Fundamentals of Television Systems. By- Kessler, Willz:.M J

Home , Broadcast transmitter, Carrier system, Color television, Stratovision, Television channel, Television station

REPOR TRESUMES ED 0200)I I. -7; EM DOD 232 FUNDAMENTALS OF TELEVISION SYSTEMS. BY- KESSLER, WILLZ:.M J. NATIONAL ASSN. OF EDUCATIONAL BROADCASTERS PUB DATE FEB 68 EORS PRICEMF-$0.50 HC-$3.28 80P.

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DESIGNED FOR A READER WITHOUT SPECIAL TECHNICAL KNOWLEDGE, THIS ILLUSTRATED RESOURCE PAPER EXPLAINS THE COMPONENTS OF A TELEVISION SYSTEM AND RELATES THEM TO THE COMPLETE SYSTEM. SUBJECTS DISCUSSED ARE THE FOLLOWING--STUDIO ORGANIZATION AND COMPATIBLE COLOR TELEVISION PRINCIPLES, WIRED AND RADIO TRANSMISSION SYSTEMS, DIRECT VIEW AND PROJECTION DISPLAY OF TELEVISION IMAGES, AND PHOTOGRAPHIC, DIRECT VIDEO, AND ELECTRON BEAM RECORDING. RADIO TRANSMISSION SYSTEMS DISCUSSED ARE VHF-UHF BROADCASTING AND TRANSLATORS, AIRBORNE AND STAELLITE TRANSMISSION, LASER TRANSMISSION, POINT-TO-POINT AND SATELLITE TRANSMISSION, LASER TRANSMISSION, POINT-TO-POINT FIXED SERVICE. APPENDICES INCLUDE A GLOSSARY AND A SHORT BIBLIOGRAPHY. (BB) Television Systems:

'16'..."1C U.S. DEPARTMENT OF HEALTH, EDUCATION & WELFARE

OFFICE Of EDUCATION

THIS DOCUMENT HAS BEEN REPRODUCED EXACTLY AS RECEIVED FROM THE

PERSON OR 0116FilIZATION ORIGINATING IT.POINTS OF VIEW OR OPINIONS

STATED DO NOT NECESSARILY REPRESENT OFFICIAL OFFICE Of EDUCATION

POSITION OR POLICY.

FUNDAMENTALS

TELEVISION SYSTEMS .

William J. Kessler, P. E. W. J. Kessler Associates Consulting Telecommunications Engineers Gainesville, Florida

February, 1968 TABLE OF CONTENTS

Page

444 Foreword 114

Introduction iv re Fundamentals of Television 1

The Studio Origination Facility 6

Compatible Color Television Principles 12

Transmission of Television Signals 16

Wired Systems 17

Radio Transmission Systems 22

1. VHF/UHF Broadcasting 23 2. VHF/UHF Translators 24 3. Airborne Transmission Systems 24 4. 2500 MegaHertz Instructional Television Fixed Service (ITFS) 26 5. Space Satellite Transmission Systems 30 6. Laser Transmission Systems 34 7. Point-to-Point Microwave Transmission Systems 34

Display of Television Images 40

Direct View Devices 40

Projection Systems 42

The Recording and Reproduction of Television Images and Signals . 49

Photographic Recording and Reproduction 49

Direct Video Signal Recording 51

Electron Beam Recording 56

Appendix A - Glossary of Terms 62

Appendix B - FCC Release, "Introduction to Instructional TVFixed Service" 69

Appendix C - Selected Bibliography 72

ii FOREWORD

This resource paper on the fundamentals oftelevision systems is an attempt to coverthe broad field of television in a brief, non- technical manner. The major topics to be discussed are:

1. The conversion of s:enes into televisionsignals suitable for wire or radio transmission;

2. Television signal tTansmission and distribution systems;

3. Television image di.;play or reproducingmethods; and

4. Television recording/reproducing methods.

The material presented is intended tobe a general treatment for the layman. Therefore, it is hoped that the knowledgeablereader will overlook the absence of a detailed treatmentof the more complex topics where such has been deliberately sacrificedin the interest of clarity and brevity.

The author is deeply grateful to thefollowing publications for the use of a few illustrationsin this paper:

Figure 7a Standards of Television Transmission,

Broadcasters, June 1964.

Figure 7b Television in Education, Sylvania, CiFfireirTMTe-177neepoilectronics, New Yorks New York.

Figures 10a 10b Ibid.

Figure 12 RCA Broadcast News.

Figure 18 Eidophor Sales Brochure.

Figure 19 RCA Catalog.

Figures 23 t 24 Ampex Booklet.

W. J. K.

iii INTRODUCTION

Ever since man learned to transmit sound overtelephone wires and radio systems, he dreamed of the day when hecould vac itrummit pictures to accompany the sound. After decades of technical evolution of numerous crude and relatively unsophisticated approaches tothe problem, the modern television system now inwidespread use was developed, it is the objective of this paper to offer a simple non-technicalexplanation of the essential components of a television systemand to relate those components to the complete system.

The fundamental building blocks of a completetelevision system consist of the following four elements:

1. The Origination Facility.

The basic function of the originationequipment is to convert the picture or scene into analogelectrical signal variations suitable for transmission overwire or radio circuits. In this paper the term, "radio,"will be used in the general sense to mean the transndssioaof intelli- gence -- either audio orvideo -- via electromagnatic radiations without the use of wires.

2. The Transmission Facility

The transmission facility may consist ofeither wires, in the form of a suitable coaxial cable, or awireless radio circuit to transport the pictureinformation 0.gra1s from the origination point to the destinationpoint or points.

3. TheReceticulail2FilitY The reception/display facility is thefinal link in the complete system and is, of course,the "black box with the cyclops' eye" which converts thereceived signals into an accurate representation ofthe picture or scene at the origination point.

iv 4. 12E11'2sac!ingilekroducing Facile

Although not necessarily an essential link in a television system per se, the recording and reproduction of pictures or television signals for subsequent use with a television system has become an essential narallei function at t!te origination. as ,11:11 as the destination, point.

Figure 1 illustrates a so-called "system flow diagram" which shows schematically the sequence in which the foul fundamental building blocks are put together to form a complete system.The usual supporting equipment necessary for operation of such a system -- power supplies, switchers, audio equipment, distribution amplifiers, etc. -- have been deliberately omitted in the interest of clarity.

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An easily understandable explanation of how a modern television system transmits pictures of images frcrm point A to point B (or multiple points) may be given by reviewing man's early attempts to transmit images over telephone wires.

One of these early attempts, devised by C. R. Carey of Boston in

1875, was, in essence, an electro-optical copy of the human eye. A mosaic of photocells (which convert light energy into electrical energy) corre- sponded to the retina of the human eye; the multi-conductor cable interconnecting the photocells and the light -bulb matrix. was an imitation of the optic nerve; and the light-bulb matrix (where the reproduced image appeared) corresvonded to the brain. Figure 2 illustrates this system, which may be labeled "s.multaneous" or "all-at-once," and the human eye

(retina, nerve and brain) model which inspired it.

In this elementary simultaneous television system light from the subject is focused by a lens to form an image on a bank or mosaic of photo- electric cells. Each photocell delivers an electrical current whose magni- tude is directly proportional to the amount of light incident on the photocell. This action is similar to the behavior of the rods and cones in the retina of the eye. which produce a neuron action potential, or "nerve current,'' when stimulated by light. The absence of light on the photocell mosaic corresponds to shadow areas in the image and no current iq produced in these areas. Conversely, the brightest highlight in the image produces

-1- maximum current output. A separate pair of wires, or circuit (onefor each photocell and corresponding lamp), is required to connect eachphoto- cell to a lamp which occupies the save relative position inthe image- producing matrix. The early Carey system, although quite workable, ex-

hibits at least two obvious limitations: 1) a very large number of minia-

ture photocells at the c_igination point and lamps atthe receiving point

(approximately 100,000 or more) would be required to reproduce animage

of acceptable detail; and 2) a separate circuit is requiredfor each photo

cell-lamp to transmit the electrical signal levels corresponding tothe

shadows and 1,4ghlights of each part of the picture.

A giant step forward was taken when earlyinvestigators substituted

a single circuit, such as onepair of wires or a coaxial cable, for the

huge multi-conductor cable by pressing into use anotherwell-kmown prop-

erty of the human eye -- the persistenceof vision. Because of this

characteristic -- the ability of the retina-brain system to storestimuli

for short periods of time -- it is not actually necessary totransmit all

of the picture elements simultaneously.Thus, it is possible to transmit

the individual picture elements in sequence over a singlecircuit. It is

necessary only tc display the receivedpicture elements in the same se-

quence of transmission in the properposition in the receiver mosaic.

This must be done rapidly enough so that the eye sees allof the indi-

vidual elements as a complete picture,

This storage property of the eye is readilydemonstrated by project-

ing a light beam on a darkened wall or screen andrapidly moving the beam

from side to side.Thus, one sees a horizontal line instead of whatit

really is -- a rapidly moving spot of light. This simple well-known opti-

cal phenomenon is the fundamental basis of moderntelevision.

-3- Figure 3 illustrates a modificationin the original simultaneous system shown in Figure 2when the multi- conductor cableis replaced by a

the originating end of the co- single coaxial cable. By rapidly switching connecting axial line consecutively toeach photocell and synchronously corresponding lamp in the receiving end of thesingle coaxial line to each

complete image on the lamp mosaic, the eye canbe deceived into seeing a

cycle must be completed in the lamp bank. However, the complete switching The sequence a space oftime less than the persistenceof vision interval. and image - described in this illustrationis the rapid image dissection reconstitution achieved through ahigh-speed sampling or scanning technique. principle of This high-speed samplingtechnique is the fundamental picture elements in a systematic modern television: rapidly scanning the variation corresponding to manner, transmittingthe electrical current and the recon- each picture element sequentially overa single channel, at the re- version of the receiver currentvariations into might elements

ceiver to reproduce the picture. de- Hower final refinement ofproducing pictures of adequate be examined. This tail, or resolution, in apractical manner remains to

is accomplished by ahighly mobile electronbeam of very small diameter

in the modern camera pickuptube. 1.11go.pw. IISIOLOMMINIG111111.11111111E.011.11111111111.1.11111MENNM 41410111!

ININANIMINWIFINWPWAY1011.7.10.11.MOIW..SII TIE STUDIO ORIGINATION FACILITY

In the television studio, where the origination facility is located,

the scene to be transmitted must be converted to electrical signals suit-

able for wire or radio transmission to the destination point (reception/

display) so that these signals can be converted into a replica of the

studio scene by the television mo;:itor or receiver. This is the function of the television camera.

In a modern television camera, the crude, coarse-grained mosaic of photocells is replaced by a pickup tube which contains either a single photo-conductive plate (vidicon type) or a photo-emissive surface (imageorthicon type).

The scene to be transmitted is projected optically by a lens onto

this plate to form either an optical (vidicon) or an electron (image-

orthicon) image as shown in Figure 4.

Every part of this image is then sampled in a precise systematic manner by a very thin stream of electrons known as an electron beam.

This systematic process of sampling is known as "scanning." The scanning

pattern is from left to right and from top to bottom in a manner identical

to the movement of the eye as this page is read. In order to permit the

transmission of motion smoothly, the process is repeated (or the image is

scanned) 30 times per second.

the rate at which the complete picture is sampled, or scanned, brings

up the question of picture flicker, which was a common problem in early

motion pictures as well as in many home movies today.At the light

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Television faces a similar flicker problem. Thirty complete scans per second are inadequate to avoid all sensation of flicker for the viewer at high light levels. Increasing the scan rate would also increase the frequency spectrum space, or bandwidth, which would needlessly waste a valuable limited ccmmodity by reducing the numbers of channels available to one-half of what we now have. Therefore, television systems make use of a technique that doubles the apparent flicker vate without doubling the spectrum space requirement by modifying the scanning pattern. Thus, instead of scanning from left to right and down as writing is scanned bythe eye in the normal reading process, the scanning patternis alternated as shown in Figure 5.

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It should be noted here that television broadcast transmission requires the use of one 2:1 locked interlace. Many industrial television cameras, intended for closed-circuit application, make use of what is termed "random interlace." In random interlace the scan for the second field frequently overlaps the first, thus reducing the vertical detail rendition (or vertical resolution) to one-half of that obtainable with locked 2:1 interlace for short periods of time.

A great deal more could be written about television cameras and associated studio origination equipment. At this point, it is only necessary to recognize that the television camera is merely a "black box" which converts the image to be reproduced at a remote location into a sequential electrical signal suitable for wire or radio electrical radiation transmission. An alternate, and more sophisticated, view is that the camera serves to convert a changing three-dimensional scene (two space dimensions and one time dimension) into a two-dimensional variable

(video signal amplitude and time) so that it becomes suitable for wire or radio transmission.

-10- However, before proceeding to thevarious methods of transmitting

serialized picture or distributingthis electrical signal representing information, it Toy be 14011to comp: re sane of the essentialchPracter- istics of television cameras employingvidicon cr image orthicon pickup

tubes. A brief and concise,although non-quantitative, corparisonof the significant operating characteristicsis made in Table I.

Vidicon (1") Thbe Characteristic Image Orthicon (311f

Light Sensitivity Good Inferior to Image Orthicon

Speed of Response Cod Noticeable Smear Good Grey Scale Rendition Poor

LPu Noise Level High

High Light Level Tolerance Easily Damagtd Rugged 10,000 hrs. Life Expectancy 5820 8093AL 1,000 hrs. STOTRii.

$250.00 Replacement Cost $1,000,00$1,800.00

Table I

This discussion would be incompletewithout a brief statement regard-

the ing a new second-generation typeof vidicon pickup tube known as

plumbicon.

The plumbicon has been publicized as a newpickup tube exhibiting

many of the advantagesof image orthicons andvidicons. The plumbicon, of in essence, employs a photo-conductivelayer of lead monoxide instead

1) high speed of re- selenium. The chief advantages of plumbicons are:

sponse and, hence, morefreedom from smearing ofhighlights; 2) improved resolution; and 3) good light sensitivity. Plumbicon tubes show a very linear light sensitivity characteristic and,thus, require gradation (tonal

range) correction circuits when used inblack and white cameras. Plumbi- cons have also attainedwidespread use la the newer color cameras.

2g2121le Color Television Principles

In recent years compatible color has literallyexploded on the commercial television scene. It is little wonder that educational,community,

industrial and medical groups are considering the useof color television

as a nme effectivecornnunicationr medium. Compatible color television

means, of course, that the additionalelectrical signals which convey

color information can be successfully combined withthe black and white

signals without demanding additional frequency spectrum space, or band-

width, within the assigned television channel. It also means that exist-

ing black and white receivers can provide an undegraded picturewhen a

color signal is available, and that the color receiver willproduce a

black and white picture when only a black and white signal is available.

The system designer can meet these requirements in a number of ways.

It is well known that white light can be produced by mixing red, greenand

blue in a particular proportion and that any other color can be obtained

by mixing these colors of light in other appropriate proportions. In tlis

case red, green and blue are known as "primarycolors." However, it is

not universally recognized that red, green and blue are not uniqueprimary

colors in that any other three colors may be used if they occupy the same

relative position in the Maxwell Color Triangle. Even less well known is

the fact that one of the primary colors may -4 white light provided the

other two primary colors are reddish orange and reddish purple (magenta).

-12- Thus, the compatible color transmission system uses these threeprimary colors; white (including the absence of white, orblack) is represented by the luminance component labeled "Y", reddish orange the"I" component, and magenta the "Q" component. The I and Q components are referred to as the chroma signal and may be negative as well aspositive in a color television system.

When a color signal is available, the color receiverresponds to all three components, Y (black and white), I(reddish orange) and Q (magenta) to reproduce scenes exhibitingthe entire color spectrum while the black and white set simply ignores the I and Qchroma components (since it has no circuits capable ofhandling the chroma signals) and utilizesthe black nTIO white Y romponent only to produce a goodblacl and white picture.

When only a black and white signal is available,the I and Q (chroma) circuits in the color receiver are idlesince the I and Q signals are not present and the set responds tothe conventional black and white signal

(Y component) and produces a blackand white picture. In this case the black and white picture is reproducedby the appropriate mixture of red, green and blue.The conventional black andwhite set produces a black and white picture with either a monochrome orcolor signal. The four combinations possible with the two types ofreceivers and two types of signals are illustrated inFigure 6. It may be noted that the Y, orluminance, component is the commondenominator of all four possibilities.

The modern color camera is actuallythree cameras in one, each of which responds to one of the familiarprimary colors -- red, green and

obtained from three separate blue. The red, green and blue outputs are pickup tubes equipped with either ared, green or blue filter through which the image is projected intoeach pickup tube. The electrical

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-14- signal 411ch represent the red, green and blue, are then converted in a c' it called the "encoder" to the Y, I and Q primaries to provide a compatible black and white color signal suitable for transmission and display on either a black and white or color receiver.The color receiver also includes a "decoder" circuit which converts the Y, I and Q components back into the original red, green and blue primaries to reproduce the original scene in color on the face of the tri-color picturetube.

Some available color cameras are essentially four cameras in one -- a conventional black and white camerapickup tube as well as a red, green and blue camera pickup tube.

In these typ'- the conventional black and white channelprovides the luminous (Y) Chat. L directly and the red, greenand blue outputs are used to provide the I and Q components inthe encoder.These four channel cameras may include an imageorthicon tube for the black and white channel and vidicon or piumbicon tubes for the red, greenand blue channels.

Other combinations of orthicons, vidicons andplumbicons are also in use.

-15- TRANSMISSION OF TELEVISION SIGNALS

Since the basic objective of television is to reproduce images and associated sound virtually instantaneously at distant locations, the transmission of the electrical signals corresponding to the pictureinformation is an essential link in the complete system.Two fundamental methods are available: 1) wired systems in which the audio and video signals are conducted from the point of origin to the destination point or points ane

2) radio systems in which the video and audio signals are combined and converted to a form suitable for radiation as electromagnetic waves (radio in its general meaning) in all directions (broadcasting) or to a single specific location (point-to-point transmissinn).

Both wired and radio systems must exhibit a given minimum transmission bandwidth (frequency response) expressed in cycles per second, or Hz., an abbreviation for Hertz, which is a term for bandwidth recently adopted in the United States to conform with international usage. Bandwidth is simply the arithmetic difference between the lowest and the highest frequency of the electrical signal used to represent a television image to be transmitted.

Because of the high picture detail content and the rapid ryte (30 complete pictures, or frames, per second) at which the picture information is

transmitted to provide the illusion of smooth motion, a relatively broad

frequency response or bandwidth requirement is imposed on any television

transmission system. The video bandwidth requirements are directly re-

lated to the picture detail, or line resolution, required in the reproduced

-16- image. These parameters are related in Figures 7aand 7b. The United

States broadcast standards, which are acompromise between acceptable picture detail and bandwidthconservation, have limited the maximumfrequency of the video bandwidth to slightlyless than 4.5 megaHertz, or. MHz. A video bandwidth of about 4.2 MHz isthe practical limit to avoidinterfer- ence between the pictureand sound signals.

The lower frequency limit isestablished by the frame frequencyof

frequency range re- 30 frames per second.This brings the transmission quirement to the range from 30 Hz. to4.2 MHz.

into per- As a means of bringing awide frequency range of 4.2 MHz qualities of spective, it may be compared tothe requirements for various speech and music transmission.

Telephone quality speechtransmission requites a rangeof approxi- of 4,200,000 Hz. is the mately 3,000 Hz. The television requirement equivalent of 1,400 voice circuits! approximately 5,000 An AM radio broadcastingnetwork requirement is

Hz. The 4,200,000 Hz. is equal to840 AM network programs! Hz. The high-fidelity FM broadcastingnetwork requirement is 15,000

retwork programs! The television requirementis equal to 280 r.M

Wired Systems cable, shown in Figure 8, A special conductorknown as the coaxial significant distance is required to pipe atelevision program over any By using spe- without serious degradationand weakening of thesignal. "squeezed" through cial equalizing networkstelevision signals may be limited dis- ordinary telephone lines olparallel conductors over very

tances !,,f a few cityblocks.

-17- 258304' c44 200- - IA A 20 15 Q.Ix The type you can rij 2zcritt 300 read at any place on 2 /AAf . 10 3 crr- thisindicateson a chart, the as horizontal seen television screen, FRANCE 5 IA'2d 400-- capableresolution of producing. the system As you is 10 01R-CC IR von-AvArIrmiorm A 500 cantheline linessee, for theat the left letters which matches duplicate thickness of _ UNITED STATES A.11"'rfflfilfil AIIIII All I 700600 -- theseresolutioncastlution reception used charts. ranging on will Standardstandard normallyfrom 275 reso-to 325, achievebroad- CO 4 /rill 800 cameraswhile video and monitors resolution can be on as properlyhigh as 800 tuned lines. IF POSSIBLE 2 GREATBRITAIN I 1 r SLOW-SCANRESOLUTIONHIGHSYSTEM - (b) I I 200 SCANNING STANDARD IN LINES PER 400 GOO 800 1000 FRAME (N) 2000 I PteOP_E letelve..mrent7,3,-,-"Crl,:r2 c8 314 (1 1.1 A,* MOMS, In fact, amplifiers to overcome the losses introduced by coaxial cables and cable equalizing networks must be placed at frequent intervals even with a coaxial line system.

With suitable terminal and line amplifier equipment, coaxial cables are capable of transmittingsignals from a frequency of zero Hz. (direct current) to a practical upper limit of 10,000 million Hz.!

Coaxial cable transmission systems fall into two basic categories -- direct and carrier transmission.

Direct cable transmission involves the transmission of video signals in the raw form as they emerge from the originating studio.Only the frequency range from 30 Hz. to 4.2 MHz isemployed. The associated audio portion is usually transmitted over a pair of ordinary telephone wires generally following the same geographical routes as the coaxialcable.

The direct coaxial transmission method can transmit only one program at a time, requires a separate telephone linefor the associated audio,

and does not take full advantage of the transmission capability of co-

axial cables.

The carrier transmission method involves themixing, or combining,

of the raw video and audio signals originating in the studiowith a third

signal of a specific frequency referred to as "the carrier."The equip-

ment used in his process is about the size of twoordinary shoe boxes

(or one breadbox!) and is a miniature television transmittingstation

which usually delivers a maximum pnwer output of about threemilliwatts.

The carrier frequency may be selected to operate C71 any oneof the regular

VHF or UHF channel assignments which permits the useof standard televi-

sion receivers along the cable. This is illustrated in Figure 9.

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'"""'"*"..."."..".10*Wr " *Si i;;;;Ak1450 ik44.3.;411.0660' `40011MaXIAvmshivoom since the No FCC licensing is requiredin the broadcasting sense

broadcast, but merely miniature transmitter outputis not radiated, or By guided along the interior ofthe coaxial cable tospecific locations. avoid spacing a number of such carrierfrequencies far enough apart to

assignment, for cicample), mutual interference (everyVHF television channel

be transmitted tk) twelve separate programs(both picture and sound) may Any ona of the programs any number of remotelocations simultaneously, the channel selector of a ronven- may be selectedfor viewing by changing

tional television set connectedto the cable.

Carrier cable transmission systems,often referred to as "RF systems," Two obvious features of are widely usedfor closed-circuitapplications. coaxial cable such a system are the multiplechannel capability over one the associated audio and no need for separatetelephone lines to transmit

channel. cable system is One well-known commercialapplication of the carrier

the CATV, or Community AntennaTelevision Systems.

Radio Transmission Systems classifications: Radio transmission systemsfall into the following

1. VHF/UHF broadcasting

2. VHF/UHF translators

3. Airborne systems (MPATI)

television fixed service(FIFS) 4. 2500 Miz instructional

systems -- orbitingand synchronous S. Space satellite transmission

6. Laser transmission systems studio to transmitterlinks 7. Point-to-point microwave systems -- (STL) aad inter-city links

-22- 1. VHF/UHF Broadcasting

VHF and UHF television broadcasting is, of course, very well known.

Therefore, no detailed description is presented in this treatment other

than to summarize a few of the pertinent facts in Table II.

Channel Channel Frequency Max. Auth. Approximate Charact-ftistics Number Range in MHz ERP in KW Service Range

Low VHF 2 54-60 100 65 If 3 60-66 II II 4 66-72 II II If 5 76-82 It 6 82-88 If If High VHF 7 174-180 316 55 II 8 180-186 ft ft 9 186-192 II ft II 10 192-198 it fi It 11 198-204 II II 12 204-210 II II 13 210-216 II 40 Low UHF 14-40 470-632 5000 40 High UHF 41-83 632-890 5000 30

Table II

OM^

Channel I is missing because the frequency range originally allocated to it (48-54 MHz) was preempted during the early days of television for use by a military high-power ionospheric scatter communications system.

It may be observed that, while the channel numbers are consecutive, the corresponding frequency ranges are not.For example, there is a 4 MHz gap between channels 4 and 5, an 86MHz gap between channels 6 and 7, and a 254 MHz gap between channels13 and 14. These frequcncy gaps are occupied by other communications services such asaeronautical/navigational communications systems, FM broadcasting, and mobile two-wayradio (land based).

Table II also shows that the frequency interval, orbandwidth, for each channel is 6 MHz Wide.Although less than 4.5 MHz is required for

-23- the picture signal, the remaining 1.5 MHz is allocated to the program sound channel and so-called "guard bands" to eliminate interferencebetween the picture and sound signals, as well as adjacent televisionchannels.

A glance at the last column in the table shows theapproximate service range in miles. This column should not be interpreted to mean that the service is perfect for all distances from thetransmitter less than the quoted service range and that no service is provided beyondthe quoted service range. It does mean, however, that less than 50% of thereceivers outside this contour are receiving satisfactory serviceand that the per- centage begins to drop rapidly as thedistance increases.

2. VHF/UHF Translators

Quite often, due to unusual terrain characteristics orpopulation distribution, an economical means of filling in, orextending, the coverage area of a high-power VHF or UHFstation is desirable.

A practical and economical means of providingsuch additional "spot coverage" of a parent station is by means of low-powersatellite stations called translators. Translators are unique in that they merely "trans- late" the frequency of the parent transmitter toanother channel to permit rebroadcasting the program on a very low powerof either 1, 10 or

100 watts. In this way the low-power translatorprovides a strong signal to the receivers in the weak-signal areabecause of the close proximity of the translator to the television receiversserved.

Translators may be used to rebroadcast VHFstations on either VHF or

UHF, as well as for the rebroadcast of UHFstations on UHF.

3. Airborne Transmission Systems

One of the major factors which limit theuseful service range of a

conventional ground based television broadcasttransmitter is the general

-24- weakening of the signal caused by energy absorption along the transmitter-

tc-receiver paths.

During the early days of commercial television, the Westinghouse

Electric Corporation engineers proposed an idea in which the television

transmitter would be airborne to high altitudes so that all the

transmitter-to-receiver paths would be unobstructed.The airborne system was called "stratovision" and was expected to provideservice ranges ap- proaching 200 miles in all directions using transmitter powers less than

that of its ground-based brothers. The idea -- which was an imaginative one -- just didn't seem to "get off theground" until September 1961. In

that year the Midwest Program on Airborne Television Instruction (MPATI) began its first full academic year.

In the MPATI system instructional program material is broadcast

simultaneously on UHF channels 72 and 76 to schools and classroomswithin

a 200-mile radius from a modified DC-6aircraft executing a figure eight pattern at 23,000 feet over Montpelier, Indiana.

The DC-6 aircraft is equipped with a 24-foot streamlinedretractable

antenna which can be lowered from the bottomof the aircraft in flight.

The antenna is gyro stabilized so that its verticalposition with respect

to the earth's surface can be maintained asthe aircraft executes the

figure eight pattern. Two fully equipped DC-6 aircraft are available, one being on a standby basis.

Each school participating in the MPATI program usesUHF converters with individual antennas oriented toward the generalposition of the air-

craft over Montpelier. If a closed-circuit distribution system is avail-

able at a given school, the received programis converted to a VHF channel

for in-building distribution to each classroom.

-25- Even though the aircraft broadcasts programs from an altitude of over 4 miles, direct in-school receptiondifficulties have been experienced in the larger metropolitan areas of Cleveland, Chicago and Detroit.

Accordingly, supplementary UHF translator facilities have been placed into operation in the weak signal areas. Reception difficulties have also beel experienced directly beneath the position of theaircraft due to the reduced energy radiation from the end of its antenna.

In January 1963 MPATI filed a request with the FCC for a license to operate as a regular airborne service of the instructionaltelevision system on six channels simultanecisly.After numerous statements were made uoth in support and opposition to the MPATI proposal, the FCCin March

1966 granted MPATI the authority to operate six channels in the new2500-

2690 megaHertz instructional television fixed service it hadestablished in September 1963.

4. 2500 MegaHertz Instructional Television Fixed Service (ITFS)

For some time educators, industry representatives and the FCChave recognized the need for additional channels dedicated to the use ofin- school instructional television. In response to this need the FCC established a. new service in the 2500-2690 MHz frequency rangewhich provide:: a total of 31 television channels for this purpose.

The 2500 megallertz system is unique in a number of respects:

a. It is a multiple-addressed fixed service rather than a broadcast system and, as such, exhibits many legal and technical features of closed-circuit systems.

b. The system combines many of the best features of point- to-point microwave systems with the operating standards of VHF/UHF broadcasting so that regular VHF receivers may be used in the classrooms.

-26- c. The allocations plan provides for a group of four channels to be assigned to a qualified applicant.

d. The receiving "down-converter," which changes the microwave signal into the VHF signal, convertsthe entire four channel group together so that only 2500 plegaHertz transmitters may be used, as needed, to meet the additional channel requirements.

e. The permissible power output of 2500 megaHertz transmitters, while not specifically limited for all applicants, has been nominally fixed at 10 watts toprovide a restricted coverage radius sothat the same channel groups could be reassigned toadjacent geographical areas without seriousinterference effects.

f. No rigid specifications regarding fixed co-channeland adjacent-channel mileage requirements between transmitter installations were made. The allocation of specific channels is based instead on reasonable channelinter- ference criteria, taking into consideration intervening terrain between systems, directional antennasand all other known interference-reducing techniques.,

One of the most important aspects of 2500 megaHertzsystems is the fact that, although the channels were establishedexclusively for educa- ticr 11 purposes, their use is not restricted toin-class instructional use. The service may also be used for teacher trainingand school administrative functions.

The complete instructional system consistsof four basic units: a) the originating studio facilities,which are essentially identical to the studio requirements of VHF/UHFbroadcasting; b) the 2500 megaHertz multiple point-to-point transmission systems,including all the outlying down-converters; c) the in-school coaxial cabledistribution system interconnecting the down-converter to the classroomreceivers; and d) the classroom television sets which areconventional VHF/UHF receivers which permit selec .Lon of any availablechannel.

The basic layout for a complete 2500 megaHertzITFS system is shown in Figures 10a and 101). It will be observed that in such a systemthe

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A copy of the original FCC release giving an authoritative description of ITFS is reproduced in Appendix B. Included alsc) is a brief description of a nationwide committee established by the FCC for the full development of the Instructional Television Fixed Service.

5. Space Satellite Transmission Systems

Space satellite transmission systems (perhaps more accuratelylabeled

"relay systems ") constitute the most modern approach to the problemof providing a 'Nigh-altitude low-power transmitter to extend theuseful service range over vast areas of the earth's surface.

Space satellite transmitters fail into two basiccategories: orbit-

ingsatellites and synchronous satellites.

The orbiting satellite, when used as a space relayplatform, is

equipped with a compact relay system capable ofreceiving television sig-

nals from any one point on the earth withinvisual range and rebroadcasting

with a power level of about 100 to 200 watts toelaborate ground stations

located at other parts of the world. The orbits of such space satellite

relays are usually at altitudes of 1,000miles or more. However, due to

the orbiting nature of these relay stations,their position with respect

to the fixed ground station isconstantly changing, which requireselabo-

rate antenna tracking equipment atthe ground sLation. Furthermore, as a

given satellite relay moves out of rangeof a given area as it orbits the

earth, another satellite must move intoposition to provide continuous re-

lay service. The operation of a system oforbiting satellites to provide

-30- continuous service is illustrated in Figure 11. It is estimated that from five to ten relay satellites would be required for uninterrupted service.

Telstar, the first privately owned satellite, was constructedby the

American Telephone and Telegraph Company and launched on July 10, 1962, by the N.,tinnal Aeronautical and Snace Agency,

Many of the problems of orbiting satellites can be overcome by launching the relay satellite into a higher altitude orbit so that the rotational period increases from about 90 minutes to precisely 24 hours.

In this way the relay satellite appears to be stationary since itis orbiting at the same rate as any fixed location on the earth's surface.

Such satellites are labeled "synchronous satellites." The critical a]ti- tude at which synchronism with the earth rotation occurs isapproximately

22,300 miles.With such a synchronous relay satellite, not only is the tracking problem of the ground station antenna eliminated, butthe coverage area is increased to about one-thirdof the earth's surface. In this way only three satellites arerequired to provide a worldwide transmission system. This is illustrated in Figure 12.

There is little question among knowledgeable authorities that relay satellites of the synchronous, or stationary, class constitutethe answer to a future worldwide relay system for all typesof communications services.

It should be noted, however, that at the present stageof development,

individual home receivers cannot receive satellite transmissionsdirectly due to the rather weak signals available from the distant low-powersatel-

lite, There is little doubt that this is only a temporary hurdlewhich will be surmounted eventually -- perhaps sooner than mLnyauthorities now

believe. MOON I no,rmF''lh"1 : °IF:. ;t: .: s, c:,,. ;,,, ,. r,;. . C"' 1, ` i^^ :! ntV_ ,' 1" " a+;' "' Ccr1*. ii,'?' , tR"*' ,""' a:;. !' tYt w"!'^ t,!' !!' lS :If,".+,t""t40.4.`'ll r..1'' 6. Laser Transmission Systems

A laser transmission system may be regarded as just another point-

to-point carrier system where the carrier frequency is high enough to fall

in the visible portion of the electromaanetie Laser beams are a different kind of light source because they are generated in a special way and because they attaia an extremely high degree of cr.-for purity (ca-

light) and high intensity.

Only recently have techniques been developed to modulate (or mix) the picture and sound signals with the laser energy so that the laser beam can be used as a point-to-point television transmission system.Laser beams, which are optical in nature, will not readily go around obstructions and

are weakened by cloud banks and heavy moisture.

Laser transmission systems hold great promise in outer space where

there is no atmosphere, no clouds and no fixed obstructions to weaken the

beam. The laser beam, because of its very high operating frequency, ex-

hibits tremendous bandwidth characteristics and, hence, is capable of

handling a phenomenal number of simultaneous television channels as well

as other communication circuits.

However, laser transmission systems have not yet fulfilled their promise for widespread terrestrial communication applications.

7. Point-to-Point Microwave Transmission Systems

Point-to-point microwave systems belong to the category of radio

transmission systems. They differ, however, in two important respects:

a) point-to-point microwave systems are intended solely for the purpose

of interconnecting originating points and broadcasting stations,and to

provide high-quality closed-circuit links between specific locationsand

-34- b) modulation standards and allocated channel spectrum widths have been chosen to provide the highest possible transmission characteristicsso that the interconnecting links contribve essentiallyno degradation to the reproduced image.

Point - to -point microwave systems fall into two general classifications -- studio-to-transmitter links and multi-hop inter-city links.

Studio-to-transmitter links (STL) are usually one-hop links which pm- vide for the transmission of the picture and sound program from the originating studio to the broadcasting plant.

Microwave systems always employ parabolic reflecting transmitting and receiving antennas so that the transmitted microwave energy, which serves as the picture/sound information carrier, can be focused into a sharp beam towards the receiving antenna.

Quite often a periscope technique is used in which the parabolic antenna (referred to as a "dish") is oriented so that the beam is vertical and a flat metal plate installed at the top acts as a reflector to change the direction of the beam.These two methods, with and without the passive reflector, are shown in Figure 13.

Multi-hop microwave links, whether used for inter-city STL purposes or closed-circuit interconnections, employ relay stations spaced an aver- age distance of about 25 miles apart, as shown in Figure 14.

When the total system is less than, about 100 miles, so that a maximum of three relay stations are required, the relay station mayconsist of a microwave receiver connected directly to the input of a microwave transmitter.Such a relay is called "back-to-back" and invariably introduces degradation of the signal available at the end of the system.

When the length of the inter-city relay system exceeds 100 miles

(or is transcontinental, such as the American Telephone and Telegraph

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Ifee,46.11 Company's TD-2 microwave system, which involves alarge number of hops), heterodyne type of relay equipment is employed.

The essential difference between theback-to-back and heterodyne relay is that all unnecessary processing o2 thetelevision signal is eliminated by converting, or translating, thefrequency of the weak in- coming signal before amplification to a higher powerlevel and retrans- mitting. The more elementary back-to-back equipmentemploys the same type of equipment located at theterminals of the system and uses demodu- lators connected directly to modulators. This introduces unnecessary signal handling and, hence, signal degradation.

Point-to-point microwave systems utilize thefrequency modulation

(FM) method of imposing the video signals onthe microwave carrier. This utilization takes advantage of the superiortransmission properties of

this system when coupled with the availabilityof spectrum space greater

than 6 Nfiz per channel. The program sound channels are usually transmitted on the same carrier by a multiplexingtechnique, which uses a sub-

carrier, W permit the separation of thevideo and audio at the receiving

end of the relay system.

The following frequency ranges and radiofrequency (RF) bandwidths

are available for non-commoncarrier television use:

Band A -- Ten channels, each 17 MHz wide,between 1900 MHz and 2110 MHz (not continums)

Band B -- Ten channel:, each 25 MHz wide,between 6875 MHz and 7025 MHz

Band C Tenty-two -.flannels, each 25 MHz wide,between 12,700 MHz and 13,250 MHz

Additional microwave channel assignments in thebands 17,700 MHz-

19,300 NEz, 19,400 MHz-19,700 MHz, 27,525Nix-31,300 MHz and 38,600 MHz-

-38- 40,000 ME: are available on a case-to-case basis. Channel bandwidth and

carrier frequency stability tolerances are to be specified in the indivi-

Cludl duLnorihdLionb. Microwave equipment for t levision purposes operating rj above 17,000 MHz is not available commercially at this writing.

r--

-39- DISPLAY OF TELEVISION IMAGES

The last link in the complete television system chainis the display of the reproduced images and accompanying sound atthe final destination point, or points. The fidelity with which the original images and sound are reproduced in the displaydevices depends on the picture and sound fidelity of the entire system.

Television display devices may be classified as: direct view devices

(video monitors and RF monitors or receivers) andprojection systems

(Schmidt optics projectors and the Eidophorprojector).

Direct View. Devices

The most important element in theteleision direct-view display device is the cathode-ray picture tube. The essential components of a cathode-Tay tube (CRT), illustrated inFigure 15, are a large glass en- velope having ashort neckto house the source ofelectrons and a beam- forming assembly known as an electron gun.Magnetic deflecting coils are placed around the neck of the tube todeflect the electron beam in a systematic mannertoproduce the scanning pattern.The scanning electron beam is projected toward the largeflat end of the tube whichbecomes the

image viewing surface. The inside of this flatviewing surface is coated with a material called a phosphorwhich glows or emits lightwhen the elec-

undeflected, the beam will tron beam strikes it. If the electron beam is of light. strike the center of the face plateand produce only a pin-point and downward to produce If the beam is deflectedrapidly from side to side

-40- mimmiammmm lwrImmeimMoVrit,VMffe koavzoarki- DePLec.-TioN VeicrtCAL cok_s 1ZASTE:z._ INIPIITGR.Ii> -ToUNI CoNlIZOL- et_sCriZoN Got.)VtDEo F),NAL GLASS FACE PLATE IMAGE-PL-Pcs Ots -DAR.14- Ag.ek T--leoDOCGD ASTER_, II -Pkty?eR_. 13RAGr1T

swawwdor.Nasexes.varsiaug116031414:WONNIAWM6101.15 the 4esired scanning pattern, the eye is deceivedinto seeing a uniformly illuminated rectangular area of light called a"raster."If the iptensity of the beam is rnntrnlled, or modulated, by the received video signalby applying the video signal to the appropriate elementof the electron gun

(the control grid input), the raster willexhibit bright and dark areas

across the face plate. Further, if the scanning pattern of the electron beam is identical to the scanning pattern emittedby the television camera

tube (that is, in lockstep or synchronization),the bright and dark areas will appear in the correct geometric position toproduce an image which

is a replica of the scene before the distant camera. Thus, the electron

beam literally "paints" a complete light image30 times each second. The

complete package consisting of the pictureCRT, video amplifiers, focus,

brightness and other controls, power supply andenclosure corLstitute the

complete video monitor. The sound reproducer is usually a separateaudio

amplifier and speaker.

The RF monitor, or television receiver, isvirtually identical to the

video monitor except that it has a radio tunerequipped with a channel

selector knob so that the video signal canbe delivered to the display CRT

from a selection of broadcast stations operatingin the area. The RF

monitor is usually provided with an integralsound reproducing (amplifier

and speaker) facility.

Video monitors rather than RF monitors are generallyused in televi-

sion studios and in conjunction with a videoclosed-circuit coaxial cable

distribution system.

Projection Systems

Quite often, the viewing group may besufficiently large that a tele-

vision picture considerably larger than the27-inch size is desirable.

-42- Under such ciicumstdnces, a projection system capable of providing a tele vision image comparable in size and brightness to that obtained with a

16mm motion pictn7e projector is required.

The most common and inexpensive type of television picture projection system is the Schmidt optical system in combination with a smaller

(5") high-intensity CRT, as shown in Figure 16.

A very high-intensity television image appears on the face of the projection tube in exactly the same manner as the larger television monitor. The Schmidt optical system (the spherical mirror and the cor- recting lens) reverses the direction of the light rays to form the projected image on the screen. The barrel serves to provide mechanical support foe the projection tube and lens system as well as protection against soft X rays emanatingfrom the front of the projection tube face.

Projectors of this type throw an image on a standard motion-picture screen ranging from 6' X 8' to 20' X 15'. The screen is placed from 15

to 35 feet away from the projector. Either front or rear screen projec-

tion may be used with the appropriate screen.

The brilliancy of the projected image is considerably less than a

typical 16mm motion p4cture (particularly for the larger 20' X 15' image)

since the total light available for projection is limited by the maximum

brilliancy of the image on the face of the television projection tube.

The problem of low image brightness is usually minimized by locating the

screen in a dark area to minimize thecontrast-reducing effects of the

ambient light striking the scre,n.

Notwithstanding the problFn of low brilliancy -- and sometimes poor

picture detail -- the Schmidt optics projector provides reasonably good

overall results at a comparatively low cost of about $3,600.

-43- I . ' , t ' - " - If?) , ) ' ?",....6: R3kStEL, 111 ,7-71 A 71 r 2- 17:162.,0ke- 6 There is general agreement among authorities that any television projection system capable of providing a large image of adequate brightness

b. eartivirvtrumil muNo.. "h;n11..;ntarcii.mr incandescent gas- filled electric light source. Clearly, the use of a constant high-intensity light source requires the use of a "light valve," or light modulator, to permit varying the intensity of the constant light source under the influence of the video signal.

The Eidophor television projector, developed in Switzerland, utilizes a xenon erc operating in a quartz glass envelopeunder a pressure of 20 atmospheres as a high-intensity light source and a unique light modulator using the "control-layer" process.The control-layer process of light intensity control, or modulation, was developed in 1939 by Dr. Fritz Fischer

Professor of Applied Physics of the Swiss Federal Institute of Technology in Zurich, Switzerland.

The control-layer light modulator consists of a concave mirror coated with a thin oil film (about Amm in thickness) which "wrinkles" under th

influence of a scanning electron beam which is in turn controlled by the video signal.As the oil surface wrinkles, its reflectivity varies, thus obtaining different intensities of the reflected light originating from

the fixed high-intensity xenon light source.The electron beam assembly

is identical to that used in a direct-view monitor and is enclosed in a vacuum chamber with the oil-coated concavemirror.

The fundamental elements of an Eidophor projector and how they are

related are illustrated in Figure 17.A photograph of the projector is

shown in Figure 18.

The Eidophor is regarded as a television projector which provides by

far the brightest television image possible with the lowest geometric

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wr7:nr?"7 *9'44r4 f.f; , *3? , (7 distortion. However, the Eidophor is relatively expensive, costing in the neighborhood of $50,000, but it is the only known device which projects

television images equal to that obtainable with a good motion picture projector.

-48- AND SIGNALS THE RECORDING ANDREPRODUCTION OF TELEVISION IMAGES

broad- Theknown nethods of recordingtelevision programs for delayed 1) photographic recording cast or use fallinto three general categories: reproduction of video and reproduction of images,2) direct recording and signals, and 3) electron beamrecording and reproduction,

Photographic Recording andReproduction The first me- Two different photographictechniques are available. the scent with a thod involves the directmotion-picture photography of Play- 16mm (or 35mm) movie camerainstead of a studio television camera. transmission is back of a delayed televisionbroadcast or closed-circuit

accomplished by a 16mm motionpicture projector coupledwith a television The film-chain camera is camera system,which is known as a "filmchain." mirror device which permits usually equipped with afixed optical or moving (such is another 16mm the film camera to be usedwith multiple film sources This movie projector or a 2" X2" slide projector) on atime shared basis. multiple in- device is known as an opticalmultiplexer. A film-chain with

puts is shown inFigure 19. playback must The 16mm motion pictureprojector used for television sequence (called be equipped with a specialshutter mechanism and exposure

differences between the 24frames per a 2:3 pulldown)which equalizes the second television second motion picture standardand the 30 frames per

limitless supply ofstandard motion standard. In this way, the almost

p.ture film is madeavailable for television use.

-49- , 10111111nanormsmr. BEAM STIATTING CASBE 30%/0% "Ree,zt.ecrifier TRANSmar)NG Movit\te M iaROR._. C411 Flea) 1 \I LENS (1.) .:::... ir... ..11...... 1=11...... 1 ,', rr" 1 1-. 4- - `IL- 13,-.,AM Si -ITT Me C6"/E: '' . FimL0 It-EN'S (M) LIM CoP; TR./201s' MI ri- t 14 RE PL.CcrINE- TZEF LE.SO CV FLPACES W , .io Fu, WI- S ufl.PAc;-:- ;1.:. - MIrtikc)R_------C----taok_E 19 F The second -- and more common --photographic method involves plac- ing the recording camera in frontof a television monitor so that the electronically displayed images may berecorded on 16mm film. In this way no photographicediting is necessary and all thespecial effects unique to television ran,be ntili2ed, This method is known as "kinescop-

ing" and the film nroduct is called akinescope4The kinescope recording/

reproducing technique was widely usedbefore the almost universal use of

magnetic tape video recording andis familiar to anyone who haswatched

commercial television in its earlydays.

The quality of kinescope recordingshas improved considerably over

the low-detail, washed out picturescharacteristic of the early days due

Kinescope largely to improved exposureand photographic process contrcis. of techniques are still utilized forthe purpose of making 16mat movies

video tape recordings for showing onordinary film projectors.

The accompanying program soundis usually recorded optically along a

track adjacent to the sprocketholes. Both single and double systems are

in general use. In the single system thesound is recorded simultaneously

with the picture; in the double system,the sound is recorded separately

and combined with the picturelater.

One of the significantimprovements in photographicrecording/

reproducing techniques is therecording of sound on a magneticstripe

placed on the film in placeof the optical track.

Edriestalleal Recording

Perhaps the most riodern approachto the recording andreproduction

of television images is themagnetic tape process inwhich the image, or

light, step is completely circumvented.In this way, the inevitable

-51- degradation in the tonal shades of the reproduced picture,due to variations in the photographic process, is eliminated,and the recording is available for immdiate reproduction -- atremendously valuable bonus.

In the magnetic tape process, the videosignal, which corresponds to the picture elements, is used to influencedirectly the positions of the magnetic coating on the tape backing.The process is quite similar to audio-magnetic tape recording except thatchanges must be made to extend the frequency ;esponse to recordtelevision signals adequately without ex- cessive degradation.

The frequency response, orbandwidth, attainable with most recording/ reproducing techniques -- particularlymagnetic tape techniques -- is de- termined largely by the ratio of themediwn velocity (in this case the velocity of the magnetic tape) tothe playback head gap width, asshown in Figure 20. With the narrowest gap width availAr;le,the required medium velocity is so great as to beimpractical for television use. In the modern video taperecorder/reproducer this problem is solvedby moving the head at high speeds across the tapesurface and moving the tape just fast

enough to separate the tracks.

Two different types of videorecorder/reproducers are in general

use: transverse scan (also known asquadruplex) machines and helical

scan machines.

Transverse scan machines usemagnetic tape two inches wide and the

magnetic tracks are placed on the tapealong the two inch dimension, or

transverse to the directionof tape motion. A rotatinghead wheel is edge of the used in which four identicalheads are imbedded into the

wheel exactly 90° apart. The magnetic tape is moved in adirection

-52- 0 Z 31:101.1 ad9 (1'43\A perpendicular to the imbedded head motion when the head wheel rotatesjust

fast enough to separate the adjacent tracks. As illustrated in Figure 21,

a continuous recording isachieved because as one imbedded head loses con-

tact with the magnetic coating the adjacenthead moves into position to

lay an adjacent recorded track. In this way a high enough medium-velocity

to gap-width ratio is achieved to provide abandwidth wide enough for

satisfactory reproduction.

The p gram audio is recorded longitudinallyalong one edge of the

tape by means of a conventionalstationary audio head.

The modern quadruplex video tape recorder is ascientific marvel of

mechanical precision and sophisticated electronics.To provide satis-

factory operation, the heads imbedded in thehead wheel pane'. must be

switched out as they leave contact with the tapeand the adjacent head

switched in as it moves into position to takeits place. Further, during

the playback process, the heads must scanthe same tracks made during re-

cording. This requirement means that the rotationalspeed of the head

wheel and the speed of the tape -ionduring reproduction must be iden-

tical to a very small tolerance to thatused during recording.Elaborate

servomechanisms to hold the head wheel motorand the tape transport

capstan-drive motor under control and constantspeed are required.A con-

trol track is recorded on the tapein much the same manner as the program

sound to provide a reference forthe electromagnetic servomechanisms.

Successful operation of the quadruplexvideo tape recorder/reproducer

involves the application of manysophisticated electronic techniqueswhich

cannot be adequately treatedin this short presentation.

A large family of lower cost --and also lower performance --video

These tape recorders have becomeavailable during the lastfew years.

-54- ,4 ., (4.4.1WWOMOVIVW1..111,,011,00,1PektriWPRIMPrif...itet),f rmlasweoximommwrivama*lownr*. machines have been labeled helical scan, or "slant-track," machines because of the configuration of the magnetictrack, as shown in Figure 22.

The helical scan machines of different makes (and sometimes even different models by the same manufacturer) use either one or two headsand either one- or two-inch magnetized tape.The net result is that no two machines sold by two different manufacturers are compatible in that a recording made on one cannot be reproduced on,the other. Needless to say, video

tapes recorded on transverse machines (quadruplex) cannotbe reproduced

on helical machines or vice versa.

The important characteristics of helical scan machines are: lower

cost ($1,500 to $8,000), reduced size andweight and, unfortunately,

lower performance standards. There is a fond hope among existing users

of video tape recorders that the performancestandards will be improved

eventually without significantly sacrificing cost, sizeand weight and

that a common manufacturing standard will beadopted so that recordings

made on any one machine can be reproduced on anyother.

When that time comes, or perhaps even before,there is little doubt

that helical scan machines will eventuallyfind a permanent niche in tele-

vision. At the present writing, helical scan machines cannotbe used for

VHF/UHF broadcast purposes without the use of anelaborate video process-

ing amplifier to reshape the synchronizingsignal adequately to meet cur-

rent FCC broadcast standards.

Electron Bean Recording

Electron beam recording and reproductionof television images is a

combination of the photographic technique(optical) and the direct video

signal technique (magnetic) alreadydescribed. Electron beam recording

-56- nilINEMBIE '4 "rlo biE ROT AT NA A e.1E-r lc.Ma. AC buS 41 -717,ek ----rp, 105------° 60YZE Pe Z2 G.ToDes techniques used for sometime in electron is a combinationof well-known television picturetubes. microscopes, cathode rayoscilloscopes and (UR). shown inFigure 23, a In the electronbeam recording process moving film andscanned across the focused electronbeam is directed at a used in television camerapickup film by deflectionplates of the type be recordedmodulates, or varies, and display tubes.The information to in a beam in preciselythe same manner as the intensityof the electron In addition tothe usualphoto-sensitive television picturedisplay tube. coating is placed overthe light- silver halideemulsion, a scintillator coating is struckby the electron sensitive coating.When the scintillator proportional to theintensity of the elec- beam, it glowsand emits light identical to theaction of thephosphorus coat- tron beam. This process is surfact of a televisionpicture display ing on the insideof the viewing The light generatedby the scin- tube described inthe previoussection. produce a :latentimage which tillator exposes thephotographic film to film to provide apermanent can beprocessed likeordinary photographic

copy. moving filmsurface with a Playback is achievedby scanning the pattern identicalto that constant-intensity electronbeam in a running As the scanningelectron beam strikes used during therecording process. light which passesthrough the film the scintillatorsurface, it emits light and dark patternof the photo- surface where it ismodulated by the

A photo sensitivecell (photo-multiplier graphically developedemulsion. light variationinto the original tube) is used to convertthe impinging is illustratedin Figure 24. electrical variation. The playback process techniques have a verypromising Electron beamrecording/reproducing limitations of magnetictape recording, future free of manyof the inherent

-58- mEt.sc.-rapr4

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-59- playback interval isrequired before even though afour-minute processing

is possible. limited to recording techniquesare Although conventionalvideo tape up to100 MHz. NHz, EBR iscapable of achieving a bandwidthcapability of 10 of development mietinvolve the use The next stageof the EBR system would elimincte electron beam. This variation a laserbeam instead of an by the the scintillatingsurface demanded the need for a vacuumsystem and directly is capable ofexposing the film electron beam sincethe laser beam

in an openatmospheric environment. exhibited by anothervariation of Some very interesJigproperties are reproduction thermoplastic taperecording and the EBR process,known as the stylus," as in employs an electronbeam "writing process. This technique However, as thescanning electron the EBR processpreviously described. the film (usuallystandard 16mm size) beam strikes theuniformly moving instantaneously to producean em- thermoplastic coating isheated almost Al- and hence opticaltransparency. bossed surface ofvarying thickness for the electronbeam, no phott;graphic though a vacuum systemis required scanning playback. Furthermore, if the processing step isrequired prior to in the chosen to matchthe scanning pattern pattern of theelectron beam is receiver, theindividual embossed picture tube of astandard television 16mm film, whichwould produce images picture frames canbe recorded on frames on standardnotion picture visually identical tothe individual used thermoplastic EBR,recording could be film. As a consequence, a signal (EBR typeof playback either to reproduce ahigh-fidelity video onto a screenwith a 16mm movie with electron beamsensing) or projected

projector as if it wereordinary moviefilm! A practical form of Electron Beam Recording has been announced recently by CBS Laboratories. This video recording/reproduction process, labeled Electron Video

Recording, or EVR, has the potential for revolutionizing the recording and reproduction of television programs.

The chief virtue of the EVR process is the low cost of making multiple copies for professional or home reproduction.

Thus, EVR video recordings may become as commonplace as

Long Playing phonograph records. Interestingly enough, the

EVR process was developed under the direction of Dr. reter

C. Goldinark of CBS Laboratories, the developer of the Long-

Playing phonograph record. The recording process, however, will require elaborate and expensive equipment. It is, thus, unlikely that low-cost video re orders using the EVR process will become available forother than professional use in the near future. APPENDIX IAA

GLOSSARY OF TERMS

AMPLIFIER - An electronic component whichreceives a weak signal from any original sound orvisual source (microphone, record player, tape-head, or television camera) and strengthensit to the point where it can drive a speaker or reproduce apicture on a television :men. While audio and video amplifiers aredesigned differently ,Iccording to their respective function, thebasic principle of a good amplifier is that it does not change(i.e., distort) the original signal in any way other than to giveit the necessary boost along the way.

ANTENNA -A device for receiving andthen conducting radio and/or television signals that have been transmittedthrough space. In television the simplest farm of antenna isthe familiar "rabbit ears" placed atop the receiver.An extension of this typeis the roof antenna which can service up tofour sets, depending upon the strength of the signal received andthe distance of the sets from the antenna. For optimum quality andconsistency of reception, the antenna is connected to a masterdistribution system with electronic amplification for allavailable broadcast channels.

AUDIO - Refers to the sound portionand the related equipment of any communications system. Depending upon the type oftelevision system in use, audio maybe transmitted either overthe same signal carrier with the televisionimpulses or may be a completely indepenaent system.

AUDIO-VIDEO MIXER (MODULATOR) - Anelectronic component of an RF(radio frequency) transmission systemthat combines (or modulates)the separate audio and videosignals from microphones and camera respectively into a single highfrequency signal fortransmission to the receiving equipmentwhere the signals areagain separated and directed to the speakerand screen. allocated by the BAND - A portion of thefrequencies in the spectrum extends from FCC for specific purposes. For example, AM radio 550-1600 kilocycles, VHF (veryhigh frequency) televisionfrom 54-88 and from 174-218 megacyclesfor channels 2-6 and 7-13 respectively, F4 radio from88-108 megacycles, UIF(ultra high frequency) television from 470-890megacycles (channels14-83). A new educational televisionband of 2500-2690 megacycles was allocated in 1963 forpoint-to-point microwavetransmission.

-62- BANTRIDTII - The frequency range of aspecific signal being transmitted. Each broadcast television channel in theUnited States covers 6 megacycles for both audio and video. For example, channel 2 covers a bandwidth extendingfrom 54 -50 megacycles.

BROADCAST - The open circuit transmissionof either radio or television signals through the air atfrequencies which can be received by an" appropriately tunableequipment within range of the transmitter.All broadcasting is regulatedby the Federal Communications Commission.

CAMERA - In television that devicewhich, by utilizing an optical system, a light-sensitiveelectronic tube and an electronic scanning de/ice, converts a visualimage into electrical impulses.

CAMERA CHAIN - One or more cameraswith such associated electronic deviees as needed to transmit atelevision picture.

CARRIER - The electronic wave bywhich audio and video impulses are carried from transmitter to receiver.

CARRIER FREQUENCY - The number ofcomplete cycles per second(frequency) of a carrier wave.

CATHODE-RAY TUBE (CRT) - An electrontube in which a beam of electrons image from a heated element, the cathode,is used to reproduce an on the fluorescentface of the tube.

CHANNEL - The segment of thebroadcast spectrum to which atelevision station is assigned or to which aclosed-circuit television The camera is tuned whentransmitting via radiofrequencies. actual channels used in anyclosed-circuit installationwould normally be those not allocated to alocal broadcast station.

CLOSED CIRCUIT (CCM - A systemof transmitting televisionsignals linked to the originating to receivingequipment that is directly lines. equipment by coaxial cable,microwave relay or telephone

line formed by two COAXIAL CABLE (CONCENTRICL1NE) - A transmission suitable coaxial conductors, eachinsulated from the other by some dielectric material such asair or polyethylene,polyfoam, teflon, etc. which permits nor- COMPATIBLE COLOR SYSTEM -A color television system signajo without mal black and whitereception of its transmitted altering currently usedreceivers. receiver or projection CONTRAST - The relationof black to white on a screen. CONVERTER - In television anelectronic device that convertsbroadcast signals from one frequency range toanother. A VHF receiver with a converter canreceive UHF channels. Or a master antenna and distribution system so equipped canservice any number ofstandard UHF VHF receivers with programsinitially telecast and received on frequencies, then converted to permitreception on any VHFchannel not being used in theparticular area. signals from DEMODULATION - The process ofremoving the video and audio their respective carrier waves. in only DIRECT CURRENT - Electric currentwhich flows through a circuit one direction.

DIRECT-VIEW RECEIVER - Atelevision set arranged so thatthe formed image is viewed directly onthe face of the picturetube.

DIRECTIONAL ANTENNA - An antennaradiating or receiving radio waves moreeffectively in some directionsthan in others.

EDUCATIONAL TELEVISION STATION -A non-profit televisionstation operating to serve communityneeds in the areas ofinstruction, cultural development, etc. received radio signal, FADING - 1) Variation inthe intensity of a 2) Electron- generally caused by changesin transmission paths. the screen goes to ically weakening atelevision picture until black.

FCC - Federal ComounicationsCommission. television system re- FIDELITY - rie exactnesswith which a radio or produces sound or picturesignals. television camera focused FILM CHAIN - An equipmentarrangement with a of projectors (2" X 2" on a multiplexerinto which an assortment directed from dif- slide, 16mm motion picture,opaque) have been make it possible toswitch ferent angles, Electrical circuits images from any ofthe projectors in turn. into the system selected especially if cen- More than a single filmchain can be installed, circuit is contemplatedin tral distribution ofvisuals by closed stations have at least oneof these an institution.All television chains. picture scene in aratio FRAME - A single completeyelevision or motion Thirty frames persecond are of 3 units high and 4units wide. twenty-four frames persecond are shown on a television screen; frame has generally used in motionpictures. Each television 525 lines. second a televisionpicture FRAME FREQUENCY - Thenumber of times per second). area iscompletely scanned(30 times a

-64- FREQUENCY - The nunber of cycles completedeach second by an electric current or a sound wave.

FREQUENCY MODULATION (FM) - A methodof modulation in which the frequency of the carrier waveis varied while the strength(ampli- E4 is the standard tude) of the carrier waveremains conctnnt. method of transmission and receptionof the sound in television.

IMAGE ORTHICON - A television cameratube so sensitive it can tele- vise (in black and white) any scenethe eye can see, even under low lighting conditions; moreexpensive than vidicon, used for professional studio broadcasting;requires expert handling.

INTERFERENCE - Disturbance in radioreception caused by undesirable signals or stray currents from electrical,atmospheric conditions, static, etc.

INTERLACE - The giv...cz of scanning alternate lines of atelevision picture to reduce flicker.

in the ITFS - Instructional TelevisionFixed Service, which operates 2500-2690 MHz band.

KILOWATT (KW) - A unit of electrical powerequal to 1,000 watts.

KINESCOPE - A film recording madeby a 16mm motion picture camera especially designed to photograph atelevision program directly off the front of a television tube. The sound portion of the program is also recordedsimultaneously. The film so produced can then be shown on any16mm projector, as well as ontelevision.

MASTER DISTRIBUTION SYSTEM - Comprisesantenna and amplifiersfor boosting over-the-air signals, pluscables and tap-off connec- tions for use of cameras and receiversthroughout a building.

MEGACYCLE - 1,000,000 cycles (1 MHz) persecond, used as a unit of measurement of frequency. 1,000 kilocycles is equal to one megacycle.

MICRO - A prefix meaning onemillionth, as "microvolt."

MICROWAVE - A method of transmittingclosed-circuit radio and television signals through the air on ahighly directional line-of- sight system from the originating station to one ormore receiving stations. Although a private system,ridcrowave transmission is regulated by the FCC.

MICROWAVE RELAY - A series of low- power,high-frequency transmitters and receivers strategically spacedand located to permit radio or television contactbetween widely separated points.

MODULATION - The process of impressingaudio or video impulses on the carrier wave for transmissionthrough the air.

-65- MONITOR - A special type of high qualitytelevision receiver used specifically in video transmission, ratherthan RF.Video monitors are not tunable to channels and mustbe used with video cameras. They normally have no provisionfor sound reception. (The term "monitor" is also usedinformally to designate any receiver being usedby the cameraman or programdirector to check the picture being sent out.)

MONOCHROME TRANSMISSION - The transmissionof television signals which can be reproduced in graduationsof a single color only (black and white).

MPATI - Midwest Program on AirborneTelevision Instruction.

MULTIPLEXER - In television a specializedoptical device that makes it possible to use a single television camerain conjunction with one or more motionpicture projectors and/or slideprojectors in a film chain. The camera and proiectors arein a fixed relation- ship, and prisms or special (dichroic)mirrors are used to provide smooth and instantaneous non-mechanicaltransition from one program source to the other.

NETWORK - A group of television stationsconnected by radio relays or coaxial cable so that all stations maysimultaneously broadcast a program. "Tape networks" bicycle tapesbetween the stations.

OSCILLOSCOPE - A test instrument thatindicates voltage and current characteristics on a screen similar tothat of a television receiver.

PICTURE TUBE - The television cathcde-raytube used to produce an image by variation of the beamintensity as the beam scans the raster.

PROJECTION RECEIVER - A television setwith a small but high-intensity picture tube. The tube in this instance operatesthrough an optical system to project imageswhich are viewed on a screen. Although the images are not so bright asthose achieved with direct -view receivers, relatively largeprojections can be achieved.

PROJECTION TELEVISION - A combinationof lenses and mirrors which pro - j ects an enlarged television picture on a screen.

RADIO - Communication through spaceby means of electromagnetic waves for transmission and reception of messages,sounds, photographs and pictures in motion withoutthe use of connecting wires.

RADIO CHANNEL - A band of frequenciesallotted by the FCC to each station for radio, communication andbroadcasting purposes.At present, the width of standard televisionchannels is 6 megacycles; R4, 200 kilocycles; and standard radio broadcastchannels, 10 kilocycles.

-66- RADIO RELAY - A station which automatically relays, or retransmits, television or sound. programs.

rAvArcalc eur- RADIO WAVE - An electromagnetic wav° p'^4"^c4 /II' /1"nnirlr of rent flow in a conductor known as the antenna, oraerial. Such a wave travels through space at the speedof light -- 186,000 miles per second.

RASTER - The pattern, or framework, of scanning lines thatilluminates the cathode-ray screen when no television signal is beingreceived.

REAR SCREEN - A system using a translucent screen throughwhich an image is projected from the rear, usually from a 3 1/4" X 4 1/4" projector, to full-screen size. This image is then taken by the television camera. A live subject can appear before the rear screen, making it appear that the scene shown on the screen is abackground for 1410 person shown

RECEIVER - Any television set; more specifically, onedesigned for tuned (radio frequency) channel reception of sound andpicture.May be either a standard "home set" or one designed especiallyfor classroom use.

RESOLUTION - The details that can be distinguished onthe television screen. Vertical resolution refers to the scanning lines one sees on the screen. Horizontal resolution refers to the number of variations within each scanning line and is variable according tothe bandwidth used. Broadcast (and RF closed circuit) television, limited to 4.5 megacycles bandwidth, has about 300lines of horizontal resolution as seen on an RF receiver. With high resolution video cameras and monitors, operating on a 10 megacyclebandwidth, horizontal resolution can be as high as 800 lines.

SCANNING - The process of deflecting the electronbeam in a camera or picture tube so that it moves at high speed fromleft to right in a sequence of rows orlines from top to bottom, thus changinglight and shadows of a scene into electrical impulses toform the image of the receiver tube,

SERVICE AREA - The region surrounding a broadcastingstation in which that station's signals can be received withsatisfactory results.

SIGNAL - Information transposed into electricalimpulses; two basic signals are involved in television transmission --the picture or video signal and tne sound or audio signal; each signalcontains electrical impulses representing elements transmitted.

SPECTRUA - The entire range of electromagneticradiations, from the long- est known radio waves to the shortestknown cosmic rays,Light, the visible portion of the spectrum, lies about midwaybetween the two extremes.

-67- selection of oneimage SWITCHER - A control devicewhich permits the is then processed from any of several cameras. The image selected into the transmissionequipment. device that synchronizesthe SYNCHRONIZING GENERATOR -An electronic appearing on the re- image scanned by the camerawith the image avoid "picture rollup" when ceiving tube. It is also required to switching between two or morecameras in asingle program.

TELECAST - A broadcastof both sight andsound. of a succession of TELEVISION - The radio orelectrical transmission to give asubstan- images and theirreception in such a manner as of an object or tially continuous andsimulanecus reproduction scene beforethe eyes of adistant observer. radio frequency car- TELEVISION BROADCAST SIGNAL -A combination of two being amplitude-modulated riers spaced by 4.5MHz, the lower one signal, the upper onebeing by a standardcomposite picture frequency-modulated by theaccompanying audio signal. in the TELEVISION CHANNEL - Aband of frequencies6 megacycles wide by a number or by television broadcast bandand designated either the extreme lower and upperfrequencies. designed to transmitelectrical TRANSMISSION LINE - Aconductor system another. impulses along a continuouspath from one place to designate Channels 14through 83, UHF (ULTRA HIGHFREQUENCY) - Used to to 890 megacycles. which operate in afrequency band of 470 designate Channels 2through 13 and VHF (VERY HIGHFREQUENCY) - Used to bands of 54-72,76-109 and 174-216 BM, which operatein frequency megacycles. fre- transmitting television,utilizing bandwidth VIDEO - A system of the picture signals. quencies from zero to15 megacycles to carry be transmitted overthe cable. Only one video signalat a time can be used for sound,if re- Normally, a separateaudio cable must superior to that ofRF, but the range quired. Picture quality is and requires morefrequent of transmission iscomparatively short line amplification. electromagnetically re- VIDEOTAPE RECORDER (VTR) -A unit designedto rebroadcast at anytime. cord television programmaterial for Tapes may be edited toimprove content. for most tube of moderatesensitivity, adequate VIDICON - A television and white); muchless educational broadcastrequirements (b1 =k does not requirehighly expensive than imageorthicon equipment; expert handling.

-68- FEDERALCOMMUNICATIONS COMIWSSION

WASHINGTON, D.C. 20554 March 29, 1965

INTRODUCTION TO INSTRUCTIONAL TV FIXED SERVICE

The "Instructional Television Fixed Service',which the Federal Communications Commission establishedin 1963, is proving to be a particular boon to educationin its use of television as an instructional medium.

It furnishes a means for transmittinginstructional material for school use on channels other thanthose used for regular noncommercial educational TVbroadcasting. This is done on 31 channels in the 2500-2690 Megacyclesband allocated for that purpose. A single central transmitter is ableto serve a number of scattered localschools, where the transmissions are converted for classroom viewing on regular TVreceivers.

The primary purpose of the new service is tosend visual and accompanying' aural instructionalmaterial to selected re- cc/ving locations in public and privateschools, colleges and universities and other instructional centers forthe formal education of students. Systems licensed for this purpose,however, may also be used forother purposes, among which are the transmission of cultural and orientation materialto educational institutions; special training material toselected receiving locations outside the school system, such ashospitals, nursing homes, police and fire stations, training centers,clinics, re- habilitation centers, commercial and industrialestablishments; professional material to groups or individuals toinform them of new developments andtechniques in their fields and instructthem in their use; in-service education; and otherrelated materials directly concerned with formal or informalinstruction and training. When not being employed for such purposes,the facilities may be used for handling administrative traffic,such as the transmission of reports and assignments andconferences with personnel.

Of special significance to educatorsis that up to five* programs (the FCC hasauthorized a maximum of five channelsto each licensee) may be transmitted and receivedsimultaneously in any given educational institution, thuslargely eliminating the major problem in previous educationalutilization of television -- that of scheduling. Not only does this system permit agiven school to receive seveL7a/ different instructional programsat the same time,

-69- but the system creates television pathways that are nolonger available in many geographical areas becausebroadcast channels have all been assigned. This new service, then, isintended to supplement -- not replace -- the standard educationalTV broadcast service.

Of special significance to administratorsis the relatively low cost of ITFS (or 2500 mc/s)transmitting equipment compared to that of standard open-circuitbroadcasting. However, while the 2500 mc/s signal is transmitted openly,the cost of a special receiving antenna and converter exceeds the costof normal home receiving equipmen:-... and, for practical purposes,only those in- st2tutions specifically utilizing the signalswould likely make the investment. Maintenance is low in cost and domes notrequire specially trained personnel.

Stations in this service may additionallybe used to relay educational material to and from commercialand noncommercial TV stations, but not to interecnnect TVfixed systems in different areas or to establish relay systemsto cover a state or region. The rules permit the retransmission of programs ofother broadcast stations, subject to the usual requirement for consentof the originating station. Eligibility in the "InstructionalTelevision Fixed Service" is identical with that of the NoncommercialEducational Television Broadcast Service in beinglimited to nonprofit educationalbodies.

Transmitter operation requires supervisionby technically qualified operators, but routine operation maybe conducted by radiotelephone third-class operators. There are also provisions forremote control and unattended operation ofcertain equipment.

Major mayuf. eturers of equipmentwhich currently install systems for this service are AdlerEducational Systems Division of Litton Industries, New Rochelle, N. Y.;Electronics, Missiles and Com- m'inications, Inc., Mt. Vernon, N. Y.;Microlink Corporation, Copaigue, N. Y., and Radio Corporationof America, Camden: N. J.

A simple form (FCC Form330P) is used by nonprofiteducational organizations in applying forCommission authority to construct an "Instructional Television FixedService" station.

* Since this original FCC release,the number of channels in each channel group has been reduced tofour channels with theexception of Channel Group H, whichprovides a group of threechannels.

-FCC- THE ESTABLISHMENT OF ANFCC COMMITTEE FOR THE FULL DEVELOPMENT OFINSTRUCTIONAL TELEVISIONFIXED SERVICE

In 1965, the FederalCommunications Commissiorestablished television a nationwidecommittee of educatorsand educational representatives to provide forthe full developmentof the In:tructional TelevisionFixed Service. Commissioner Robert E. Lee This full committeeis chaired by with Dr. Robert L.Hilliard, Chief of theEducational Broadcasting Branch of the FCC asExecutive Vice Chairman.

One of the first actsof the committee wasto establish continental United States four geographicalregions within the coordination between to provide machineryfor channel-group to providecontinuous liaison withthe qualified applicants and developments of ITFS commission relating toproblems, needs, and plans throughout the U.S.

The regional committees areas follows: Bernard Cooper Northeast RegionalCommittee, Chairman: 1. William Smith Southern RegionalCommittee, Chairman: 2. Lawrence Frymire Midwest RegionalCommittee, Chairman: 3. Alan Fink 4. Western RegionalCommittee, Chairman:

In addition the FCCappointed the Rev. JohnCulkin Chairman Committee has also been of the National Groups. An Executive established composed ofthe above namedRegional Chairmen, Mr. Lewis Rhodes ofthe NationalAssociation of Educational Broadcasters, and Dr. HaroldWigren of the NationalEducation Chairman of the Association. Commissioner Robert E. Lee is Executive Committee and Dr.Hilliard is ExecutiveVice Chairman. holds great This is a uniquea6ministrative concept and promise for the orderlydevelopment of this newinstructional television service. APPENDIX C

SELECTED BIBLIOGRAPHY

Prentice 1. Anner, George E. Elements of Television Systems. New York: Hall, Inc., 19.51.

2. Boyce, William F. Fundamentals of Color Television, Indianapolis, Indiana: Howarrirrni.g-aTTETTRE:TOTT7-

3. Clarke, R. Walton. 1966 Schoolman's Guide to ETV i:ommurications. Philadelphia:Jerrold Electronics Corporation:7;6157--

4. Ennes, Harold E. "Television Tape Fundamentals" (Reprint from Broad- cast Engineering) Pittsburgh: 3-M, Magnetic Products

5. E ul ment Guide for Classroom Television. Sylvania, General Telephone an ectronics, "ew n.d.

M'Graw- 6. Lewis, Philip L.Educational Television Guidebook. New York: Hill Book Compiy;Tric.71761:

7. McClung, David R., ed. "Electron Beam Recording. . ." Readout. Vol. 5, No. 2, 1966, pp. 10-14.

8. Micro-Link. .Your Guide to Better ETV.Micro-Link Systems, Varian sociation,opiague, , n.

9. Mitchell, William G.Through the TV Tube. Gainesville, Florida: University of Florid5717617------

10. The Needs of Education for Utilization ofSpace Transmission Tech- 70.-F6g7-- ationa sociation o ationa roa casters, y IN27 Broadcast and 11. Reed, Oscar, Jr. Educational Television Technolo3: Other Distribution Systems. Jansky and Bailey, ashington,1671C.

12. Rubin, Melvin L. and Gordon L. Walls. Studies in Physiological Optics. Springfield, Illinois: Charles C. Thomas,

13. Scheraga, Morton G. and Joseph J. Roche.Video Handbook. Montclair, N, J.: Boland and Boyce, Inc., 1949.

-72- 14. Standards of Television Transmission.National Association of Educa- tional Broadcasters, June, 1964.

15. Television in Education. Sylvania, Ceneral Telephone and Electronics, New York, N. Y., n.d.

16. Wentworth, John W.Color Television Engineering. New York: McGraw- Hill Book CompariTErTETN55.

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