claim: 1. Am !astttic bi.-filai@ @-Lr@tnsformer comi)rrsIA,. r@'dii,-gs -x%,,otm-d ing primary-anft seconctary i @Bo bifilarl--, siinil-al- pai-ts of ti-iefdaments,of said windin'('s I)ein(, -arxam@-ed i@,i close juxtaposi,,-ion throughot'ittheirileh-tii-,, said -iviindings comp-nsing tivo:axialiy sl:)acecl sectio-ns substanti,,tlly-(,qualin size and,ol3positely-woiind. z5 2. An astatic bifil@.ir transfom-icr -ccmpris:Lr@o, pri.-.iar-y and second-,tty -,v@,linclin s -Nvound 9 bifilai-ly, similar pirts of ol@- ,,uid i se j@- LixDaposi"-'andino,s -@being: n cio' fion thro,,i(rliout,tlieir lengths, s,-,id - winclin(3,s 60 coiliprisi-Ti(,- tivo co-axiillv!aa-rain@i@ed @sections eqli,,ll in size a-.i,7d o-p,,positely -woi-ind. 3. A-n:ast,,ttic bifilar tr@in'sfoTp,@ier coinp-risn in(r I)rii-narv ind secondary ividdim@cyswou d n ,bifilarly, similir patts of the -filanent-s of 65 s -windings beiia _g arranged in close, ju-xtaBEST AVAILABLE COP'@T position throughout @their le4gt-hf@, said wind-, ixigs!coi4prising @ @.-two, @ections substalitially equal in size and @oppositely wound said seetions beina @arranged -co-axially 'w@ith the separation between their centers . sub@ta-ii- @o tially eci ual to the tverage, diameter -of ac6il section. 4. An asteitic bifilar transformer comprising primary and secondary windings wound bitilarly, sin-iilar parts'fof tlle - .filaments of said windings being arranged in close juxtaposition througliout their lengths witli a substantial unity coupling, -said windings comprising t%vo sections eqiial -in size md qpoo-itely wound, said sections being separated so a chstance substantially equal to the ave-rage diameter of - a,coil @section. 5. Am astatic transformer con-iprising prii-i-lary and secondary windings wound in the saine form@ said windings together:compris- s5 i-,iu. two axially s,paced sections s@ubstiantia-Ily equal in @size and oppositely -wound. 6. An,astat-ictransformer,comprisino,,pri-7 @iiary and.secondary windin-as wound@t-ogether III the san-le fbrm said windings to-00 getlier,comprising two eb-ax-ially arranged sections, the @aid @:@e@tions@@haviitg - windings c-.qual in number and oppositely wound. !7. An astatic transfbrmer comprising prirn@rv -itnd -,,,econdary windings @coupled to- 95 gether with a substantially unity@coupling, sa;id wiiidings comprising two @coil 'sections substantially equa;l in size 'and . oppositely wound, said sedtions being arranged co-axially with the separation betwdeii their cen100 ters stibstantially:equal to the @a'vera-e diameter of a coil section. - @8. An astatic t@ansfo@mer comprising primary and secondary windings,divided into two coil s--ctions, said sections having wind10.5 ings stibstanti:illy equal in number and oppositely wound and said sections being arranged co-axially with the sep--ration betiveen their centers substantiall equal to the avel-age diameter of a coil section. 9. An astatic coil comprising two coil seetions arranged co-axially, the said coil see.- tions haviny windings equal in number and oppositely wound, the separation between:tlie centers of said windin-s being substantially 1-15 eqiial to the avera@iye (flaitieter of a coil seetion, the said coil sections having windings in size, niiinber and arrangement to produce a hi(rh resulti-ng inductance with a si-nall distributed 6aT)acity. 120 10. An -.static bifilar transformer comprising primary and secondary windings wound bifilarly, 'similar parts of the filaments of said -windino-s bein-o, arranged in close juxta'@ posit,.on throufyhoit their lengths sa:id wind125 in(ys coinprising a plurality of axially spaced coil sections connected in circuit, said coil sections beincr wo-Li-nd in opposite clireetiolis to zn produce opposit6l3, dirce'Led flu.-,es and beiiig spaced a distance apart to produce a result- 130

1,732,99@ ing self-inductance of substantial i-iiagnitucle, the spacing between and the prodret of the number of turns and are,,t of each of said oppositely wound coil sectio,,is being such as to produce substantially neutral'lzi-n(T liiagiietic fields at a distance' 11. An astatic bifilar transforiner coiliprising prim-ary and secondary windinos v@ oun@t bifilarly, simil,- r pai-ts of the filaments of said windin s beino, arranued in close 0 9 11 juxt@,I)osition thro-,,ighou-'Ll their lengths, each of said windings coinpri-siilg a plurality of coil secti.ons coiinected in circuit, said coil sections being wound and coi-inected to pro15 duce oppositely clirected fluxes of ubstantially equal n-it,,,nitLide a.Tid beinu spaced axially a dist,,tnee apai-c to prodtice ,L reslilting se'Lf-iiidtietance of the coil of substantial magniti-ide and to produce substantially nelitral20 IZID9 MagDetic fields at a distance. 12. An astatic bifilar transformer comprisin(y pil-imary aiid secon-,Iary AVIiidin@@s wound bifilarly, siinilar parl'-@s of the filamen'Ls of said win-,Iings beii-io- ari-a nge d in el6se juxtaposition thro-Lighout their lengths, said Nvinclings comprisitig a p!Lirality of coil sectioiis wound on the same coil alld connected in circuit, said coil sections being wound in opposite directions to produce op:,o positely directed fluxes and beino, spaced a distance olpart to produce a restiltiiio, self inductance of substantial magnitude, the prodtict of the number of turns and area of op" coil section beino- substantially equal to the product of the number of turns ind area of the other coil seet'on, and the distance betweeii saic[ coil sections bein(y substantially small wherebv nelitralizing magnetic fields are 1,)roduced at a distance. 40 13. An astatic transformer coiiiprising similar p, two -\iindin-(Ys trts of the filaments o'L said w'ii@dings being wo-Lind with a siibst,,tnti,,tlly tinity couplliig therebetween, said -windinas conlprising a pltirality of coil sec45 tions w@ou@nd iii ol)posite directions to produce oppositely directed fllixes and[ beino, spaced apart a distance to produce a resulting self-inductance of substantial magii@.tude, the said coil sections bein spaced a art and 9 p 5o the prod-Liet of the number of turns and area of one coil section being related to the product of the number of turns and area of the other coil sectioii so as to produce neutralizin,, macnetic fields at a distance. 55 14. An astatic transforiiier comprising two -windinos, similar parts of the filaments of said w.ii@dinas beiii(y 'v@,ound with a stibstantially unit g therebetw en, said y couplin e windings comprising t plur,,Ility of coil sec(so tioiis wourid in opposite directioiis to produce oppositely directed fluxes and being spaced apart a distance to produce a resulting selfindtietance of substantial magnitude, the prodi-ict of the nuinber of t-Lirns and area of 65 one coil section being related: to the product of the nuiiiber, of turns and area of the other coil section so as to produce neutralizing magnetic fields at a distance, the said coil sections having windiiigs of a size, number and arraiigeiiient to prodlice said resulting self - 70 indu-Itance of substantial mao-nitude combinecl with a small distriblited capacity. 15. An astatic transforiuer comprising two windings, similar parts of tl-ie filaments of said windings being wound bifilarly, simi75 lar parts of the filaments of said windings beina arranged, in cl6se juxtaposition thr6ugliout their lengaths. said windings comprisino, a plurality of coil sections wound @n in opp6site directions to produce oppositely 8o clirected filixes aiid being spaced apart a distance to produce a resultiug self-iiiductance of substantial magnitude, the said coil seetiolis being spaced apart and the product of the nulnber of turns and area of one coil 85 section beii-ig related to the product of the iiumber of turns and area of the other coil section so as to produce neutralizing magnetic fields ,tt a d'stance. I Sicned at New York, in the county of New 90 Yoi.1,7: and State of NeNv Y6rk, this 28th d,,iy of May, A@ D. 1927. LESTER L. JONES. 05 100 105 110 115 120 125 13q

Patented Oct. 22, 1929 BEST AV.AILABLE COP@ 11732@937 UNITED STATES PATENT OFFICELESTER L. JONES, OF ORADELL, NEW JERSEY TITANSFORMER AND COIL SYSTEM Application filed June 1, 1927, Serial No. 195,631. Renewed September 10, 1929. This invention relates to transformer' and coil @y@tems, and has special I reference to the provision bf improved transformers and coil systems adapted for use with electron discharge devices or relays.sucli as tire e,mE)Ioyed 15 in radio circuits or systems. A prime object of my present invention centers about the provision of a transformer specially adapted for use -with tliree element electron discharge devices or relays, espe10 cially for the securing of . aniLplificatio-.1 of alternating currents having a -tvide range of frequenev without -adjustment, such- transformers being of the socalled untuned or i;-) broadband type. It has been found that such transforiners of the untuned type do not have a constant amplification ovet the whole frequency band for which tliey are intended. This tindesirable ch,,iracteristic is noticeable in audio frequency- transformers and is especially objectionable in radio frequency transforn@ers. In transformers for the amplification of the freqi,,ency band of 500,000 to 2,000,000 cycles per 25 second the v,,iriation in amplification is most pronounced, and to such an extent as to render the applic,,ition of this methocl to this frequency rangre distinctly non-commercial. I Iiive folincl tllat a pirimary factor in the production of a high rate of variation of amplification witli frequ@enev in amplifiing transformers of prior tvpes is the oceiirretice of a second mode of oscillation i-@i the wi.qd:35 in(rs which I desionate or call a slioi-t v,7,,ive t, t@ oscill,ttion. All prior types of transfor@- ,,iers a,ire subject to th;.s mode of short ivave Oscill ti-On in ,t frequene.), band closely adjacent to the freqtieiicy bind for ANhich the tra,-Is,lo former is des-igned. In the pr;-or art, attempts bave been iiiade to utilize @LIiis se-lon(-l mode of oscillation bv iiioclifvino,, tl,.e design so as to include it in the f requenc3, bancl for Nvliicli tl-ie transformer is designecl. I have fou,.id that this short wave mode of oscillation is primarily due to the leakage of magnetic flux bet'"Ieen the priinary and seeondary windings. In transformers which are wound in opposite di@ectioiis the sl-iort wave mode of oscillation -niay be predetermiiied from the leakage iiiductance of the trans. 50 former and the distributed capacities of the cOl-Is- In a,,general, '- *ay, in this type of transformer, thefrequency of the short wave oscillation is determined by a capa6it@ *hi@h is mainly the sum of the.distributed cap I aci- 55 ties;of. the primary and se6ondary windings and an inductance which is approkiiiiately ry 'lie parallel induct nee, of the prima and secondarv..-windings, wbieli parallel indiic-; 60 tance may be defined as El, L,- M2 L, + L. + 2 @4-1 In transformers wound in the same direc- 65 tion the short w,,tve oscillation is . again determine-,l by a capacity, wliich, liowever in this clase, is mainly the capacity between the prin,iary and secondary -",indings and an incluctance wliieli is approxiinatel3, the series in- 70 ductarce of the primary a , nd se I condary windngs ivh;.cli may be defined as L,+L., . 2JI lp. these formulas L p @self-inductance of primary L,=--self-iiiductance of secondary 75 Al= mutual inductance between primary and secondary I. 1-iave discovered that it is feasible to com. pletely suppress this objectionable short -wave mode of oscillition by eliminating com-, so pletely or substantially completely the leakage indtietance between the windings of tl-ie trinsformer. This I have founcl can be aecoi-iiplisl-ied by -winding the primary and secondary of the triisfo--mer bifilarly, - with the 85 fil,,tments of said -windin@,s arranged in such close juxtaposition that"'the leali:age induetance bet-ween the -wi-ndinas is substantially completely eliminited.. I 1-iave discovered, in order to completely suppress this objecti'on- 90

able short wave mode of oscillation, that great care must be taken in windi-ng the priniary and secondai@y filaments of the trai,.sformer so as to produce a substantially unity coui)lin(r betnveen the priiiiary a,iid sec,,)ndary tr,,t@sfor-mer windi.ngs; and by this I mean that the primary ,tnd seco-tidary windin(,,,- should liowhe e be separated by a space grea,r er than the space occupie(i by the ill S L, t @', tioii 10 coverii-,os of the wires or filaiiie.-i@-s. it is a.,prime-.de@Sideratuin there-Lore, oL' iny present in-v('.-ution to pi--.ovide @a trinsforme'r- li,aving- a, I)i'filar coiisL-r'u-cfior. so designed as to ettect the eliminatio@,i of the 15 leakage inductance b6twee-m 'the v,,i..n dings, all to the end of obviatiiilr or coM _pletel,,7 suppressing the short wave - 0 lation. A further prime-obj'ect of m presep-t iny 20 .vention centers about the provi-siou rof a frangfo-rnier, preferably of the bifilar,type, i t i @.@i@h. is astafic. As is well kno s a de@ideratuni -of.certaiii types of selee-tiATe aiid 66nsitive ra( . lio.,'rece'i'ving appa-ratus and in ,T5 ai)i)aratus em@loyable near ti-aiisnaittinst-ations, to constxuct the @coils or -wiiadin@s @f the. receilvi-ng apparatus so that the3, are @ne6upled iiia(-;iietic@lly to othe-r coils ft.-d ap.paratus', 1;n the xeeeiving eircu7it or to the @so 'td-ansmitting appara@tus. To accomplish tl-ie -ma,ometic une.oupEng.,.of the coils @to other apparatus, various ty.pes of ci6il - -win(lin-s have hitherl gned, stich os. d ible b witid-ings, toroid windings.and-hinocular @,,o5 coils.@ These p@ior types @of coil -windings have, however, been found insufficient to produce the desired: re,,@ults on7.account of tl-ieir relatively large ie:!@t-ernal fields near the coil Nyhi,ch produce considerable coul)l.ing to other .,n parts, and Pven between simil-,ir coils -wben ,place-! a:t a moderatedistance ai:)art. To retwep, diiee the inter-maonetic couplincvs be Similar COilS iR the radio -@@eceiving set @.vith f@e use of - siieh prior stru4@tiires. it bas I)een 145 found Tiecessary, to so relafively arr,.tn(ye tlie collsone ATitli@-respect to the -otl-ior in the raclie, recei'vin-g set as to mini-niize.tbe re,- ,ctip-(fields. Otb,er strtigttiril difi'.cillt;es, stiel-I Is the 1,,ir(ye vol;Lime oT -,wirdin(y reqtii-red aD-,I.:tlie @,80 di-fficqiltv o@f winding metlao-,'tsliave also'bin,de@Tod-t-lic iise of these prior and'li:no-wn tvpes of winding coils. It'i@ therefore a priiie desiciere-,,,,iii-i Of mv presen+, i vetition to provide a t,",Iilsfori-ner n or a,,i inductance coil Ustein de,@,ti@Tnecl iD-,l co'nst-ri-icted so -th,@it the eyterial - m eti(- 'field is reduced to such ,t -niin;miim th,,t the -itially de-coiiplecl m.,iznetic@ 11-V coil -is Si--O,)Stg Trom siirroii-iding tl)p.,-Lratti-, Pn.@l' may 1-1-o@-to Tilaced in close @proximi@y to ctlier coils of t rtaio recei-vin(y svqte)--q -,vitheiit irte-r-magnet,ic,illv reacting -wtli qai-re. To ihe accoi@T)Ish-me-.nt o'L -t-lie @or-c@(rfin-r and slich other 6bjects ,is iv-tll bere,-'@n-l.Tter ti) 't,5 pear, m3T inventioii c 'ts onsists in the eleme-@l 9Fq T AV AIL AB LE CO P\ 1,732,937 and their relation one to the oti),-,i-, as lie-reinafter more pai:tictilarly sotigli'u- to be dep@-lied in the el.a;.,-@is; beiii- had to the accoiiipaiiv-n-- drav,,Ill,@-1". -which sho-vv tl-ie prel@errecl (,,i in, 7 inventioi-@, and in iihicii Firy. 1 is a perspective ile-@v stiov,,- Il"g a 1)1- 0- ferred forin of construct'on f 4-1 I 0 - i e b i l i l a r -.tstatic transforiner of iiiy Fig. 2 is an eiilargecl fron'L. elevitioii,-,! Yicw 75 tlieieof del)icting the of '-lie seelions of the transfor.,iier I)ortr@,@17' tli@, of tl-ie cor,.sti.- tiction, Fi(,,. 3 is a cross-sectiontl v;le-,v tliei@e-of draw-n to a-n eni@trged se,-Lle slioivli-io- the pi-e- so m ferred matbe atical relat'on t-l-ic M. Ti en@iohs th@reof to seel.-,re as'at;c-'sln, Fig. 4 is a view sl-ioiiing m,-,iiner o'L prodiicin(, cl.os,,- j,,ixta-,oosi@(,;oi o--r th-, L - f@@ments of the tran@@foriier. 85 Fiol. -5 is a crosssectioral vl'eiv o'L .,t modifled -'Lorm of tlae transformer eit]-i-,r a step-do-%vn or step-,,,.p rit-oo of 'Lrans-' formation, Fig. 6 is a wir;iif,r .ani2riatic of co Fia. 5 F--,gs. '71 ancl 8 ae tnvo otlier n-iodific,-,t,@ois of step-up or stel)-Oo-w-,-i tr,,iiisforiii-.tions bodying the inventioi-t. -tiid Fig. -9 is a side face i,iew 6f the --hown in Fig. 8 dr,,i-wii to -,i reciiieed scale. To -,iccompli,,;Ii t@lie restilt of s ul)T,)ress,-Icr iipbl,e short w,,i-Ne mode of 'tion, t-li-e tra-,is-,o-ri),Ier Of my inverition;coiiiprises primarIT aiici se(- oiidorv windiiigs P ,tricl 'S wollild bifiivtly, tb,,,it i@s @o say, %voui-id so -that the filaments of IL-he -windii-igs .Lre tli---rang(@d in @c@lose, -uxtapositioii s-Libsttnti-,-LI'lv -thrclqghoiit -tl-ieir entire leii(,ths, :.is :cle,.ii7lvl -shown in Figs. 11.2,,iTid zl. of the dr-,iwliic,,s, aiid .,,ts l@l,.agramm, atic@illy illustrated ill 1)?,i-t of Fi,),. 6 of th6 drtiv, ii-i )rrangel'.'leii'L, of tlie priiiiir.@7 a d contigi.@.ous @ 11 secandaryfil,,,aneifts@P and.Sls s,,ich vsto pro'-al -Lil)l' -@l n I 11 duce substa@it-i -Luiitv co .1) e'c , e e i'. c - wiiadings, tl@lLt. is to s-a-%,, t@ie secolidary filariients ire se--.)a--ated 'IO gre',-,Lter than the sptee 'o-,ciipicd b.@,- -ill@i,,, i;,isilla4u"hio, cok7ei,iiig 'of tle I-;-ires Oi This is del)ictcd ir, Fig. 4 of 'Lic, ii,here i -i-i.cl i' design-.@eit,@e iialys Of' tl-ie pi-iiiia@il aiid f,,iam(@nt,@,, -P aiid S respecti - vely. To as.?,,st 1-.q pi,ocluein(-" tl-iis el,-E;e iuxtaidos@.tioii sub@:'.-a,-.iti,1113, tl-"-' 'I'liole le@igt'li @.,f tl.e P @iiicl a,.e It-,Wistocl 'che w'ncliileiltq 'P-9 opp-ration initi ',tr,,,e pitcli, that is to sav, witi-i f,. pitch iil 'cli 4s 11 t,,,-el3T large comparec,, to the of IL-lik@ f-If@,iaieii's. Tli;s -s slo-w,,l iv i@l, u -1 I @i 1.11,71., Fi,,@s. 2 ,,iid 4 of tl-ie cl@,aivin-S the iiigs -,Ii-e sho--,@7ii traiisposed by twists in i-egions clesignated as t, t. This 'Lreq-,ien'. @c-i,,,iispo,-itioii of tle windings material!-; a'ds iii li-oldiiig the wires or filaiileiif' s i,@ 5 0 105

BEST AVAILABLE COP@ 1,732,937 3. close together throughout their entire;lengtli, this so as to produc6- the intende@d @ results. IITIile I pref@r,,fo,r ease and@e(,,onomy, of operation, to e:ffect the close juxtaposition by t-wisting, it will be apparent that the same result ma3, be accoiiiplislied in otlier ways, as for example, by securing the , filarnents -to.: gether,-,tpoiiitsalongtlieirlengths..:. I h,,ive found that ,,t transformet constr;tict10 ed and -wolind iii this manner-exhibits xtremely desirable ch-,iracteristies. , By exercising care to @prevent a sel3ara-tioii bet'w'eeii the filaments greater than the -septrati6@ produced by the ii-isiilati.on, I -,m enabled to elimijr, nate the undesired leaka-e inductance between the -win,din-s substantially col-nplet4@ly. I have found the transformer su'itable for au-@@ tomatic tiiningiiid when so used I have found the same to give higher tverage amplification 2 D with a more constant value over the wave length@band thaii any other type of;transformer thiis far developed. TI-ie transformer 43f my invention may t)e use'd without autoin.%tic tlinilig iii aliy wtiy whatsoeve'r witl-iout @25 qeveloping distur@ing interstaoe oscillations '\Vhicli have been the bugbear @f prior types of transformers ',,ind whicli gii,-e rise to the iiecessity of iron coi-es to ov,erdainp the transformers and stop oscillation, 'or the @ use of .@-o grid biasing potenti met-ers to reduce the tube O@ .,ind 1 @ai-nplification , nerease the @econdary losses of the transforiner by reason of -passai@ ofexcessive@,rid.,-urrent. Theefficieneyoftl,@s . tn tralisformer construction;is in some measure 35 clue to,tlie Iiigli cal)acity between the windir@gs which accompanies the 6lose spacing of i5lic priiiiary aiid secondary filaments thr6uoh-: out their'entire len<ytli@. 'The twisting of The f lament pair in effectively @preventing any 40 primar@y turn from developing appreciable capacity at a differeiit potential witli respect to a secondar3, turii ,ilso contribtites to the efficielicy of the transformer. Anotlier efi'ect ivliieh is contributory to the successful result 45 produced is the obtaining of relatively large air spaces iii the wind,.ng due to the fact that the t-wisted pair may be wound. at random; and these air spaces tend to reduce the distributed capacill-v of the coil whicli should be 5o ,t minimum for the pur@ose of untuned amplification. . To produce the ma,-neticall37 astatic results hei@einbefore described, the triiisfor 'Mer of iiiy iiivention is macle to comprise two coil sec53 tions A ,ipd B sho-v,-n particularly in Fi s. 1 to 3 of the drawiiias, each coil section ing coliiposed of a pfurality of VV'indings, the wiiidiiacs of tlle sectioiis 2@ and B beiiicy -wound in opposite di@ectio-.is, as clearly shown by the arro-%is in F@-g. 2 of tl-ie di-awin(ys. To prodv..ce these co;! sectioils I pro-,,icLe-a spool 10i',-ormingthetr,ilisformereore. Thissj)ool naay be ii-i,,ide ol ivood or other insulatioit m,,iterial, s,,tid spool pi-oi,ided @vith grooi7es ,,12inw i 6,5 1 1 tinc' li'cli the coil sections are wotiiid. To pioduce i magn6ti6, field at a distance which is substantially equal to zero, I have found that the coil sections A and B should desirably be arrari@ed co-axiauy with the windings'of the coil section @.k equal in number to the windings @ of the coil section B. Optimum @results,@are obtained when the coil -B i 'o separated by a distance secti6ns A and, r e qual to the av6ra&e diaiiieter of a coil seeti on,, and @this is dep icted in Fig., 3 of the d rawings 'WI@ere the separation between the c oil sections A 4nd B, that is to say, the Sepa ration b4@t-ween their centers is repi-esented b y "D" and -whete the average diameter of the c oil section is one-half the sum of the mini8 0 ni um diamet@6r d' and the--maximum diamet er dl.;: The distance D is thus preferably m ade, equal @to one-half the sum of @ the diamet e'rs d' and d2. @ I have found @ that; -where the c oil sections are fa:rther.apart:tl-ian t-he dis.8 ,5 ta nce D, the coil system loses astaticism -%,ery r apidl@, and on. the other. hand, -where the c oil sections are closer together than t-he dista nce D, th@@ useful inductance decreases rap - id ly on acco'unt of the growth of the bueldng @oo o rreversemutual.@ It will be-appar6nt@that the astatic characte ristic of' the transformer may be used, witlio ut the le.akage elimiiiatinb, chiiracteristi6 and vi ce,,versi, it being underaood that the p@e@go ferred transformer, coiistriietion shown in Figs. @l @to-4 @emb6dies both - characteris'tics in th6 @referred manner. It,will be also appreciated that -the astatic characteristic is gen6ric to inductance coil systems whether or not ',100 sii eh system@ are m'ade in the. form of a transfo rme@. @ In Figs. 1 to of the drawings, th6 transf6 rmer is made with a @one to one ratio of tr ansformation. The @bifilar i tr.ansformer of io 5 m y present iirivention,' howe,@er, may be made w ith either step-up or step-down ratios of tr ansformation,- and this is depicted in Figs. 5 to 9 of the drawings. In the modification shown in Figs. 5 and 6 lio of the drawings, the transformer is shown to c omprise prim,try and secondary vvindings P and S having portions wound bifilarly with th e filaments arranged in el6se juxtap'ositioli a nd forming one transformer section with one @115 of said windinlys having a portion fo,@ming a single wire Y@ound.section. Thus the prim ary and secondary windings P, S are wound bi filarly in a section designated "bifilar", the s econdary -winding having a portion desig1 20 n ated "single wire winding" which represents th e ingle wire wound section. As shoivn in Fi g. 5, the single wire wound section is prefe rably first -wound on the core 10' on which th e bifilar section is 'Wound. The te@minals @125 of the prin-iary and secondary windiiigs are c onnected to audion circuits as indicated by th e reference characters at such terminals sli own in Figs. 5 @ind 6 of the drawin(rs, the '1 30 reference @ charieters being "r for fil@me;nt,

4 ,.PI' for Pla;te, ",GI' for g 'd, :a:nd B-+ for t,lie @positiive.@side of tlie B ba@ttery. ivith a cons'Lruction sueh as sliown 5 and @6 -it,,becoizies possible @,to use ,, tt-raii-sformer of otlier than a one to @olic ratio @h-aviiig a very higl-i n-iutual induct&nce,.or avert low lealia,ae a:nd yet s6cure dic,,Ieotr@c @ nd ia ca,pacity lossc-s. @ .1-n -aml),la37ino-,at irei-ytliid,h, fr.equencies, @oiie of (thce chief difficult@es;.Iies 10 in the.,elii-niha@tloh of -,ta@oss,it-he.see-@ ond,try Nvinding. ',Fhe in these Figs. b ii nd 16 permi-i's of 7a step-up transformer htvinrg ininimtim, fdigtrlbtited capacity and mnaiiiiui-ii mutua:]- iiidiicta--qc6 witliout the!use of lioii 60,xes. I-n. Fig. 7 @of the, drawings I sliow an alternatin"e f oi-m !C;f :construc,@icia i %vhich -tflie bifil-ar coil is wotind in a groove @-13 of I-,,he spool ror core 101,:md t@lic @sin-ie Nxire - ,,,,@inding 20 is twound iii -a groove --L4 i,,ii sti"@d, :,%,I)ool. - T@lie terminals of the c-omposite -Nviiidiiigs -are,,designated -in -Fig. 7 t-he characters @as those i'n.Fig. 5. : I ! . 1 .Another -alternati-ve co.-,istruction 6f this 2z composite windiiig;issl@io-v,-i) dm of the drawiligs whereiii tlle cci.L is wound superposed oiTer the sin-le c6il iai --i V-shaped chaniiel 1-5 pi-o-,@,ided in@ihe c6re o@r spool 103. Preferably:this @..I)ool@'as ,proN@ided zo ivithorifices 16 -16 pioducedby,drL@llingotit the insulatioii i-,or.-,,the 'pulT.ose:-,ol f@Trtlxex iiiinin-iizi.n-.the@e,t.pacity. i'lie,itern-riiials,ijf the windincys in -8 P.Te.idi@siomated by referenc6 ch-aracters:simila xtothoseoi,Figs. @35 5 t.,o 7. The use and operatibn @t-he metl-.iod -of wihding and the advantages of the traiisforme@ and @coil system -of -my 4c@@n I t iaivention:,ivill iii the main be appare-iit filom the above de.40 t.%iled description thereof. -1,1,'hile I'llraAle shown and deser-Lbednay. 1,Teferred form it wil@l a;lso be la,,Iparent ;th.Tt, ma--ny cha;noes ,tnd n-iodifiaitio-iis niay be n iiiade in the structure dliselosed vtithout de,a ,45 p rtii -icr from the spirill of bhe iiiveiidoi,., defined in the following claims. I