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W F FRIEDMAN 

FACSIMILE ENCIPHERING SYSTEM 

Filed March 6 1943 

2,552,548 

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• • REF ID:A105156 

Patented May 15, 1951 2,552,548 

UNITED STATES PATENT OFFICE 

2,552,548 

FACSIMILE ENCIPHERING SYSTEM 

William F. ~edman, Washington, D. C. 

Application March 6, 1943, Serial No. 478,193 

5 Claims. (Cl. 178-5.1) 

(Granted under· the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 

1 

The invention described herein may be man~-: 

factured and used by or for the Government for 

governmental purposes, without the payment to me of any royalty thereon. 

The subject matter of this invention is a system for enciphering facsimiles. ' 

This invention relates to means for secretly 

communicating information by transmitting . a facsimile of the message in a graphic form Or 

any sort such as a writing, type-writing, piCture, photograph or the like. Secrecy is obtained 

by transmitting a series of impulses caus_ed in 

part by the message to be transmitted and in 

part by a control in graphic form such as ally 

writing, picture or random arrangement of dots 

or lines. Such a control does not necessarily 

have any intelligibility in itself. It operates as 

a random key. At the receiving end, a duplicate.of this control is employed. This duplicate 

control is moved in synchronism with the movements of the control at the transmitting end and 

causes a series of impulses which co-operate with 

the impulses received from the transmitter, the 

interaction between the two series Of impulSes 

serving to produce a facsimile of the original 

message. 

It is an object, therefore, of my invention. to 

provide apparatus comprising a transmission system including a transmitter section and a receiver section. Each of said sections has, as a part thereof, an electric circuit including ·the 

contacts of a plurality. of relays interconnected 

in such a way as to cause a plurality of impulses 

to circulate in said circuit. In the transmitter 

section these impulses represent the combined 

effects due to the message to be transmitted and 

to a control element. An impulse can only occur in this circuit when both of the relays have not 

moved their contacts to the same position. In 

the receiver section these impulses represent 

those caused by the original message, since the 

impulses due to the control have been removed 

by the use of a duplicate of the control in the 

receiver section. , 

For a further exposition of my invention reference may be had to the annexed drawings and 

specification at the end whereof the novel features of my invention will be specifically pointed 

out and claimed. 

In the drawings: 

Figure 1 is a circuit diagram of the transmitter with parts designated by blocks bearing appropriate labels. 

Figure 2 is a tabulation illustrating the impulses comprising the intelligence transmlt~d. 

2 

Figure 3 is a circuit diagram of the receiver 

in block form. 

In the one embodiment of my invention which 

has been selected from among others, my device 

fl is shown as comprising a transmitter section 

having a motor I driving shaft 2 carrying transparent drum 3 surrounded by message sheet 4 

and also carrying transparent drum 5 surrounded 

by control sheet 6. Within drums 3 and 5 are 

10 located electric lamps, l and 8 v;hich serve as 

sources of light and which are energized from a 

source of electricity 9. Opposite lamps l and 8 

so as to receive a beam of light therefrom and, 

respectively, under the control of message sheet 

15 4 and control sheet 6, are located light-sensitive cells I 0 and I I which form parts of circuits including amplifiers 12 and 13 and relay 

coils 14 and 15. These relays also include movable contacts 16 and 11 biased in one direction 

20 by springs 18 and 19 and, in the other direction, 

by coils 14 and 16, respectively, \\rhen these coils 

are energized, and engaging one or the other of 

stationary contacts 20 and 21. Contacts 16, 11, 

70 and 21 form parts of a circuit, including a 

25 source of current 22 and relay coil 23, 'vhich, 

when energized, attracts movable contact 24 into 

engagement with stationary contact 25, overcoming the pull of spring 26. Contacts 24 and 

25 control a circuit including transmitter 21 

::o having an output element 28, shown as an antenna. , 

At the place to which it is desired to transmit the intelligence, there is located a receiving 

system having a receiving element. indicated 

,,;, as an antenna 29, forming part of receiver 

30 which is connected into circuit so as to control relay·coil 31. This relay also includes movable contact 32 stressed away from coil 31 by 

spring 33 and co-operating with stationary con-

·10 tacts 34. Motor 35 drives shaft 36 carrying transparent drum 31 surrounded by second control 

sheet 38, which is a duplicate of control sheet 

6. Within drum 31 is located electric lamp 39, 

energized by a source of electricity 40. Oppo45 site lamp 39 so as to receive a beam of light 

therefrom under the control of second control 

sheet 38, is located light-sensitive cell 41 which 

forms a part of a circuit including amplifier 42 

and relay coil 43. This relay also includes mov50- able contact 44 biased in one direction by spring 

45 and, in the other direction, by coil lJJ, when 

this coil is energized, so as to engage one or 

the other of stationary contacts 46. Contacts 34 

and 46 form parts of a circuit including a source 

6~ of electricity 47 and a relay coil 48. This re: 
• 9REF ID:A105156 

2,662,648 

3 4 

lay includes movable contact 49 stressed away duced in coil 48, which is represented in Figure 2 

from coil 48 by spring 50 and co-operating with . by the line labeled "Message." Following 

stationary contact 51. Contacts 49 and 51 are through the other columns of Figure 2 shows 

parts of a circuit including a source of electricity that when coils 31 and 43 are simultaneously 

s·2 and coil 53, which is the operating element G energized or de-energized, no impulse appears in 

of a facsimile reproducer of any convenient type. coil 48. Likewise, while either coil 31 or 43 is 

The operation of my.device is as follo\vs: The energized when the other is de-energized, coil 48 

message and the control sheets are in any graphic iS Cnertiized. The energization of coil 48 causes 

form such as a writing, printing, drS.:wing, photo- coil 53 to be energized and coil 53 operates a graph or the like. They may be said to consist .10 stylus or other marking mechanism and thus 

of pluralities of spots or elemental parts each of message sheet 4 is reproduced. 

which is either black or white depending upon It will be understood that, whereas the forethe part of the message which it ,forms. Rela- . going ·description calls for the transmission of a 

tive movement is provided between lamp 1 and sign:il when one only of the coils j 4 and 15 is enermessage sheet 4, between lamp 8 and control sheet 15 · gized, the apparatus will function just as well and 

6, and between lamp 39 and second control sheet achieve just as great privacy if rearranged 

38 in any convenient manner heretofore used in slightly, as by giving an opposite bias, a normal 

the art of facsimile transmission. This• causes closed condition, to switch 24-25. In such case, 

the beam of light emitted by each ·lamp to scan ·of course, a signal Wu1 be transmitted whenever 

every spot or element of the message or control 20 coils 14-15 are in the same condition instead of 

associated with it. In the transmitter this scan- when they are in different conditions. 

ning thus produces a series of impulses 'in the I Claim: 

amplifying circuits through the action of:the Ught 1. Means for secretly transmitting graphic insensitive cells :I 0 and 11. ·For convenience of de- formation, said means comprising, a message in 

scription, these impulses can be said to be pi·o- i!5 graphic form which ·it is desired to transmit, a duced by black spots in the message or control. scanner arranged to scan and feproduce said 

Thus coils 14 and I 5 are energized every time message as a series of electric impulses ·of vary- an impulse occurs in.the amplifying.circuit asso- ~ng intensity, a screen having varying portions, 

ciated therewith. The action·of the relays con- ll- second scanner arranged to·scan and reproduce 

trolled-by these coils produces in the circuit·asso- 3U the variations of said screen as a second series of 

ciated with them a series of impulses distributed electric impulses of varying intensity, a relay 

in time as shown in Figure 2 of the drawings in connected under the control of said scanner and 

,which the term "X" represents an impulse. This arranged to 'be moved by each of said impulses 

figure shows the·four possible cases. Thus it will to one of two pasitions, a second relay connected 

be seen in column 1 that energizing coil .14. by ~5 undei- the control of said second scanner and 

message.sheet 4 without energizing·coil I 5 by ccn- arranged to be moved ·by each of ·said second imtrol sheet 6 causes an impulse in the circuit.co~- pulses to one-of two positions, an electric circuit 

taining coil 23 and labeled "Result" ·in 'Figure 2. includirig parts of said relays and adapted to be 

This energizes coil 23 and causes transmitter ·21 cIOSed only When there is instantaneollsly .an "imto emit an impulse. A13 seen in column 2, \Vhen 40 pulse· in either series but not in the other, a 

both coils 14 and 15 are energized no impulse transmitter -connected under the ·control of ·said 

appears in the circuit containing coil 23. As seen electric ·circuit so as to emit impulses whenever 

in column 3, energizing coil ·I 5 ·but not energizing said circuit is closed, a receiver arranged to recoil 14 causes an impulse-in the circuit containing ceive the impulses emitted by said transmitter 

coir23. Column 4 shows that \Vhen no impulse is 45 and having an output comprising a third sertes 

present in either amplifier 12 or 13 and, ·Conse- of electrical impulses of varying intensity, a 

quently, neither coil 14 nor 15 -is energized, no second screen. duplicating said first mentioned 

impulse appears in the circuit containing coil 23. screen, a third scanner arranged to scan synchroTo put it another \Vay, an impulse only appears nously with ·the scanning of said second scanner 

in coil 23 and, therefore, an impulse is only sent 50 and reproduce the variations of said second screen 

out from transmitter 21, v1hen coils 14 and 15 are as a fourth series of electric impulses of varying 

not ·in the same condition, i. e., are not-·simul- intensity, an electromechanical interlock contaneously energized or de-energized. This is due nected under the control of said third and of said 

to the fact that simultaneous energization or de- fourth·series of impulses and arranged to be enerenergization of coils 14 and 15 causes ·movable 55 gized whenever an impulse occurs in one of said 

contacts 16 and 11 to engage stationary contacts third and fourth series and no impulse occurs 20 and 2 I, respectively, which are coiinected to simultaneously in the other of said third and 

the same side or polarity of source ·22. fourth series, and a recorder connected under the 

The series of impulses emitted by the output control of·said interlock and arranged to operate 

element 28 of transmitter 21 is received by the 60 whenever said interlock is energized and to 

input element 29 of receiver 30. Each impulse th·ereby reproduce·said message. 

so received energizes coil 31. Motor 35 produces 2. ·Means for secretly transmitting graphic inrelative movement between second control sheet formation, said means comprising, a message ·in 

38 and light 39 so that control sheet 38 is scanned graphic form which it is desired to transmit, ·a 

in synchronism with control sheet 5. Since sec- 65 scanner arranged to scan and reproduce said mesond control sheet 38 is a duplicate of control sheet sage as a ·.series of electric impulses of varying 

6, coil 43 is energized in synchronism with the intensity, a screen having varying portions, .a 

energizations of coil 15. Referring a.gain .to Fig- second ·scanner arranged to scan and reproduce 

ure 2, the line labeled "Result" represents the the variations of said screen as a second series of 

impulses \\'hich pass through receiver 30 and ener- 70 electric impulses of varying intensity, an electrogize coil 31, while the Une labeled "Control" repre- ·mechanical interlock connected ·Under the control 

sents the simultaneous impulses caused by con- of. ·both of said series of impulses and arranged 

trol sheet 38 and which energize coil 43. Figure'2, to be energized \vhenever an impulse occurs ·in 

column I, shows that. when there is an impulse one of ·said series and does ·not occur simultaneln coil 31 and none in ·Coil 43, an impulse is pro- 76 ously.· in· the other of said series, a transmitter 
•. 

• ~ REF ID:A105156 

2,GMl,048 

5 

connected under the contro1 of said interlock so as to emit impulses whenever said interlock -is 

energized, a receiver arranged to receive the impulses emitted by said transmitter and having 

an output comprising a third series of electrical 

impulses of varying intensity, a second screen duplicating said first mentioned screen, a third 

scanner arranged to scan synchronously with the 

scanning of said second scanner and reproduce 

the variations of said second screen as a fourth 

series of electric impulses of varying intensity, a 

second electro-mechanical interlock connected 

under the control of said third and of said fourth 

series of impulses and arranged to be energized 

whenever an. impulse occurs in one of said third 

and fourth series and no impulse occurs simultaneously in the other of said third and fourth 

series, and a recorder connected under the control 

of said second interlock and arranged to operate 

\vhenever said second interlock is energized and 

to thereby reproduce said message. 

3. Means for secretly transmitting graphic information, said means comprising, a message in 

graphic form which it is desired to transmit, a scanner arranged to scan and reproduce said 

message as a series of electric impulses of varying 

intensity, a screen having varying portions, a second scanner arranged to scan and reproduce 

the variations of said screen as a second series 

of electric impulses of varying intensity, a relay 

connected under the control of said scanner and 

arranged to be moved by each of said impulses 

to one of two positions, a secoild relay connected 

under the control of said second scanner and arranged to be moved by each of said second impulses to one of two positions, an electric circuit 

including parts of said relays and adapted to be 

closed only when there is instantaneously an impulse in either series but not in the other, a 

transmitter connected under the control of said 

electric circuit so as to emit impulses whenever 

said circuit is closed, a receiver arranged to receive the impulses emitted by said transmitter 

and having an output comprising a third series of 

electrical impulses of varying intensity, a second 

screen duplicating said first mentioned screen, 

a third scanner arranged to scan synchronously 

with the scanning of said second scanner and 

reproduce the variations of said second screen 

6 

transmitting graphic information, means for 

scanning a message to be transmitted to derive 

therefrom an electric signal irregularly assuming 

a succession of values responsive to the photo5 graphic density of the message at the point of 

scanning, means for substantia1ly simultaneously 

scanning a camouflage message to derive a second 

electric signal irregularly assuming a succession 

of values depending upon the photographic den10 sity of the camouflage message at the point of 

scanning the second said electric signal being nonsynchronous with the first with respect to the 

variations therein, a switch having two circuitclosing positions, means for causing said switch 

15 to assume one of its circuit-closing conditions 

when said :first-mentioned electric signal assumes 

one value and the other of its circuit-closing conditions when the said first-mentioned signal assumes another of its values, a second switch hav20 ing two circuit-closing conditions, and means for 

controlling said switch responsive to said second 

electric signal, a third switch, a control circuit 

for said third switch said circuit serving to close 

said switch when the first-mentioned two switches 

25 are in predetermined circuit-closing positions 

only, and means for transmitting a signal when 

said third switch is in closed condition. 

5. Means for secretly transmitting graphic information comprising a device for scanning a 

30 message to be transmitted and reproducing said 

message as a series of electric impulses of varying 

intensity, a second device for scanning a camouflage message and reproducing the same as a 

series of electric impulses of varying intensity the 

35 impulses of said second series being non-synchronous with the impulses of the said first series, 

a relay connected under the control of said first 

device and arranged to be moved by each of said 

impulses to one of two positions, a second relay 

40 connected under the control of said second device 

and arranged to be moved by each of the impulses of said second series of said impulses to one of two positions, an electric circuit including 

said relays adapted to be closed only when pre45 determined combinations of closed positions in 

said relays occur simultaneously, and a transmitter connected under the control of said electric 

circuit so as to emit impulses on1y whenever said 

circuit is closed. as a fourth series of electric impulses of varying 50 

intensity, a third relay connected under the control of said third scranner and arranged to be 

moved by each of said impulses of said fourth 

series to one of two positions, a fourth relay 

connected under the control of said receiver and 55 arranged to be moved by each of said impulses 

WILLIAM F. FRIEDMAN. 

REFERENCES CITED 

The following references are of record 

file of this patent: 

UNITED STATES PATENTS 

in the 

of said third series to one of two positions, an 

electric circuit including parts of said relays and 

adapted to be closed only when there is instantaneously an impulse in either said third or said 60 fourth series but not in the other, and a recorder 

connected under the control of said circuit and 

arranged to be energized whenever said circuit 

is closed to record the original message. 

4~ In an apparatus of the nature described for 65 

Number 

l,310,719 

l,312,574 

1,657,366 

1,763,358 

1,848,839 

1,868,967 

2,300,664 

Name Date 

Vernam ------------ July 22, 1919 

Pierce ------------- Aug. 12, 1919 

Belin -------------- Jan. 24, 1928 

Jenkins ----------- June 10, 1930 

Ranger ------------- Mar. 8, 1932 

Cartier ------------ July 26, 1932 

Francis ------------- Nov. 3, 1942