• 

REF ID:A39774 

• • 

Ootober 4. 1935 

....... ud. 111.Yelo~ Di.Tial•· 

(TtUma War Plana ~ TralJd.111 DlT11lon) 

1. .ltt.aobed. h..W are draft .,.S.t1cat1ou aad atx: dJ'awiac• 

OO'f9r1ag 8 - t.Jpa ot cOllVoll.lDg ..... tor OJ17Pt.Op'apble •oldael 

udng rotatable oo• atatol'•• !he ado pr11aolpl• 111, 1n "if op11d.•, 

aonl aad ft17 Yal.11r&bl•. It 1• euap.Ufted 111 several eabodlaent.. 

ahO'ID 1n the clrawinga. 

2. Tbi8 1a tbe Jo1at. J.lwatioa of the mdva1ped and OM o£ 

llJ' asaiata.at~, llr. l'r&Dk B. Boslett., laior Cr,rptan•qst. 

3. lt. is reca•_.ed. t.taat patent be appUed tor at once, to 

l!Pllegurd the pwerment'• lntweet., ._ t.haa&h lt _, aot 1-

de•lrable to allow the plteD't. to p to i... for 8Dll9 UM. 

•ola. 

I>ntt. 8P•oUioaUaaa, 

6 drawbge. 

pproved for Release by NSA on 09-30-2013 pursuant to E.O. 

13526 

!/ 
REF ID:A39774 

---

• 

The object of this invention is to provide new and useful improveaemts· in cipher maehines or cryptographic me<>Banisms utilizing rotatable 

commutators for enciphering a plain-language message by what is commonly 

known as a process of substitution, the latter being accomplished in a 

systematic manner so that the process of substitution may be automatically 

reversed in deciphering such an enciphered message, thus recovering the 

original plain-language message. 

In-the cryptographic mechanisms referred to there is usually .Provided 

a keyboard of the typewriter type, which controls a set of switches 

corresp0mding to message characters, and a set of signaling devices which 

may consist of a bank of glow lamps or magnets to indicate the message 

cllaraeters resultbg from operation of the keyboard. The set of switches 

of the keyboard and the set of sigrJaling or indicating devices are connected 

to eaeh other electrically by circuits and apparatus by means of which the 

aforesaid substitution is accomplished. 

The cryptographic principle of sueh cryptographic mechanisms, which 

will hereinafter be termed simply cryptographs, is based on the establishment of a plara~ty of electrical circuits or paths between the keyboard 

switches and the indicating devices through commutators of a special type 

now well known in the art. These commutators are constructed' in the form 

of flat disks bearing an annular set of contacts on each face, individual 

contacts of one face being connected by insulated conductors passing through 

I 

the disk to individual contacts of the other face in an arbitrary manner. 

In the literature of cryptography such commutators are <;alled "cipher wheels", 

"coding cylinders", and the like; but, for purposes of greater clarity in 

description they will hereina£ter be referred. to as "substitution commutators." 

In a single cryptograph there may be several such commutators juxtaposed on 

a common shaft. Thus, when more than one substitutio_~_~ommutator is used, · 

. ..., ~· 

the cipher letter obtained upon 4,epressing a kq of the keyboard is the re~:. <.,-, 

.0! ' the passage of an eleetrioal a~~ ~ a.long a complex path set up t~ -:.· tr 

all th.e juxta.poseG. subst~utators, thil!I path being coape:sed ~ as . ..._,~~ 

ma.DY' sub-paths joined sequent\all.7. •s ~ere ar.e eo.-.mtators. 

~fC~.~~) 
REF ID:A39774 

• • . ' . Gryptographs of the foregoing ~riptien may be divided into two 

categories. Into one gategory may be placed all Cr)"pt.ogr-apbs having· o:ae or ~ ... -, , ... , -

more substitution commutators~ rotatably moun.t~d on a shaft between two fixed 

end plates, each end plate blaring an annular ring of contacts, the latter 

being so.disposed as to coincide exactly with the contaets on the faces.of the 

substitution commutator·s. In e:cyptographs falling into this category the ke;ying 

switches of the manually operated keyboard are connected tp the contacts of one 

of the end plates, while members of-the bank of indj.cating devices are connected 

· ot twi~er:~tlll&1J1' eonta~ as· tae~-e<a-~ -ea the;~keybearcf ~t·A "d'~. to the contacts of the other end plate. Also a reversing switc£iiis provided, 

whick enables the aperator to interchange the connections between the two end 

plates, the bank of i:edicatimg devices and the keyboard switches so as to provide for enciphering and deciphering equivalency. Into the other category may 

be placed all cryptographs having a single end plate of the typ~ descr~bed. 

1 

J 

I 

.j 

·~ 

The latter aontacts are, however, connected to the movable members of a set 1 

of single pole, double throw switches, the number of switches . Oeing the same 

as the number of contacts provided on the end plate, and so constructed ~bat 

the switches are contro1led by the keys o:f the manually operated keyboard. 

Adjacent to the above-described end plat~f. are mounted one or more susst~tution 

- . 

commutators, the final co~utator, that is, the one most remote from the end 

plate, being what is hereinafter <,iescribed and referred to as a "reversisg 

commutator8 • The purpose of the reversing c~tator is to return a current 

. - entering the commutators at one contact on the end plate to some other eonts.ct ... t1tus cc>mes · 

on the same end plate1the current, H• • _g intq. the reversing plate via one 

. ,~£.~' . complicated path through the commutators anp. ,,.x·s pgi wrg to the end plate along 

' 

another path through the commutators.· Thus, in this category o:f cryptographs 

' . enciphering'-deciphering equivalency is ef:fected without the us~ o:f a reve~sing 

switch which is necessary in cryptographs of th~_ first catego!j. :~ - .. . ,;l 

· In both categories of .cryptographs it is usual t.o prGvide ~11s fer angUlu~~,:~ 

displaci~ or rotating the commutators, the reason for whiah will be briefly 

discussed. If, in cryptographs utilizing substitution commutators Gf the type 

described, no provision is made for their angular displa:c~nt during the course 

·Of enciphering a plain-text message, the reSttlting cipher ~ext will be mo~·· · 

\ - . . alphabetic in character; that is, only one su15stitution alphabet will' have been 

2 -
REF ID:A39774 

used in the entire encipherment. It is a well-known fact that such 

monoalphabetic cryptograms offer little resistance to cryptanalysis, 

and, in order to increase'the cryptographic security of such cryptograms, 

factors other than mere change of alignment of the substitution commutators 

from message to message must be incorporated therein. Heretofore several 

types of cipher machines have been invented in which one or more of the 

substitution commutators are rotated step by step with the encipherment 

or decipherment of each 'letter, but in a regular and/or meter-like manner. 

Such cipher machines provide a considerable increase in cryptographic security 

(that is, resistance to cryptanalysis) over those cipher machines in which 

no angular displacement of the substitution commutators takes place, but still 

not sufficiei:rt to insure practical indecryptability for cryptograms produced 

by their use. This is because the latitude of variability offered by the 

substitution commutator. displacement mechanism is limited and all forms 

thereof may be readily reconstructed from a mQdel of the cipher maehine. 

It is the object of this invention to provide a means of effecting the 

angular displacement or rotation of the substitution commutators in an 

irregular, completely aperiodic manner, thereby greatly increasing the resistance to cryptanalysis of cryptograms enciphered by cryptographs of the type 

described. 

A basic feature of the invention is the provision of methods and means 

for controlling the angular displacements of the substitution commutators 

by electrical circuits which also pass through rotatable commutators. The 

latter thus constitute, in effect, commutators for the control of the 

substitution commutators; for sake of brevity and clarity in description, 

commutators performing this function of controlling substitution commutators 

will hereinafter be designated simply as ncontrol commutators". Several 

specific embodiments of the basic invention will be described. At this point 

it will merely be mentioned that the control commutators may form an independent unit physically separate from the substitution commutators but 

electrically associated with the latter; it is possible, however, to make 

one and the same set of commutators serve both as control commutators and 

- 3 -
.. .. 

REF ID:A39774 

substitution commutators, there being provi"ded assaciated1means designed to· 

keep the control functions electrically separate from the substitution functionJ •. · 

The. several different embodiments of the invention and the modes of 

·operation of .the various forms are explained in this specification in detail 

sufficient for comprehension by those skilled in the art. The explanation is 

made in eo:nneetion with the aecom.paeying drawings, Figs. 1 - 6. 

Fig. l is a schematic diagram of the simplest embodiment in which there 

is shown a first set of commutators for performing substitution functions ~nd 

a second set of somewhat differently constructed commutators for performing 

control functions, together with the associated circuits and contacts for 

proper operation of the cryptograph. Fig. 2 is a schematic diagram of a set 

of commutators also designed for performing control functions but in this 

case these commutators are similar in construction to the substitution commutators. Fig. 3 is a schematic diagram of another -embodiment in which a single 

set of double-ring commutators of novel construction perf o~s both functions 

of substitution and control. Fig. 4 shows a front and sid~ elevation of one 

of these double-ring commutators. Fig. 5 is a schematic diagram of another 

embodiment in which a • gJ set ot dOu!lle-ring comnrt;ators is arranged with 

associated switching mechanism so as to perform both functions of substitution 

. . . ..,..,a· - .. and contrQl~(-t•at ~~.UJiJ4..cif:.;.a~.eYersf.ng~co · · ·.ator. :tFilz. 6 is a scaeqiatici diagram 01· ~ ..em.~~--~M~.tr 'S~. :·•Ollllm aJ\ilint ar-e· -1!lsed· Jicw th s 

e e eae- eomma•tOr-, · ·• ··· · · ·--co · er. ·· · · · parp Wererring now specfl:~:tt ro~~ .. e= s aesignated by the numbez-s 

1 to 4, inclusive, are substitution commutators of the normal type hereinbefore 

described, in which there is a single ring of 26 contacts on each face, the 

contacts on one face being connected irregularly to the contacts on the other 

face. Commutator S is also a substitution commutator,lbut differs from the 

"' 

others in that onl~ one face of the commutator bears a ring of contacts, the 

latter contacts being interco:aneeted irregularly in pairs. A current entering 

one contact of the single ring of contacts is merely carried along on insulated 

conductor to some other contact, from which it ,emerges from.the commutator. In 

other words the current enters the commutator at one contact and leaves it at 

another, on the same face of the commutator. 

referred to above as a revers~ng commutator. 

This is a eolDllUta.tor of the type 

.. Comtm1tatGrs 6, 7 and 8 are eo~l~~ . ,..~ 

commutators of which 7 and 8 are similar in principle.to substitution commutaV 

tors 1 to 4, except that they have only six contacts instead of 26 in a ring -4-

·:. 1 
•" ...... 

.. 

REF ID:A39774 

• • 

oR eaeh face; commutator 6 is a reversing commutator and is similar in principle 

to refersi:ag commutator 5, except that it has only six con.tacts inst~a of 26. 

The s~titution commutators are mounted upon a common shaft 20 upon whieh 

they may ·be indep:endently angularly displaced s~epwise 1/26 of a revolution, 

. b~ring p1't.~:.302',·~ ~:.19itt"eF , between fixed end plate.-( 301 an!¥'~~··~:;;:Silt serving merely as a retaining 

plate and having l'lQ. eontacts or conductors within it. The commutators are' 

separated by' f1+ed pla'te.s 305, 306, 307, and 3'QS which.bear rings of 26 contacts 

suitablj··disposed for -bridging between successive commutators, in order to 

provide f.or electrical contiBUity from one commutator to its'negt adjacent one. 

The contacts in these ~epa,~ator plates are:ba.11-be~ring spring contacts exerting 

' ' suffici:ent outward pressur~ to insure ~ood con~aqt~- The eontrol commutators t'-' r "I >~ • ' , • ~ .. 

are .mounted upon the same common shaft'20 .u_pon w~ieh they may likewise be a~- , . 

-¢a.;1Jr' displ~~ed si;~pWi·a~ 1/6 Qf a revolution, :Between fixed end plate.?. 3Q4 .. b@;d.gg.~J..a:$ie 30,3 ¥ :~ ~lattent'- ._ ,,. 

a~_,liJildd>iJ"'~m;jj!f· serviag me:reJ.y as a retaini~ plate. 309 and .310 are 

' ' 

separators similar in construction and functiofi $o separators 305'to 308, 

except that they have rings of but; 6 contacts. The motion of the t~ee control 

commutators, is meter-like, commutator 8 being moved 1/6 of a revolution for 

each eharaeter ciphered, commutator 7 being moved 1/6 of a revolution per complete revolution of commutator 8, and coDDBUtator 6 Qel:ipg moved 1/6 of a revolution per complete revolution of commutator ~. This set of three commutators 

has a comiaJ.ete period (return to an initial position) of 216; that is, afte~ 

216 charaeters have been enciphered or deciphered the commutators return t0 

their initial relativ~ rotatory positions. The means for moving these commutators ·will be described presently. 9, 10, 11, 121 and 13 are magnets, here. 

termed substitution-commutator selector magnets, which when energized, determine which of the substitution commutators 1, 2, 3, 4 and 5 are angularly 

displaced, either by acting directly on the commutators or by releasing an 

actuating mechanism which acts directly on the commutators. 14 and 15 are 

two or a set of twenty-six indicating devices sueh as glow lamps or magnets 

. - for operati:ng a printing mec~sm, ~uch indicating deviees being well kBown 

in the art. Each indie~ting device corresponds to a letter of the English 

alphabet. 18 and 19 a.re two of a set of twenty-six single-pole, double-throw 

./ - 5 
REF ID:A39774 

""' - . 

switch levers operated by the keys of a typewriter keyboard. The keyboard 

is also provided with a universal bar 44, which controls switch lever 17, 

the functions of which will be described later, and it also controls switch 

lever 117 and contact 45, which control magnet 31, the latter serving to 

displace commutator 8 one step per depression of arry key of the keyboard. 

When commutator S makes a complete revolution, it closes contact 32 which 

controls magnet 33, the latter serving to displace commutator 7 one step 

per 6 depressions of keys on the keyboard. When commutator 7 makes a complete 

revolution it closes contact-34 which controls magnet 35, the latter serving 

to displace commutator 6 one step per 36 d~pressions of the keys of the keyboard. Contacts 32 and 34 are operated by rollers on spring levers. These 

rollers normally ride upon the.peripheries of commutators 7 and 8, but at a 

certain point on each commutator there is a transverse slot which allows the 

roller to drop sufficiently to close the contact concerned. Of course, these 

three commutators could be displaced mechanically, by means of ratchets and 

pawls and direct control from the universal bar of the keyboard. To the right 

in Fig. 1 is shown a side elevation of fixed end plate 304 which adjolns~ 

; .·.~ • f 

control commutator 8 on the exit face of the commutator. The 'fl'lMle lines 

show the co~uctors leading away from the ? contacts on the right side of the 

the dotted lines aha the conducto11s 1leadil1g frGDl ihe left si-de 0£ end p;l:,e.t.i;; 304; 

end plate 30~into commutator 8. " • 1 

r'\ , 

Having now particular reference to Figure 1 with a view to giving a 

complete description of the action of this form of the invention, the sequence 

of events which transpire during the encipherment of the plain-text lettezswill 

be related in detail. In ~der to encipher a ~ssage, it is necessary first to 

mount the commutators upon the shaft according to some prearranged order, it 

being obvious that commu1;ators 1, 2, 3, and 4 may be interchanged in position 

amongst themselves, and commutators 7 and 8 may be interchangek; commutators 

5 and 6 must remain.Jn the positions shown, since they are reversing commutators 

and cannot be replaced by the other commutators or by each other. Next it is 

necessary to align the several commutators, as regards their relative rotatory 

-6-
REF ID:A39774 

positions upon the sna.tt~ ~ecording·to a pref!U"ranged k~. After all this . ___ _._,h~- ,. ~f'?~~Wl'l'·v_.& ·.. I 

has been accomplisbed.a.Lswitch'.36 is cloW,, setting,tij) .a·Gircuit as follows: ·~osed co~r "'.'il. , - From battery 16 tctswitch 3~contac:t lever 17, closed contact 21, conductor 

26, contact 27 on the fixed end plate 304, into, through, and out of the 

control commutator unit via the route ~hrough S, 310, 7, 309., 6, 309, 7, 3l0; 

~8 as ilidicated to contact 28, thence along conductor 38 to selector magnet 

10, conductor 43 and bacj to battery 16. When magnet 10 is momentarily energized 

it causes substitution commutator 4 to be displaeed. angularly through l/26th "

1 

of a revolution. The machine is now ready for enciphering. If the letter A is 

to be enciphered, the key corresponding thereto is depressed. At the beginni:tlg 

of its downward travel the universal bar 44 causes contact lever 17 to move away 

from contact 21. The key bar A causes contact lever lS to break contact at 46 

. and to make contact at 22, setting up a circuit as follows: From battery 16 w elt~ - along qonductor 23 t2.fcontact 22, contact lever 18 and conductor 24 to a contact 

29 in end plate 301, thence into substitution commutator 1, through the commutators and separators 1, 305, 2, 306, 3, 307, 4, 308)into and out 0£ reversing. 

' 

commutator 5, back through separators and comm~tators 308, 4, 307, 3, 306, 2, 

305, 1, out at contact 30, return along conductor 25 to contact lever 19, · 

contact 47, thence to indicating device 14, which in this drawing corresponds 

. -

to the letter Q, conductor 43, and back to battery 16. At the end of the 

downward travel of the universal bar 44, the latter moves switch lever 117 and 

" ' closes contact 45, momentarily closing the circuit for energizing magnet 31. 

This causes control commutator S to oe angularly displaced through 1/6 of a 

revolution. When key A is released, the universal bar 44 is returned to its 

normal position by a retractile spring and contact lever 17 returns to contact 

21, reestablishing the ci~cuit from battery 16,-SlPlitch 36, ~ever 17, contact 21, 

conductor 26 to contact 27 of f'ixed end plate 304 .. ~ JD.ue to the anplar 

'tr ,the ·eurre•t-1.wi.U -11ow: · 

displacement of control commutator 8~~-traverse a new path through the 

" 

control unit and back to some ot-her contaet of end pl.ate 304 from whence it ... ' ' 

passes through one of the selector magnets 9 - 1.3, to battery 16, es.using one . . -

or the substitution commutators to be di@laeed, and tima pr.aviding a new. 

subeti tution al.phabet for the eneipherment of the uex1;" plain-/ lettel'. 

-7-
REF ID:A39774 

The deciphering operation .of this machine is the same as the, .. encipheri:ng 

operation, the enciphering-deciphering relationship being by na:ture reeiproeal.. 

,'... . ~ .. 

In t,Jetting the machine for deciphering, the same procedure is fallowed as,-i'or ; } ..:.. I 

enciphering; that is, the commutators are arranged and aligned at the benc}a , - ; 

mark according to the prearranged key and switch 36 is closed, whereupon suhr- , ~. . 

stitution commutator 4 is angularly displaced as hereinbef'ore described. The ~.J 

key corresponding to the cipher letter Q is depressed, which causes cont~ct . . lever 19 to break col',ltact at 47 and to me.Jee etmtact at 42 causing current to - ,• ·- ' ~-~Sil.~ij ;" ' 

f;Low from batter.y 16 thro~,.-c~uctor 2.3~·$ntaet lever 19 and cond~~tor 2,,. .. ' . . ~ contact 30 on end .plate 301 of the substitution commutator unit. The current. 

passes int!D and through, the latter along oa.~ path .and returns .~ong another. ' ~ "i • 

path as des:cribed before;· it ~e:rges at· cd'nt~t,~ on end plate 301 arui flots ~ l 'r • 

along conductor 24 to c~nta~t.'lever 18,, closed ·contact 46, to indie-ating device 

- 15, which correspomis to the l~ter A. -'rhe<universal bar 44, operated by th~ 

depression of the key correspeDding to the letter Q, clo~es contact 45 at the 

end of i.ts downward travel and causes control commlitator 8 to advan°". When 

the key corresponding to the letter Q is releas-ed, the universal bar 44 · 

returns to its normal position, causiJw .. CJ:mtae't 1-ever 17 to reestabli~h contae'\ 

at 21 thereupon causing a substitution commμtator to move farwaTd, as descJ;"i~d.. 1 • ,., ,,j, 

In Fig. l the eo:strol comm'lltators were pnwi:&ed with rings ef but six 

contact surfaces on each face, whereas the substitution commutators _were pro..- . ' 

vided with rings of 26 contact sur.faces. There is, however, ltO ,;t>ea:smi. why . " 

the substitution and the control commutators should not be ieentieal in thd.a 

' . " 

regard., thus providing tor their interchangab-ili"t'J amd gre14tly inereasi»g ' - ' 

the keying possibilities of the cryptogr.aph. 

In Fig. 2 is. ·shown JMw ·teie-homologo~s e'l:emeat-s of Fig. 1 may be modifiied 

to accompli~h t~s ef£eet. End plat.e: .304 and ·t:he'·CID:inmu.:tators .. 6, 7, 8 now . . .,. ~' .... . . 

bear rings of 26 contaeta. instead ef ri.Dgs e-f ~ 6 e~e'ts. CO'Dt.aet .. 2,'_l - y 

remains a single contact for the' ent~ o€ the eurre.;tt into the coa.t-7~1 ' . ~ 

cenmm.t.ators, leaving 25 contact~ 011 ead. pla-t.e ?04 for the e.-:tg~ ,fJf .~ 

current from the control cq11;unutate-rs.. Tkese. 2i e'.f.>~ -~~e-~j~· iflr 

·' 

5 sets of 5 contacts each, t'o the five Ctmdl.tet.ers 37, .. , ~Ji., .40 a!Jli. Ai .. · . . I ' 

- s -

,;: 
REF ID:A39774 

Other groupings in respect to the ~ber~_and identities.. of contacts co~- it ...... .,. ... 

stituting each of tlfe five gr~ups may be preferab~e, or this JQB.Y be ~ubj~~ ; 

to variation, according ~o a ke;y'. 

The arrangement shown in Fig. 2 provides a sequence of keying impulse,s 

w¥ch will not begin to repeat until control commutator 6 has made a comple.te - . 

revolution, or after 26 x 26 x 26 = 17,576 depressions of the universal bar, 

corresponding to the encipherment of exactly 17,576 letters of plain-text • . . · 

Due to the irregular manner in which the irxternal connections of the cofirel 

' 

~tators are made, the substitution commutators will be caused to rotate 

through unequal angles, so that when the second cycle of the control commutator , .... ll .a. 

unit is begun, the alignment of the substitution commutators will differ from 

its initial alignment. As a consequence of this new alignment of the substitution commutations, the period of the sequence of selection of substitution . . . 

alphabets will be greater than 17,576 by some multiple of that number, depending 

upon the wiring of the three control commutators and the manner in whieh the 

contacts of end plate 304 are connected to the selector magnets. This substitu-

'-" .. 

tion period is ther~re one of tremendous length. 

A third form of the invention is schematically depicted in Figure 3. From 

a cryptographic sta~dpoint the essential difference between this form and the 

first described form lies in the utilization of a single commutator unit, which .. serves both as a ~ubstitution commutator unit and as a co»trol commutator unit, 

the two functions being per~ormed by independent, concentric rings of contacts 

borne on the same commutators. In Fig. 4 there is shown a S".!de view of one 

sueh commutator. In this £igure there is on -each face of tae commutator an 

to'r the sake of el.id:1:~y, 

outer ri»g oi' 26 equidistam contacts,,..~~e~-s-~indicated b,y numeral 

48l ee-ahf.nrll., and a ccmcent.ric ·inner rhg alao Gt 26 equidistant contacts, 4-

• . 

wM:ea-en4t-sb. indicated 'by numeral 49~&Te-shewfr. The contacts 48 of the 011ter 

ring on one face are irregularly CODnected by insulated COBd~cters.50 to the 

contacts ~.S of the outer ;-ing on the other face. Similar~ the contacts 49 

of the inner ring on one face are irregularly connected by insulated conductors ~· .. 

150 to the contacts 149 of thEf inner ring on the other face of the co111m11tator,. · 

The two rings are therefore entirely independent of each other, though they 

- 9 :-
... ,... .. ~ .. 

REF ID:A39774 

are hth carri84 • en the same commutator. Oommutaters • ot this type will 

hereinatter be termed deuble-ring cOIDlll1ltators. 

Reference is DOif made to Fig. 3 in which this embodiment e£ the invention 

is also shown mere]¥ in sehematie f'orm. lGl, 102,.10.3, 104 and 105 are doublering CODID11ltaters mounted on a eommon shaf't 20, separated b,y separators 305; 306, 

307, ud 308. Meua are provided to cause the commuta~s to be closel.1' pressed 

against one aaether so that positive electrical contact •7 be made between 

adJoiniag commutators and separators and between commutator 101.and end plate 

301. A side elevation of end plate 301 is depleted at the left in Figure .3, 

showing the connections between the contacts thereGn and the seleetor magnets 9, 

10, 11, 12, and 13. The dotted line through the conmmtaters 101 to lOS iDdieates 

the path ef the current through the inner rings of contacts while the eontineus 

line marks the path thraagh the outer ring of eeata.cts. 

The sequence et events during the enciphermeat of a letter is as fellows: 

When main switeh 36 is close~, at the c._aeeipent o£ eperati9n, a circuit is set 

up as follows: From ba.tt917 16 through el.osed main switch,,, comlueter 51, contact lever 17, contact lever V, closed contact 21, c&Dducter 26, imler-ring 

eoiatact 127 et end plate .301, into commutators 101 to lOS and eut 9£ them aleng 

broken-line path to another imaer-ring centact 128 &£ -8 plate .301, thence 

along eollftctor 38, through selector magnet 10, along cenduetor 4;, laa.ek to 

batter;y 16. . Wlum selector magnet 10 is m0111entariq energized it causes e. 

mutator l(i)4 to be angularlT displaced 1/26 of a revolution, thus setting up a. 

path thrcmgh the cammtators for en~iphering the first l'8tter, sq letter A. 

When k91' A is depressed, universal bar 44 is caused te amve 4ownward, me~ 

contact lever 17mra:r from contact 21 and allowing current to pass frODl Ba.14eq 

• f 

l6 aleng oonbetor 23, through closed contact-.22; contaet lever 18, eondUcto-~ 

24, outer-ring coutact 29 ef end plate .301, into the COllllllUtaters thr.euga which ,, 

' . 1 t renews 'the eG>Dtimaous liDe a,nd retlll"Ds via nter-ring cO'Dt;act 30 et end 

plate 301, eollductw 25, contact l.ever 19, Blesed c:ontact 47 to iBdiea'ting 

device 14-, eeDd.11etor 43 and Ba.ck to 'batt_., 16. .After the let-ter '• corresponding to iadieati:ag device 14, llas beea recoried, key A is released and 

brT-aks eeataot at 22, at the same tim~ allning aiversal bar 44 to return to 

. -

its normal position. When universal bar 44 returns to its nermal position 

ceiltaet 21. is closed reestablislling a cireuit through the inner-rbg contacts 

. •, 

,~ ~._, I' ~ --v ~~~---~- .. ., '=--~·;:t%~ i'--'" _ .... ~-~ - 10 -
REF ID:A39774 

• 

et the eomnutaters. But conmnrt.ator 104 having lJeen displaced an entire:q 

new path tllr011gh the C:Ollll'JD1tators is now available for en.ciphering the letter A, 

if it is again to be enciphered. 

The decipherment of the letter Q takes place in an analogous ID8Jlner. 

T)le machine baVing been reset to the key, 

_/'the elosing of main.switch .36 as het'ore causes a current to flow through one 

of the inner-ring contacts to selector magnet 10, moving commutator 10.3 one 

S'tep torn.rd. Depression of kq Q estab11shes a eircuit as follows: latter,y 

16, closed switch .36, conductor 23, closed contaet 42, contact lever 19., 

conductor 2S, outer-ring contact .30., thence along the continuous line i!ito, 

through and ba.ck through ~e CGlllDl1ltators, emerging at outer-ring coataet a,, 

conductor 24, contact lever 18., closed contact 46, indicating device lS) eorresponding to the letter A, conductor 4.3, back to batter,y 16. When k61' Q 

. is released, uiversal bar 44 retur.ns to its .aormal position and again a 

circuit is established through the inner-ring ccmtaots of' the commutator. 

But since cemmutator 10.3 has been displaced, a new path is now available for 

deciphering the l~tter Q ~t the Q kq is again depressed. 

The period or the sequence of alpaali>et selection produced b7 this arrangement is variable and will depend upon four variable factors, mmely (1) the 

wiring of the imler rings of contacts of the double-ring.eomnmtators; (2) the 

horizontal permutation of the$e commutators en the shaft; (3) the alignment ot 

the eommutators and (4) the mnner in whicm the inner ring ef' eontaets on end 

plate 301 are conneeted to the selector magnets. , 

In Fig. S the invention as regarcls double-ring commutatGrs to perform 

substitution and control functions is embodiefl in a er,yptograph of the f'irst 

category as brief'.q described in general terms in the first pa.rt of this 

specification. It will be recalled that in eryptographs et this categor;y, 

there are two end plates ot identical construotion and a reversing switch 

whicm, ~en set in the enciphering posi.tion, connects the switahes of the kqboard to tha:cantacts et one .of the end plates, say the right-end plate, and 

the indicating devices are connected: to the contacts of the other end plate, 

say the left-end plate; while when set in the deeiphering pesitioD, the 

reversing switch reverses the order of eonnectiens between the switches of - . -

the ke.ybeara~_ eontacts·, et th'& end:p-!ites, ~nd the iadhating derues, so that 

the ~ cnritehes -~ :;&w e~eted. te tJte 1~-ea~ -P~-lmd the ia.ti.eatlllg 

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REF ID:A39774 

devices are connected to the right end plate. 

Accordingly in Fig. S there is shown a keyboard 52, a bank ot indicating 

devices 53, a lei"t end plate 301, a right end plate 302,, and a reversing 

switch 54, together with other parts homologous to those shown in the precertaiilNof the certain of the • 

ceding figures. Only~ keys of the keyboard and I-indi0&ting devices of 

the ha.Dk of indicating devices are shown in circuit relationship, it bei.Bg 

understood that the remaining keys and inclieating devices are coanected 1n 

homologolUI manner. 

Assuming that the cryptograph~is to be o .. erated for eneiphering,ithe 

sritah S4 is set to enciphering position, which arrangei tor circuit eontinuit7 

al.Ong the continuous lines SS to 58. The main switch 36 is now olosed and 

a circuit is established as follows1 Battery 16, closed switch 36, conductor 

23, universal bar switch lever 17, closed contact 21, conductor 26, inner-ring 

cont.a.et 127 ot right end plate 302, through the commutator unit, to inner-ring 

contact 128 of left end plate 301, cond11ctor 38, selector magaet 10, conductor 

43 baak to battery 16. Gomutator 104 is a.ngularq displaced one step. lay A 

is now depressed. The circuit through the iDBer-ring of contaets ot the eommutators is now l>roken, as universal bar M. breaks the contact at 21. At the 

aame time a Qircuit is established through the outer-ring ot contacts of the 

commutators, as fellows: Batt817 16, closed switch 36, e~~ductor 23, contaet 

lever 18 operated b,y key A, closed contact 22, conductor 24, through the reversixag sritoh 54 along eonductor SS, conductor 224, outer-ring contaet 29 of 

right end plate 302, into and throap commutators 105, 104, 103, 102, 101, v1a 

their outer-ring contacts, an outer-ring oontaet 229 of left eD<l plate 301, 

conductor 243 to the reversing switch 54 through the latter along conductor 58, 

thence along conductor 343, indicating device 14, corresponding to the letter 

Q, conductor 43 to battery 16. When key A is -released, aiversal bar M. returns 

to its normal position, reestablishing eontact at 21. Again a current nows 

through the 1maer riDg c•tacts of the commutators, entering at coata.et 29 but 

now emerging at some contact other taan 128 on lei"t end plate 301, since 

commutator 104 has been displaced. A selector· magnet is energised, and a mm 

path is set up for the passage of the next eneiphering eurrent if A is agaia_ · 

depressed. 

- 12 -
It key Q is deFessed., iastead of kq A, the circuit is as follows: 

Battery 16, closed switch 36, conductor 23, switch lever 19, closed contaet . 42, eonduotor 25, through reversing switch along path 57, conductor 325 to 

an outer-ring contact 30 ot right end plate .302, t-hence through commutators 

to an 011ter-ring contact 230 ot left end plate 301, conductor 425, through 

the reversing switch alollg pa.th 59, conductor 443 to some one of the indi.eating 

devices or S3, say the one corresponding to letter z. In other words, the 

relationship between A and Q is DO"t reciprocal, when the ~ 3 an 

at the eneiphering position, as is the case in the preceding figures. Here 

A in plain text gives Q in cipher, but Q in plain text gives Z in cipher. 

··m ..._..to et.feet decipherment, the reversing switch 54 111t1st l>e set for 

the deeiphering function. This caues the paths through the reversing switch 

54 to follow alozig the dotted lines instead o.f along the continuous lines. The 

operation 1mmediatel.7 subsequent to closing main switch 36 is now exactly the 

same as before, when the encipherment of letter A was deseribed. This is 

because the circuits to the selector mgneta are associated with the innerring contacts o.f the commutators, and these contacts are not eonnected to 8JV' 

of the contacts 1n the reversing switch 54. In the first enciphering operation, 

the letter A was enciphered 'bJ' Q. The decipherment or Q will now be followed. 

Depressing the Q k97 causes universal bar 44 to break the circuit at 21, as 

before, but the substitution circait is now partl.7 clitterent from what it was 

when k8J' A was depressed in encipherment. The cireuit is now as f'ollowss 

Battery 16, closed switch 36, conductor 23, contact lever 19, closed eontact 

42, conductor 25, through reversing switch 54 along dotted path 257) coaductor 

243, outer ring contact 229 of left end plate 301, through the outer-ring . 

contacts ot the commutators to an outer ring contact 29 of right end plate 302, 

conductor 22.4, through reversing switch 54 aleng dotted path 255, conductor 

225, indicatiDg device A, conductor 4.3, to lettery 16. Thus Q ii!. cipher ;yields 

A in plain 1.anpage. If kq A 1s depressed instead or Q, the ce~trol eircu.1 t is exaetq the same as when Q was depressed but the substitution- circuit is as f'ollows: Batte1"1' 16, closed switeh 36, conductor 23, contact 

- 13 - J ' -

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REF ID:A39774 

1~ 18, eleaed contact 22, conductor 24, through reversing switch S4 

along dotted path 255, condacter 52S to an outer-ring contact of left end 

plate 301. The current will emerge at someouter-ring contact of right 

end plate 302, thence go to and through the reversing switch 54, and from 

there it would go to some one o£ the indicati.Dg devices of S3, the exact 

one not 'being indicated in the figure. In u;y case it will be the plaintext letter which was enciphered when the eryptograph was in the homologoas 

position in the enciphering cycle. 

A fifth embodiment of the invention utilizes single-ring coJlllllUtators to 

serve both as substitution commutators and control commutators by means of a 

gang switch ot 26 contaets inserted in the circuits through the cOJ1111D1tators. 

Figure 6 shows a schematic diagram ot this form o£ the invention. 

Having now particular reference to Figure 6, with the exception et the 

gang nit.ch and relays which will be described presentq, the elements shoo 

therein are similar in construction and function with the eorrespending elements 

shown in the preceding figures. Gang switch 85 is mereq a device tor breaH• 

one complete set of 26 Qontaets simul taneouely' and at the *1ae time meld ng 

another set of 26 contacts simaltaneousq. It is operated bT magnet 83 and 

associated relays. The action of this form o£ the invention is as follows: At 

the begimdng Gf operation, switch 36 ls closed, setting up circuits through relays 113 and 114, as tollowsa batterr 16, conductors 23, lll, switch lever 17, 

elosed eontaet 72, conductor 112 rel.qs 113 and 114, conductor 124, to 1tattery 16. 

Relays 113 and ll4 are energized, causing armtures 80 and 108 to establish contact at 81 and 109, respectivel.J'. BT means of a mechanical locking arrangement, 

once arniature 80 has been attracted b3' relay 113 the contact established at 81: .. 

is locked until released b7 the action ot rel.q 68; s1m1larJ.7 when ~"ture :·· 

108 of rel.a7 114 has been locked into contact position at 109, it ~s . 

looked until relay UO is energised. Consequent~, although contact 72 must 

be clos~ in order to establish contact at 81 and 109, atter the latter 

1' '·· 

contacts have been established they will remain so evma it contaet 72' ls 

broken b;r depressing universal bar 44. When key A is tlepressed mdversal 

-14 - / 
REF ID:A39774 '"'?'!"""''"",,. .-..... ,,, ........ ~~- --- -

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bar 44 causes contact lever 17 to make contact with contact 21, setting 

up the following circuit: from source of power 16 through conductors 23, 

111 and contact lever 17, to closed contact 21 through conductor 79 end locked 

lever SO of relay 113 to contact 81, thence through conductor 82 through gang-

;3Witch magnet 83 and conductors ll6, 124 back to source of power 16. When 

gang-switch magnet 83 is energized, armature 86 is attracted, causing gangswiteh 85 to disengage a lower set of twenty-fix contacts and to engage an 

upper set of twenty-six contacts. Switch levers 88, 1881 288, 388, 488 ~nd 588 

are five of the set of 26 switch levers controlled by gang switch 85; contacts 

90, 190, 290, 390, 490 and 590 are five of the set of 26 lower contacts controlled by the switch levers of the gang switch 85; contacts 91, 191, 291, 391, 

491 and 591 are five of the set of 26 upper contacts controlled by the switch 

levers of the gang switch 85. Referring to contacts 91 and 191, which have 

been closed by energizing gang-switch magnet 83 as noted above, there is set 

up a circuit as follows: from source of power 16 through conductor 2' to 

closed contact 46, (the key A still being depressed) through contact lever 18 

and conductor 119 to closed contact 91, through contact lever 88, and conductor 

76 to a contact 29 on end plate 3011 commutators and separators 1, 305, 2, 306, 

31 3071 41 308, and 5. Cormnutator 5 is a reversing commutator, and therefore 

the current goes back through the commutators and separators 5, 308, 4, 307, 

31 306, 21 305 1 11 and returns to end plate 301, emergi.ng at contact 30 on end 

plate 301; thence along conductor 84 and eontact lever 188 to closed contact 

191, through conductor 93, contact lever 19, closed contact 42 along conductor 

121• to indicating device 14, thence along conductor 43 to relay magnet 68 and 

back along conductor 77 to battery 16. 

When indicating device 14 is energized, a type bar is caused,by means not 

,is _, 

shown,to pr~nt the letter Q.; ~~which~ the cipher 

equivalent of the_plai'n-text letter A. When relay magnet 68 is energized, 

contact lever 80 disengages contact Sl'and engages contact 100, deenergizing . switch control magnet SJ and ~!lowing gang switch 85 to disengage the upper 

set of 26 contacts, among which are contacts 91 and 191, and engage the lower 

set of 26 contacts, among which are 90 and 190. This sets up a circuit as 

- lj -
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REF ID:A39774 

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follows: batte17 16, conductors 23 and 1111 universal-bar cellte.et lever 1'1, 

closed conta~t 21, conductor 791 contact lever ao, co,p~act 1001 ccmdu..ctor )2;2, _t" - - - - 4 - ' , ' ' " -:. 

selector magnet 13; c~nductor 106, closed contact 190, oontact l~ver 188, 

conductor 84, contact 30 on end plate 301, to, thr~ugh_an~ ba~ through 

commutators 1 to 5, contact 291 conductor 76, contact lever SB, .closed 

contaat 90, conductor 107, contact lever 108, closed contact 1-09, relay magnet 

1101 conductors 123 and 124, back to battery 16. 

When selector magnet 13 is energized, commutator l is angularly displaced 

through l/26th of a revolution, and a new set of circuits is formed in the 

commutator unit. Relay magnet llO having been energized, contact lever 108 

is caused to disengage contact 109. This breaks the circuit through the 

selector magnets and prevents energizing select~r magn~t 13 a second time. 

No further action of an;y part can take place until the two re1ays 113 and 114 

are again actuated. This happens when key A is released, which es:t;ablishes 

a circuit a$·follows: battery 16, conductors 23 and 111, c?ntact lever 17, 

closed contact 72, conductor 1121_ magnets 113 and 114, back to battery 16. 

~s explained above, armatures SO and 108 are locked in contact~Jiia.king 

_ positions at 81 and 109 until another key of the keyboard is depDessed, -

causing the device to operate in the same manner as hereinbefore described. 

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