Film-Tech (III)

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NATIONAL 1SCHOOl.S‘* l.OS ANGELES 37, CALIF.

PRINTED IN U.S-A.

souun P|c1'um:é mm“-

L E S S O N N O. SP - 2

SOUND RECORDING ON FILM

- IN THIS LESSON HE ARE GOING TD DISCUSS A TYPE OF SOUND RECORDING,

WHICH IS ENTIRELY DIFFERENT FROM THE DISC METHOD ABOUT WHICH YOU LEARNED

IN THE PRECEDING LESSON. NOV, HE ARE GOING TO DISCUSS SYSTEMS IN WHICH

THE SOUND EFFECTS ARE RECORDED ON A STRIP OF PHOTOGFZAPHIC FILM; THE SAME

AS THE PICTURE ITSELF; SO THAT NO DISC RECORD IS REQUIRED‘

I

we GENERALLY REFER TO THIS METHOD ‘

or souuo RECORDING AS "Souuo-ON-F|LM" ‘

OR SIMPLY "FILM RECORDING". Two POPULAR

svsvzns EMPLOYING THIS METHOD ARE THE

WESTERN ELECTRIC ("Mov|:ToNE") AND THE

R.C.A. ("Pnoropuows "). ALTHOUGHBOTH

or THESE svsrsms RECORD THE souuo on

FILM, YET THE PROCESSES INVOLVED av

EACH ARE DIFFERENT. THEREFORE, THESE

Two SYSTEMS v|LLBE DESCRIBED SEPARATELY

IN THIS LESSON.

HOWEVER, BEFORE GOING INTO THE

DETAILED o|scuss|ou or EITHER or wuss:

svsrsns, IT us ADVISABLE THAT YOU FIRST

BECOME FAMILIAR HITH A u~\1, WITHOUT

HHICH NEITHER SOUND—ON—FlLM NOR TELE-

VISION WOULD as POSSIBLE. THE uunr IN

QUESTION |s THE PHOTO-ELECTRIC CELL.

BY sruovunc ITS coustaucruon AND OPER-

ATION AT THE azcuunune OF runs Lesson,

YOU HILL READILY UNDERSTAND ITS APPLI-

CATION TO souuo PICTURES AS vz PROGRESS F|e.

warn THE INSTRUCTION. Sruozuts WORKING on PROJECTOR

PAGE 2

SOUND PICTURES

PHOTO-ELECTRIC CELLS

Two D|FFERENl TYPES or :HoTo-ELEcTR|c cELLs ARE SHOWN |~ FIs.2 AND

THE SYMBOL FOR THE PHoTo~cELL, AS IT IS FREQUENTLY CALLED, as SHOWN IN

THE LOWER PORTION OF FIG-2- THE CELL

THE ACTIVE OR LIGHT—SENSITlVE MATERIAL

PLIED T0 A METALLIC COATING ON THE INNER SURFACE OF THE

FORMING THE CATHODE.

AT THE LEFT IS KNOWN As THE "V|s|-

TRON" PHOTO—ELECTRIC CELL AND nu

THIS cAsE, THE CATHODE CONSISTS or

A CONCAVE METAL SURFACE upon WHICH

A LIGHT—SENS|T1VE MATERIAL IS DE-

POSITED AND THE ANODE |s |~ THE

FORM OF A,CENTRALLY LOCATED WIRE.

BoTH or THEsE ELEMENTS ARE sEALEo

WITHIN A GLASS EuLE,wH|cH IN SOME

cAsEs |5'EVACUATED HH|LE IN OTHER

cAsEs BEING FILLED WITH some INERT

sAs, SUCH As HELIUM, AHsoH,oR NEON

AT Low PRESSURE. CELLs OF THE LATI

ER TYPE ARE GENERALLY REFERRED To

As BEING or THE GAS—F|LLED TYPE.

FH0H ITS OUTER APPEARA~cE,TH|s PH2

TO-CELL SOMEWHAT RESEMBLES A RADIO

TUBE.

THE PHOTO-CELL AT THE RIGHT

OF F|e.2 |s A "RAYTHEON" AND an

THIS cAsE,THE SHAPE or THE GLASS

BULB IS DIFFERENT AND THE ANQDE

TAKES THE FORM OF A METALLIC RING.

IN THIS RAYTHEON PHOTO—CELL as A5

cLAss BULB, THUS

A CIRCULAR PORTION OF THE GLASS, HOWEVER, IS LEFT CLEAR AND THIS

IS KNOWN AS THE "WINDOW" AND THROUGH THIS TRANSPARENT-PORTION, WE PASS

A BEAM OF LIGHT FROM THE OUTSIDE SOURCE- SO MUCH FOR THE CONSTRUCTION

OF PHOT0—CELL$ —‘ NOW LET US CONTINUE WITH THE DISCUSSION CONCERNING

THEIR OPERATION.

OPERATION OF THE PHOTO-ELECTRIC CELL

In FIG-3 wE HAVE A FUNDAMENTAL

PHOTO—ELECTRIC CELL CIRCUIT AND As

vou WILL NOTE, THE POSITIVE END or

A sATTERv IS CONNECTED To THE ANODE

or THE PHOTO-CELL THROUGH A H|cRoAH§

ETER AND RESISTOR WHILE THE NEGATIVE

END or THE BATTERY |s CONNECTED To

THE cATHouE SURFACE or THE cELL. THE

ANODE or THE CELL now connzspouos TO

THE PLATE or AN ORDINARY RADIO TUBE

AND THE CATHODE TAKES THE PLACE or

THE FILAMENT on cATHonE or A RADIO

LESSON no.2 PAGE 3

In ALL TYPES or RADIO Tuszs, WE nenznn uwon HEAT, IN ORDER TO OB-

TAIN AN EEEcTnon EMISSION Ann THE HEAT IS FURNISHED BY A FILAMENT cunn-

znr. In THE CASE OF THE PHOTO-CELL, wE HAvE no HEATING ELEMENT sul In

PLACE or THIs,ELEcTR0ns ARE EMITTED FROM THE CATHODE DUE To THE EFFECTS

or LIGHT RAYS STRIKING THE LIGHT-SENSITIVE SURFACE or THE cATHonE.

MANY SUBSTANCES WILL EMIT ELECTRONS WHEN PLACED UNDER THE |NFLU~

ENCE OF LIGHT BUT CERTAIN SUBSTANCES WILL EMIT MANY MORE ELECTRONS UN-

DER THESE CONDITIONS THAN OTHERS. ALKALI METALS OR ALKAL|—METAL HYDRI-

DES ARE QUITE SENSITIVE TO LIGHT RAYS AND AMONG THE MOST COMMONLY USED

ALKALI-METAL HYDRIDES FOR PHOTO~CELL PURPOSES ARE SODIUM HYDRIDE,POTASS-

IUM HYDRIDE AND CAESIUM HYDR|DE- THERE ARE STILL OTHER SUBSTANCES, WHICH

EXHIBIT PRONOUNCED EFFECTS WHEN SUBJECTED TO LIGHT RAYS BUT THOSE MEN-

TIONED ARE THE MOST EFFECTIVE MATERIALS, WHICH HAVE SEEN FOUND UP TO THE

PRESENT TIME- WE SPEAK OF THESE SUBSTANCES A5 BEING "LIGHT SENSITIVE".

SHOULD THE PHOTO-CELL OF FIG-3 BE PLA— sauna T?ack

I

CED IN ToTAL DARKNE$5,THEN THE MICROAMMETER

WOULD INDICATE no CURRENT FLOW BECAUSE no EL- ifia; ‘"”§g§;

ECTRONS ARE BEING EMITTED FROM THE cATHonE = ‘

SURFACE- Now IF A BEAM or LIGHT WERE To as

DIRECTED To THE LIoHT~sEnsITIvE SURFACE or "

THE cATHonE, A STREAM or ELECTRONS WILL as E-

MITTEP FROM THIS SURFACE AND SINCE THE Anon: 3=<~;;§$£;;;;§C) I

Is AT A POSITIVE POTENTIAL, nu: Tn THE BATT~ ;;; @?§§§§

ERY CONNECTION, IT WILL ATTRACT THE EHITTEd §?*\'§§§§C3

ELECTRONS.THE RESULT IS THAT we HAVE A STREAM _"=w _H+H

OF ELEcTRoNs AT THIS TIHE FLOWING FROM THE j§§%a VEEECD

CATHODE oven To THE ANODE Ann THEREFORE CURR- v __H_H

EnT wILL FLOW THROUGH THE SYSTEM As INDICATED, ’I*.~~* ’“*““;3

K] UIU U U U U U O U U U U C

-1-:-I-I-I ‘Q-I-Ii‘-£ -£31-I-ii-I-I-I+Z-I-I-IT.‘-I-I  I-I'-Z£‘-I-J-I*I-Z-I-I'I-Ii-I-I

 _ ‘      

THE SAME As PLATE CURRENT FLOWS THROUGH THE $fi¢é%;A§;§§§;c3

CONVENTIONAL RADIO TUBE. ' I?

_»‘~;:a_

IF THE LIGHT BEAM Is INTENSIFIED, THEN §§§; _§ §§§C>

THERE WILL BE An INCREASED ELECTRON EMISSION ‘*§§§f\ §g§§§§

rnom THE cATHonE, ACCOMPANIED wITH A CORRE5- Dflv¢'T?acg”{‘

PONDING INCREASE IN THE so CALLED "PLAT: cunn , ,

V H if — 

EHT" on PHOTO-CELL CURRENT; ThUS'IT Is SEEN FIG 4

THAT THE CURRENT FLOW WILL VARY As THE |NTEN- S¢=£kn o a Him as uszd

SITY OF LIGHT, wHIcH Is rocuszn upon THE PHO- 01 Eh: Amwkfane Qfl/am.

To-cELL VARIES.

THE PHOTO—CELL CAN as COMPARED vsnv NICELY To A MICROPHONE, FORTHE

MICROPHONE cHAncEs AIR PRESSURE VARIATIONS INTO ELECTRICAL CURRENT VAR-

IATIONS or CORRESPONDING FREQUENCY, WHEREAS THE PHOTO-CELL CHANGES LIGHT

VARIATIONS INTO ELEcTRIcAL CURRENT VARIATIONS or CORRESPONDING FREQUENCY

TH: CURRENT THROUGH THE PHOTO—CELL Is so SMALL THAT IT IS MEASURED IN Hi

CROAMPERES (H|LL|onTHs or An AHPERE).

GAS-FILLED PHOTO-CELLS ARE MORE SENSITIVE THAn THE VACUUM TYPE-THE

REASON ron THIS IS THAT THE PHOTO ELECTRONS IONIZE THE INERT sAs IN

THEIR PASSAGE rnon THE CATHODE SURFACE ovzn To THE ANODE- THAT Is, THE

PHOTOELECTRONS FLOW FROM THE CATHODE oven THE ANODE AT SUCH A TREMENDOUS

FAG‘ b souuo PICTJRES

vELocITY, THAT WHEN THEY COLLIEE wITH MOLECULES oF THE INERT GAE, TIFY

BREAK THEsE MOLECULES up INTO THE ELECTRONS AND PROTONS or WHICH THET

ARE COMPOSED- WE cALL THIs ACTION "IoNIzATIoH av coLLIsIoH". THESE EXTRA

ELECTRONS ARE THEN ALso ATTRACTED To THE POSITIVELY CHARGED PLATE, IN

ADDITION To THosE LIBERATED BY THE cATHooE AND THE RESULT I5 THAT THE

PHOT0—ELECTR|C_CURRENT IS INCREASED OVER wHAT IT WOULD BE wITH THE FLow

OF PHOTO—ELECTRONS ALONE» (PHoToELEcTRoHs ARE THE ELECTRONS WHICH ARE E

MITTED FROM THE CATHODE oF THE PHOTO-CELL AND THE PHOTO—ELECTR|C CURRENT

coRREsPoNbs'T0 THE BLATE CURRENT or AN ORDINARY RADIO Tuss.)

NoT ONLY Is THE PHOTO-ELECTRIC CURRENT AFFECTED av THE INTENSITY

oF THE LIGHT DIRECTED uPo~ |Ts cATHooE SURFACE BUT A CHANGE IN THE PO-

TENTIAL APPLIED To THE AHo0E WILL ALso PRODUCE A PRONOUNCED EFFEcT UPON

THIs CURRENT.

THE WESTERN ELECTRIC SYSTEM

Now LET us TURN OUR ATTENTION To THE WESTERN ELEcTRIc SYSTEM oF

PRODUCING souno PICTURES. IN FIs.h, YOU ARE sHowH A PIECE 0F FILM AS us

' 0 1 brages DUE To THE DARK AND

LIGHT SHADING, SIMILAR

To THAT WHEN YOU HOLD

A NEGATIVE CAMERA FILM

FIG'5 AGAINST A LIGHT.

T/2: L/qhé I/a/we far Maw/'eian¢ Pecan!’/‘n9.

A CONTINUOUS Row

0F EQUALLY sPAcEo NOTCHES ARE LocATEo ALONG EAcH EDGE oF THE FILM As

SHOWN IN FIe.h. WE HAVE LABELED THIs As THE“0RIvE TRAcK"aEcAusE SPROCK-

ET coes MESH WITH THEsE HoLEs, so As To PULL THE FILM THROUGH THE PROJE£

TOR.

AHQTHER NARROW sTRIP Is INCLUDED BETWEEN THE PICTURE STRIP AND THE

LEFT DRIVE TRACK AND THIs IS THE SOUND TRACK. THE souwn TRACK CONSISTS

0F A LADDER—L|KE BAND or sHALL LINES AND THIS Is THE FILM souno RECORD.

As YOU wILL NOTE, THEsE TINY LINES IN THE souuo TRACK ARE or CONSTANT

WIDTH BUT THE DENSITY VARIES , THAT Is, SOME PORTIONS ARE BARKER THAN

oTHERs.

THE PITCH OF THESE FILM RECORDED SOUNDS IS REPRESENTED BY THE NUM-

BER OF CHANGES FROM DARK TD LIGHT AND BACK AGAIN IN A GIVEN LENGTH OFTHE

LESSON no.2 PAGE 5

SOUND TRACK, WHILE THE DIFFERENCES IN THE INTENSITY OF SOUND ARE REPRE-

SENTED BY THE DIFFERENCES IN THE DENSITY OF LIGHT AND SHADE ALONG THE

SOUND TRACK- SINCE THE SOUND RECORD IN THIS CASE IS AN ACTUAL PART OF

THE FILM’SYNCHRONIZATION BETWEEN SOUND AND SCENE PRESENTS NO PROBLEM IN

THIS SYSTEM, BECAUSE THE RELATION BETWEEN THE SOUND TRACK AND THE FILM

IS PERMANENTLY FIXED.

THE SECTION OF FILM IN FIG. H REPRESENTS A FINISHED FILM, READY TO

BE RUN THROUGH A PROJECTOR BUT BEFORE WE CONSIDER THIS PART OF THE SUB-

JECT;'YDU W1LL OF COURSE FIRST WANT TO KNOW HOW THE SOUND ON FILM IS OR-

IGINALLY RECORDED.

THE MICROPHONE PICKUP, MONITORING.AND AMPLIFICATION OF THE AUDIO

FREQUENCIES IS TAKEN CARE OF IN THE WESTERN ELECTRIC SYSTEM IN THE SAME

wAv As DESCRIBED RELATIVE

To THE VITAPHONE on DISC R5

CORDING SYSTEM or THE PRE-

wous LESSON. Tn: MAJOR oy-

FFERENCE BETWEEN THESE Two

souuo naconouus SYSTEMS rs

rouuo AT THE RECORDING UNIT

ITSELF.

THE LIGHT VALVE

IN PLACE or THE CUTT-

vuo DEVICE or THE VITAPHONE

sYsT:M,A LIGHT VALVE IS us-

co ron THE souno RECORDING

av THE WESTERN ELECTRIC pno

L ml,” VALVE is SHOWN IN I,-|G_ C'o/1/1:c£/"nu Befween L/5/:25 /a/vg and Am/-v/.

5. Tans ozvncz CONSISTS or DURALUMIN TApz 0.006" wnoz AND 0.003" THICK,

WHICH |s SHAPED INTO AN OBLONG LOOP AND suspsnozo an A PLANE AT RIGHT AN

oL:s-To A MAGNETIC FIELD.

Tu: anus or THE TAPE ARE szcunso AT THE WINDLASSES A5 SHOWN |N

F|o.5 AND IT |s STRETCHED TIGHT av A SPRING-HELD PULLEY ovzn WHICH THE

Loop |s pAsszo. A PAIR or INSULATED PINCERS co~p|u: THE CENTRAL ponrnous

or THE TAPE azrwczu THE w|NoLAss:s AND PULLEY so As To FORM A SLIT op

SPACE or 0.002" BETWEEN THE Two SIDES or THE Loop AT THIS POlNT.$UPPORT-

nus THIS Loop AND THE ADJUSTING DEVICES IS A METAL SLAB WITH A CENTRAL

ELEVATION, wnncn CONSTITUTES THE ARMATURE or AN ELECTROMAGNET. Tn: CEN-

TRAL PORTIONS OF THE DURALUMIN LOOP ARE SUPPORTED on INSULATING BRIDGES

JUST ABOVE THE FACE or THE ARMATURE AND HERE THE snnzs or THE Loop ARE

cznrsnzu oven A TAPERED sLoT.

Tn: Two SIDES AT THE CENTRAL PORTION or THE LOOP CONSTITUTE A sL|T

0.002" HIDE BY 0.256" Lone, WITH ITS snocs LYING IN A PLANE AT RIGHT AN-

GLES TO THE LINES or ropcs AND APPROXIMATELY czurzpzo an THE AIR GAP-THE

suns or THE Loop ARE CONNECTED To THE ouTpuT TERMINALS or THE RECORDING

AMPLIFIER AS'SHOVN an F|o.6,wneR: THE LIGHT VALVE as ILLUSTRATED To ex-

AGGERATED PROPORTIONS FOR THE SAKE or CLEARANCE- Ir THE MAGNET as znqg

onzzn AND THE AMPLIFIER PASSES AN AUDIO rpzousucv CURRENT THROUGH THE

[AGE 6 souno PICTURES

Loop, Tuen Tue LOOP w|LL open on spReAu APART Ann AGAIN cLose |n AccoR-

oAnce w|Tu Tue CURRENT vAR|ATzon THROUGH IT. NOTICE |n F|o.6TuAT we uAve

NOT INCLUDED Tue MONITOR on OTHER ACCESSORIES Ano JUST Tue BACK—BONE or

THE svsreu I5-SHOWN FOR Tue SAKE or s|uPL|c|TY.|r A BEAM or LIGHT as 0|-

RECTED AT Tue CENTRAL PORTION or THE Loop,wueRe we uAve Tue NORMAL sepA5

AT!0N or .O02",|T as oav|ous TuAT Tue LIGHT BEAM pAss|nc THROUGH THIS R5

STRICTION w|LL ae MADE wuoep Ano NARROWER Acc0R0|Ns To Tue openane Ano

CLOSING or Tue Loop. Fon THIS REASON,IT IS CLEAR wuv THIS oevnce as cALL

eo A "LIGHT vALve".

Wuen one 5105 or THE AUDIO wAve opens Tue vALve To 0.00M" Ann Tue

OTHER s|ne cLoses IT coupLeTeLY, THEN FULL MODULATION or Tue APERTURE

on OPENING ms AccoupL|sueo. Tue NATURAL eneouencv or Tue vALve |s seT av

ADJUSTING Tue TENSION or Tue TApe Ano expeulence uAs suown TuAT sesr RE-

SULTS ARE osTA|neo av TUNING Tu|s LIGHT vALve To A epeouencv or 7000 cv-

CLES pen secono. Unoen Tuese cono|T|ons, ABOUT 10 MILLIWATTS or powep

ARE REQUIRED eon FULL MODULATION AT FREQUENCIES FAR AwAv epou RESONANCE

BUT ONLY AaouT 1/100 or THIS powep |s REQUIRED AT THE RESONANT FREQUENCY.

SOUND RECORDING WITH THE WESTERN ELECTRIC SYSTEM

Tue nexT 5TEP rs To see uow Tu|s LIGHT vALve IS useo IN Tue necogg

ING or souno F|LM- A

Source. of Fi\I'Y\

. _ _ , _ M F SIMPLIFIED DIAGRAM oe

Inqhlz Lsqhk beam Lxqhfi valve ta?  THE WESYERN ELECTFHC

_ souno RECORDING peo-

,— \\ /,- \\\ cess |s suown |n FIG-

— _ “ _ “*; Ymiqe Y AND eon THE PRESENT

’/ \ // . 1

T’ \\ -/ °€ hqht we suALL DEAL ONLY

Ia‘.

// \\

valve

Bwrwez WITH Tuose essenT|AL

.;.-Am, Condensing line _ ‘ PARTS ueue ILLUSTRATED

-.f*l:;;;;,5{ Ob5z=l:|\/e Ens ‘

_.-

_=l , .

 _  AT Tue LEFT or

F1s.7, we uAve oun

Mnmghgng Ampufier _ soufice or Lrcur rn THE

F‘6 7 eonu or A RI8BON—FlLA—

M°"’“*°”Z p’°C“$ 5/ 5:’“””/ ‘*'¢*?- MENT TYPE ppooecnon

LAMP Ann THIS rs FOCUSED upon Tue VARIABLE sL1T or THE LIGHT vALve av

ueAns or A conoens|ns Lens SYSTEM.

_4__‘~I'

/4’

\

/

/

Qo

"\

-—?_-Y

Assuu|no eon Tue PRESENT TuAT Tue necopovno AMPLIFIER IS nor YET

|n OPERATION, Tue SLIT or Tue LIGHT vALve w|LL pAss A ~ABEAH~ or 't4GHT,

wu|cu IS 0.002" w|oE Ano 0.256" LONG Ann THIS |s DIRECTED upon An OBJEC-

TIVE Lens , wurcu on TURN FOCUSES THIS seAu WITH A Two-To-one REDUCTION

upon Tue PHOTOGRAPHIC FILM AT THE FAR RIGHT. Tue openans or Tue LIGHT

vALve now APPEARS on THE FILM HALF—SlZE op As A LINE 0.001" wcoe Ano

0.128" LONG, WITH ITS LencTu ee|ne AT RIGHT ANGLES To Tue DIRECTION or

FILM TRAveL.

Now IF Tue uncnopuone CURRENTS ARE AMPLIFIED Ano penurrreo To ACT-

uATe Tue Loop |n Tue LIGHT vALve, THE WIDTH or Tue LIGHT vALve opennno

w|LL VARY AT AUDIO FREQUENCIES Ann Tue SYSTEM |s Tuus ae|ns uoouLATeo.

Tue LIGHT vALve |s now OPERATING As A CAMERA SHUTTER Ano Tue w|oTu oe

LESSON NO-2 PAGE Y

THE LIGHT LINE UPON THE FILM WILL VARY WITH THE souuo cuRHEHTs,wI-IIEH ARE

SUPPLIED TO THE vALvE. IN THIS WAY, THE FILM RECEIVES EXPOSURE TO LIGHT

or FIXED INTENSITY BUT oumms THE VARYING TIME REQUIRED FOR A GIVEN

POINT or: THE FILM T0 PASS THE VARYING OPENING or THE LIGHT VALVE sLIT.

THIS BEING THE CASE, WE FIND THAT AS THE FILM MOVES PAST THE FOCUE

ING POINT OF THE OBJECTIVE LENS, THE CONDENSATIONS AND RAREFACTIONS OF

THE ORIGINAL SOUND WAVES WILL BE RECORDED AS LIGHT AND DARK VARIATIONS,

DUE TO THE CORRESPONDING VARIATION IN EXPOSURE OF THE FILM T0 LIGHT AS

CAUSED BY THE vALvE. '

Dunms TH_E FILMING OF A PICTURE, THE souuu Is RECORDED on A FILM

SEPARATE FROM THAT WHICH RECEIVES THE PlCTURE- TI-IIs PERMITS THE us: oF

TWO MACHINES, so THAT DUPLICATE souno RECORDS CAN BE MADE AND CONSEQUEN-

TLY, IF ONE SHOULD BE DEFECTIVE FOR SOME REASON OR OTHER, THE szcouo

WILL COME IN MIGHTY HANDY- ANOTHER IMPORTANT REASON FOR HAVING SEPARATE

NEGATIVES FOR souuo AND PICTURE Is

THAT THIS PRACTICE PERMITS A SEPAR- Ron cf Wm A,

ATE AND SPECIAL DEVELOPING PROCEDURE

FOR EAcH. THIs Is ESPECIALLY DESlR- Lamphouse \~

AEILE WITH RESPECT To THE Souuo FILM Gears Mcrrar

BECAUSE IT IS NECESSARY THAT THIS I E;¢Id<@1I \ /

L;

FILM as DEVELOPED To UNIFORM |NTEN- V;I,,¢ \»

SITY THROUGHOUT ITs ENTIRE LENGTH, \ ' ‘ T‘ ' ~’ T“ _

IN omen To PROVIDE PROPER s0uNu PRO— . 39, gfl "  '3 I);-

DRIVEN IN PERFECT SYNCHRONISM WITH

JECTION.

M_'*’ ‘\_

_ Inf __

"bi ,

I 4 1 /

_ _ . E_- _ _ '

,, .

= , » ._ - _

TI-IE souun RECORDING MACHINE Is C,

THE CAMERA AND TD INSURE AGAINST ANY

VARIATION IN THE VELOCITY or THE 

souuu FILM PAST THE LINE or LIGHT EX-  1 ’ I

PosuRE, THE SPROCKET WHICH CARRIES  Fqgm

THE FILM AT THAT POINT IS DRIVEN THRU

A MECHANICAL FILTER, WHICH HOLDS TI-IE

INSTANTANEOUS VELOCITY CONSTANT TO F16. 5

ONE PART IN ONE THOUSAND. M,,,/,'¢,_¢Q,,¢ 5,”,-,4 ,2gwm/=r:

IN FIG- 8, YOU WILL SEE SUCH A RECORDING MACHINE, WITH THE DOOR OF

THE EXPOSURE CHAMBER OPENED SO THAT THE INNER CONSTRUCTION CAN BE OBSER-

{EO- IN ORDER THAT THE OPERATORS OF THE RECORDING EQUIPMENT MAY KNOW THE

QUALITY OF THE RECORDING DURING THE TIME IT IS BEING MADE, A SOUND PICK-

UP DEVICE IS INCORPORATED WITHIN THE RECORDING MACHINE. IN THIS WAY, THE

SOUNDS CAN BE REPRODUCED DIRECTLY AS THEY ARE BEING RECORDED.

THE PICK-UP DEVICE FOR SOUND REPRODUCTION

THIs PICK-UP DEVICE CONSISTS OF A PI-IoTo-cELL, WHICH Is MOUNTED

WITHIN THE EXPOSURE CHAMBER OF THE RECORDING MACHINE BEHIND THE LEFT

HAND SPROCKET As VIEWED IN I-'Is.8. FREsH FILM TRANSMITS ABOUT II% or THE

LIGHT wHIcH STRIKES IT AND so THE BEAM 0F LIGHT PENETRATES THE FILM AS

SHOWN IN FIa.9 AND ENTERS THE wnwow _OF THIS PHOTO-CELL.

THE AMOUNT OF LIGHT, WHICH ACTS UPON THE LlGHT—SENSITIVE MATERIAL

PAGE 8

SOUND PICTURES

OF THE PHOTO CELL,WlLL BE DETERMINED BY THE DENSITY OF THE PORTION OF

THE SOUND TRACK,WHlCH HAPPENS TO OBSTRUCT THE PATH OF THIS LIGHT BEAM AT

ANY ONE INSTANT- THEREFORE, THE INTENSITY OF THE LIGHT ACTING UPON THE

PHOTO-CELL WILL VARY IN DIRECT PROPORTION TO THE LIGHT AND I DARK POR-

TIONS ON THE FILM SOUND TRACK AND SINCE THESE ARE DISTRIBUTED ACCORDING

/0 /nay.

v'~<

§Q\.

I'|'l'|'

TO AUDIO FREQUENCIES, THE LIGHT BEAM ACTING upon THE PHOTO-CELL WILL

Mcfian ii / }q\m Condenicr rneouzucv.

cf f1:  7 Tub:

6¢- Ph°£°_GeH THE ELECTRON sn|s-

Ey ~ SION FROM THE PHOT0—CELL'S

_ /, /) § CATHODE WILL INCREASE AND

L"3I‘t j ,  '. 5 DECREASE IN PROPORTION 1'0

b“""\'  I I N ‘ rues: VARIATIONS IN LIGHT

"I INTENSITY,VlTH was RESULT

THAT THE PHOTO-CELL cunn-

__ ENT noes LIKEWISE. Tnus

““' av HAVING A VARIATION or

F|e.9

Man /for//15 P/10/'0 - ce// P/2k — up .

VARY AT A CORRESPONDING

PHOTO-CELL cuansur FLOWING

THROUGH THE 2 MEGHOM a:s|§

TOR OF FIG-9,SIGNAL VOLTA-

sss or connzspononue raz-

QUENCY_ARE DEVELOPED ACROSS THIS RESISTOR AND THESE SIGNAL POTENTIALS

ACT THROUGH THE FIXED CONDENSER AND IMPRESS THEMSELVES ACROSS THE GRID

CIRCUIT OF THE AMPLIFYING TUBE-

Tnssz AUDIO SIGNALS, wnsu APPLIED TO THE GRID CIRCUIT OF THE AMPLI

FYTNG Tuai, uwosaso CONVENTIONAL A.F. AMPLIFICATION A~u’av ADDING ADDI-

TIDNAL AMPLIFYING STAGES, THE SIGNAL ENERGY CAN as RAISED TO A SUFFICIEN

TLY HIGH LEVEL SO AS T0 OPERATE A SPEAKER IN THE CONVENTIONAL MANNER.

THE SPEAKER IN THIS CASE IS IN THE MONITORING ROOM,THE PRELIMINARY

AMPLIFIER or F|c.9 |s LOCATED asnow THE

EXPOSURE CHAMBER or THE RECORDING MACHINE,

AND tn: ADDITIONAL AMPLlfIER |s one SEPAR-

ATE FROM ‘run some THE REGULAR RECORDING

AMPLIFICATION.

RECORDING PRACTICE

In sTu0|o PRODUCTION,THE MIXER open-

ATOR as STATIONED |u THE MONITORING ROOM

AND HE vlzws THE "szr" (STAGE SET-UP) THRU

A DOUBLE w|uoow nu THE sTuu|o WALL AND nu

ADDITION TO OPERATING rue MIXER PANEL ron

COMBINING THE cournnaurnous or SEVERAL un-

CROPHDNE5, HE ALSO CONTROLS THE GAIN OFTHE

AMPLIFIERS ron THE RECORDING MACHINES.

BY MEANS OF RELAY SVlTCHES,THE MIXER

OPERATOR CAN CONNECT THE MONITORING HORN

CIRCUIT EITHER DIRECTLY TO THE RECORDING

AMPLIFIER, AS WAS SHOWN YOU RELATIVE TO Vi

LESSON No.2 PAGE 9

TAPHONE OR DISC RECORDING IN THE PREVIOUS LESSON, OR ELSE HE CAN CONNECT

THE HORN CIRCUIT TO ONE OR THE OTHER OF THE PHOTO-CELL PICK UP CIRCUITS

WHICH WAS DESCRIBED A FEW MOMENTS AGO-

1

DURING THE TIME THAT PRELIMINARY TESTS ARE BEING CARRIED OUT SO AS

TO DETERMINE THE BEST MIQROPHONE POSITION ON THE SET ETC., THE MONITOR-

ING HORN CIRCUIT IS CONNECTED DIRECTLY TO THE OUTPUT END OF THE RECORD—

ING AMPLIFIER. THE PROGRAM IS THEN REHEARSED ON THE SET UNTIL A SATISFAC

TORY ARRANGEMENT OF THE MICROPHONES AND OF AMPLIFIER GAIN IS DETERMINED-

TH: ELECTRICAL cHARA¢T:HIsTIc or THIs MONITORING CIRCUIT IS so 0:-

SIGNED THAT TH: souun QUALITY HEARD IN TH: MONITORING HORNS sHALL a: TH:

SAME As TH: QUALITY To s: EXPECTED

IN THE REPRODUCTION 0F TH: POSI-

TIv: PRINT IN TH: TH:AT:R. TH:

wALLs or TH: MONITORING ROOM ARE A

cousTIcALLv TREATED IN SUCH A wAT

THAT ITS REVERBERATION CHARACTER-

IsTIcs WILL a: THE SAME AS THAT IN

TH: THEATER AND TH: MONITORING LE1

:L Is so ADJUSTED THAT TH: MIXER

OPERATOR HEARS TH: SAME LOUDNESS

THAT H: wouLo wIsH To HEAR rnom

THE THEATER HORNS. IT Is VERY IM-

PORTANT THAT TH: OPERATOR JUDGE

HIs PICK-UP on TH: BASIS or souND

cLos:LY IDENTICAL IN LOUDNESS AND

QUALITY yITH THAT To as H:AHo LAT-

ER IN THEATER REPRODUCTION.

P201: cTcw. BO‘

u>~uT

- '1'uT;uTAlI..!

WITH EVERYTHING ADJUSTED To

TH: POINT DESIRED, TH: OUTPUT or

TH: RECORDING AMPLIFIER IS DISCON-

NECTED FROM TH: MONITORING HORNS

AND Is How CONNECTED To TH: LIGHT

vALv:s or TH: RECORDING MACHINES

AND TH: MONITORING HORNS ARE CONN- Pied] -

:2*::;:I:::;::*:.:::;Ls""Iii: A    W

no FILM IN TH: MACHINE AND AT, A 0'5‘ a”J Eb” E'C°r°6”9'

CONVENIENT LAMP CURRENT, A COMPLETE REHEARSAL Is MADE so As To VERIFY

TH: OPERATION or TH: LIGHT vALv:s AT TH: PROPER L:v:L. FILH Is TH:~ LoA3

:0, TH: CAMERAS AND souuo H:¢onn:Rs ARE INTERLOCKED AND STARTING MARKS

ARE MADE on ALL FILMS EITHER av MEANS or PUNCHES OR ELSE WITH FLASHES or

LIGHT upon TH: STARTING POINT or TH: FILM.

MAGAIIME

THE STUDIO AND RECORDING ROOM SIGNAL TO EACHOTHER BY MEANS OF

LIGHTS AND SO WHEN THE RECORDING EQUIPMENT IS READY FOR ACT|ON,THE REC-ORE

ING ROOM WARNS THE STUDIO BY MEANS OF A LIGHT SIGNAL~ THE LIGHTING EFF‘

ECTS ON THE STAGE ARE THEN PUT INTO OPERATION AND THE STUDIO THEN SIG-

NALS BACK ITS READINESS TO START-

THE MACHINE OPERATORS START THE CAMERAS AND SOUND RECORDERS,BRING—

I um. M;;;u.~= ‘

I 1

Two INTO A SINGLE rTLH,wTTH THE

souno TRACK RUNNING ALONG THE

EDGE OF THE PICTURE PORTION OF

THE FILM As SHOWN IN FTs.h. In

PRINTING THE souun NEGATIVES |~

COMBINATION WITH PICTURES FOR

PROJECTION IN THE THEATEn,|T IS

CUSTOMARY TO FIRST PRINT THE

P4CIUR£~NEGATI¥E,MA$KING (Cc¥ER;

ING) THE sPAcE NEEDED FOR THE

souuo TRACK Ana To RUN THE RE-

SULTING PICTURE POSITIVE _THRU

THE PRINTER AGAlN,TOGETHER WITH

THE souuu ~EsAT|vE,TH1s TIME

MASKING THE SPACE ALREADY PRIN-

TED. In PRINTING THE sou~o ~E§

AT|vE,THE LIGHT IS REGULATED TO

RESULT"1N 35% TRAHsH1ssion or

THE UNMODULATED TRACK AFTER Pqg

ITIVE DEVELOPMENT-

UPON COMBINING THE souno

TRACK w|TH PICTURES UPON A

SINGLE E|LH,THE souno RECORDING

AT THE SIDE OF ANY one PARTICU-

LAR PICTURE FRAME DOES NOT con;

ESPOND To THE ACCOMPANYING PIC-

TURE. To |LLusTRATE TH|s, STUDY

Frs.IO CAREFULLY AND YOU WILL

NOTE THAT WE HAVE LABELED ONE

or THE PICTURE FRAMES (A). THE

souuo Rsconouue T0 CORRESPOND

w|TH FRAME (A) IS AT THE POINT WHICH |s LABELED (A). BETWEEN THEM THERE

as A SEPARATION OF 19 PICTURE FRAMES DR IU.5".

THE REASON FOR USING SUCH AN ARRANGEMENT IS THAT IN THE THEATER

PROJECTOR, THE souun GATE |s LocATE0 IH.5" aELow THE PICTURE sATE,|N OR-

DER To PROJECT THE souun RECORDING AT A POINT WHERE THE FILM IS IN cou-

TINUOUS MOTION. TH|s WILL BE SHOWN MORE CLEARLY DURING oun o|scussao~ or

PROJECTION v:TH THE MOVIETONE SYSTEM.

THE MOTION PICTURE PROJECTOR FOR SOUND ON FILM

IN FTe.11, YOU w|LL sEE A MOTION PICTURE PROJECTORJWHICH-IS EQUIP-

LESSON NO.2 PAGE II

PED FOR BOTH SOUND ON DISC REPRODUCTION, AS WELL AS FOR THE REPRODUCTION

OF SOUND ON FILM- THE INNER CONSTRUCTION or THIS sAME PROJECTOR Is SHOWN

IN F|G.12.

BY REFERRING To FIG.I2, You WILL sEE THAT TI-IE FILM Is THREADED

FROM THE UPPER MAGAZINE PAST THE PICTURE PROJECTOR LENS AND THENCE PAST

THE souuo FILM LENS UNIT AND INTO THE LOWER MAGAZINE. VARIOUS SPROCKETS

AND ROLLERS ARE USED IN sucH AN ARRANGEMENT so THAT THE FILM IS FED THRU

THE MACHINE AT A UNIFORM RATE AND uuocn PROPER TENSION.

NOTICE THAT THE PICTURE LENS IS ABOVE THE SOUND FILM LENS,SO THAT

ANY POINT OF THE FILM MUST PASS THE PICTURE PROJECTING LENS BEFORE ARR-

IVING AT THE SOUND FILM LENS UNIT- OBVIOUSLY, THE SOUND RECORDING MUST

BE ADVANCED AHEAD OF THE CORRESPONDING PICTURE F'RAMES,AS ALREADY DESCRIE

ED, SO THAT 3OUND REPRODUCTION WILL OCCUR SYNCHRONOUSLV WITH THE CORRES-

PONDING PICTURE. E

PI1nI'o<ceII F'Im A

A POWERFUL LIGHT AND LENS SYSTEM PRO— APEFIZOFQ Plaflq

/

JECTS THE PICTURE UPON THE SCREEN OF THE ' Lam

TI-IEATER,As THE sounu EQUIPMENT REPRODUCES ‘ / P)

THE sounos IN SPEAKERS LocATEo BEHIND THE ‘

A

SCREEN. ,

LZHS

souwo REPRODUCTION Window A"'L“'“

CONSIDERING THE SOUND PICK-UP DEVICE Lamp

or FIG.I2 IN GREATER I:IETAIL,wE sEE rII=IsT THE B F"-“N Lens I

"ExcITEI= LAm>".TIIIs Is A SMALL INCANDESCENT S

LAMP, wmcu HAS A RELATIVELY HIGH CURRENT ‘ 1

AND Low VGLTAGE cAPAcITY,coI~IsuMING eETwEE~}2 '  ‘

AND Y5 wATTs. THE CURRENT FOR LIGHTING THIS T ‘

FILAMENT MUST EE A PURE DIRECT CURRENT BE- IA/M aP,,Iu,.e I

Windcvw

cAusE ANY VARIATION IN THE CURRENT wILL Lani

cAusE A CORRESPONDING CHANGE IN THE PMoTo-EL

EcTRIc CFLL CURRENT. THAT Is, IF A 60 CYCLE L 5 f FIe@§ ,

A.C. SUPPLY WERE USED FOR THIS LAMP,ITs FlL- ‘"5 17‘7”5 %f‘d '”

AMENT WOULD cooL AND HEAT up ALTERNATELY AT Ah'7‘f°”e rbflbzgri

THE RATE or I20 TIMES PER SECOND AND ALTHOUGH THESE CORRESPONDING VARIA-

TIONS IN LIGHT INTENSITY WILL BE UNOTICEABLE TO THE HUMAN EYE, YET THEY

ARE READILY DETECTED BY THE PHOTO-CELL, WITH THE RESULT THAT A I20 CYCLE

ROAR WOULD BE EMITTED av THE sPEAKERs. In FAcT, EVEN THE ARMATURE RIPP-

LEs or A D.C. GENERATOR ARE REPRODUCEO BY THE PHOTO-CELL, IF usEo As THE

FILAMENT SUPPLY FOR THE EXCITER LAMP.BATTER|ES ARE THE SOLUTION To THIS

PROBLEM.

TI-IE NEXT THING IS TO FOCUS THIS LIGHT OF THE EXCITER LAMP upon THE

souuo TRACK or THE FILM AND THIS IS ACCOMPLISHED av THE souun FILM LENS

UNIT or FIG.12.

TI-IE DETAILS or sucu A LIGHT FOCUSING ARRANGEMENT ARE snovu IN FIG.

I}. Oun OBJECT now IS To IMPRESS A sMALL SHARP RECTANGULAR SHAPED GEAM

or LIGHT UPON THE sounn TRAcI< or THE FILM. THE EAsIEsT wAv 70 no THIS Is

ILLUSTRATED AT "A" OF FIG.1}, WHERE wE HAVE AN "APERTURE PLATE" PLAcEo

" IN ‘wn

DTH IS CUT IN THIS

BY MEANS or A

SUITABLE LENS, THE

LIGHT FROM rue zxc|1cn

LAMP CAN as rocuszo u-

PON THIS SLIT AND ruus

PENETRATE THE FILM

souno TRACK IN rue

SHAPE or A SMALL NARR-

ow RECTANGLE-THIS M215

OD,HOWEVER, |5 nor Pni

CTICAL BECAUSE A SLIT

As THISQWITH AN AREA

or ONLY ABOUT 0.0001

So. IN-,CANNOT as KEPT

FREE rnon FOREIGN MArl

ER ron ANY LENGTH or

run: wucn PLACED CLOSE

AGAINST A RAPIOLY HOV-

nne FILM.

Fon THE REASON

MENTIONED, THE svsrcm wAs IMPROVED TO THAT snown AT "B" or F|e.1}. In

runs cAs:, THE APERTURE SLIT |s novso AwAY rnon ITS :xPos:u POSITION

NEAR THE FILM, |r |s SEALED w|1u|u A LENS svsrzn, MADE CONSIDERABLY wng

an AND LONGER AND THEN OPTICALLY REDUCED TO A LIGHT RECTANGLE or 0.001"X

0.1" on tn: FILM av MEANS or THE svsrsn OF LENSES- Tuus tn: RESULT IS

THE SAME AS OBTAINED AS WITH THE CLOSE~UP SLITSYSTEM BUT WITHOUT ITS DI§

ADVANTAGES-

THIS NARROW BAND OF LIGHT, WHICH I5 THUS FOCUSED UPON THE FILM

SOUND TRACK, WILL PENETRATE THE FILM AND THEN BE DIRECTED AGAINST THE

LIGHT-SENSITIVE ELEMENT OF A PHOTO-EL ECTRIC CELL

AND THE ‘INTENSITY OF THIS LIGHT,WHICH IS PASSED

BY THE FILM HILL OF COURSE BE GOVERNED BY THE DEN

SITY OF THE SOUND TRACK,WH|CI-I I5 EXPOSED TD THE

L IGNT.

THl$ PHOTO-CELL us COUPLED To A Pncx-up AM-

PL|r|:R,As ALREADY snowu YOU IN F:s.9 or rnrs

LESSON, AND rnus THE PHOTO-CELL cunnzur HILL VARY

ACCORDING to THE LIGHT AND DARK PORTIONS on tn:

rnnn souuo TRACK- Iu 1n|s wAv, LIGHT VARIATIONS

or AUDIO rneauencv ARE CHANGED '”iWTO ELECTRICAL

cuancur VARIATIONS or connsspononns Fnzaucucv.

Tu: FHDTO~CELL PICK—UP AMPLIFIER |s sausa-

ALLV azrsnnza TO As A "Pzcn AMPLIFIER". THIS AMP-

LIFIER USUALLY CONSISTS or rwo on THREE STAGES or

CASCADE AMPL|FlCATION,USING VARIOUS TYPES OF sou:

LING, BUT RESISTANCE-CAPACITY COUPLING PRODUCES

Sound I:I'7c.L ‘;";:‘:;':

' /

LESSON no.2 PAGE 1}

THE BEST REsuLTs. THE CURRENT usED FOR OPERATING THE PECK AMPLIFIER HDET

BE PURE D.C , SUPPLIED EITHER av STORAGE BATTERIES DR DRY cELLs. DuE T0

THE FEEBLE CURRENT FROM THE PHOTO—CELL, THE PECK AMPLIFIER HAS To MAGNI~

rv |T FROM ABOUT 100 TO 200 T|MEs AND THEREFORE ANY VARIATION aw THE P0!

ER SUPPLY FOR THIS AMPL|r|ER, NO MATTER How LITTLE, WILL BE REPRODUCEO

AT GREAT VOLUME BY THE SPEAKERS.

Iw FIG. TH, YOU WILL sEE THE LAYOUT FOR THE REPRODUCTION or souwa

FROM FILM. Two PROJECTORS ARE REQUIRED IN THE PROJECTION sooTH,THE sAME

AS FDR DISC RECORDINGS 0R EVEN FOR SILENT PICTURES FOR THAT MATTER. No-

TICE How THE Exc|TER LAMPFOR EACH PROJECTOR IS SUPPLIED w|TH BATTERY FIL

AMENT CURRENT AND How EAcH or THE PHOTO-CELLS FEEDS INTO A PEEK AMPLl-

FIER- BoTH or THEsE PICK-UP AMPLIFIERS FEED INTO A EADER, THROUGH WHICH

THEIR ENERGY PASSES INTO THE MAIN AMPL|F|ER. THE MAIN AMPLIFIER THEN RA§

SES THE AMPLIFIED AuD|o CURRENTS THROUGH THE HUGE sPEAKERs,wH|cH ARE LO-

CATED BEHIND THE SCREEN upon WHICH THE PICTURE |s BEING PROJECTED. THE

SOUND THUS APPEARS TO THE AUDIENCE As COMING FROM THE REPRODUCTIONS on

THE SCREEN. A MONITOR HORN IS LOCATED IN THE BOOTH FOR THE 0PERATOR'S

USE.

To Amp]. Lamp___}

THE FILM IS RUN THROUGH THE Lhh£_¢°P :=;'t

PROJECTION MACHINE AT THE RATE or ' / 1 K :

90 FT- PER MINUTE AND |T IS ESSEN- M;"Or <1 _ W '5;

TIAL THAT TH|s SPEED BE KEPT CON— i 45) A

sTA~T,As oTHERw|sE THE PITCH OF _D~ ;u",_“

THE SOUND WILL CHANGE IN THE sAME ‘Q’ _ _ ,<

MANNER As WHEN THE sREEo or A F'HO§ ‘  D

OGRAPH TURNTABLE vAR|Es.As A RuLE, S:fl;_/

A LARGE FLYWHEEL IS DIRECTLY COUP- _

LED To THE FILM FEED SPROCKET FOR mg: AP¢'*W? PF*¢§' ’f

THE PURPOSE or INSURING A STEADY om“5"'!e“5

ROTATION or THIS sRRocKET,so THAT ;|G_|g

THE FILM WILL BE cARR|ED PAST THE

BEAM OF LIGHT FROM THEExc»TER LAMP

AT A CONSTANT SPEED-

Phnéo/:/mr/= /€¢¢ara’/Hg Dc»/ice.

THE PHOTOPHONE SYSTEM

Now LET us TURN OUR ATTENTION To THE PHOTOPHONE SYsTEM or“ souno

RECORDING ON FlLM- A SECTION or FILM, As usED ev TH|s svsTEM, IS SHOWN

IN F|c.15 AND As A wHoLE, IT IS QUITE s|M|LAR To THE Mov|EToNE FILM IN

THAT IT HAS A SOUND TRACK rm CONJUNCTION WITH THE PICTURE sTR|R.THE PHOI

OPHONE SOUND TRAEK, HowEvER, IS or THE CONSTANT DE~s|Tv,vAR|AELE w|DTH

TYPE AND THE DEGREE OF SHADING |s THE sAME BUT A VARIABLE PORTION OF THE

souuu TRACK IS DARKENED.

|N PRODUCING A PICTURE WITH THE PHoToPHoHE SYSTEM, THE MICROPHONE

PICK-UP, MONITORING, AMPLIFYING ETC- |s ALL CARRIED OUT IN THE sAME MAN£

ER As WITH EITHER DISC RECORDING OR Mov|ETo~E RECORDING. ALL or THEsE 51

STEMS DIFFER FROM EACHOTHER MATMLY AT THE RECORDING DEv|cE ITSELF AND

THE RECORD!NG UNIT, As usEo WITH PHoToRHo~E, as DIFFERENTFROM ANY so FAR

snow" vou. THE PHoToPHoHE RECORDER I5 CLASSIFIED As A VARIABLE AREA RE-

CORDER AHD IT IS DIAGRAMATICALLY ILLUSTRATED IN F|s.16.

fAsE IR souno PICTURES

THE RECORDING UNIT FOR THE PHOTOPHONE SYSTEM

WE coMMEncE In FIs.16 WITH oun SOURCE oF LIaMT,wMIcM IN THIS cAsE

Is A LAMP OPERATED AT HIGH BRILLIANCY FROM A 6 To 8 VOLT STORAGE BATT-

ERY. A SPHERICAL LEns "A" FocusEs THIS BEAM or LIGHT THROUGH A MoLE In

THE "LIGHT-STOP" WHICH SERVES As A FRAMING oEvIcE. TME BEAM or LIGMT,

WHICH PASSES Tnnoucn THE OPENING oF THE LIGHT-STOP Is DIRECTED TOWARDS

ANOTHER SPHERICAL LEns "B" Ano THIS LEns IN TURN FocusEs IT upon A

sMALL MIRROR, wMosE DIMENSIONS ARE AsouT V20 or An INCH on A sIoE.

TMIs MIRROR REFLECTS THE LIGHT BACK THROUGH LENS "B" AT An AncLE;

As snown av THE Annows, Ann THE BEAM Is THEN DIRECTED THROUGH THE sno-

ovE or A scALE uPon WHICH THE AMPLITuoE oF RECORDING cAn LATER BE MEAs-

uREo. THE LIGHT BEAM CONTINUES THROUGH A CYLINDRICAL LENS "C",A SPHER

IcAL LENS "D", Ano THENCE THROUGH A NARROW sLoT In THE APERTURE PLATE?

THE OBJECTIVE LENS GENERALLY MAs A REDUCTION RATIO or U TO 1, so

’V&ra%r ad_ £ L ITHAT IF TME_sLIT IN THE APER-

- J“‘ m="* TURE PLATE Is 0.320" av 0.00h",

Mfirc, TME IMAGE PRODUCED on TME FILM

a&uflHmn{ wILL as 0.080" av O.O01".TMAT Is,

THIS sMALL RECTANGLE or LIGHT u-

PON THE FILM WILL BE 0.080" LONG

(HORIZONTALLY wITM RESPECTTO THE

FILM) Ano 0.001" wIoE, Ano THIS

WILL PRODUCE A souno TRACK 0.080"

wIoE, WHICH Is cLosE To THE sTAn

DARD WIDTH USED IN PRACTICE.

,_AUDJD,MODULAI!ON WIT

1

P

m

x

H

I TME TInv MIRROR Is cEMEn-

;|G ;7' TED To Two sIoEs or A WIRE LOOP

,q,,,,',,y,,-,,,/,4qI,1,,-15,-r,¢,,;é;(,7/%/1¢@,¢,,,-,/a- Ano THIS WIRE LOOP Is STRETCHED

TAuT AT RIGHT AneLEs TO A MAG-

NETIC FIELD. THE Enos or THIS LOOP ARE CONNECTED To THE OUTPUT TERMIN-

ALs or THE RECORDING AMPLIFIER AND THEREFORE wMEn THE AuoIo FREQUENCY

CURRENTS FLow THROUGH THE LOOP, THE RESULTING VARIATIONS In ITs MAGNET-

Ic FIELD wILL REACT WITH THE PERMANENT MAGNETIC FIELo so As TO Faooucz

MoTIon. TME MOVING PART In THIS cAsE Is THE WIRE LOOP wITM ITS ATTAcMEo

MIRROR AND wITM TME LOOP TURNING BACK Ano FORTH on VIBRATING AsouT A

VERTICAL AxIs In DIRECT STEP WITH THE AuoIo FREQUENCY CURRENT VARIA-

TIONS THROUGH IT.

TME WIRE LOOP Is STRETCHED TO TME POINT WHERE THE RESONANT VIBRA-

TING FREQUENCY Is ABOUT 7000 cYcLEs. TMIs ENTIRE VIBRATING SYSTEM, con-

SISTING or TME LOOP WITH ITs M|RfioR, Is MOUNTED IN A cAsE CONTAINING A

DAMPING FLuIo, wMIcM Is GENERALLY A MIXTURE or CASTOR OIL Ano TuRPEn#

TINE. TME LENS "B" SERVES As THE wInnow 0F TME FLUID-FILLED CELL IN

wMIcM TME MIRROR IS MounTEo Ano THE FLUID Is CHANGED EVERY FEw MonTMs,

so THAT IT Is ALwAYs TRANSPARENT To THE LIGHT In THE THIN LAYER INTER-

POSED aETwEEn THE MIRROR Ann LEns "B". In REALLITY,TMIs DEVICE IS no-

THING MORE TMAn An oséILLocnAPM, WHICH Is A LABORATORY INSTRUMENT usEu

LESSON No.2 PAGE I5

FOR THE RECORDING OF ALTERNATING CURRENTS-

THE ARRANGEMENT I5 SLIGHTLY TILTED IN PRACTICE, so THAT THE LIGHT

REFLECTED av THE MIRROR WILL CONTINUE ALONG THE AXIS TOWARD THE FILM As

SHOWN m F|c-.16.

RECORDING WITH PHOTOPHONE SYSTEM

THE WHOLE SYSTEM IS LINED UP, SD THAT ONE EDGE OF THE HOLE IN THE

LIGHT STOP IS IMAGED IN THE MIDDLE OF THE SOUND TRACK ON THE FILM WHEN

THERE IS NO INPUT TO THE MICROPHONES AND WHEN THE MIRROR IS IN ITS NEU-

TRAL POSITION. IF THE FILM IS MOVED PAST THIS RECTANGULAR BEAM OF LIGHT

AT A CONSTANT SPEED OF 90 FT- PER MINUTE WITH NO SOUND IMPINGED UPON

THE RECORDING MICROPHONE, THEN THE RESULTING RECORD AFTER OEVELOPEMENT

WOULD APPEAR AS A DARK BAND ON THE SOUND NEGATIVE, COVERING HALF THE

WIDTH OF THE sounu TRACK.

Now WHEN THE H|cRoPHo~E,AH-

PLIFIER ETc. ARE IN 0PERATION,THE

AUDIO FREQUENCY CURRENTS WILLFLOW

THROUGH THE WIRE LOOP, THEREBY

CAUSING THE LOOP AND ITS ATTACHED

MIRROR To OSCILLATE ow ITS PIVOT-

TH|s MOVEMENT or THE MIRROR IS IN

DIRECT STEP WITH THE AUDIO FRE-

QUENCY CURRENTS FLOWING THRU THE

LOOP AND THE MIRROR WILL DEFLECT

THE BEAM RAPIDLY T0 ONE SIDE AND

THE OTHER,THUS CAUSING THE LIGHT

IMAGE ou THE FILM To VARY IN

WIDTH ACCORDING To THE AUDIO FRE-

QUENCIE5 WHICH ARE aznwe RECORDED.

THAT us, THE sounn TRACK WILL BE

OF VARIABLE WIDTH As ILLUSTRATED 7Z= (Em /e/e ,4>-sem/S/ea @¢¢=»—d=r_

IN F|s.‘I§. /0

FIG.15

THE HOUSING AND ADJUSTMENT DETAILS FOR THE MOVEMENT,WHlCH REC-

ORDS THE LIGHT VARIATIONS ON THE FILM, ARE SHOWN IN FIG-I7,WHEREA5 THE

MOVEMENT AND ITS ASSOCIATED APPARATUS IN THE COMPLETELY ASSEMBLED Hecog

DER IS snown IN F|a.18.

IT REQUIRES SKILL TO ADJUST THE VARIABLE AREA TYPE OF RECORDER AS

JUST DESCRIBED. THE WHOLE SYSTEM MUST

ATELY, SO THAT THE BEAM OF LIGHT WILL

I6- THIS I5 ACCOMPLISHED THROUGH THE

BE LINED UP AND FOCUSED ACCUR-

FOLLOW THE PATHS INDICATED IN FIG-

USE OF A SERIES OF ADJUSTING

SCREWS.

- THE WIRE LOOP IS ROTATED BY ONE OF THESE ADJUSTMENTS AND IT IS

SET, SO THAT THE LIGHT REFLECTED BY THE MIRROR COVERS JUST ONE-HALF OF

THE SOUND TRACK- THE EDGE OF THIS LIGHT BEAM WILL THEN COINCIDE WITH AN

INNER VERTICAL LINE ON THE SCALE, WHOSE POSITION IS SHOWN IN FIG. I6.

WITH THE SYSTEM BEING MODULATED, THE AMPLIFIER GAIN MUST BE SO ADJUSTED

THAT WITH THE MIRROR OSClLLATING’THE SPOT OF LIGHT SHOULD NOT EXTEND BE

PAGE I6

YOND

THEN

TONE QUALITY-

THE SCALE DURING THE LOUDEST PORTION or THE RECORDING- IF IT ooEs,

THE SYSTEM Is BEING "ovER-MonuLATEn$ WHICH CONDITION HILL sPoIL THE

IN RECORDING;THE PHOTOPHONE SYSTEM USES ONE MACHINE FOR PHOTOGRAPHY

AND A SEPARATE MACHINE FOR SOUND RECORDING, EACH HAVING ITS OWN FILM BUT

BEING SYNCHRONOUSLY DRIVEN. THE STARTING POINT OF EACH FILM IS MARKED;

AND THEY ARE THEN COMBINED INTO ONE DURING THE DEVELOPING PRQCES5;IN THE

SAME MANNER AS DESCRIBED RELATIVE TO THE MOVIETONE SYSTEM. HERE,TO0, THE

SOUND PRECEDES THE PICTURE BY ABOUT IH.5 INCHES; SO THAT THE THO WILL BE

REPRODUCED SIMULTANEOUSLY DURING PROJECTION OF THE FILM IN A THEATER.

IN THE PROJECTION OF SOUND AND SCENE WITH THE PHOTOPHONE SYSTEM;THE

sAHE PROCESSES ARE INVOLVEDAS DESCRIBED

THAT Is, THE SAME PROJECTOR cAN BE USED

ENERGY STRIKING THE PHOTO-CELL THROUGH

VARY IN PROPORTION To THE WIDTH or THE

THEN, SINCE THE HIQTH OF THE

AUDIO FREQUENCIES, THE LIGHT

RESPONDING FREQUENCIES; AND

CELL CURRENT. THEREFORE, BY

SPEAKER SYSTEM As USED HITH MovIEToNE,

RECORDING FROM PHoToPHoNE FILM-

EXAMINATION

VARIATIONS

RELATIVETO THE MOVIETONE SYSTEM.

FOR EITHER SYSTEM, BUT THE LIGHT

THE PHOTOPHONE SOUND TRACK, HILL

SOUND TRACK AT ANY GIVEN POINT.

SOUND TRACK VARIES ACCORDING TO THE RECORD

PASSED BY IT WILL VARY AT COR-

THE SAME IS TRUE VITH RESPECT TO THE PHOTO-

MEANS OF THE SAME SOUND AMPLIFYING AND

HE CAN ALSO REPRODUCE THE SOUND

QUESTIONS

LESSON NO. SP-2

Ir A BATTERY AND A SERIES RESISTOR ARE CONNECTED ACROSS

THE TERMINALS or A PHOTO-ELECTRIC CELL so THAT A PosITIvE

POTENTIAL Is IMPRESSED UPON THE ANooE or THIs PHOTO ELEC-

TRIC cELL, THEN UHAT occuns IF A LIGHT or INCREASING

INTENSITY Is DIRECTED UPON THE cATHonE or THE cELL?

WH|cH Is MORE sENs|TIvE,A VACUUM TYPE PHOTO-ELECTRIC cELL

on A GAS—FILLED PHoTo-ELEcTRIc EELL?

ls THE SOUND TRACK ON THE MovIEToNE FILM or THE coNsTANT

DENSITY AND VARIABLE HIuTH TYPE?

WHAT IS THE PURPOSE or THE LIGHT vALvE IN THE MovIEToNE

RECORDING SYSTEM?

WHAT IS THE EXCITER LAMP or A “souNo-0N-PILH" PROJECTOR

uszo Fon?

WHEN MAKING THE SOUND—0N—FlLM RECORDING; Is THE SOUND RE-

CORDED DIRECTLY UPON THE sAHE FILM wHIcH Is RECEIVING THE

"PIcTuRE"?

WHAT TYPE or souno TRACK Is USED ON THE PHoToPHoNE TYPE

FILM?

EXPLAIN How THE sounn cAN BE REPRODUCED DIRECTLY FROM THE

sounn FILM G'THE MovIEToNE SYSTEM ASRECORDING PROGRESSES?

How ARE THE SOUND MODULATIONS RECORDED on THE FILM or THE

PHoToPHoNE SYsTEH? -

CAN THE sAHE MOTION PICTURE PROJECTOR aE USED FOR THE RE-

PRODUCTION or SOUND AND scENE FROM EITHER A MovIEToNE on