BSTJ 10: 1. January 1931: A Multi-Channel Television Apparatus. (Ives, Herbert E.)

7.3 MB·English

A Multi-Channel Television Apparatus *

sci itt ty ie gata dees ot goutcta an unde
aE? amen aeeal nar hana ees ‘hres
Se presets CS ne Se

Pin a received slevision image, the individual image cements se
fe they shold I, of chm size a to he jot ineitingshable, or
Unresolved, 2¢ a given observing distance, the number of mage ele-
rents ineeares dirs with the area of the image, The mimber of
Sich “ntistngaéshable elements in evenylay scenes, the
Pheroeraph, or in the Emme of an ordinary motion pictus is
Fphingsy ages Aa eeetially tenance plutageaph& inches by 7
ins in size, saving 109 seeing scpe per ach, has a ed of View
anal a epee sf slfnition of detail, which, experience shows ae
equate (alsoasl with Tile mens) for the majority of ewe even
tictares 1 i aude pieture ot this sore that the television
thud haw nthe hack of his i when he predicts carrying the
Sage and the motion pietase screen jato the home over ele rca
fomsuusication chacae's. Ta this qictare, tae mabe of ge
feanets fy BSNINN. Ata repeltion speel of 20 yer seul (20 yer
second ae sane rcs standard wits sound Eine) thie mec the
nba of ews rela he rte T,000,000 er oe
a frequency Vand af 31/ million cycles on a single sideband bass
This may be compared to the 5000 cycles in each sideband of the
vate! econo as

oud aio preprat, oF BL may be eu
fuivalear of chnasand taleptione eae

‘Wien we esate what fae Been achieved thus fas fa television, we
fird chat che type of image successfully twansmived fall very far
host of the Exel derailed plete just corsidecee. Probably the
‘wos! satisfeccors exarape at “elevision rhs fan eeronetiated i the

Dox 8
ey DeLE SisrEs TecsvreAL soORKAL

ine pcre used inthe two-wiy tlevisionteleohone instalation a
the American ‘Telephone and ‘Telegesph Company in New York?
ere the olject to be eransmited e definitely retro tn the Taman
ace, whir ile che whole fel of view. and is sdearatey rendre! by
the 4.500 image elements we

‘The vay Iw ncen te 4H elensents of this image eed the 480,000,

considered hove ie enor, #02 cay [3 figtces, at jn berms of
echnical wosilility of bridging. Even if we ave fore to eaten
furthves with celativel™ simple types of scenes for ievision trans
Iniesom ill he fact mvt Iw aly feed thae very much larger

rules image elements rt Ie tranesiced cha has dhs far been

oud ysis ad far wide frequeney band wile Than tas ever
‘Deen wee in ony commuicusen prablemt. Now che situalinn is
Simpy stat, tat all past of he deo sto eve elroy sing

Sevins dithlty Oy antl the 4300-cemeut image. Consequently
Sin fate fie pia i todo means ete

Ti will fe wouch stile to eurvey briefiy the pts in television
-vsten whee dificult sane encountered whe he attempt is made
“iv inereae the amount of age éctal ad the aecospanyng band of
Cramitied fenuences, Coasder in curm che caning discs at
Senling and receiving ends, the photoelecrie eis, the amplifying
pets the seanemtieion chynel che reosseng lam

Tv the seanaing ose at the 2ceding en's whist we ell eseume
seranged for diveet sewing, ineveased devil mess cchee Tess of
light or incvease in these 0° Ue disc. In wither ease the Factor of
hog: fnvolved it lange. For instance, sf the number of scanning
‘ales is doubled in dine of yven size proving ons cies the umber
of snageelenaeas, che hie rn be spaced at al che ungular distanre
bor, nal tmice the number of holes, irsgived paged end co end
trv be elude! inthis half diamerar seanning fehl, The holes will
Cherrfowe eof one-cuartes the sanecer or 316 the wea, The light
Fating va Te photelerrc cell a ary instant se the ight trasanit!
by one ale: inthis ee. 1/16 the arcount with the disco! half the
mover af holes, In gener che Fight cersinitad by the die to the
Fall erent athe square nthe mire of ianage elements. 1 the
tise ss enlarged eo av to helt the transmittal ght unchanged, its
Mlnmeter increases direily sw che number of image elements. Te i
hiv that aby considerate igeceaae in che muanber of image le=
fentewsuch ae ten tim-slemande lther riamanonsle neteare
sonitivenss in wir poto-eaponsive devices, or uit Fabulous snes of
Sub 950 78
lites. Perhaps the most pestinent encom frm this savy ise
the ise, while cute the simplest “yeaa foe seuss images c-few
leneals envy impractical wher reall cee aucens uf Page

flements ate ia question. Av sei, homereh Eo practeal snaiine
for the dice of essential diferent ries rte= hye appeared
‘Turing aow to the phaticectric ell, The question of alee

sensitivesem to Lgl large mamber of image clement is itimately
fconserted wil he method of scanning, et bas just been Drought cut
serthat re simple answer is posible, Ie is. however, proliile thet ©
‘very considerable inereaze in enstiveness aver nything now available
Tua be anticipate, whatever scanning device t aopted. nthe
rater of femqeney range there is definite information’ yale
depending on ys armpliestion [sich as asgon or seu} character
behavior is alk nif of apa with Frogueney, gener the higher
the vee ine, which, Keceming naiceabie at bus 20H rye,
nay at HOON cycles eso considerable ne tw vette a prattical
Mork to transmission. Vacuum cells are Tree trom this falling,
are much less censitive. Systematic experiment and development of
thocoelectie eels with partici refer sn wstending helt tange of
Irequeney response is indicated a & neessacy step in the attainment
of umanselerent mae,

“Taleo mexe the cuits asscetatel wit we potorletsc eel, we
fan iv general, that che higher Iequeees progresively euler cin
He eletical capacity of celle and asecciacal wiring amd ampiner
tubes, Ths ‘a tun calls for ausitiey smqaliing crete, Wh
autenlant probes of phase adjustment, and for increased amplitcar
Sion.” Ampliersexpable of handing fregueaey bus eset fr
low frequencies up to 100,00 eyeles or over oer xeric plies

Communication elansely, either wire or rao, sre sharaterzed by
increasing dificult of traaatis a the freqveney band i widened
Tr rade, tang dicen at diferent eegues cies and varia fun
inverlerwce stand = the way of seruning 1 wile Treen hanes
vriform eficesey. In sive. prgressive acento a: higher fe
quency sist 0” ghuse. aul cone duction betwcee.siseitn ner
Serious obstacles. Tvansfo-mers snl iotermetate amplihers 07 18
raters capable oi handlixg the wide Freyvenry bare ere in question
ho present seriows pres,

Ac the serving wil of the television eysrem, conditions are sinlar
to the seading ead. The neon glow lamp, commonly awe for ree
txption, Je eletady failing to felow the television sighala well low
40,000 esces. and. iz che cow af the 4.SOd-lemene amg ahiowr
seferral 10, the neon ramet be assisted by = frequency senewed a
tnixture of hydrogen, which again cannot he expected to increaw the
Troguerey sange Fdefely. In the ecznriag disc, a9 at the sending
fod increaag the auer of image elemeris rapidly reduces the
fmooune of Tight in the image. With a plate glow lamp of given
Lghtnens, the apparent righ aess of the image be inversely as the
umber of fmage elements,

‘From this rapid survey, ii lear that at practically every stage in
tne ‘eleven ayscent, ne enosonier serous dificalties when a large
increase in image elements is contemplated. It is not claimed thet
these diiculties.aeineupeveble, One af the chet ts of Laulation
‘ot dilieltce i ak! in marshalling the attace upon them. But che
‘Disting situation fs that ia many element television image is called

Tes moc avaible, aad one be cis braces he dint
i tanayeting wed socering signa extending ser sede
Freeney bras.

he allernalive, which vrompted the equerimental work to be
ceria lon, isthe su of utile scanning na malted
lreramissinn. ‘The general ies, which is obvious from the name given
fo the method, is t divide the image into groups of elements, dhe
Vavinus groupe to be sunllscuely seanvel snd cami the
‘foun the severl grew coup separate tananision channel
Tye of spparatus to xeserate aval toms frequency had of
tela, we arange me scnaise procmves each to plovide frequency
bands of ni ees ills ne Eeingchowen a wichin rhe Fite ae by
the aveleble practical elements of television syste. 11 will appear
that the maitre! which Ras bee developed does provide an image of
Ianyfold mane image elements Uhas leretofore, axl may make easier
the probetn of transmisies ver practical transis Tins

Descaurniey of 4 Trnee-CHANNEL AbPABATUS

The snultnseanning apnratua which os Dees constructed and
sven experimental test uses acanaing discs aver Whose oles are
sineed prim of several ferent angles. AL the sczding end, the
Thea of lighs from scraive Roles are thereby diverted vo different
photocectie cell.” AE the reviving end, the pists similealy take
Fpeams of light (rom several amv and divest them to x enmunon
Gisetion. The shoe of action of the prise i ilusteated in Fig. ta,
Uahere# three chanael arrangement is shown, which iv that actually
ted in she experimental apparate. Ln the figure, the ine hoes are
Shown disposes) in a epaly at suck aagular distances apart chat
Tire holes are always inside inthe frame f. Over the fist hole of
se of vee is place prison Py which civeris the necmally indent
Ughe upward: the second hole is Jett clear; che shid is covered by a
prism P, turned to divere che licht downward. I we imagine the
Deis removed and a single chaanel used inated the Theve that are
‘proposed ie clear thatthe hoes would Rave tobe epaeed three times
fas far apart so that no more than oe would he included in the Frame f
‘atone tune, "The diameters ofthe hots un te al separation of
the fet andl Tast in the spiral would be unchanged, Quite apt
therefore, from the smaller frequency bande whieh are suficene e0
carry each of the thee ses of signals, which i the priaspal objective
ought, there is ealized in thisserangenien rede sine of apparaton
fo the rae sve of se Hole

Sudving more clo the division of che Hit int essex of
seas, iis ntportant te note thatthe signal naam by ony ame
ff the nee sets of Tes ce miu ae ee hok of given pre

rion pases cat the Cee the wre che same sis en
The signals generate i each photoelectae eal ace accoinpy exactly
Tie thee of singel system

[Before describing te details ofthe appara, se general relacion=
ship hesween she auntbes af nage eesti, Tova wih, number of
‘anne and shape of picture maybe develop, Tor th parpne,
let the fallow symbols be ase.

Areruency bard available 9 ane chas.in eycler yer second
repeiton frequency of amages, pe seen
rambe>of communication cha nee

22 = total moar af seaming hae

ab — natin of tangential to rata’ dimers of nae

gla sing of fen
We stall sssume that the picture elements into which the tame is
Imagined divided ave syannetsival in sine, 4 ils ics squaes
We then have shat
‘the number of picture elements in the radi! ditertion — menor of
holes =:
the umber of picture elamets in dhe tangsntil liection = (a)
[Now the nuunber of sgaal cycles currsuting this wumber of
elements (1/2) (ba
‘The number of cycles per sco0d fis one trail. the frame
= (12) Gib):
aoe picture i is (1/2 (ais — (1/2 Fa
anh the number of eseles por second Zor vat chanel = (6)
U2} Fe —
“The angalar opening: of che frase w= Sle x 6

“The number of psn: leateate — Wa

frag: be azed wpm asnig values for any’ of the
variables, to x the values of the other. Tn Uke pucseat case, it was
Teil for teagons ef sfunliity to sestit the mune ef channels to 3.

tele pr
“The band wideh as chen a tht Zonsd fesible in the lwo-way
television system, namely #000 evel. Tae picture shape ekoeen
fer that of the soune motion plete, for which af — 6. The
Tepetcien freqweey.sssuinee Was 18 pee send, agcin following
Covey that of exis ing, espevimenral sytchroniaing apparscus. Sih
itucing t3eee valves fa the forms rearranged to give, pet for
he rmer of ole,

ai fr

Hs so dere,
forthe mabe ot pcr
5 = Gane x2 = 13608

Jn utligng the prin dig: puiaciple at the sending end, direct
conning, in which the object is imaged on the se, was chosen, sinve
heam scanning, Would inteocuoe the probient of separate the Fight
rulected from tie abject from the 2everal spots simultaneously pro-
eee feom the dice. Since the light zoing Muough the dsc must be
‘eparaced into seveval Seam te he estat fen aerate plouelertre
fel the fall apertee ef che image forming lena mse e dived by C,
"re nue: af channels, with 2 consenaea properties ight to

cel ech. {This nv cousterialcrs the decreased sie of disc above
rte.) "Ic therefore hocnmee necessary to iastze avery high ila=
sation of the et Ta the grater, fea eid to ve motion
bichire lia to prowide she nig en image, since this can have st
Targe amount of ight concentrated shrogh it by a appiogwiate:

The ase of motion picture fn yeraitved a implication of the
tnvmamicting disc, which is Wbustratad in Pig. We This consists in
frravging the scanning holes iu a rine intel off spiral end pro-
Hlucing the longitudinal seanine nf the lem by ving Tea concn

uniform motion at right angles to the motina of the seaming holes

Te eontinseus nti af the fi lea avoids the low of transmission

time ta: a intermisvene motion demazds forthe xt er sterva
At the receiving end, = eplra of bee is ame ge tion fn Fig

eve again, Deca of the ders the igh ata hee bears. the
mule whic a benno ye Ce Highs soe on san) ix
hnstrewsl, Tn consequence the nem ig eathods are a =r sa,
snd a Tene ste: as ees wl tft thee mages on the pup of
the observer's eve. “Osher eal of sering, ahi pooate to be

Tees etrered gto position ef observatin, are Dossale, howeven, $=
Faced Beton
Wikh this survey of vera uf dhe wore important features of he

seit, we may proceed wo a more dead account ol che apart
rooseueted The genetal seangeaten. nf juris i shown in Fig, Le
nd is the photogeaphe, ies 2,3, anal Sia of which the symbols
ate uuiforn. Roth sending snd receiving diss were, for simpliity of
Bpevatin, monn on the same ase, duiven bythe war This
‘means thi no question of eyachvonization eter. Synchronization
icin fact a separate prablem, having nothing va do with multi-channel
‘pesto sh been very comaletely sca in oxmiectinn with other
Levis profes! Tk it shoul be eeedad tn tre the omit
‘channel uae te distant print, eRe apparatus could he exe i two
ad each ed, ster separation t the desied distace, coetatad by:
Svnchronoss soto eoatrllel in saprowe Fshion, Similarly, wo
lw Iravsmssion fisee wets fade
Starting st the estreme right ent of the schematic drawing Fig. te,
weave an aelamp 1 ey indica ees Ey, a condensing ens Le the
feu lenses tngethes concentrating, Tow of ight on the alm B Be
toeeen the ih and she cine fs a lene Ly whieh images the flm on the
The. Disecly bined the cise Dy, el its circle nf prism covered
hole, ia soon elidel ler 7 wtih concentrates se ceasitted

light fterally, nun che sige photosectric ells Sh, Sy Se By wire
of this lens acrgenent, the Hight falls upon the cells in chice stall

Dractcally starionory spate, Additionsl appasatus not chown i the
agra be vse a he pliotogzaphe are gears iy meaus of which the
films driven fru ve dvs wale tarough a dilferental, which pevrits
the fia tobe framed up and down. The iit beam is directed chrough
the film a right gles to che axe ofthe divs by meass of exo prisms
whereby certain onvenioness in driving and handling the Slm are
tained,

“The yitoeeciuie ells ae similar to ones previously describe
“The tmifer syotem was subetenaly Meatial wth chat used inthe
two-way television eysres, sd nee net be described zgzin. Sin
lacy, che amplifiers atthe receiving end weve che etal se usd inthe
reccloe televieon apparatnpresioely described

tthe seceiving end. the thee ats of signals were supplied to the
‘hoes elactiedes of epesia neon Tanyp Ne shown fy Fig. Sy which ie
provided with & hiogen valve to ene to reel the higher
Frequencies Condensing leases Ly nad Z image the three electrodes

at theese, where snother les Zs place atthe eve te focus the face
OF the dise 2. By this-syster, sine electrode images ere Sormed of

Ip totes, ail cessive seanaing holes a6

hich reac pe
hie viewing avangement

seen lnivsted by each recta in tne
by whieh the isage is visible to only a single eye, ie adequate for an
tsperimental investigative of the sult -asuel mata, tse her
Scherr wul of course be need if he etal wee developed into
fil fort. OF several schemes, mention ‘willbe mde here onl
aie

oF the peau of a trgle gril of neon tubes, using a
two of the type used in displaying images to ierge iene in our
initial work ia 19

Dheyscos om Rests

he dieennccl apparatus, whew all pt ane prope famelion
agreement wil the theony wri ing
Finaye, in resolving parser stl

ing, yield soley sil

iteomatructiog, The 15,S00-cewen

_—esving ef aes eso sopra

tof deta handled, is a asad saan over dhe single-channel
‘Sement image, Eves 20, she experiewrs of manag Uuough ©
Cullecion of motn picture Is ef all eps finappoiniag, ia that

the number of ssbjecs reudeced adequately by even this rome ot
Geal of acto ane sepoduced with vonsiderable eatisaction, bat
cones vontaning 4 munber of ful length figures, where the natone of

uch that facial mrss should Le watched, ane very