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INRRPLY 

RllPBR10 WAR DEPARTMENT 

OFFICE OF THE CHIEF SIGNAL OFFICER 

WASHINGTON 

MEKOBAN.OOM FOR: Colan.el Jlinokler 

0-3-C 

Ifovanber 6, 1941 

Herewith is prelimim.ry write-up with rough drawings 

ot the reoognition-authentication deTioa oonoerning 11hioh I told 

you 79aterda7. 

Reoommend (1) that 118 be penaitted to start at onoe to 

build a first model in our shop. Jlaterials for same are practically 

all on hand, except tor olock :mechanim. 

(2) that Lieut. Rosen be sent to see clock 

manutaoturera, with a view to finding a clock suitable tor the 

purpose of the proposed new deYice. 

(3) that oopy ot these papers be forwarded 

to Signal Corps Patmts Board for processing. 
e REF ID:A67602 e 

Preliminary description ot an invention cu.cerning a mechani11111 tor producing 

seoret recognition, identificatian, or authentication symbols. 

A. 'l'his deaoription consists of this sheet of explanation and four figures. The 

following elULm:ta are incorporated in the device: 

l. Three or mare rotors, CGDV'm.tionall7 wired, and arranged with aasooiated lam.pa, 

bar kay and battery as ahom in the circuit details diagram., Fig. 1. 

2. A olookwDrk mechanism 10 arranged aa to driTe one ot the rotera periedioall7 

at apeoified time interTals. Thus in diagram of •step meohani&llL details•, Fig. 2, 

is ahom a torm ot drive suitable tor rGtating rGtor in number 2 position tor•rd 

at speoified time inter'l'&ls by means of a olockwort, cam.shaft, cam. an.d a1aooiated 

pawl. The clockwork is also provided with a ooDV"entianal dial (preferably of the 

24 hour varie't7)· Thia dial 1a further subdiTided into 26 segments, marked 

alphabetically as ahom in the general view, Fig. 3. 

3. Both the left and right end stator wirings are variable, and can be ohanged by 

means ot a plug and jaok arrangement. 

4. A ring so constructed that it will fit on the outside ot &DJ' one ot the rotors 

is provided. Details ot this ring are shown in the figure showing retor details, 

Fig. 4. 

B. Operation ot the a.chine is &00C111.pliahed in this •Y• (all settings according 

to key}s 

1. The ring referred to in 4 above is placed on the retctr llhioh will be placed 

in position 2, the arm cm the ring falling into the appropriate stepping notch 

in the rotor. 

2. !he end stator wirings are fixed. 

3. Rotors are inserted. 

4. 'i'he clock is 11VD?ld and set to the correct time. 

5. Center rotor is set to letter oorrespcmding to that shown by olook on its 

alphabetical dial. (Letter visible through the cover window on rotor in f2 

position is actually the letter on the rmoveabla ring rather than the true rotor 

letter.) 

6. Set other rotors and end plate to hourly setting. 

? • Challenge is letter showing through the oover window of rotor in number 2 

position. 

e. .Anawar is letter '1r letters) mown. b7 lights when key bar is clepressecl. 

9. It challenge letter does not oorrespond to letter shown in cOTer wiDdow of 

rotm- in number 2 position., this rotor is reset manually before ohallm.ge is 

anawared. 

10. Rotors are reset :manually on the hour. Del&)"ed setting oan be DB.de b7 cheating with alphabetical dial on. oleot. At beginning ot setting period new setting 

is sho111 by the taot that the challenge is a letter at the beginning ot the 

alphabet. (Rotor in number 2 poaitian will not move tram Z to A automatically.) 

Therefore if challenge ia received as a letter near the beginning of the alphabet, 

it is known that the new setting is :l.n effect. (This provision is for the purpose 

of eliminating possible errors due to alight differences in cloak speeds and thus 

syatam does not require accurate aynohronization. 

Disclosed to us at Washington, D.C., 

on November , 1941. 

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Invented at Washington, D.C., 

November 3, 1941, by 

1V;eD. o·· 'a=:~eoL,,..~ William F. Friedman 
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A.~~· ~.;,:ec/O'.t~ ~~~fr'~~ . . The following elements are incorporated in the device: ~ 

1. Three or more rotors, conventionally wired, and arranged with 

associated lamps, ba'1:' key and battery as sho·;m in the circuit 

details diagram, fi. \. 

2. A clockwork mechanism so arranged as to drive one of the rotors 

periodically at specifiedf.tmrne intervals. Thus iq:I!agrarn of 

"step mechanism details"/l~· Slto':Wl a form of drive suitable for 

rotating rotor in number 2 position forward at specified time 

intervals by means of a clockwork, camshaft, cam and associated 

pawli The clockworkfis also provided with a conventional dial 

~. (preferably of the 24 hour variety). This dial is further subdivided 

into 26 segments, mmrll!:e: marked alphabetically as shmm in the 

general view") fd. 3. 

3. Both the left and right end stator vnrings are variable, 

be changed by means of a plug and jack arrangement. 

. t\S !>R()d\'Pc't>) -\- \ ~ L~. A ring iJ3 ptt l~d so constructed that it will..._on the 

any one of the rotors. Details of this ring are shown 

showing rotor details, f1 •4-. 

and can 

'B. Operation of the machine is accomplished in this way4 (G.:ll"according ~ to key)·. 

1. The ring referred to in· 4 above is placed on the rotor -1vhich '.'!ill be 

placed in position 2~ the arm on the- ring falling into the 

appropriate stepping notch in the rotor. 

2. The end stator wirings are fixed. 

3. Rotors are inserted. 

4 • The clock is ""'s_.e-r""""l'""'.o--...,...e--c'.'""'.o-r"'.:'r-"e""".c-:t--:t~1-

. 5. Center rotor is set to letter CJ3rresponding to that shown.by clock on 

l,o-f·J-vi:,· ·its _alphabetical dial. (c~' rZlea.' letter visible through the 0v~ 1 ~ -c-over w1ndowA is actually the letter on the removeable ring rather than . ·y~· - \ ...,,, the true rotor letter.) 

6. Set other rotor;;; and end plate to hourly setting. 12-

7. Challenge is letter showing throughthe cover window of rotor in number \.\~-

2 position. ct71-ktta..n) y / 

8. Answer is itetter,._ shm1m oP;:4...l-ights when key bar is depressed. 9:?f~ 

9, ~ If challenge;;:croes not correspond to letter shown in Jl 

cover window of rotor in number 2 position, this rotor is reset manuallY.. 

10. Rotors are reset manually on the hour. Dela~d set~ing can be made by 

checking with alphabeti'cal dial on clock. At ~"'~~e:"._tJng perioS}_,1,vb,. 

new setting is shown by the fact tl1at the challenge is°'"~~he W 1"'of 

the alphabet. (Rotor in nunJ:er 2 position will not move from Z to A 

automatically). Therefore~ challenge is received as a letter near 

the beginning of the alphabet, it is knol'm that the new setting is in 

effect. (1'his provision iS f~ for the purpose of eliminating~~ 

possible errors due to tit' slight differences in clock speedsk ~ ~ 

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