' :I 

' ~: •, 

·,· I' 

': 

. i 

·j 

I . 

I . 

. I 

I 

I . 

I 

I 

REF ID :.1'.4161578 
. "i --

.REF ID:A416157B 

March 24, 1925. 1,53(),660 

w x 

I 

A B' 

W. F. FRIEDMAN 

-PRINTING TELEGRAPH SYSTEM 

Fi.g.1 

u 

u' ------

Fig'.2 

u ------

V' ------- Yig,3 

Q 

Com19/ele 

recewlng ,!;ef,,-T Conrrolleo' h!J r1t1 

w' 

J\ 

q 

Jn,-ve.n!o-i; 

Mihm ;: Fne(/m.:;n 

-._,,,,, 
... ' 

REF ID:A416157B 

Patented Mar. 24. 1925, 1,530,660 

UNITED ST A TES PA TENT OFFICE. 

WILLIAM 'F. FRIEDMAN, OF WASHINGTON, DISTRICT OF COLUMBIA. 

PRINTING-TELEGRAPH SYSTEM. 

Applic~tion filed July 26, 1922. Serial No. 577.,649 . 

To. aU rnlwm, it may concei'n: method dcscrihecl below. These relays actuHe it known that I. }Vrr,LTAJ\f F. Fnrnn- ate magnets which set np combinations of 

>IAN, citizen of _the United States of selecting discs in a printing mechanism, and 

America, rnsicling at 3220 17th Street N\;V., each character of the message is determined oo 

5 in the city of Washington and District of by a different combination or arrangement 

Columbi·a, have invented certain new and of these selecting discs. Usually there are 

nsdul _Im.provements in Printingc Telegraph g2 snch combinations, 26 for the ordinary 

Systems, of which the following is a spcci- letters and G others concerned in certain 

fkation. functions of the printer, such as carriage re- 05 

JO This invention relates to imprnvements in turn, figure shift, 0 and so on. The signals 

electrical ~ignaling systems, more pai:ticu- for .message characters as commonly used 

larly to pl'Inting telegraph systems, and has in these systems, constitute what is usually 

fo;· its object the simultaneous transmission termed a five-unit code, that is, it consists 

and reception of a plurality of code signal of pcrmut.d.ions of two elements taken five 70 

Jii inqrnlscs representing the ii1dividual ele- nt a tirnc. In one system of operation these. 

rnents of the messa !!C cha ractcrs that a re two elements may be positive and negati vo 

tra.nsrnitted. ~ potentials, in which case the code signal fot· 

:\ f111-tl1e1· ob.it!c:t is to l:ecluce very nrnte- n cl1nmctm· consists of the distribution 

ri:dly the length of time necessary in the through time of five elements composed of 75 

"U heretofore prevalent printing telegraph sys.- positi vc a.nd ne.gati ve impulses. In another 

tems to transmit the code signals_ represent- s_ystem of operation the ·two elements may 

ing the rncssa.ge charncters and thus increase consist of a time-inten'al when an impulse 

the ea.pacity -of the line 01· ·channel· em- is se~t., and a time-intm'vaJ when no impulse 

ployed. is sent, this being the method of closed and 80 

?!i A fnrthct object is to inc1·ease the mun- open c_ircnit operation. The code signa.l for 

her of separate messages which can be trans- th~ letter "A:', for example, is"++---", 

mittecl ·and received simultaneously, thus. which in the positive and negative system 

also incr.easing the capacity of the line 01' of operation means that the first and second 

channel emp]oyecl. . · 11nits of the signal are positive impulses, the 85 

30 A further. object is to eliminate the ne- third, fourth, and fifth, are negative imccssity for the employment of synchronizing pulses. l;n the open a1i.d closed circuit sysmcchanisms such as are required in the here- tern of operation, this code signal means that 

toforo prevalent systems. only the 5rst two time units are occupied 

.Tl:e invention will here be ill11stratecl as by the passage of cunent, the lnst three, un- uo 

:i::; :tpplied to <t li'Cll known form of printing occ11pied. · The per·11111tn.tions rrl' transmitte;l 

t.degrapl1 s,vslnns, b11t, as will be rnallily nn- inqrnlses :U'e g1wer1ted by it set of 111ake aml 

derst.ood. ·is applicable to ma11y other t~lec- break keys operntell at the trnnsrnitting end 

tric.:al systen1s ancl clevit.:es wl1id1 aL (Jl'esent rnarn1ally, by me1u1s of a sending key'boa.rd 

necessitates the 11se of more or les:'l compli- simihlr .in l'on11 to the or·dinary typewrite1· n,-, 

'l:l cat1~il synd11·oniz.i11g devices. . keybm,u:d, or a11to111atically by means of a_ 

'The fonclarnental principle of my inven- transmitter 1.;ontrol1ec1 by a perforated tape. 

tion is tl1e substitution of a plurality of In order that a. plurality of relays shall 

moclulaterl high frequency oscillations of be controlled by nnpulses of equal potenclilferent frequencies nll trunsmitted simul- tinl, an<'.]. all coming over the same line, or !Co 

4.J taneously and instantaneously for a plu- through the same channel, and that the pei·-

ra1it_v of similar, equal potential, direct cur- mutation of relays actuated at the distant 

rent impulses distributed through time. encl shall correspond to the permutation of 

In the heretofore 1prcvalent forms of clep1'essecl keys at the sending end, in the 

printing telegraph systems, the automatic heretofore preYalent systems, connection is rn.-, 

GO operations concerned in causin,g a printing momentarily estnbl ishecl between each key 

rneclrnnisrn to function at a distance are con- at the sending end and its c01Tcsponding retrolled by groups of equal potenti:1l, direct .. lay at the receiving encl and the five temc11i'l'e11t dectl'ical impulses which pass over pora.ry connections between the five pairs of 

one and the same line, and aetuate tt set of. keys a.ncl relays are established in a fixed 1 :n 

55 !'clays, each impulse iii the grnup affecting seq1te11ce, one afte1· the other. Thus, fol' 

the operntio11 of a particular. relay, by .·a exa"niple, in. the case of five. relays respec-
REF ID:A416157B 

i,530,660 

. . 

tively eontrolled by five make and break the det<lilccl foHowing description based 

keys, the_ time necessary to se'nd the signals thereon, set forth an embodiment of the 

for one message character or letter is di- . same. 

vided up into five equal intervals; during Figure l is :t diagrammatic sketd1 of one 

5 the first interval key 1 at the sending e1Hl form o:E a·rrn11ge111ent of circ·uits whereby 70 

is connected with its corresponding rcl:ty 1 each of a plumlity of high fr~quency alternt the i·eceiving encl; during the second in- nating cnnents may be rnodnlated or n~nterval, key 2 at the sending end is con- modulated in permntations conesponcl mg 

nected with its corresponding relay 2 at the to code signals for message characters, the 

10 receiving end, and so on. The method of modulated currents impressed upon a line, 7J 

effecting such a correspondence in action by and the modulations isolated at the receivtransmiti11g similar impulses through one ing end by a plurality of selectively tuned 

and the swine ·channel i1wolves the use of a circuits. · distribnto'I: and vario'us other apparatus in- Figure 2 is a cliagramm;1tic sketch o:f one 

15 eluded nncler the general term "synchroniz.. form of arrangement of circuits whereby a [W 

ing mechanism." plmality of complete sets of modulated alThe principle of the synchronizing dis- ternating currents a're simultaneously imtributor is this: Two similar rings, one 011 pressed upon a line, the members of each set 

the sencling fuce of a dislrib11tor at the being i"sohtted at the receiving encl by a 

20 t.rnnsmitting station, the other "On the receiv- plurality of selectively tuned circuits, th11s s;; 

ing face of an identical clistribt'itor at the effecting multiplex operation. r~cei,·ing staticm, .ne e:rch ·divided into at Figirre 3 is a diagi:·ammatic sketch of an 

least five e<111al segments. A pair of rotat- · artangement of circuits for the simultaneing brnshes '01\ these distributors a·rc eon- OllS or)er;'1:tion of transmitting and recei\'ing 

25 nected to the line, and \\'lien these brushes sets <Lt the sa1ne end of the Iine so that nr 1 

revolve they sweep ovm· and make contact stations may tninsrn!t and receive messages 

with the segments of their respectirn i-ings. at the same tim~ at both ends of the line. 

Tire 1lJl'11slres at the two ends of the line start Figute '4 is si111Uar to Figurn 1, except 

froin the same relative position and sweep Llhlt the a1Tangements in the former are 

:iu over the contact !::cgments with the same adapted for communication by riHlio. 

unifo1·m nngnlai- velocity, thus connecting Having morn particular reference to the 

the ffrst segment of the ·ri:n'.g of the sendihg c11·iiwings nnd in connection with '\7 hich like 

·clistributor with the fiTSp segme·nt of the charncters of reference designate similar 

ring of the receivii'1g clis'tribut9r once per pal'ts tln·oughout, in Figure 1, A, B, C, D, 

35 rernh1tion of the bl'nslres: Like\vise, the an·d E, are somces of high freq11e11cy nltersecond, third, fomth and fifth segments of nating cui'rent of cliffetent frequencies. 

the sending distributor are connected once cttllecl hereafter "can:for waves" each of 

per rev·oiut'ion 'of the h'rushes with the cor- which is modufated telegi'aphicnlly, by 

rnsponding- segments 0£ the receivi·ng dis- me·ans now wellcknown in the art th'rough 

40 trilmtor, the i11tcrval of each connection t.he .JI.1 1positi'On of mocluln,ting__ frequency by 

being the time of one-fifth of n. l'evo'1ntion mod'lllators F, G, H, I, nml ·,J, ·rnspectively, 

of the rotating br11shes. Th11s, each ·1nes- when keys K, L, :M. N, and 0 are opernted. 

sage cha·rader is transmitted as a combina- Q is :L sending keyboard of well known 

tion of five sepah1te or discrete impulses f01'ni1., or nn au"tol1~atie "ttipe-eol'itrnlled trnns-

,15 dislrih11ted equally itncl in a d~ifini'te sc- milter, also o"I' weH known fur111, 1Yhich go\·-

<Jmmee tl11·011gli an intenal of tilllc, ai1d for crns the adion of the keys K to 0 in :l pel'-

each revolution of the l.1rnslws, the code irn- mntati,·e man11er ;1ccorcling the the comhinap:ilse <.:ombinati011s for one and only one tirn'is of the eode s·igna1s rep1·escnti11g mescharacte·r 01· lettel' a1'c transmitted and re- sa!.!,"e cha.rndcrs. 

50 eei,'ed. Th.e synchronizitt:.ion !of the two t,et us SLippose, for pui.·poscs of illustrndistributors so that the respective bl·ushes tion, that A is a source o'f: carrier wave c(1rrevolve with ·exactly the same angu_lar ve- rent of :t I_l'cquency of 20000 cyeles per 

locity is a very complex featme of these second; B is a. som·ce of carriei' wave curprint~1ig te.Iegra ph ·systems, -and ·acts as a rent of a frequency ·of 30000 cycles per 

[i:J li1'niting factor upon the speed of operatiO'J'L second, and so on, 'tip to E, which is a stil'1ree 

In my system no such synchronizatioi1 is of carrier wave ct1rrent of a frcqum1cy of 

necessary, for all of the signals comprising GOOOO cycles per·second. · F moclnbtes cal'l'ier 

the combiwttion of impulses for a single wave A 'by 1000 cyclds per second when key 

charncter are transmitted simnltmieonsly, K is closed; similarly G, H, I, n.nd .J moch1-

r.o uncl at the receiving ei1cl are properly iso- late the carrie1· waves B, C, D, and E, reJnted by five selecti\'ely tuned ·circuits. spectively by 1000 cycles per second, when 

In ·order that the invention and i·ts mocfo keys- L, M, N, and 0, respectively, are 

of appl1catio11 may be readily 1mclcrstood dosed. The modulated carrier waves are 

by persons skilled in the art, I have, in the impl't!ssed upon the lines U :rnd U', which 

G;_; accompanying ·illustrative <fr:twings, and "in at the rcceivil\g end brr111ch off into the fin 

100 

105 

llU 

lliJ 

120 

12:) 

130 
REF ID:A416157B 

1,030,680 

bridged across the lines U and U', I do not 

wish to restt·ict myself to this method of 

co11ncctiuns, for the mod11laterl eanier waves 

11iay j11st as frasibly be insprte1l di1·ectly in 

5 sel'ies witl1 the line circuit. 

Furthern1ore, sinee the rno1l11lating frequency is Llw same for al1 the carriet· waves, 

instead o-f 11aving separate llHH_h1lating elements such as those shown in F, G, H, I, 

10 and .J, it is, of conrsP, q11itc possible to have 

a !-Jingle modulating Plement suitably conneetell to the keys K, L, )f, N, and 0, so 

that the modulation may be imposed upon 

any of the carrier waves. 

15 Furthermore: the gPnerators here described have a single period, but multi-period generators may be used, in which case 

the individual frequencies would be used in 

the separate transmitter circuits. 

20 It is to be understood that eitlwr tl twowire complete metallic circuit, or a si'ngle 

wire grnnnd return circnit is possible. In 

the drawings, the fonner method is shown. 

'Vhile I have. illustrated my inrnntion as 

25 utilizing a colle consisting of five elements, 

it is ol>vions that a catle of a g-reate1· nurnbet· of de men ts n1ay j ui:;t as easily Le used, 

llcpencli11g upon the printing mechanism 

that is employed, and I theteforn do not 

30 wish to limit myself to a. code consisting of 

any particulnr number of clements. 

It is also obvious that instead of using a 

line upon which the modulated canier wa.ves 

are impressed, the modulated carrier waves 

3:3 may l>e of ra.dio-frequencies and radiated 

intci space Ly means of an antenna or any 

other suitable radiating device. This is 

shown in Figure 4 in which an antenna Q, 

with its ground, R, sel'VeS to radiate the 

40 ,,·aves into space and at the receiving station u corresponding antenna Q', with its 

gmnrnl, H', serves to lw·.ci\·e the nhliated 

wa ,·cs. Jn this Hg111·c "' and 'V' rPprcsent 

all the elements inclrnled 11nde1· P a.nd P', 

45 re-;1wdi1·ely, i11 Figu1·e 1. The method of 

l'!itploying 111ot'h1latetl <lifferenL freq_nenc)'. 

carrier wnn•s to eli111inate the necessity ot 

s1·1whrol'li:.-:in'!,' 111L'dia11iH111s e:rn also be. ap1;1 il'd to H_ysi l'lns othm· than pri11ti ng tele60 graphs, and it is iute11ded that this foatul'e 

be indmh•ll among the others of my invention. 

In fad, sewral modifications of the system are possible without departing from 

65 the spirit of the invention or the scope of 

the cluin1s. 

\Vhat I chim ns i.ny i1wention is the followin.,.: 

1. I~1 a p1'inting telegl'uph system, the 

oo combination of a set of gt'nerators of racliofreqneney oscillations of different ~·aclio­

·l'req uencics, means for telcgI"aph icnlly 

moclll lating said oseillatio11s by a single 

modnlating frequency, a set of make and 

05 break keys respcd i vcly eo11troll i 11g the 

modulation or non-modulation of snid set 

of oscillations by said modulating frequency, llieuns for operating said set of keys 

si11111ltancously :rnd pemrntatiwly to <.:Ol'respond to the permnt:t!ions of a pl11ral-1111it ;·1l 

signaling code 1"Bp1·esenting rnessage eltar:H·-

tr•rs, means fo1· radiating said per111ut:it io1Js 

of mollulatcll and non-modulakd oscillations si nrn ltnneonsly into spacP, means for 

recei,·ing and detecting said radiated oseil- 1.; 

lations, sai<l Inst. mimed means being associah'll "·ith a set of l'Pcei \'ing instruments 

suitably arranged to isolate the respecfrrn 

said oscillations, means for detecting the 

presence or absence of modulation in each so 

of said isolated oscillations, each of saill 

last-named means being associated with a11ll 

controlling a relay which is energized w·hen 

said modulation is present, but is unenergized ''hen said modulation is absent, aml 85 

a printing or recording mechanism controlled by the pernnitative operation of sai~l 

encqrized and unenergized relays. 

2. In a multiplex print-ing telegraph sy+ 

tern, the combination of a ph1rality of gen- DO 

crntors of radio-freqnency oscillat-ions of 

different radio frequencies, means for telcgrnphically modulating said oscillations in 

each set by a single modulating frequency, 

a plurality of sets of mnke and break key,; D.:i 

respectively controlling the modulation or 

non-modulation oscillations by said modnlating frequency, means for opemting said 

sets of keys simultaneously and permutati vely, to con'espond to the permutations of 

a plural-unit signaling code representing 

message characters, means for raclinting snicl 

sets of permutations of modulated and nonmoclulatecl oscillations into space simulfaneously, a plurality of s~ts of receivi!1g instruments tuned to rece1Ye and lo isolate 

said radiated sPts of oscillations, 111!'a ns for 

Lll'teding the presence or absener of mod11-

Intio11 in ead1 of said isoLitt>il oseilla1ions 

i 11 pac-h of said sets of usl'i llations, en ch of 

said lnst-nallled 11wans hrin~ a!lsneiatPd 'rith 

and controlli11g a 1·l'l:ty \\'f1ich is Pnl'rgiz('il 

when said rnodulati<111 is p1·p:-pnt, linf is 

11nPnergized when !'mid 111odnlatio11 is nuPl'ttt, 

and a plurality of printing or rN·o1·ding 

mechanisms indi,·idnally conh·olkll by tl1c 

permutative operntio11 of suitaLle groupings of said relays into operative sets. 

3. In a system of multiplex printinglelegraphy, the combi11ntion of nn antcmrn, 

a set of transmitters and a set of receiwrn 

electrically associated 'vith said antenna, 

said transmitters generating r:lllio--freqnency oscillations of clifferPnt frequencies, 

nnd said set of recei,·p1·s being ndjnstecl to 

Le separately in resonnncc for freq11P1wies 

corresponding to thosP generated by the 

transmitters at some other stnlion from 

which signals are received, means for klcgraphie:tlly 111otlnlating said oscillations in 

l;.J 

}•'.i 

110 

11:; 

l~O 

]~!) 

1:w 
REF ID:A416157B 

1,530,660 a 

sei1:ctively tnnecl circuits A' to E', each of 

which is r~sponsive only to a certain predetermined frccp1ency. For example, in 111y 

ill11stl':1tio11, A' is a, circuit responsive to ·a 

5 carrier wave current of a. frequency of 20000 

cycles· pee seco11d, and no other; 13' is rcsponsi ve only to a carriel' wave current of a 

frequency of 30000 cycles pe1· second, and 

so on, u1) to E', which is responsive only to 

JO a carrier wave currc11t of a frequency of 

CTOOOO cycles per second. . 

F' is a circu.it for rectifying the high frequency current received by. A', and thus 

converts the high frequency current into a 

15 low frequency .cnrrent which is the modulating frequency, and then this cmrent 

passes on to i·el;iy K', tuned to respond to 

the modulating frequency imposed on the 

carric!' wave A by modulator F. Current 

20 will flow through F', fol' example, only 

when key K i·s closed, or, in other words,. 

when carrier wave A has Leen modulated by 

F. 1;Vhen this key is· open, n.o current will 

flow tlmrngh F', t:hns leaving relay K' in2:i operative. G', H', I', and .T' arc sirnila1· circuits, adjusted in the same w1ty as F' for 

rectifying the high frequency crnTents rccei vecl by B', C', D', and E' respectively, and 

tl1us keys L to 0 and circuits G' to .T' con30 trol the operation of relays L' to O', respectively in the same manner as key Kand 

circuit F' contL-ol relay K'. Relays K' to 

0' are operatively connected to R, which is 

a printing mechanism of well known form: 

35 and is controlJecl by the permutati~ ely energized and unenergized conditi'ons of these relays so that it prints or records the message 

characters. tmnsmittecl from the sending station . 

.JO Let us suppose that it is desired to transmit the signals for the letter "Z ", the code 

combi11ation for whieh is re1)J'esented by the 

symbols "+---+". This means that 

rnbys K' and 0' are to lie miergized, the 

45 others am to rem:i.in 1111energized. Tlte key 

"Z ': on the ma11w11l_y operated keyh011nl: 

Q, is <fopreSSl~d, or an ai1to111atic tape-eontrolled trn nsn1 i ttcr :f1111ctions, to causf: ke_ys. 

K n.nc1 0 to be closed simultaneously, thus 

50 en.using the modulntors F and J, respectively to modulate the carrier waves from A and 

E, respectively, but leaving the ca.rrier waves 

:from B, C, and D, unmodnlated. In my ill11stration, lines ·u and U' will be simultii55 neously traversed by waves of the following 

frequencies: 19000-21000, 30000, 40000, 

150000, and 59000~61000 cycles per second. 

At the receiving encl circuits F' and J' will 

be the only ones that will a.llow current to 

fill reach the relays, for circuits G', I-I' and I' 

will just neutralize the unmodulated carrier 

'waves from G, H, and I, respectively, and 

tl1erefore only relays TC' and O' will be 

energized. This action corresponds therr~-

Q::i Jore·-1.o the perm11h1tion of clnsecl keys nt the 

transmitting end. It is thus seen that Hlthongh the five relays J(' to O' a re a 11 operated hy c111Tenl:s simultaneollsly traversing 

the line U-U', Lllll operation of a1ly one of 

the five relays is independent of nnd will 70 

not be inl.edered with by the operation of 

any other of the five relays. Tlte heterogonous· combination of modulated . carrier 

wiives is broken up into the homogenous elements of individual impulses .in a penmd;it- 75 

tion corresponding to the ·proper code signal 

for the character transmitted. It is apparent, 

furthermore, that in this system not only is 

the time necessary to transmit a single character reduced to one-fifth of the time re- so 

quired· in the heretofore prevalent systems~ 

but also the speecl of the transmission and 

reception can be materially increased because no limiting speed o:f operation is introduced in this method by any synchroniz- s:; 

ing devices. · · · 

It i_s obvious' that the system here proposed permits of multiplex operntion of a 

single pair of lines, since a wide mnge of 

non-interfering frequency Lands arc avail- !HJ 

a\Jle for nse and .since a plurality of high 

frequency wa.ves of different frequencies 

may be impressed upon the same line an<l 

sdectively sepa.ratecl ;it the receiving end 

by extending the system described. -This is !I.) 

shown ·in Figure 2 in which W and X are 

transmitting sets, each of which is similar 

in constnrction and operation to the single 

transrnitting set P, of Figmc 1, and 1;V' rind 

X' are their corresponding receiving sets, L:J 

each o:f which is similar in construction and 

operation to the single receiving set, P' of 

Figure 1. It is to be understood that i;y 

and "'T' of Figure 2 comprise all the clem~nts included in P and P', respectively of Jc; 

Figure 1. It is of course nnnecessary that 

all of the transmitting sets be located at one 

end Of the line, and n.11 of the rccei\'ing sets 

at the otlH!r end of' the line, and in fact this. 

would not be the practiual rnctltnd of oper- i 1.1 

ation. A .plurality <.rf' transmitting sets and 

a plurality of receiving sets rn:t.Y en-exist 

at both ends of the line with no i11tedercnce 

whatever, so long as proper freq11en<.;ies arc 

selected :for the operation of ·each cotTe- 11.; 

sponding transmitting n.ncl receiving set. 

This is shown in Figurn 3 where A ~nd B 

represen.t complete transmitting sets comprising all the elements included by transmitting set P of Figure 1, B and B' repre- l ~o 

sent complete receivin,g sets comprising all 

the clements incl.uded by receiving. set P' of· 

Figure 1. Transmitting set A controls receiving set A' and transmitting set B contrnls receiving set B', but transmitting set l~:; 

A and recei,•ing set B' a.re located at one 

,end of: the line, while transmitting set B 

and recci\·ing set A' am located at the other 

<'nd of the line. 

·while l ha l'e shown the t1·;rnsmitting sets mo 
.. 

! 

--, __ 

REF ID:A416157B 

1,530,080 

r; 

l:l 

eacli of said lr:rnsmitters· by a single 111od11-

lating frequency, a set of make and break 

keys associated with each of said sets of 

transmitters, each of said set of keys respccti vely controlling the modulation or 

non-rnodnlation of the oscillations of the 

set of transmitters with which set of keys 

is associated, means for operating each of 

said set of keys simultaneously and permutativcly to correspond to the permutations of a plmal-unit signaling code representing message characters, means, associated with each of said receivers, for detecting the presence or absence of modulaJ.i ti on in the oscillations recei vcd by each of 

said rccei vers, each of said last-named 

means being associated with and controlling a relay which is energized when_ said modulation is present, but is unenergized when 

zri said modulation is absent, and a printing 

cir recording mechanism, said mechanism being controlled by the pcnnutative operation 

of said energized and unenergized relays. 1

1:. The method of radio-telegraphically 

effecting a. currcspondence and sim11lt:a11eity 25 

of action between the clements o:f a. set of 

controlling electrical instruments and the 

corresponding elements of one or more sets 

of controlled electrical instruments, by 

means of a plurality of carrier waves of 30 

different frequencies, said carrier waves being permutatively modulated or non-modulated by a modulating frequency according 

as the respective elements of said set of controlling instrnments are operated pcrmub- 35 

tively, the several carrier waves being isolated inclividuallv at the controlled stations 

by selectively tm1ecl circuits associated with 

said sets o:f contrnlled instruments, the presence or absence of said modulating fre- 40 

quency in said isolated canier waves respectively causing the clements of said set 

of controlled instrnments to be actuated or 

non-actuated as the case may be. 

In testimony whereof I affix my sigw1- 45 

ture. 

WILLIAM F. FRIEDMAN. 
• 

• 

REF ID:A416157B 

Patented Dec. 11, 1928. 1,6·94,87 4 

'U.NITED s·TATES .PATENT OFFlCE. 

WILLIAM F. l!'RiEDM'AN, OF W .b..SHINGTON,'"DISTRICT ·OF COL'UMBrA. 

METHOD OF ELECTRICAL SIGNALING. 

Applicatibu filed July 10, 1922. Serial No. 573,981. 

(GRA:tl'l"ED UNDER THE ACT OF MARCH 3, 1883, AS AMEND~D APRIL 30, :iS28; :ito 0. 'G .. 757.) 

't'h is. invention rel:1tes in general to 01ectric1al signaling systrms :rnd more partitulrrdy to systems fo1: the simnltaneons transmission of a plurality -of messnges through 

5 one and the same channel, and has for its 

objrct the proYision of a new nrnl more 

simple system of circuits for achie1'ing 1.his 

encl. 

A further object of the i1wention is to 

10 effect a recluction of the length of time necrssary to trnnsmit aml receive each of a 

plurality of messn.ges by the hcre.tcfore preYalent sy:-<tems of multiplex printing telegraphy, :mcl thns increase the capacity of n. 

15 single channel. 

A further object is to effect an increus? in 

the nnrnbel' of telegraph mcssnges which 

can be trnnsmii:tPd over a single channel by 

1.hc 11eretofore prevalent systems of multi20 ple·x telegraphy. 

A forther objl'd is to nehieve a system of 

nl1lltipkx radio 1elcgrn1Jhy hy i lrn use of a 

si11gle wtwe instead of a pl nrality of \Y;ffes 

of ·different freqflencies. 

25 The f.undamental _principle of my i111"en-

·tion is the differential modnbtion of a siHgle 

i!atTier w;we and the !-::elective isolation of 

the sc\'Cral rn0clulatiug freqnencies at the 

l't'C'eiYin~ enll, ~nch so isolated mmlnlating 

::o wa ,.e affecting a different independent circuit. · 

In order that the invention an<l its mode 

of 'applica'tioi1 may be ren<lily understood 

b:r pei'~nns skillPd ii1 the art, I havP, in the 

,,i) •accompanying illustratiYc clnnYi.ng~;: a-=id in 

the ·detaile11 folJo,ving desc1·i1itio11 has:.'cl 

thereon, set forth an embodiment of the 

same. 

F4\·1i.re 1 is n diagrnmmntic shkh o [' one 

•JO form of anang~ment of circuits wherdiy a 

hit._ri1 frcqnenl'.y curr~nt. carrier wnw is 

rnoli11 1a1.rll by severnl motlulators of di:trcr-

·e1it d1aracte1·, the modulat<!d ca rricr wave 

impressed npon a line nnd the se\·ernl modu4:~ la ting frequencies seledively separated at the 

other encl of the line . 

Figure 2 is tt diagrammatic sketch of Qne 

form of ~lrrang~ment of circnits whereby 

n plurality of high frequency canier wi.n·es 

:;o ~re ~ach 1nocluktecl bv several modulators 

of ·different charncte1:s, and at the other 

end of the line these 111-0dnlated carrier 

"waves ·arc first separated by tu·ninrr to the 

frequencies of the carrier waves n":id then 

tuni_ng again to the modulating frequencies. 55 

F1gures 3 and 4 are the same as .Fi·g-ures 

1 anrl 2, respect.iYely, except. that the arrangements in Fig1ires 3 and 4 at'e nclaptecl 

for radio transmission instend of line transmission. oo 

'lfn,:ing rndrc partict1lat reference to the 

clrnwings, ancl i'n connection with which 

like charactel'S ·of refel'etlcc designnte similar pat·ts throughout, in Figm'e l, A is a 

sontce· of high frcqmncy oscillnti<Jn:o of con- 05 

stunt freqncncy, desigrfated here:i:fter as the 

carrier \\ave·; B nnd C are a1Tirngements 

for modulating the cahier wave, each differentl.r ·mod ula tirrg the canier wave A; 

D and E are key·s which respectively con- 70 

tl'ol the modulation clements B and C. 

These lteys may be opei'ateLl man nall y by 

inqivi~1nrd operators 'employin~~ the l';forsc 

cnLte S1g'n:1 ts Lint iJ.s shown in the figure they 

are here ilh1Stratecl as operatively connected 75 

to I, which is a sending keyboard or an a11toli1atil' ta po-controlled transmitter, both of 

well known form. F imcl F' constitntc the 

line which the rnrrier wave trnverses. B' 

and C' nre selectively tm1ecl circuits respon- 80 

si \'C~ to the carrier wave A; D' and E' repre:;cnt circuits selecti vcly tuned to respond 

individually to t11e respective modulating 

frequencies; G and II are rela:ys ''hich may 

be of iYell known forms, and are operable s5 

by the ClllTl'nts .passed by D' and E' respectiwly, but they may be auy other form of 

device suitable fo1; making the currents of 

the isolated frequencies perceptible to the 

e.yc or ear, or for recording these currents oo 

in a suitable manner. The figure, howeYer, 

shows G and H to be relays opei·n.tiYely connc~ctecl to J, a printing or recording Jevice 

of am; of the well known forms . 

. Let·' us ~uppose t!rnt A impr~E~es. upon the 95 

lme F-11 ' a earner wave of ::iOOOO cycles 

per second, that B modulates the CtllTier 

wave by 1000 cycles per second and that C 

modulates the carrier wave by 2000 cycles 

p2r !:'econcl. Therefore a carrier wa,Te modu- 100 · 

lated in one instance to a 49000-51000 cycle 

wa Ye. nnd in the othet instance to ·a. 48000-

52000 cycle wave is impr~ssed 11"po11 tlie .lfoe. 

At the receiving end of the lirie k and C' 
• 

REF ID:A416157B 

2 1,694,874 

are circuits tuned to the carrier frequency ing telegraph systems ·which employ code 

of 50,000 cycles, and the carrier wave cur- signals consisting of a plurality of elements 

rent will divide, part, passing to one cir- or units affecting a plmality of relays assocuit, B', and a, part passing to the other cir- ciatcd with a printing or a, recording .mech5 cuit, C'. But D' and E' arc arranged to nnism. It may be desirable to discuss brief- 70 

respond to different modulating frequencies, ly this aspect ·of the invention .. that is, one \Vill be acted upon only by the In the heretofoi'e prevalent forms of print1000 cycle modulating. frequency, n,ncl the ing telegraph systems, the automatic operaother will be acted upon only by the 2000 tions concerned in ca.using a printing mech10 cycle modulating frequency. In that way anism to function at a distance are con- 75 

the different modulating frequencies are trolled by groups of equal potential, direct 

separated. Hence relays G and H will re- current clectricn.l impulses ·which pass over 

sponcl selectively to the modula.t.ing. fre- one and t.hc same line, and adnnte a set of 

qnenc.ies o.f B and C. · rcla.ys, each impulse in the group effecting 

15 The tuning of the receivers B' and C' to the operation of a. particular relay, by a 80 

:o modulated wave which covers a narrow method described below. These relays acband of freq·uencies as in the preceding ex- tunte magnets which set up combinations ofample, 49000 to 51000 cycles or 48000 to. selecting discs in a pTinting mechanism, and 

50000 cycles, may be accomplished by the each character of the message is determined 

'.!O well known methods in the art, which may by a different combinatio11 or arrangement 815 

be by the use of band filters, or :iny other of these selecting discs. Usually there are 

:rn1tuble circuit arrangements. ' 32 such combinations, 26 for the ordinary 

In the same wa.y a plurality of c<tuier letters and 6 others concerned in certain 

waves of different· frequencies may be em- functions of tlte printer, such as carriage 

:LG ployed, each carrier wave separately mod11- return, figure shift, and so on. The signals IJO 

lated by several modulations of different for message charncters as commonly used 

drnracters, and at the receiving encl the dif- in these systems constitute what is usually 

fercnt frequency carrier waves are fo·st sepa- termed a five-unit. code, that is, it consists 

rat.eel by suitable tuning and by further tun- of permutations of two elements fatken five 

30 ing. the individual modulating frequencies at a time .. In one system of operation these IJG 

on each carrier wave may be isolated. Thus two elements may be positive ancl negative 

a prnltiplex system of extremely wicle rnno'e potentials, in which case the code signal for 

is macle possible. This is shown diagra1~1- a character consists . of the . distribution 

matically in Figme 2, where A represents through time of five elements composed of 

;15 one unit of carrier wave current of one fre- positive and negative impnlses. In another 100 

quency from source C, with its associated system of operation the two elements ma,y 

modulating frequencies D and E, and B consist of a time-interval when an impulse 

represents another unit of carrier wa.ve cur- is sent, and a time-inter1al when no impulse 

rent of another frequency from source F, is sent, this being_ the method of closed and 

40 ·with its associated modulating :frequencies, open circuit operation. The code signal for 105 

G and I-I. A' represents a system of circuits the letter "A" for example, is"-- - - -," 

comp1-ising. circuits C' nncl C" selectively which in the positive and negative system 

tuned to the frequency of the carrier wa:rn . of operation means that the first and second 

C, and circuits D' and E', selectively tuned units of the signal nre positive impulses, 

45 to the modulating frcquellCies. D and E, the third, fourth, and firth, arc negative 110 

\Yhich are produced at A, and I, J', are re- impulses. In the open and closed circuit 

lays actuated by circuits D', E', respectively. system of operation, this code signnl means 

B' represents n, system o.f circuits comprisin" that on] v the first two time imits a,rc occn- · circuits F' and F", selecti vcly tuned to th~ pied by" the pnssnge of currcrit, the last 

50 :freqirnncy o-f the carrier wave, F, and cir- three, nnoccupied. The permutations of 115 

cnits G' and H', selectively tuned to the transm.ittcd impulses arc governed by a· set 

modulating frequencies, G and I-I, which of make and brenk keys operated at the 

are produced at B. and IC, L ai·c relays ac- trnnsmittin.O' encl manually; by means of a. 

tnatecl by circuits G', H", rcspect.iv.cly. M, sending lrnyboard simi1ar in form to tl~e 55 N, 0, and P are the keys controlling the ordinary typewriter keyboard, or automati- 120 

modulating circuits at A and B, and Q, Q,' cally by meai1s of a transmitter controlled 

is the line. - by a. perforated tape. .· · 

It is ob\'ious also that transmitting sets In order that a plurality of relays shall' 

can be placed at both ends of the line, ahcl be cm~trolled b;y impulses of equal potcn60 their corresponding receiving sets at both tial, and all coming over the same line, or 125 

ends of the line; so that multiplex operation · through the same drnnnel, and that the pcris possible. For such operation a plurality rirntation of relavs actuated at the distant 

of single period generators or a single multi- end shall corresp-~ncl to the. permntation of 

period generator can be employed. This depressed keys at the sending end, in the 

05 arrangement is ·especially adapted for print- heretofore p1:evalent systems, connect.ion is 130 
'' 

• 

RE.F ID :A416157B 

:i,694,874 3 

established between· .each key at the sending multaneously;·:and: at. the receiving end· are 

end--and its cori,esportcling relay at the re- -properly isolated. by five selectively tuned · <0ei ving en~l at a. different instant, and .the circuits. c • . .. 

several connections necessary· to transmit the -• There is, of course, nothing novel in modu5 code signal for each message character are ·lating a carrier "'ave either telephonic;illy iO 

made in ti·clefinite, fixed sequence. Thus, for or telegraphically.. The novelty of my 'inexaml)le, in the case of five :relays respec- vent ion consists j n. modulating a single car-

·t.:i:vely .controlled by five make and· break riet' wave telegraphically by several cliskeys, the time necessary to send the signals · tinct modulating· frequencies: and isolating 

10 for· one character is chvidecl. up, into five each modulating freqnency individually: Jn 75 

equal intei'vals; ··during the- first interval telephonic modulation a relatively wide band 

-conn·ection is estaolished between· key 1 at of modulating freqnencies is imposed upon 

the sending end -and its corresponding relay the carrier· wave,, and this band of heter1 at ·the rec~iving end; during- the second ogeneous side frequencies is faithfully re15 interval: conncc~ion is estrtblishccl between produced -by th'e telephone receiver at so 

key.-2 at the sending end ind it:s· correspond- the receiving encl. . The human· eat; hears 

ing reln.y 2- at the t·eceiviilg ·end; and so .on. nll of· these heterogeneous side freqnen-

.The method· of effecting- such i1 cori·espond- cies -simultaneously, but is· able to disencc in action by .transmitting siri1ilt1l' im- tinguish t,Jrnm lrnd hear them separately if 

2u pulses through one nnd the same channel an effort is made. ·For example:· when oi·- 85 

'involves tlrn ·use· of a di'sfTibuto·r ·and· \'arj- chestral music is being· transmitted -by radio 

ous other a1:iparatus-included tincler the gen- telephone, the rriclio audience hears the eneral tenn "S}'nchron izing incchil.i1isn1:" semble effect but there is absofutel); TIO ·di fThe principiil of -the synchronizing dis- ficulty in distingui~hing the 1nusic produced 

25 tributor is this:· two :simmn· rings, one, on by a violin-'from that produced by a cornet .. uo 

the· sen~ling face· of a· cl istributor at· the Both sounds are being transmitted on one 

transmit.ting station, 0 the ·other on the 're- and the same vehicle or. carrier wave, ·but 

ceiving· face of an identical distrib11tor at ·the modulating· frequency of the sound .vithe·'receiving station, are each diviclecl into brations of the violin'is 'different·from that 

30- five. equal segmerits: A pair of rotating of the comet. ''Thile in the illustration giv- 1!5 

brnshes off-these distributors are ·connected en above the separation of the modulating . to the line, hnd when these brushes revolve frequencies is effected by the car; in the ar-

'they sweep over and make contact with the rangement of this invention the separation 

segments . of their respective rings:· The of Hie modulating frequencies is accom35. brushes at· the two ends of the line start from plishect by mechanical or electrical tuning 1 uo 

the same relative position and sweep over devices; . the cont.act segl'nents with ·the same uniform In Figure 3 the arrangements of circuits 

angular velocity, thus connecting the. first is identical with that shown in Figure 1, 

segment of the ring of the sending djstribu- ·bu~ instead Of h:J.;ving a line upon which the 

40 tor with the first scg1~'lent ·~f the ·ring of the moclnlatecl carrier wa\1 es are ·impressed; a 10.:i 

receiving .distributor ·once per revo1nt.ion of ·£rnnsmitting ai1tenna, F, with its· groimd ·I, 

the brushes. Likewise "the sec<;md, third, serves to radiate the niodulated· waves· into 

fomth, and .fifth segments of the ·sending ·space; and a recei,iing antenna. F', with its 

clistribntor·are.connectecl once per revolution gi·ouncl I', serves to receive the waves racli45 of the brnshes with the corresponding seg- atecl by ·F. · ll o 

men ts of the rccei:ving · disti·ibutor, i;he in- · · Iri Figui·e- 4, the :arrangement of circuits 

terval of each connection being the time .of - is identicnJ · with that shown i11 Figure 2, 

one-fifth of a ·revolution of the. rotating b1it instead of having a line upon 'vhich tlie 

brushes. Thus, each message character is modulated carrier waves are impressed, ·a 

50 transmitted as a combination of five sepa- transmitting antenna, Q, with its ground R, ~ I.15 

rate or discrete impulses.distributed equally serves to tadiate the modulated wa.ves into 

and in a definite sequence through nn inter- space, and a receiving ant.enna,·Q', with its 

nil of time, and for each revolution of the ground, R', serves to receive the waves rabrushes, the code impulse combinations for cliated by Q,. 

55 one and only one character or letter are It is obvious that the arrangements shown 120 

t.rnnsmittecl and received. The synchroniza- in Figure 1 for controlling the operation of · 

tion of the two distributors so that the re- the keys governing the modulating circuits 

spcctive brushes revolve with exactly the and for controlling the operation of the 

same angular velocity is a very complex printing or recording mechanism, when a 

oo feature of these printing telegra1)h systems, syst.em of printing telegraph is employed, 125 

and acts as a limiting factor upon the speed also apply to Figures 2, 3, an~ 4. But it is 

of operation. In my system no .such syn- also obvi<?us that the mod~la~1~g keys may 

chronization is necessary1 for all of the sig- be operated manually by md1vtdual operanals comprising the combination of impulses tors, as stated before, and at the receiving 

65 for a single character arc transmitted si- end, instead of having relays, several oper- 13Cl 
REF ID:A416157B . ~· 

!>].'j694_;87.4 

... ators-'.Il1~y: 1.'00eive· .fihemessages0 .tra.~1smitted said· ·resonant ·cirtuits .·bei1~g•associwte~lr.with 

· -.i:n·-ordinary 1Morse ·char.acters 1by usmg :tele- .. and d.llcl a.pteEt-t0 cm1t11ol. a rnla,y '";hich· ,is"o.p- 55 

phone receivers. . . .. . eira.t1i¥e -when ,,the -m~ltilat.ing. frequency to 

: ,Jit is ohv.i:0us 1 'thn.t · mdi o-freq neDGy. osc1l- mhich · the: respect.i-ve; •l'esono!nt, oh,cu ft,,is ·rer, 1:la.tions 11mrist ·be "emriloyed fer' ua~li0 ·com- -.sponsive -is··present;-a.nd• is- ino})e1:11;ti-ve ":.hen 

. .muni.Gatiowby-,the systems "iUU$PYated ·in the the cn1odulabing ?frequency to i,whioh 'SUJid 

fast ·two ·fig.mes. · · · · -resonant ·cir.ouits is ·responsive is !not tpresent, 60 

···while I ·have not i11t!licatec}. in .t.Jrn figu·res •a .plurality of -l!elays• acting .as "a~ single"unit 

any. !particulars rega;rEliing· the. means to be associated with a, p1-.inting,•meclianism,. said 

· rn ·()mployecl in1 ~J·roducing. the carrier wave.-or · ·p1tint..iing mechanism. being• contl'0lled, as-"ta 

the nnanne1: .of modula.tirrg the cmrrie1"wo:ve, ; unit by the joint a.nd. parn~utati"e-.u:ction 0f 

·.or, ;the manner.tin which th:e modullatecl car-· ·s, id set• of relays ri·n such ,a manner .as to 65 

-rier .. ,,\,a<>.:Cfiillrl'e' inlp"ressed <W!the hne:or radi- .-pr.int. t e .message c u1.o1·ao ers represented -by 

ated into•fl:pace:, it1 ;is to· .be understood .that r tne--:: )e1:1F1ufati:vel ' >inod-ufo.Wd . tran:sm:ittecl 

· J-5 a.ny. 0f -tirn mea-Rs ,n.nd -methods rnow ,:well .-,arnl q·ece1vec CJa7J.·.1•1cr wave . 

. known. in, the -~rt . .may be employed. Nor .• 2 .. tu.a.Jn'm't:fug, telegraph,systeh11 cm'l!!J!>risha,,e,I ind.foated.any,deta.j1siwith ·respect to ,,i.ng a sourc-e.oLh-igh-:frequency eleotl'ical os-_ iO 

the exact·· means to ,be 11sed in recei:vi.ng.,. the ci1)ations .constitu,ti..ng 1a-:Cthl'l'·ier , ;\\!fil\<e, a, set 

moatula:t,ed .:can:ier ,\\mv&s, .se.leyti·vely. sepa- o;f n1odH1at©-rs 0 •of di·ffe11eat1 modulating, f.re20 rating .the moaulati.ng-frequencies, :md c"aus- r-quencies which . can be . imprestmd >lll .. a 

i~g· them ,to .a.ff.ect selectively tuned rela:ys permutative ma,nner --r~resenti11g. message 

or .l'ec01;di,n:g.,,de.vi:i.ces, for here .. a1so .ithe cha1:acters .• in !R ))luuail-w.nit ·co<>:le •upon the 75 

'lnea.ns and methods no:w· well kne>l\vn in the said,·ca.i-rie-r ;:wave hy.-')}1ea,ns Of :a,.Jn~y;boarcl 

: a1~t, a.pply to this inv:ention .. ", , _. . : : ". •Itrechan.ism -con.-t-1:0lliwg "a set :of.<:k(?_ys, ~·gov-

:.:!fi • What I,iclaim as.my imv~nti91?. is.the. fol- .-erning thMwtio-1H>f;said-set-O:hno'tH1lrutoi's;1a 

10'"\ving: . , . . . . · i•eceivcr ca-pa.blef of, reoeiv~·Ji(g t·lM l 1pru·mHt:a-

, :L ~li1\a p:i.;~·:nting teleg1~if.Dh .systein, .a. saurce ti vely mod u.Ja.ted carrier . w.a ve. i:~1~r·eseFJ:ti-ng so 

of high frequelilCY el~ctr.iqaloscillations con- message cha-1.·aicte11s, .ra· set @f resonant cir-

·Stitqtip.g a. carr:ier\,:avc;1a set of· rno.cl.ul~o:r.s ,. cuits, each of .sai<l.:res0:e.ant ~ircuits, being 

30 -0.f Gl.iffer~nt 'IlloUl\iila.tin:g :frequmrnies wh~ch · re~e>n.si1'1e t@:q.ne indi.v~du~l:·and. onl~" one of . 

ca;n .be rim pressed J¥ pl;m.sa.icl ca nj_el' 'rn ve, eac11 · su·id mod u1ating. fr(!q.uerrcics;- .a~ set, of ;l'elays 

-0£ said .an(i)dulatoi:s :being •associated ;with·-a · Cl)Jntn>Hed .. as 'a •tnrit .1~m·n11!J.tativ-ely by. tihe 85 

. iuake and : break lrny . 'Yihiqh ·detenhines .,said: set of. resona.1~t, c~nmits,--~p.d ,.a .:pi·int-i11.g 

:whetliei'. th!-'J ,wodu1ating -.l1:equ~nc;y co~- , meclumi.sm contl'.0lled by;.tJ~e sa.4c1 set 0f,re3·;:; . .troUe,d rthe.reby w.ill ©r :will ·no~ be jnwressed li\}'S iaml suitable 1for ~t>rint..i.ug rthe rec:ei vetl 

·upon the sa:icl carrier wave, ·sa.id k~ys to- m~ssage.<;.ha.1cacte.1~s, <the meth~l of '.):>erm.1\1-

.gether cOJn}'rio;i~:ig .a.,si.nglc•se~'. of lqiys !tc!,ing .. ta.tive·~y .. a.rid sill:1}ultaH.oon,1s~y .;i,~pressillg-,the 90 

, 1as.,a,,sj?J,gle. :uD.it .. asfio©iatec1 w~th-,a 1kcyb<:m1:d ·.sa,id modulating freq11eBci-es u~~n ·th'C· said 

mecl'itmism, siid.keyboa.rcl.mecha.nism, being car.r-ier wa1"C~ -transmitting an~l ·subsequent 

·40 .• s~109ru;ti~utecl .as to ,c9ptrol sa.i.~ set. of 1 keys · l'~cei;ving .. and cieteotii!!:g ... the >siiicl p~i·n.mtap~rmn_tatwely. ':l?· a um.t . .accordmg to a .p_lu- · uvely on:i.0<'l:1.1Jate<l oar·r~er,w-ave;cleteet,i:ng-.;.M1d 

n\1-mnt coole smtm.ble for thcTri.presentatI?n :isolra_ting the 3'.1-id. mod'l!l!iiting cJreqtl!Emcies, !l5 

.o_f .mcssmge charac~ei:s, .nreans for tpmsm:t- ,,mHisH1.g ·tihe rsa.1d ,a,ool·ated ';\ft>d'l.rlati.IDJ.g 1n'etmg the .perm~1tat1ve]y rnlQ~lulated ca,rrner -qt:i•errcies to contl'ol1.the·<>17e1'3A:i~n·of •ii1s1Wbf 

•45 wav~ ~·epresen~.rng tlrn message ?lntract~r?, .. a re1a 1s, )eo1·mu·tat.ivd · r:tct'ohl.ing·to·the•, ~h1f!al1~ce1vrnig sta.ti.-0n, means at said receivmg ui.1it Co( ,e ·re )l'esen rn t -e me8f:>'l1<+e charac-

.-sta~i01:i for detecting -sniid ~:ansmittecl ;per- :tie:s.trai_1sm1tte ;Um·sa.~cl--set o!f·re~ ~g 100 

.mubatiivel:y modulated carr.re1: wave,_,me~ns .as :a. umt·to cbB ro th'e ;ffcti011 ·of aip·rinting 

,for_ detectmg the .pr~~nc~ of arncl fo~· .1s?- -mec iamsm sui·table-for p:rintirr'gfthe-m:essage ·so ~atmg each modulatmg .frequ~mcy of ,smd cl~te'rs. . · . · 

, .permufati vely -n:i;0du~a.ted earr~.er wave, ,said iln't!estimdn:v '""hei·eof·Iilifti:nny: signattl!"e. 

latter .nma.ns ,compnsmg ;a ·set of resonant , , , 

circuits ap,p1;opriate .for the purpose, ~ac-h of WILLI:A:M J( ·FRIEDMAN. 

JI/ISO 

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D~ 11, 192_8. 

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REF ID:A416157B 

W. F. FRIEDMAN 

METHOD OF ELECTR!CAL SIG"NALING 

Filed July lO. l922 

-,F 

_Fi~. 3. (J ": 

l 

1,694~874 

t vned.. •1'D Mod.-

vlcitin9 frequencies 

a a.nd. c res· . pec.t1vel':I· 

Re.c.e1vera t'Uned. 't.o mod.~ Reee.1ve.rs tuned. to c;i ula.t111g frequanc.ies modula.t1n9 frequenc.iea 

0 E ct.111el~, · 8:. H reopect.n1"~Y·_ 

By 

Inventor 

Willia.rri F. Friedma.n. 

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REF 

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