawings accompanying the present specication and it is a characteristic of the system that when ciphered messages are being transmitted identical arrangements of connections between the cipher coding relays and the stepping switch banks are established at both stations and the brushes of the stepping switches are adjusted to the same starting points and are advanced together by local control individual to the stations, so that the cipher coding relays at the receiving station establish the same connections from the conductors 44 and 49 to the distributor code segments as are established at the transmitting station. It has been shown that the cipher coding relays have no effect upon the output relay I'I when the input relay I 6 responds to the start signal of spacing nature and therefore thatthe output relay follows the input relay to spacing condition. When the start signal of spacing nature is received from the distant station it is repeated by the repeater to the input relay I E which completes a circuit over conductor litandthe start segment of the receiving distributor, which was released for rotation when the start signal was received, to the locking winding of input relay I6 and the output relay II goes to spacing.

The first message code impulse was previously assumed to be of marking nature with the cipher code circuit established over conductor 44 and it was found that the output relay transmitted a marking signal. Accordingly, the input relay of a receiving station would go to marking condition and would complete a circuit over conductor 44 identical with that which was described when the first impulse of text code was assumed to be marking. The polarity on this circuit is such that the output relay I1 is operated to the marking condition and impresses a marking signal on conductor 32 which is repeated to the selector magnet I2. In this way the original text marking signal, which was treated in such a way by the cipher code relays that it was transmitted unchanged as a marking signal, is received and similarly treated through an identical arrangement of the cipher code relays and is repeated unchanged as a marking signal which is used to control the receiving printer. Corresponding deciphering operations occur with reference to the other three possible conditions. Thus with a text code impulse of spacing nature controlling output relay I'I over conductor 44 and causing the relay to transmit a spacing signal, the received spacing signal, controlling relay I'I over conductor 44 causes the output relay Il to generate a spacing signal which is repeated to the printer magnet I2. A text code marking impulse, controlling the output relay I1 over conductor 49 to cause the relay to transmit a spacing signal, is received in cipher as a spacing signal which, controlling output relay II over conductor 49 causes the relay to generate a marking signal which is repeated to the selector magnet I2. Finally a text code signal of spacing nature controlling the output relay I 'I over conductor 49 to cause the relay to transmit a marking signal is received as a marking signal by the input relay I6 and, controlling output relay II over conductor 49, causes the relay to generate a spacing signal which is repeated to the selector magnet I2. From this it will be apparent that the deciphering of received signals in order to derive the plain text codes therefrom is accomplished by ciphering received codes under the same conditions that were employed at the transmitting station to convert the text code signals into ciphered signals.

Reference has been made previously to the fact that the chain circuit arrangements of armatures and contacts of the cipher coding relays may differ from the arrangement of the contacts and armatures of relays BIAR toV B5AR and of connected to the brushes associated with contact banks |3|A to |3|E, respectively, of a stepping switch which is operable by stepping magnet |3| and which has a sixth contact bank designated |3|F. The contacts of the five stepping switch banks |3|A to |3|E are connected in a manner similar to the contacts of stepping switch banks |215A to |25E, but in different combinations, to ve conductors |36, |31, |38, |39 and |40 which extend to the inner right-hand armature and to the four left-hand armatures of a relay |4l. These five armatures cooperate with front contacts from which ve conductors |46, |41, |48, |49 and |50 extend to the lowermost group of ve single circuit jack spring elements of multiple jack H8. A multiple plug |5| has ten prongs which enter the ten lower jack elements of multiple jack I8 and each of the lower ve prongs of plug |5| is connected to one of the upper five prongs of that plug. Several plugs having diiTerent connections as between the lower five and the upper ve prongs may be employed for varying the connections between conductors |46 to |50 and the third group of ve jack elements of multiple jack I8, counting the groups from the top. From these five jack elements conductors |6|, |62, |63, |64 and |65 extend into Fig. 3 and connect individually to one terminal of each of the stepping magnets 8| to 85, the other terminal of which is connected to battery. It will be apparent that as conductors |33, |04, |09, |4 and ||1 receive ground connection selectively under the control of certain of the relays controlled by the stepping switch banks in Figs. 2 and 3, such ground connections will be extended to certain ones of the conductors 2|, |22, |23, |24 and |25 depending upon the arrangement of interconnection of the prongs of plug H9, then to certain ones of the conductors |26, |21, |28, |29 and |30, depending upon the position of the brushes associated with stepping switch banks I25A to |25E, then to certain ones of the conductors |36, |31, |38, |39 and |40, depending upon the position of the brushes associated with the stepping switch banks |3|A to |3|E, through the inner right-hand and the four left-hand armatures of relay |4| when that relay is energized, through conductors |46, |41, |48, |49 and |50 to certain ones of the conductors |6|, |62, |63, |64 and |65, depending upon the arrangement of interconnection of the prongs of multiple plug |5l, through the windings of certain ones of the stepping magnets 8| to 85 (Fig. 3)1, to battery to cause the energization of the stepping magnets. The energization of the stepping magnets will occur upon the energization of relay |4|, and the release of the stepping magnets upon the release of relay 4| will cause the stepping switch brushes controlled thereby to advance one step, since these stepping switches are of the type which advance the brushes on the back stroke or release of the stepping magnet.

One terminal of relay |41 is connected to grounded battery and the other terminal is connected to conductor |42 extending into Fig. 1 and there connected to one contact of a normally open contact pair |43, the other Contact of which is connected to ground. Contacts |43 are operable by a cam |44 carried by the driving shaft 54 of distributor 3| and the cam |44 is arranged to close contacts 43 after the brushes have traversed the start segment 41 and t0 permit the con tacts |43 to open just before the brushes encounter the rstop segment 46. From this it will be apparent that the stepping magnet in Fig. 3 will be energized prior to the transmission of the first code impulse of a code combination and will be released to effect the advancement of the stepping switch brushes after the transmission of the last code impulse of a code combination has been initiated, so that the cipher coding relays will not be disturbed during the ciphering or deciphering of a code.

The outer right-hand armature of relay |4| cooperates with a front contact which is connected to ground and the armature is connected by conductor |32 to one terminal of the winding of stepping magnet |25 the other terminal of which is connected to grounded battery. Thus each time the relay |4| is energized theenergizing circuit of stepping magnet |25 will be completed and upon the release of relay |4| stepping magnet |25 will be released to effect the advancement of the brushes associated with stepping switch banks |25A to |2511', concurrently with the advancement of the brushes of the stepping switches shown in Figs. 2 and 3.

The stepping magnet |3| has one terminal connected to grounded battery and the other terminal connected to the middle right-hand armature of relay |4|. From the front contact with which this armature cooperates conductor |33 extends through Fig. 1 into Fig. 2 to the front contact of a relay |34, the armature of which is connected to ground. One terminal of the winding of relay |34 is connected to grounded battery and the other terminal is connected by conductor |66 extending into Fig. 1 to one contact of a normally open pair of contacts |61. Contacts |61 are closed at the same time as contacts |43 by cam |44. The other contact of the contact pair |61 is connected by conductor |68 extending into Fig. 2 to one terminal of the lower winding of relay 92, the other terminal of which is connected to the single contact with which the armature of the relay cooperates. The armature of relay 92 is connected by conductor |69 extending into Fig. 3 to the front contact associated with an armature of relay SEER. This armature is connected by conductor to the front contact associated with an armature of relay 84ER. This armature is connected by conductor |12 t0 the front contact associated with an armature of relay 83ER which is connected to ground.

From the foregoing it will be apparent that when relays 83ER, 84ER and BEER are energized, ground connection will be extended over conductor |69 to the armature of relay 92. If the armature of relay 92 is operated into engagement with the right-hand contact, the ground connection will be extended through the lower winding of relay 92 and over conductor |68, through the contacts |61 when closed and over conductor |66 and the winding of relay |34 to grounded battery so that relay |34 will be energized in series with the lower winding of relay 92, which is a holding winding. With relay |34 energized ground connection is extended over conductor |33 to the middle right-hand front contact of relay |4| which will be energized since when contacts |61 are closed, contacts |43 are also closed, and through the middle right-hand armature of relay |4| and the winding of stepping magnet |3| to grounded battery. When contacts |43 reopen and relay |4| is released the energizing circuit for stepping magnet 3| is opened and the magnet advances the brushes associated with the stepping switch banks |3|A le to ISIF to the next contacts. The operation of stepping magnet I 3I to effect the advancement of its associated brushes is thus observed to be dependent upon two factors which do not have cyclic occurrence, namely, the operation of the armature of relay 92 into engagement with its right-hand contact and the energization of relays BSER, 3ft-ER and SEER. Other factors also involved which do have cyclic occurrence and are introduced for timing purposes are the preparation of the energizing circuit of relay |34 at the cam-operated contacts IST and the completion of theV energizing circuit of relay I 4I at the contacts |43.

The operation of relay 92 to complete the energizing circuit for relay |34 is dependent upon the occurrence of a marking impulse as the second code impulse of plain text code signals, by Y which is meant code signals before being ciphered or after being deciphered, The requirement that relays 83ER, MER, and BSER be energized in order to extend a ground connection through to the armature of relay 92 provides that relay |34 Shall be energized only in response to some of the occurrences of a marking impulse as the second impulse of text code. The reason for this is that in a permutation code, one-half of the total number of available codes will have the second impulse ofV marking nature so that if the stepping magnet I3I were controlled solely in accordance with the operation of relay 92 the average frequency of operation of the stepping magnet would be once for each two codes received or transmitted. It is preferablethat the stepping magnet I3I shall operate less frequently than this since the stepping magnet |25 operates to advance its associated brushes once for each code combination received or transmitted. By supplying the ground connection for operating stepping magnet II through armatures and front contact of the three relays MER, MER and HER, the average frequency of operation of stepping magnet IBI will be once for every eight characters received or transmitted.

lIhe operation of relay 92 lwill now be described J and the situation involved in the transmission of signals to a distant station will iirst be considered, this involving signalg generated `by the transmitting contacts I3. Two facts are to be noted with reference to signal transmission. One is that the input relay I6 directly follows text code signals generated by the transmitting contact I3. When a marking signal is generated, relay IE goes to marking in response thereto. The other is that each time the transmitting contacts I3 are operated to generate a signal contacts 93 are closed and complete the energizing circuit for relay 9| (Fig. 2), so that its armatures engage their front contacts. Assume that relay I is in marking condition for the second impulse of a code signal and that the relays 8|BR to 853B, are energized in combination to interconnect conductors 44 and MB. The circuit is traced from negative battery on the marking contact of relay |'6 through conductor S'I to the bridge corner 353, through the branching paths of the bridge network rejoining at bridge corner 43 through conductor lili, front contact and outer left-hand armature of relay 9i, conductor 44B, armatures and contacts of certain of the relays BIBR to GEBR, conductor 51B, uppermost winding of relay 92V entering at the top of the winding andk leaving at the bottom of the winding, front contact and inner left-hand armature of relay 9|, conductor 6l, No. 2 code segment and inner ring of distributor 3l, conductor 29, locking winding of relay I5 and resistor 26 to ground. The windingsv of relay.92 are polar and Whenthe `circuit is as traced With theupper terminal of the upper Iwinding of relay 92 at the marking battery potential and the lower terminal connected to vthe path to ground, the Awinding is energized in the direction to drive the armature to the single right-hand contact to complete the energizing circuit for relay |34. The circuit includes the lower or locking winding of relay S2 which `becomes energized to .hold the armature on the right-hand contact. The locking winding of relay 92 is subordinate to each ofthe `other three windings so that upon the energization Vof one of them in the direction to restore the armature to its left-hand position, the locking winding will not prevent such restoration. It'merely holds the armature on the .right-'hand contact to hold relay |311 energized until that relay is released bythe opening of contacts |67 so that the circuit of stepping magnet ISI will not be interrupted and the brushes associated therewith stepped until after the transmission of the last code impulse of a code combination has been initiated. Relay 92 preferably has bias Which may be either mechanical or electrical but which should, however, be subordinated to all of the four windings shown, including the holding winding, tending to restore the armature to its left-hand position so that after being operated to the right-hand position and held there until after the last impulse of a code has been initiated, the armature will be restored to the left-hand position upon the interruption of the holding circuit and Will not remain in the right-hand position until one of the upper three windings becomes energized in the direction to drive the armature to its left-hand position. Thus the armature of relay 92 will remain in the right-hand position only during the remainder of a cycle of distributor 3| in which it was operated to that position due to the occurrence of the marking impulse as the second impulse of a text code combination.

If at the time that the relay I6 was operated to marking in response to the second impulse of the code signal being rgenerated the relaysI SIBR to BR had been energized in such combinations as to connect conductor B'IB to conductor 49B,

"i the circuit would be traced from the armatureof relay I6 through the branching paths of the bridge network from the bridge corner 38 to the bridge corner 48 and then over conductor 49, the front contact and right-hand armature of relay 9| 'to conductor 49B then to conductor 61B through the armatures and contacts of the second row of cipher coding relays in Fig. 2 and then to the upper terminal of .the upper winding of relay 92 the same as before. It makes no difference whether the circuit from the marking contact of relay I6 is completed over conductor 44 or over conductor 49 the Ibattery polarity applied to the upper winding of relay 92 will besuch as to drive the armature to the right-hand position. When the second impulse ofthe code generated by transmitting contact I3 is of spacing nature, the circuits, traced over conductor 44 or conductor 49, depending upon the condition of the second row of cipher coding relays in Fig. 2 will be the same but the polarity applied to the upper Winding of relay 92 will be reversed, ground being connected to the upper terminal of the winding and negative battery being connected to the lower terminal of the upper winding through the locking winding of relay I6. The upper winding of relay 92 will thus be energized in the opposite direction, tending to drive the armature toits lefthand position to which it has already been operated by its mechanical or electrical bias.

The operation of relay 92 in response to received signals involves a different problem. Relay I6 is not now responding to text code signals but is responding to ciphered signals and these signals are deciphered so that the plain text signals appear at relay I1. Accordingly, it is necessary toI operate the armature o-f relay 92 to its right-hand position when relay I1 is driven to marking for the second impulse of a received code combination. This is accomplished by the two middle windings of relay 92.

YWhen signals are being ireceived, contacts 93 are not operated so that relay 9| remains deenergized. For an understanding of the operation of relay 92 by its two middle windings it is necessary to remember that when the circuit of the operatingl winding of relay I1 is completed from the marking contact of relay I6 over conductor 49, the armature of relay I1 goes to spacing, that when the circuit is completed from the spacing contact of relay I6 over conductor llt the armature of relay I1 goes `to spacing, that when the circuit is completed from the spacing contact of relay IS over conductor 49 the armature of relay I1 goes to marking, and that when the circuit is completed from the marking contact of relay I6 over conductor 44 the armature of relay I1 goes to marking.

Taking the first of these four conditions the circuit is traced from the marking contact of relay I6 over conductor 31 to the bridge corner 38, through the two branches of the bridge network r'ejoining at the bridge corner 49, then over conductor 49 to the lower terminal of the third winding of relay 92 counting from the top, then from the upper terminal of this winding through the back contact and right-hand armature of relay 9| to conductor 49B, through armatures and contacts of the second row of cipher coding relays of Fig. 2, conductor 51B to the back contact and inner left-hand armature of relay 9| where the circuit of the uppermost winding of relay 92 is now open, conductor 61, No. 2 code segment and inner ring of distributor 3|, conductor 29, locking winding of relay I6 through resistor 26 to ground. The armature of relay I1 is caused to go to spacing when the circuit and battery polarity is as thus traced, from which it follows that the second impulse of the deciphered text code is of spacing nature and the armature of relay 92 should not be operated to the right-hand position. Accordingly, the third winding of relay 92 is so polarized that with negative battery connected to the lower terminal of that winding and ground connected to the upper terminal the magnetic field produced by the winding tends to drive the armature to its left-hand position, which position it already occupies.

For the second condition the circuit is traced from ground on the spacing contact of relay I through conductor 31 to the bridge corner 38, then through the branching paths of the bridge network to bridge corner 43, then over conductor 44 to the second winding of relay 92 entering at the right-hand terminal and leaving at the lefthand terminal thereof, through the back contact and outer left-hand armature of relay 9| to conductor 44B, to conductor 61B through armatures and contacts of relays 8|BR to 85BR and from this point over the path traced in the preceding paragraph to ground through the locking winding of relay I6 and resistor 21 to the negative ter` minal of battery 28, the positive of which is grounded. The circuit arrangement and battery polarity are such that the armature of relay |1 is driven to spacing from which it follows that the armature of relay 92 should not be operated to its right-hand position. Accordingly, it may be stated that with ground on the right-hand terminal of the second winding of relay 92 and negative battery on the left-hand terminal the magnetic field generated is in the direction tending to drive the armature to the left-hand position.

For the third condition the circuit path is identical with that described for the rst condition but the battery polarity is reversed so that ground is connected tothe lower terminal of the third winding of relay 92 counting from the top and negative battery is connected through the locking winding of relay I6 to the upper terminal of the third winding of relay 92. This causes the armature of relay 92 to be driven to the right-hand position which prepares or completes the energizing circuit for relay |34 as the case may be. The circuit arrangement and battery polarity is such that the armature of relay |1 is driven to the marking contact.

For the fourth condition the circuit connections are the same as those described in connection with the second condition but the battery polarity is reversed, negative battery being connected to the right-hand terminal of the second winding of relay 92 and ground being connected through the locking winding of relay I6 to the left-hand terminal of the second winding of relay 92. This f causes the armature of relay 92 to be driven to the right-hand position and the armature of relay I1 to be driven to the marking contact.

Figs. 5 and 6 show apparatus which in cooperation with the stepping magnets 8| to 85, |3I and |25 and with the sixth contact bank of each of the stepping switches, designated 8 F to 85F, I3 |F and |2'5F, provides for selectively adjusting the stepping switches shown in Figs. 2 and 3 and the left-hand stepping switch in Fig. 4 to any of a plurality of starting points and for adjusting the brushes of the stepping switch at the right of Fig. 4 to the No, 1 contact as a starting point. Referring rst to Fig. 5 a group of seven jacks 20| each having tip, ring and sleeve contacts have those contacts connected to twenty-one of the twenty-two contacts of stepping switch bank 8IF. These connections may be made to contacts 1 to 21, inclusive, of the stepping switch bank or they may be made to contacts 2 to 22. It is of no consequence which one of the contacts of bank SIF is left unconnected but at all stations it should be the corresponding contact. Similarly twenty-one of the contacts of bank 82F are connected to the twenty-one contacts of seven jacks 202, twentyone contacts of bank 83F are connected to the twenty-one contacts of seven jacks 203, twentyone of the contacts of bank 84F are connected to the twenty-one contacts of seven jacks 204, twenty-one of the contacts of bank BEF are connected to the twenty-one contacts of seven jacks 205 and twenty-one contacts of the stepping switch bank |3IF (Fig. 4) are connected to the twenty-one contacts of seven jacks 206 (Fig. 6).

By means of three patching cords, each having three conductors and provided at both ends with three-circuit plugs, connection may be made from any selected three of the jacks 20| to three jacks 2I|. From the ring contact of the uppermost jack 2II, from the sleeve contact of the middle one of jacks 2II and from the tip contact of the lowermost jack 21|, individual connections extend to conductors 22|, 222 and 223, respectively, in Fig. 6. In addition, a connection is extended from'the lower or ground terminal of stepping magnet 81 over conductor 21S into Fig. 6. Other sets of three jacks are designated by the reference numerals 212, 213, 214, 215 and 216. The ring contact of the upper, sleeve contact of the middle, and tip contact of the lower of jacks 212 are connected to conductors Y223, 221 and 228, respectively, in Fig. 6. The lower or ground terminal of Stepping magnet 82 is connected to conductor 225 which extends into Fig. 6. Similarly, the ring `contact of the uppermost jack 213, the Ysleeve contactrof the middle jack 213 and the tip contact of the lower jack 2|,3 are connected to conductors 23|, 232 and 233, respectively, in Fig. l6. The ground terminal of stepping magnet 83 is connected to conductor 234 which extends into Fig. 6.

Ten manually operable keys 231 are associated with the conductors 219, 22|, 222, 223, 225, 226, 221, 228, 23|, 232, 233 and 234 in Fig. 6. Each of the keys 231 has three pairs of normally o'pen contacts. Considering rst the lower pairs of contacts, one contact of each pair is connected to conductor 219 and the other contact of each pair is connected to one of the three lconductors 22|, 222 and 223. In the specific arrangement shown in Fig. 6 four of the other contact springs are connected to conductor 22|, three are connected to conductor 222 and three are connected to `conductor 223. Of the middle pairs of contacts one contact of each pair is connected to conductor 225 and the other contact of each pair is connected to one of the conductors 226, 221 and 228. Of the upper pairs of contacts, one contact of each pair is connected to conductor 234 and the other contact of each of the pairs is connected to one of the conductors 231,232 and 233.

A second set of ten keys 238 is similarly associated with twelve conductors, nine of which extend from contacts of jacks 21d, 215 and 2|5 and the remaining three of which extend from the ground terminals of stepping magnets 84, 85 and |3|. The connections from the contact pairs of keys 238 to the twelve conductors with which the keys are associated have been shown as corresponding to the connections from the contacts of keys 231 to the twelve conductors with which they are associated. It is necessary that the connections be alike only as regards the three conductors extending from the ground terminals of stepping magnets 84, 85 and |31 but as to the connections to the conductors extending from the jacks 2|4, 215 and 2|6 the arrangement may be dierent and in actual practice would probably be different. It should be noted also that the recitation of connections from conductors 22 222, 223, 228, 221, 228, 23|, 232 and 233 to specific contacts of jacks 21|, 2l2 and 2|3 is solely by way of example in order to enable circuits to be traced over which the keys 231 eiect a control, and that in practice the connections between any one set of conductors, such as the conductors 22 I 222 and 223, and the contacts of the jacks to which they are connected, in this case the jacks 21|, may be transposed.

As shown in Fig. 6, a normally open key 24| has one contact connected to ground and the other contact connected to one terminal of a relay 242, the other terminal of which is connected to grounded battery. Relay 242 has seven armatures all connected to ground and seven .front 24 contacts from which conductors 8W, 82V, 83V, 84V, 85V, |3|V `and |25V extend through the interrupter contacts of stepping magnets 8|, 82, 33, 84, 85, 13| and 125, respectively, to the ground terminals of those magnets.

A relay 8|FR has one terminal connected to the conductor 81V and the other terminal connected to the brush associated with stepping switch bank 3|F. Relays 82FR, 83FR, 84FR, BSFR, |3|FR and |25Fl=|l are similarly connected between the conductors 82V, 83V, 84V, 85V, |'3|V and |25V, respectively, and the brushes associated with stepping switch banks 82F, 83F, 84F, 85F, |31F and |2515?, respectively. Each of these relays has a single armature and front contact. The front contact of relay 8|FR is connected to one terminal of lamp 25|, the other terminal of which is connected to ground. From the armature of relay 8|FR a vseries or chain circuit, open at the armature and front contact of each of the other. relays, extends through to the front contact of relay |25FR which is connected to grounded battery. The last contact in stepping switch bank |25F is connected to the ground side of stepping magnet and no other contact in that bank has any connection.

For the purpose of describing the operation of establishing starting points for the stepping switches, several assumptions will be made. It will be assumed that patching cords are connected from Athe three jacks 21| to theV uppermost three of the jacks 28|, that patching cords are connected from the jacks 212, to the middle three of the jacks 232, which would be'the third, fourth and fifth of those jacks counting from the top and that patching cords are connected from jacks 213 to the lower three jacks of the group 203. Patching cords will also be connected from the jacks 2|4, 2|5 and 216 to three jacks in each of the sets 264, 205 and 206 but the conductive paths established thereby will not be Vtraced in detail since the mode of operation will be fully exempliiied by the description relative Vto the jacks for which specific connections have been assumed. It will also be assumed that the extreme left-hand one of the keys 231 is operated, these being locking keys, and that some one of the keys 238 is operated.

A control circuit may now be traced from the lower or ground terminal of stepping magnet 8| over conductor 2|8 through the lower pair of contacts of key 231, now closed, conductor 22| t0 the ring contact of the uppermost one of the jacks 21|, through the patching cord assumed to be connected from the uppermost jack 21| t0 the uppermost jack 28| and through the ring contact of the last-mentioned jack to the twentieth contact of bank 8|F, assuming that the tip contact of the uppermost jack 28| is connected to the twenty-rst contact of bank 81F and the sleeve contact of the lowermost one of jacks 20| is connected to the No. 1 contact of bank BIF, the other contacts of the jack 28| being connected in order from bottom to top around the stepping switch bank 8|F in the direction of rotation of the brush as indicated. Since the brush associated with stepping switch bank 8 IF is probably not engaging contact No. 20 at this time, no circuit will be completed over this path as a direct result of the operation of the Aextreme lefthand key 231.

A second conductive path may be traced from the ground terminal of stepping switch 82 over conductor 225 through the middle pair of closed contacts of the left-hand key 231 to conductor 228 which, as previously stated, is connected to the tip contact of the lowermost jack of group 2I2. The path is extended over the patching cord which is connected to the lifth jack in group 202 and as the tip contact of this jack is the ninth jack contact counting from the bottom, it is assumed that the path extends to the No. 9 contact of stepping switch bank 82E'.

A third conductive path is traced from the ground terminal of stepping switch 83 over conductor 234 through the uppermost pair of contacts of the left-hand key 231 to conductor 233 to which the tip contact of the lowermost jack in group 2I3 is connected. The patching cord extends to the lowermost jack in group 203 and the path is extended over the tip contact of this jack to the No. 3 contact of stepping switch bank 83E since the tip Contact 0f the lowermost jack is the third contact counting from the bottom.

The particular one of the keys 238 which has been operated completes similar conductive paths from the ground terminals of stepping magnets 86, 85 and I3I to a contact in each of the stepping switch banks 841, 85E and ISEF. When one key in each group in Fig. 6 has been operi ated, the advancement of the stepping switch brushes to their start positions as selectively determined by the particular ones of the keys that are operated` and by the arrangement of the patching cord is initiated by the operation of key 24H which completes the energizing circuit for relay 242, and which must be held while the brushes are being advanced. Ground is applied through the armatures and front contacts of rebrushes are advanced by buzzer operation of their stepping magnets. Assuming that the brush associated with bank BIF is the first to reach the contact to which a conductive path has been extended by the left-hand key 231, namely, the

contact No. 20 of that bank, a circuit may be l traced from grounded battery through the winding of stepping magnet 8l over conductors 2I9, lower contact of the left-hand key 231, conductor 22I, ring contact of the uppermost jack of group 2H, patching cord, ring contact of the Y, uppermost jack in group 21H, contact No. 20 and brush of stepping switch bank 8IF, winding of relay SIFR, conductor BI V and front contact and armature of relay 242 to ground. Over this circuit the winding of relay BIFR is placed in series with the winding of stepping magnet 8| in shunt relation to the interrupter contacts of stepping magnet 8I so that the energizing circuit for stepping magnet 8| is not interrupted as a result of the opening of the interrupter contacts and the brushes controlled by stepping switch 8l remain in engagement with the No. 20 contacts of their respective banks. The relay BIFR becoming energized prepares the circuit of lamp 25|.

As the brush associated with each of the stepping switch banks 82E' to BSF, and I3IF reaches contacts to which a conductive path has been eX- tended by contacts of keys 231 or 238, substitute energizing circuits for the stepping magnets are established in shunt relation to the interrupter contacts and including the relays BZFR to BSFR,

. 26 and I 3IFR so that the stepping switch brushes are arrested and the circuit of lamp 25| is further prepared for completion. The brushes controlled by stepping magnet |25 advance until they reach the last contact whereupon a substitute energizing circuit for stepping magnet I 25 is completed to the last contact and brush of bank l25F' in shunt relation to the interrupter contacts and including the winding of relay I25FR. which becomes energized. Thus the brushes controlled by stepping switch I25 are invariably stopped on their last contacts.

The order in which the several sets of stepping switch brushes will be stopped and the relays 8IFR to 85FR, I3IFR and I25FR become energized will depend upon the distance the brushes must travel from the random positions which they occupied before key 24| was closed to the positions at which they complete substitute energizing circuits for their stepping magnets. When the last of the relays has been energized the circuit of lamp 25I will be completed and the lamp will be lighted. This serves as an indication that the brushes have reached rest positions as selectively determined by the operated ones of the keys 231 and 238, whereupon key 24| may be released to permit the release of relay 262. Relay 244 upon release removes the ground connections from the energizing circuits of the stepping magnets and of the lamp controlling relays so that the magnets and relays release, the magnets advancing the stepping switch brushes one step on the release stroke. This advances the stepping switch brushes to the next step beyond the one at which they were arrested and in the case of the brushes controlled by stepping magnet I25F the brushes are brought into engagement with the No. 1 contact as the starting point.

From the standpoint of operating routines, the changing of connections where there is provision for such changes may be made once each day, such as upon the starting of the days business in the morning, or more frequently if it is thought that greater assurance of secrecy is needed. Such changes may involve changing the locations ot plugs such as the plugs SICP, 85DP and 85EP through which connections from the stepping switch banks to the cipher coding relays are established, substitution of other plugs for the plugs I I9 and I5I in Fig. 4, and in connection with the establishment 0f new starting points for the stepping switches7 the rearrangement of the patching cords with reference to the jacks shown in Figs,'5 and 6. New starting points for the stepping switches may be established as frequently as is desired under the control of the keys 231 and 238 and must be established before intercommunication can be had in cipher between any two stations where a systern involves a plurality of stations of thetype shown in Figs. 1 to 6, inclusive, any two of which .may be interconnected through a central switch-

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