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~I', i ' REF ID:A4148846 ' 

The Hagelin - Gretener Cipher Teleprinter 

The Hagelin - Gretener cipher teleprint·er is an apparatus similar 

to the standard teletype machine, operating on the start-step princjple, 

which accomplisbee automatic enciphP-rment of • electl'ical L'll:pulses 

on line. Messages at both ends of a commtj.nicaticns link appear in 

plain text or unenciphered form. The principal feature of the machine 

is the ~ey-generating unit; this unit may be used with teleprinters 

employing tbe internationnl or Baudot five-element code, or with the 

ETK-teleprinter, a machine invented. by Gretener using a fourteen-element 

code. In the latter machine'· each plain-text symbol (letter or numeral) 

iG printed by forming a combination of one to fjve signs selected from 

a set of fourteen available elements. These fourteen elements are 

coaxi2lly arrenged in the printing part of the mechanism and are selected 

according to the particulAr plain-text character key which is depressed. 

In the cipher unit devised by Hagelin and Gretener, the generation of 

key under the fourteen-eler1lent : code .. intr0duces a number of 

which is considerably greater then is possible with the Baudot f'ive-e!eme 

code. Thus, efter the plaj_n-teYt chnracter (one to five element£;) ha !lli 

br-ien added to the keying character (one to fourteen elements), ~:ccorcl '""' ;rig, :1: 

(Q ~ ... :,- ' c--I 

to the 9:El!ff!•iil!!i"filiC • 1 i non-Vernam rule for combining margt1~pd 0'~~--:;)-1 ~~ t.n 

spaces, the resulting cipher charActer may be 

r~ I ' ' 

~'.'"' ':· \ composed of one tp, l.f6.ur ·~· .... ' ~:' rl:;~I 

I~~ een ~ - ,:::=·3 

~~ Of these, only 'a~but , =- .:;:\ ... ('.".~ ~·:::211 

rn,n.,S -4;wo 

elements in 214 or 16,384~possible combinations. 

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forty are readable symbols (letters and numerals); the remaindef ;~~ n t ~ ~g\ 

readable and, if produced in printed form, would appear AS rneanfrtg1\.ss · i? 'I,_ 

C'D' 

characters. 

a .... Like the teleprintE:r, the key generating mechanism operat ::,-.... 

Declassified and approved for release by NSA on 11-17-2014 pursuant to E .0. 1352a 
on the start-stop principle. Through one revoluticn-of the control 

shaft, the teleprinter and key generator run synchronou_sly, the teleprinter producing the printing im,pulses (at its own terminal) ano the 

generator emitting the keying impulses; both si.gnDls are combined on 

the fourteen levels and tr~nsmitted as an enciphered si~nal over a line 

or by radio. Decipherment and plain-text printing take place through 

similar apparatus at the. receiving station. In the particillar embodiment shown for use of the f0urteen-element code, tbe machine operates 

on'+ the neutral or single current system (current or no current) p in 

contrast to the polar system, in which there is constant flow of 1 current, 

during both marking and spacing intervals, but in opposite directions. 

The eeneration of_ cipher key for this machine is accomplished 

through the medium of f'ourteen condensers. These condensers are part of 

a circuit conEisting of a chain of fourteen polarity reversers, the 

chance operntion of \•Jhich determine whether a condenser is to be charged 

or not. Each condenser leuds to one segment of the distributor, where 

the charge (or no charge) is taken off in sequence by the rotating brush 

ant1 carried to the mixing cj rcui t. Here the cipher key impulses are 

added to the plain-text impulses in the conventional manner to form the 

enciphered signal. The unit whicb rendomly determines the condensers to 

be charged includes fourteen variable pin rotors of different sizes. 

(As sho"l'm in the uescripti ve write-up provided by the company, these 

wheels haw29, 31, 32, 34, 37, 38, 39, 41, 42, 43, 44, 45, l6~ and 47 

positions, and are not prime-sized to each other.) The pins, which can 

be slid axielly by hand, proJect from the sides of the rotor, just below 

the periphery, either to the left or to the right. Each pin rotor 

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controls, through two feelers, four make and break contacts, of which two 

are mounted on one side and two on the other side of the rotor body. The 

two make and break contacts on the right side are combined into one double 

make and break contact (designated by the letter A); there are fourteen 

such contacts, each controlling one of the fourteen polarity revet•sers 

in the key generatjng circ:uit. The two make and break contacts on the 

left side (B And C) function as individual make and break: contacts; 

contact B controls the operation of a (stepping) magnet associated with 

each pin l'Otor, ann contact C operates to bring its in di vi dual condenser 

,.,, into connection with the positive or negative branch of' the polarity 

reversing circuit. To insure that the position of the contacts on one 

side of a rotor will not be complementary to the position of the contacts 

on the other side,'- (a condition that would result from the use of a single 

reading station), the feeler assocleted with each set of contacts is placed 

on a different level. In the descriptive example, the feelers are mounted 

one pin diviSion apart. In order, further, to break the rule t~aj;__~ pin, 

once it has been set, will activate only those contactG on its own si~d , --

so 

single pin&, e.gq one or two pins on each rotor, Hre mad llD long"'tha/ 

they project on both sides of the rotor body' and other si~~ pins arr 

made..- short~that they project neither to the right nor to(tb~~ 

Of course these two types of pins are not settable. --

, I """\ 

The variable pin rotors do not step J;"egularly. Instead, their di~ted 

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motion pattern is obtciined by interlockingly connectint: the fourteen\_ ~ 

control magnets through contActs B. With each depression of a keyboard ~\~ 

cbarecter, a universal bar is caused to swi.ng away from a lever lj nked with~~-~ 

each rotor. This lever, impel=-ledb: 1by1 a spring, c1mses its associated :pawl 

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and ratchet to move the rotor forward by one pin division. If, however, 

an armature has been lowered by an energized control magnet, depending 

on the positioning of its make and break cont~ict by an , 'active pin, 

then a blocking effect takes place, and the pin rotor is not permitted 

to advance. 

The cipher circuit now consists of a chain of fourteen polarity 

reversers, the action of each of which is dependent on the influence of 

a right hand rotor pin on contact A. Inserted between each two polarity 

reversers, a condenser is brou~ht into connection with the positive or 

negative branch of the polarity reverser chain through the action of 

contact C. All condensers are connected on one side in series and to 

the negative pole of the ·:bl::put. -These condebJ'ers may therefore become 

charged or not. wnether condenser no. 1 is charged depends on the 

position of its related contactsA and C. Whether condenser no. 4 is 

charged de9ends on the poRitions of the first four contacts A and 

no. 4 contact C. 

The input to the chain of polarity reversers takes place through 

a rotary feed switch. The chain of polarity reversers must not form 

a closed circuit and is therefore broken at irregular intervals and at 

different points in the circuit. by means of a rotary separator switch. 

Both rotary switches are mounted on the s?..me shaft as the variable pin 

rotors; the switches rotate in opposite directions with relation to 

each other. The irreeular stepping of the rotary switches is dependent 

on separate control magnets, which, in turn, are controlled by variable 

pin rotor contacts B. The descriptive write-up on this version of the 

machine does not specifically identify these contacts, but it is evident 

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that they may be any of those among the fourteen availeble contacts, 

used either singly or in a multiple arrangement. A separate polarity 

reverser, through which current is introduced into the reverBer chain, 

the variable pin rotors (not specifically 

identified) through a relay hose control magnet is constantly without 

current. This rotor, therefore becomes a fast wheel, stepping each time 

a key is struck, and prevent& a condition in which all the variable pin 

rotors stand still, i.e., all the control magnets are energizerl. 

If, for example, at a t;iven setting, the rotary feed switch is at 

polar! ty reverser no. 2, and the rotary separator switch' has broken 

the circuit between polerity reversers nos. 7 and 8, then condenser 

no. 7 will receive its charge (or no charge} through the lead-in polarity 

reverser and reversers nos. 2,3, 4, 5, 6, and 7, and no. 7 contact C. 

If, when the next character is struck, the feed switch stands still 

while the separator switch advances one step (so that the separation 

of the chain of polarity reversers is between reversers nos. 6 and 7), 

then the charge of condenser no. 7, after the next key is stntck ~ depend~ 

upon the lea<'l-in polarity reverser: and reversers nos. 1, 11,, 13, 12, 11, 

10, 9, 8, end 7. In this way, the charge of any condenser is dependent 

on a constEmtly changing number and a constantly changing configuration 

of rotor pins. 

As the si:xteen wheels are aljgned at the start of a message, the 

condensers will become charged or not, according to the particular 

configuration of pins and their effect on the various single and double 

make and break cont11cts. During the single revolution of tlie control 

shaft of the cipher unit, while one message character is being enciphered 
and transmitted, the advance of the variable pin rotors must take place 

si.!llultaneously. The latter movement will result in a change of positions. 

of the contacts A, B, C. In order that, despite this chanee, the 

condenser charges may remain constant during a complete revolution of 

the collector brush on the control shaft., all condensers are cut off 

from the verieble pin rotor contacts C by a set of cam contacts shortly 

before the start and are connected up again shortly before the stop. 

The condensers thereby store their charges for a sufficient interval. 

Additional variation may be introduced into the cryptoe;raphic 

circuit by arr·anging for tbe following changes of wiring:· 

Interchan~ing the poleri ty reversers so that a new sequence . 

is formed; 

interchanging the order of contacts C in the chain of 

polarity reversers; 

interchanging the order of the storage condensers in the 

chain of polarity reversers; 

interchanging the order of the control magnets (each of which 

is asciociated with a specific voriahle pin rotor) am.ong contacts B. 

Accordingly, an initial random. wiring is selcted for each or these 

components, and encloAed within a rotary permutation switch. Each of 

these switches hRs 1'ourteen positions and is normally set by hand; once 

set, the switches remain fixed in their positions for one or more messages. 

Their rotation, ther~fore, becomes equivalent to a slide. As a further 

variation, the dAscriptive write-up cites the possibility of employing 

two or three of each type of the ;:iermutation sv-ri tches and conr..ecting 

thein in series (similar to a bank of wired rotors), all of them to be set 

manunlly. 
In another variation of the circuit, which imposes some major 

pla~ changes in the wiring, the wri te-u:p discu1;;ses a · Q, that eliminates 

the two rotary switches (feed and separator) and the hand-set permutAtion switch that interchi:mges the control magnets. The remaining three 

permutAtion switches now have twenty-eight di visirms, with their internal 

wirin~ changeable by plugging. Two of these switches, those for i,riterchanging the order of the contacts C and the order of the condensers, 

are mounted on the shBft with the variable pin rotors and are subject 

to irregular stepping by having their control magnets come under the 

influence of pre-selP-cted contacts B. The third permutation switch, 

for interchanging the polartty reversers, is set only by· hand and 

remains fixed thereafter. The input of the feed voltaces into the chain 

of polarity reversers now occurs at four arbitrarily selected points. 

From time to time at the feed inlet, the chain of polarity revcrsers is 

separated by cutting off the interchangeable leads. (The method for 

accomplishing this separation is not clear, since the write-up states 

that the separator switch is eliminated in this version of the machine.) 

In this way, there arise four distinct chains of polarity reversers, 

whose composition is different from the wiring of the polarity-reverser 

jack and plug 

switch at each switch position. The connec ions of the fourteen control 

magnets as well as the connections of the control magnets of the two 

rotary permutation switches w~th their related contacts B ar.e made by 

hand at the time that the keying elements are set up in the m~chine. No 

permutation switch is provided for this purpose. To guarantee a constantlychanging configuration of pins, tbe fourteenth contact B is controlled b:yr 

a variable pin rotor whgse control mognet is "p~rmanently without current, 

i.e., this wheel always steps.