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REF ID:A105027 

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l!\pproved for Release by NSA ?n 12-04-2~14 pursuantto E.O. 13s2e. 
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REF ID:A105027 

, '' 

·Investigation of Telegrap..11.one as a Means 

for In traducing a Time Deley Ll'l s. Signal 

Network 

. ' 

v} 

_ ........... . .2' . ' 

' ' , :./-" .. .. .. _ 

.. .- -... I'\ 

: j • ' 

February 9, 19J2 

WAR DEPARTMENT 

SIGNAL CORPS 

LABORATORIES 

FORT MONMOUTH 

OCEANPORT, N. J • 

·, 

. . , . 

•,.'"I 

I I l'r 

----- .. _ ----- ---
-I 

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REF ID:A105027 

SIGNA.L OORPB LABlRATORIZS 

FORr MOlllMJU'lR• RllM' 3RSEY 

ENGINEERING REPORl' m. 20 

In.veat1gat1on of Telegrapho:ne as a Means :tar 

Introducing a Time Delay in a Signal Network . 

Feb1'tl!l1'7 9, 1932. 

This report oonaiats ot a pa~. 

• 
REF.ID:A105027 

SitBA.L CORPS LABO~TORIJ!S· 

FORT J.l)Nll>UTH, ND J'l!llSEY 

El«JDlEERIRG REPORT BO.· 20 

-· -r.---

. wmt:D . 

February 9, 1932. 

stJBJJDT: Investigation of 'lelegr.aphona aa a Ileana tm: Introdua:lng a 'l'1m.e 

Del..Q' tn a Sigml Network. 

OUTLINE OJ' REPOR'l' 

I. PUHPOSE: 

II. P,ROOEDUBB: 

A. Test Set and Testing Technique. 

B. Materials anpl0l'9d and Kethod of Diapos:blg. 

III. RESULTS i 

A. InHl'tion L:>ss ot 1he Telegraphone. 

B. l!'ide111;J" 

1. Frequanoy 

8. Amplitude 

3. "Masking" 

o. Ph.7aiaal Malm-up ot the Record. 

IV. DISOO'SSION: 

A. Choioe at Jra:terial.. 

B. Disposal at Mlter1al.. 

0. Inaar"t1on Lo as. 

Do Filter Action. 

E. .Am.pli tude non-11near1 t:r. 

F. "Masking" 

G. Dispersion 

B'. Time Del&.'f' Attainable. 

V. OONOLUSIONS. 

I. PORPOSE: The purpose of tha wo:dc reviewed in this report 1a the 1nveat1-

sat1on ot the perto:rmanae at the telegraph.one aa a means tor fnt~duci~ a 

variable time del.a\v 1D a s1gnil network, together with the _detel'lllination of the 

factors a:rteatiJJg this pertomanae, Blld a. catua.y ot methods ot 1mprOY1Dg it. 

The ultimate objective ia to utilize tl:la in:f'oaation obtained in the design ot 

11Ubaqueous sound :rangiDg equipment. The 1nvast1ga:Uon was par19ued in accordance 

with instructions tram the Signal Oorps Laboratories and was design,ated as 

Project 85-E in 'the Sound Section. 
--·--·------------------. -·-·--- ------··-------·-- ___ ... ______ . ..:..-=---------=----:: .. -::-::-:::-:=-..••.. ______ .. ___ _ 

REF ID:A105027 

E.R. #PJJ Im'est1gat1on of Te1egraphom as Ileana rar Introducing a TiDLe 

Delay in a Signal Netwcrk. Sheet ·12. 

I I. PROCEDURE: 

A. Test set and Test:lng Technique. 

An m;perimenta.l test set •s designed whieh •s uae4 to measure the 

"insertion loss" in deoibala of the telegraphone aa a function ot all the 

variables known to influeme this loss. These factors are: (l) · kind ot 

n:aterial usea_ (2) method ot utilizing the material, (3) method at diapoalng 

recording ('f) ,. erasing (E), and recei'Ying (R) coils with respect to the 

Dll18D6t1c material, (4) speed ot coils relative to m.g:netio material taking 

the record - here:lnaf'ter r~erred to as speed, (5) signal trequ.e.071 and 

(e) signal strength. The test set permitted these faators to be studied in 

detail. A sketch showing this set in rough outline is eho11D. in Fig. _l • 

• The "insertion loss" was measured ·by a substitution method, 1ihat ia 1 

the teleg:raphone under controlled experimental conditions was inserted in a 

signal network and then. an attenuation box under 1he aa. ooDdi t1onil waa substituted tor the telegraphone to reduce the aigna1· to the eame extent. as had 

the telegraphone· itself. · 

Further, a study was nad.e ot the aotwll phy'sical make-up of the masnetio 

record by means ar :maenet1e ccmpasae~ -~. anall .explor'.ns ooila. "{rtrious modes · 

or recording were inVestigated.. 'DJ.e. actual procedd.re will be di~ouaaed more . 

:tul~ as needed in i.resenting results. · 

B. Materials anplOJ9d a:ad method at Dillpoatng Materials. 

1. Following emplOJ'Sd 1D disk tarm. · 

a. Low c,arbon cold roll:ed a1;.,el. sheet ·tl'ODl illeglumy steel Oo. h Allegheny Eleatr1o Metal - 4.~ Ni, 5d :re, o.- Mil. traces ot 

s, o, etc., - from Alleghen.7 Steel Co. 

c. B:Yf'lm: 01".&Z"ameateel f'ran Iildiana Steel P.rodm ts Co. 'L: High carbon orucible steel saw blank tram Henry Disston ud sou • 

.!.!.. High oa:rbon crucible steel Formosa aw. 

2. Following an.ployed as aiDgl.a wire wound on the peripherJ" at a balmlite drum. ·~ 

Soft iron annealed wire 0.042". 

High earbon steel drill rad o.o4s". 

Piano wire intollowing diameters: 0.00'1", 0.013" 1 0.024" 1 a.Oil", 0.038", an'! o.oee". 

Piano wire in 'three grades from !Jammaoher, SCblemmer an4 Oo. 

o.ol3" diameter. 

3. Following emploJ&d b7 wtnding on the peripbSl.'y of a bakal.ite dram 

a single layer piano wire band 1/2" wide~ 0.00'1", 0.013" aDl Oo038". 

-2-
REF ID : ALQ·50 2 7 . 

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REF ·.ID :A105027 

:s.:R·. /J.PJJ Investigation of Telegraphom a·a Means tor Introdu.o ing a T::lmB . Delay 1n a Signal Network. · ·· · · Sheet· /14 •· 

4. Wound a strip 30" long~. 3/4" wide, am. l/lB" thick with appro:z:.imately 3000 turns of 0.00'1" p1$.11.o wire and secured this strip 1io the periphery 

of a 9" bakelite drllD 'for transTerse reo.:>rding. · 

5. .Placed a cast irqn· spaoer._betnan two saw blank_.· :tor ·dou.ble disk. 

radial record.1115. · ·..=--

III. BESUL'l'S: 

A. Insertion Loss of ihe Tel esraphone. . . Table I gives the reaul ts obtained when employing the .d i:rtereut; materiala 

and using ditterant methods ·or di.posing than. "1.D. order 'to gift the meal!IU.Nllents 

any meaning tor comparison Plll'Poses, it wa1i'_neoesaa.:ry to fix on a apeed, impressed 

frequency,. and a:lgnal strEinsth. Choice here was d:lotated by oonaiderations of 

the t'requene1es am signal strengths met · 1n. pract1oe as wall ea the time delay 

desired. The speed chosen was '10 tt. per. second, the trequency an.ployed waa · 

400 cycles, llhil.., 'the sigml strength epl.oyed was represented by a aurren:fii ot 

25 ma. through a 500 ohm T-ooil. In column I is given the insertion loss under 

these apeoitied conditions. In general the treqmncy ail which leaa1; attenuation 

occurs depends upon speed. Thia 1a· shown. by J'jg. 2 where the m1Dimlun. attenuatto:n. 

takes place ·at mo oyoles f'or .eoo r.p.m,., 400 oyales fbr laJO r.p.m., and 800 

oyclea for 1800 r.p~m. The dlak d:i.am.eter was 15· inahea. From these relations 

it follows that 1he lm~ ot ~ tra.ok used rar recordiq one ·OJOlc fer minimum. tt"ttm.ua"t1on 1'Bs app:rox2mately constant, namely, 2.3.inches in the preaant 

oaae. This coutant length of souild track used 1n recording a single c;ral.e ot 

some frequency -·determined by speed - tor least attenuation. 111 given "tor 1ihe 

various ma ter1ala tested iD. Ooluinn ·°II, 'l'able I. l'urthar, ·we arb1 tre.rily de'tina 

Uie high trequanc~j"aut-ott aa the. frequ.mcy tor w'b.ioh the atwnuation is 25 db 

greater 1han the minilll.im. To each 8PEt.ed ·'lib.ere aorreaponda a high f'requenay cutat't. The .length of aound traalc: oOaupied b7 one oycle ia again t~un.d ~ be Tery 

nearly indei>eiident o't ·apeed. Oolunm 111, Tabla. I, gives this length ro·r the 

Tar1oua me.terials am affords .a tU,reot measure or the ab1111;y o'f' a material -to be 

used 1JJ. tranani ttiDS high frequm.ci es. The ·background or noise arising trom the 

rotation ot the niagmt1o material by· the oo1la was highly obj91?tionalil.e in the 

case ot tranirverse. recording due 'to :lmpertections and 1rregu.larit1ea in 'the 

windine as well as mm 8:1.ngle turns at ·wire ware· used due w the jo:lnt. ijowner, 

when emp'.J,oying disks or the wire bams~ _this backeround noise was o'f .the sue . order ot magnitude as the output llDIPlitier .D?iae. · : · 

Disks 

Formosa saw 

Oold Rolled Steel 

Allegheny E_leotric 

Diaaton Saw 

Hyt'lux Chromesteel 

11'8.ble.·1 .. ··I .... 

Imiertion Loss 

70 

60 

63 

53 

51 

.. 

II 

Inchea per cycle 

2 •. 2 . 

B.4 

3.1 

2.2 . 

2.2 

. III . lnahes. par oyale o.5 ·. -0~1 

o.55 · . .-·o.·5 

. o.4. 
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I REF ID:A105027 

E.R. Hoo Im'ast1gatioa ot lfelegra.phone ""aa lleBDS tor "In.tro4uc1ng a Time 

Delay in a Sign.al Network. Sheet /16. 

\'lire 

Bott Iron 

Drill Rod. 

Piano Wire .068"-

.058" · Piano Ylire .031"-

.007" 

Wire Band l/2 imh 

wide · 

I 

IDsert1on Losa 

58 

. 158 .. 

43 

40 

30 T ~ .013" PillD.O 35 

?o 'l' or .oo?'" " 155 

Double Diak Rad:lal 

Record 1ng Int 1ni ty 

Transverse Reoordine; on wound atrip 85 

Transverse Reaor4-

1ng when strip waa 

out to tom elementary U-ahaped DB.gnats Inf'ini t;v 

II 

Inahea per 

a.3 

ra.4 

2.4 

8.3 

a.3 

8.3 

:_..- 2.3 

...... ,~, ... 

B. Fidelity ot 'the Telegraphone. · 

cycle 

.. ..... t- ·! . 

III 

Inches per onle 

0.9 

o.515 

.. 

. 0.3. 

0.3 

0.3 

0.3 

A disoussion of 1h is tao tor re&Olvea · 1tsel:t into a study ot ·three eontribu.ting causes ot ·a laok ot tidel1ty. · · 

1. Frequenoy. The cUl"Yea of Fig. 2 were taken When employing a baDl 

ot 40 tu:m.e ot o.013" p18110 wire• Insertion loss is plotted 

agn:lnst :tJ:equ111107 tor &8Y&1'Bl '98.lues ot apeetJ.. - It becomes widen.if 

tran an exam1nat1on at this family at aunes that Tf!lrY serious distortion ot a 0>m.plez signal must normally be ejcpeoted due to .the 

exceaaiTe a1itenuation at the higher trequmoiea. ·Also attenuation 

is aem. to depend upon speed whiob tao1i miSht well be used :lD the 

design of a low-pass tiltel" whose cheraoteriatios depan.d on speed. 

Speech sign.al.a tranau.1ttad ove the telegraphone are not unintelligible but Ui.e dev:l.oe certainly plays havoo with qmlity~ ·. · · 

2. Amplitude. 'rb.e OurTes ot l'ig. 3 show the 'n>ltage mBasu.red acroaa the 

output of an ampltt ier ccmnected to an R-aoil plotted against the 

voltage 1m.preaaed acro•a 1he T-ooil tor tour d1tterent trequenciea, 

300 oy,el.es, 400 cyGlea, mo cycles, an4 600 aJb].es. Up to an· inpit 

"V011age ~ 10 volts the response is neul.y linear. ·The 61.aganala 

marked 35 db. etc., are oonatant attenuatimrlines. lror these ourTes 

I 

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E.B. )II> Ian•tSsatioa of Telegl'aphone u a ltll8D• tor IDtl!'ltclua.tng a '1'1• 

Del.11¥ ta a s1991 Knwol'k. Sh•t .,, / 

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E.R. #PJJ Inveetip.tion ot Telegraphone as a NeaD8 tor Introdu.oing a T:lae 

Delay in a Signal. Network. Sheet (JB 

speed •a maintaimd ooastant. ObTioual.y, tor f'aithf'U.l 

reproduction oTer a wide range of ampl11u.de insertion 

loaa ab.Olll4 rmmin conatant irrespective at ampU 1u.de. 

The departure t.ran 1h1a acndition lihown in J'Sgure 3 predicts 

distortion arising fran 'tibia oauae. 

3. Masking ot high trequenciea by the amultaneoua recording 

ot a low frequency •. The aunea Fis. 2 are misleading ill that 

tlley presuppose only a aingle reoording frequency. 'l'hia 

factor at "m.aaking" baa not bee iuest1gate4 ill detail by 

qumti 1at1Te •aau:ranm ta. But wben muaio or apmoh is being 

tranamitted by 1he 1i•legraphon.e am the atmultamou.sly a law 

constant trequcay ia impre...S., there is a mrked deterioration in qt.all '7 due to poorer tranamial!lion ot the high frequencies neceaaary tor high QJ&lity. Thia .deterioration 

1ncreaaea aa 1be amplitude of the "aaaking• low trequenoy is 

inareeaed. In short, the pr1Mtple ot superpoaitioa does not 

hold for the telegrapbone aa an. element Sn a •igaal network. 

'1'hue the dnioe ta worse than the GUJ.'l'ea ot Fis. 2 would 

indicate. 

o. Physical Make-up of the Magnetic Record. 

When recording a pure frequency on a d iak b7 me8118 of a U-ahaped '?-coil 

with both poles in one aide ot the diak, a.Di d18poaed tor longitudinal recording, i.e., longi tud1nal aa opposed to radial, it •• toUlld that a aertea at 

consequent :magnetic poles appeared on bo'tlh surf'aoea at 'the <Uak. When the 

lines ot force in the impreaeed reoord lie parallel to tb8 direction of motion 

ot the record naterial w11h re•peot to tbe T-0011, we define 111• record aa a 

"loJ18itudinal" ar "-angent1al" Olle, and when at right an.,_e• to the d1reo'1on. 

ot motion as "rad1al". The t i:rat pole to intlueaoe Tirgm ~,aetie •tertal 

reaulta 1D a "longS. tudinal" reccrd d1ttel'iDS in pha•e b7 1eo· trca that one · 1Jllpreaaed 11' the eeoond o:r t:ra111Dg pole whioh l•Te• the tial am alao a 

longi'tudinal record. The nature ot thta :reoord ia 1ndioa1led in the l':lg • .fr 

below 11bich ahowa a cross section ot the dilllc. . . 

.. ·~ . : ·. ~~ .~ : ·· .. v: .. .. ."·~"' .· . \ 

. ...... . 
.· 

. ·--'-'--'-"=·""'====··-'=--=~..:.=-= . .:.:.: ::....:........:._:. : . .:::: . -=-=-=-==-------- - . --- ---·-- --··---, 

REF ID:A105027 

E.R. #'l!JJ Investigation of Tel.egraphone as Means :tor Introducing a Time 

Delay in a SianaJ. Hetwork. Sheet {le 

These conclusions were reached as a result of e:a:perim.en:ta involT1ng obserYS.-

tions on the polarity of the impreaa::lng magnet and e.xperimeD.ts employing iron 

f'ili:ogs, compass, needles, and small exploring coils used in pairs am capable 

ot being mo'ftld about inde11Jndentl.7 on either ·side of the disk. 'l'h.e system 

ot "wave-lengths" in the steel oould thus be explored. These exploring coils 

were connected in series en:~ then· to the input of an amplifier. A complete . 'I. 

cycle was thus tound to be recorded in the length of aaund 'tl-ack canputed tor t. 

1 t on the ba1Us ot a knowledge at speed and frequency. · • 

Single pole T-ooil reccrdi.Dg was also accomplished only it is less 

effective tb.en double pole tangential recording due to the 'high reluctance· 

magn.etic pa1h used and the 1ncreaeed pialc-up due to stray magiietic fields. Thia 

kind of recording resulted in a longitudinal record. 

lV. "'DIS6UBSION: 

.A. Ohoice ot ?Zterial. From Table I it will be sem that the ·matori,ala 

which are "hardest" m.gnetical.ly l!lh.ould be emploJ'9d 1n the · telegre.phone ~or 

hig'best et:f'ioim.cy. Bi{rll. re-tentivi ty is the pr:lme desideratum in the choice of : 

material rather th.an high penneabil1 ty or· a com.promise ·between high permeability 

and retentiTity. In general, high permeability- materials retain very feeble 

ma8netic records. · 

-9-

l 
-·-·- -·----- - ----· r··-----------·-------~--i-·----·-··--····----·-··-···-·---------·-----···-·-·-----·------~-----·- .. ---------- - ___ .. ____ ·-- ------- ·, 

REF ID:A105027 

E.R. #20. Inveetiga.tion ot Tel.egraphone .as Ileana tor Introducing a Time 

Delay 1n a Signal Netwmok. · - · . · . · Sheet IA 

B. Disposition ot llaterial. For the present 'fhe best mthod ·tound tor 

disposing the material was 1n 1he tom Qt a wire band on the· periphery ot '-

drum. This method was chosen beeaus6" materials can more rea4117 be Pr~pared in 

this to:m than in- disk form, eddy currents ere thereby· partially ei1m1Dated1 

overall Elf'tioienc7 is greatly increased· (See Table I) 1 ·1t *• relativel.7 •:hniPle 

to adjU.st the amount ot megnetio material anplojed, a true l'llD.ning :meohanioal 

assanbly can 2:'eadilJ" be arranged, the· filaments 'thus longitudf.nally 4ispoaae4 

are properly proporUoned to give us 1nlierently stable alamantary magnets, and 

a su.perior frequency cbaraoter:l.stio is attained.( S.e<:. r .... blc !. C .. \:4....,,,1Jij 

c. Insertion Loss. The low ett1c1anoy actually obsened DBY' be vined 

in ei thor o:r two ftY'B• A recording process 111ab. as 1h1a one inTOl.ves at the 

T-co11 relatively- large amounts ot energy while the emirgy abstracted b7 the 

material depends upon cmngea 1D. 1he magn6t1o hy"steresia losaea due to motion 

ot the mB8D.etic material. With the material at rest the losses looking illti> a 

T-ooil are (1) olmio due to 111.e resistance ot the copper, (2) iron lonee ~· 

to hysteresis in the cores of the T-coil, pole pieoea,- ·and the material tar_ 

reoording, and (3) eddy CUl"rent losses. Noma.l~, the hyaterea:la loases are· 

high. The chsnse introduced in. 1tlese•hysteres1s loeaea 1D the :magnetic aam.ple_ 

by the motion ar the nater1al gives ua the actual power absbacted by the DK>~ · · 

:material rrom 'fhe electrical input circuit. Needless to my, it is a ho~leas · . . :. 

and thankless task 1D at'fiampt to deal w:I. th these loaaes by caa.Tant1011al methods . ar math•atical ahaly'aia. Or,· we may view 1;he system lie a tranatom.81' witi · _.-· ··~ 

extranely loose coupling betwem primary (T-coil) am ·seconcla.17 (R-coil) win41:asl!I · and with a species of wave propagation introducing a "time del&.1' between tile _. I ~ • 

windings. The coettioim:t ot C011plitJ1S is illdeed low it we employ the inaert:lcm. 

loss as a measare ot it. -

D. Filter action of Telegraph.one •. The f'act that the telegraphmie a11·.aet 

up does not transni t high treque:lioies 11611 is :to be explained on 'lie basis that 

the length at sound track iD.Tolved in recording ·a single· oyele 1a i1o ah.Ort ~at· 

the elementary mgneta involved in the record an e·aae:n.tia117 ot .8ll unatabl.8 

torm. The condition tor stability - a high ratio of length to.di•eter ~ iiL ··· violated at high frequencies. The relation of' cut-oft :trequaney to ~pee4 llhOWD.' 

in m,B,l, indicates that 'this explanation is :ln the :ma'.ln oorreet. .bo~ . .. 

factor at course is the increase in eddy current losses at tha higbel' tre-· 

quencies. Equalizing networks are the remed;y needed to' gl.Te' ua a ·f'la:t :treqmn.q 

characteristic tor a reasonable frequency l'BJJ8e, only these at coarse do not · __ _ ad"- signal components already lost. · 

E. Non-linearity w1 'th regard to ampl11ude, The tel.egra-ohone ;whea..-·1Uerte4 · in a signal network 1'9 a non-l~near ·eian:ent excepting tar.;.e·-.U,::~- ~--~:..:..'!..;.' ·. · signal ampli1udes. Why this ia so ta best understood by ref'errlng 1so .the 'JU.g. : ··· 

5. 

.JO,.: 
----·--·-·----· 

[----------~-- ··--------·-------·--· ·--····-· -·----------··. -··-·---

REF ID:A105027 

' I 

I 

I 

I 

1-

E.B. #20 Investigation of Telegraphone aa Means for Introdu.ct.ng,a Time 

Delay in a Signal Network. · Sb.e~t #J1. 

• ..... 

•' :; ·····-·· r= ..... ,."1"· .... ,.·· ~ . 

O represents tb.e point in the B-H. plane about which we "lfOS our. material. The 

position of 0 1s determ:l.ned by the erasins bias am the polarizbg bias. That 

is, the atate at virsin materiai with no a.c. signal 'la represented b:y the 

point o. Jn impressed signal represented by OH brings the m.terial to a state - represented by point O and a:t;ter the material paaaes from the inf'lwmoe of the 

'!'-coil, tbe fiDal state is represented by 1;b.e po1111i A. B1m11.arl7 an :lm,pr•ssed 

signal represented b:y ox, leaves the Dlltel"ial in a state represented b7 B. 

OA an1 OB meaEIUl"e the inf'lue:noe of" 1ihe sSgnal on 'the •ter:lal •. The :tao-t; that 

g~ · 1- : tor,. l!u'se ranges in X is. esaential:b' responsible f"or smp~itude_ distortion. Theoretically, it is poasib le to employ proper biasing fields. to :m1Di•. 

mtze this distcrtion. The present work has not indicated that 1"t can be . 

eliminated, but future work might well look into the pof181b111ty ot tranmnitting 

taith:f'ully a wide range ot aigml amplitudes. · 

'l. ''Masking". "Masking" might well be studied :1n more detail by the u ae 

o'f tilter c:lrcuita to a1al.d;v the. attenuation. One trequenoy suffers as a result 

ot the s:l.mu.ltaneous impresa:!Dg ot another. Whether anything osn be dC)Jle to 

correct it is S11othsr question. 

G. Dispersion. Dispersion els suoh in the telegraphon.e Cloea not appear 

to be a serioUs taotor in mtrocmoing distortion. 'lhe veloo1 v ot travel o:t 

all sign.ala onoe tJiey are reoarded ·is not likely to be aerioualy ditt~rent tar· 

different frequencies unless there should be an unsu.apected •now" in the 

record 1 tselt. Thia 1a not :Im.possible as a pole appearing on the aurtaoa o:t 

1ibe :material - which in tb.e last analysis ia .the only· inkling we Java that 

there i a a record at all - ~ t conceivably ae'title into an equilibrium poai tion ·· 

11fich depenia on what other aigmla are being reoarded. Thia statement my 

also be applied to the case of "maak:1.ng". 'l'hua the time del.Q' suffered b:v a 

signal JDB1' dlJpend not only on the relative. positi.oni!I of T and R ooils but on 

the accidental "en'Vironment" or the signal, that is, the preeenae or absence 

ot other trequenaies which nay or may not be •iaPl.J' related .in wave-lm.gth to 

1 t. The non-linmr properties at 1he tranaui tting_ medi• otter alibis fol' a 

mnltitnde of telegrapllone·sins. 

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REF ID:A105027 

••. rE.B, (lao IureatigatiOD. ot Tel.egraphone aa a '&ena tor Introdlic1ng a T:lm~ 

Delay in a Signal Network, Sheet h.a. 

H. Tim.e Dela:y J:tta.ina.bl.e. Tima delays d the order ot 105 mioroaeoonda nay be attained with a very reasonable-mec~ioal an.ci eleotriCal 

design o't the appiratus. ot oou:..-seli:oger dela.78 Ulan 1;h.1s become poaaible it 

we uae tbe instrument as designed t~ df.01;aphone purposes but for con.tbiuous 

recording and reproducing 0.1 eecODl '-8 a ~·onable 'f'll.ue. Thi• 1a the - ahief advantage of the dertoe in a. 11Stwo:rk. · 

V. OOBOLUSIONS: !he deta Ued conolusiona '1'1 th regard to performance ot the 

telegraphone are givan. under reaU.lts BD4 disousston. The :lnstrment As 11; 

stands 111 th the f.mprcn"ements 1n design. resulting from. present choice and 

disposal at material leads itself well to the fntmduation_ of relatively long 

tiDB delays in signal netwarka. However, aigaala are thereby diatarte4 and 

this is objectionable ~or aom.e a_pplioatiou eapeciJA.llY when the aa011rate 

presena:t1on ot arig1Dal phase relations is ·easeati.al. Ce.used- r4 distortion 

have bean examined, measurmaenta talmn., and methodsot m1n.1mizing atu41ed .• 

'l'h.e t\mdamental oauaaa of' dj.atot1i1on lie in 'the n.on.-linear properties_ o'f _the 

nag:mtio material and in the ocmdit1ona which :must b.e met for stability in 

a pEIL"ED&D.t :mngn.et. HoW'S'Ve;r, in. spite of the mbaran.t faults of the" devioe . 

it ma7 prove useful. - eve.n. with its d~tortion - in underwater sound appli--

catfon. because of its ability to introduce a Tfirfable am known t1mB c1,elay 

in. a signal network. ' 

APPROVED: 

S. H • .ANDEROON 

Chief, Sound & 14.gb. t Section. 

,,, ')--. t.. · .. •- _, •• ' • I. -

W. D • BERSBBERGER 

Aaaooiate Physicist. 

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