Modern Cable
`Television Technology
`Video, Voice, and
`Data Communications
`
`WALTER CICIORA
`Consultant
`
`JAMES FARMER
`Antee Corporation
`
`DAVID LARGE
`Media Connections Group
`
`t4 (~®
`Morgan Kaufmann Publishers, Inc.
`San Francisco, California
`
`Comcast, Exhibit-1108
`
`1
`
`

`

`Senior Editor Jennifer Mann
`Director of Production and Manufacturing Yonie Overton
`Production Editor Cheri Palmer
`Editorial Assistant Karyn Johnson
`Cover Design Ross Carron Design
`Cover Photographs Daniel Motz and Richard Graulich for Cox Communications, Inc.
`Text Design Rebecca Evans & Associates
`Copyeditor Robert Fiske
`Proofreader Jennifer McClain
`Composition and Illustrations Technologies 'n Typography
`Indexer Steve Rath
`Printer Courier Corporation
`
`Designations used by companies to distinguish their products are often claimed as
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`
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`340 Pine Street, Sixth Floor
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`Telephone
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`© 1999 by Morgan Kaufmann Publishers, Inc.
`All rights reserved
`Printed in the United States of America
`
`03 02 01
`
`5 4 3
`
`No part of this publication may be reproduced, stored in a retrieval system, or
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`recording, or otherwise-without the prior written permission of the publisher.
`
`Library of Congress Cataloging-in-Publication Data
`
`Ciciora, Walter S.
`Modern cable television technology : video, voice, and data
`communications / Walt Ciciora, James Farmer, David Large.
`p. cm.
`Includes bibliographical references and index.
`ISBN 1-55860-416-2
`1. Cable television. I. Farmer, James, (date)
`David, (date) III. Title.
`TK6675.C53 1999
`621.388'57-dc21
`
`II. Large,
`
`98-35328
`CIP
`
`2
`
`

`

`4 Chapter 1
`
`Introduction to Cable Television
`
`1.1
`
`Introduction
`
`Currently, cable television service is enjoyed by nearly 65 million U.S. house(cid:173)
`holds. This is a market penetration of nearly 67 % . Cable service is available to
`96. 7 % of U.S. television households.1
`Cable television is an important part of the way in which the citizens of the
`United States are informed and entertained. It is a means of providing large num(cid:173)
`bers of television channels to more than two-thirds of the U.S . population in a
`cost-effective way.
`Because cable television has been so successful and has enjoyed such vigor(cid:173)
`ous growth and acceptance, it has spawned competitors, including prerecorded
`media (tape and disk sales and rentals), direct broadcast satellite (DBS), as well
`as the interest of the telephone industry. Cable's high visibility has also attracted
`the attention of regulators and legislators. Important public policy issues are in(cid:173)
`volved. Understanding what cable television is, how it works, and its economics
`will help decision makers in these arenas. This understanding will also aid tech(cid:173)
`nologists in determining which technologies are appropriate for cable television
`applications and which are not.
`Television has long been the preferred source of information for the general
`public, and cable television offers viewers more choice than ever before. In fact,
`if cable had to be described with one word, that word would be choice. Choice
`is made possible by cost-effective bandwidth to deliver programming to almost
`70% of the households having televisions in the United States. Since cable is
`available to more than 90 % of television households, nearly everyone has the op(cid:173)
`portunity to subscribe to cable. In the United States, more people have televisions
`than telephones, and most of those people have cable.
`There are more than 160 programs on the satellites that feed cable headends.
`Cable systems must select some of the programs they will offer to their subscrib(cid:173)
`ers from all those available since no analog cable system has sufficient capacity to
`carry them all. In addition, cable systems carry the local broadcasts and some
`programs locally originated or designated for local citizen access. In some cable
`systems, the local schools, library, or government has channels to deliver pro(cid:173)
`grams of special interest. In this way, the needs of a democratic society are served
`while citizens are well informed and entertained.
`The broadband cable infrastructure can deliver an appealing analog service
`while adding hundreds of digital channels. This hybrid service is important for
`the transition to digital television since an abrupt changeover from analog to digi(cid:173)
`tal television would be chaotic. Most citizens will continue to enjoy analog tele(cid:173)
`vision for many years to come. Even those who purchase a digital television
`receiver for their principal viewing room will have analog receivers in the rest of
`the house.
`The same broadband cable can carry high-speed data service to subscribers,
`making Internet-based and other information services fast and convenient. The
`cable infrastructure is inherently two way, requiring only modest additional in-
`
`3
`
`

`

`1.4 Cable Network Design 9
`
`$
`~
`c:
`0
`·~
`::;
`c:
`OJ
`~
`
`22
`
`20
`
`18
`
`16
`
`14
`
`12
`
`10
`
`8
`
`6
`
`4
`
`200
`
`400
`
`600
`
`800
`
`1,000
`
`Frequency (MHz)
`
`Figure 1.1 Coax cable attenuation versus frequency.
`
`and operating frequency. A ballpark figure is 1 dB of loss per 100 feet. Half-inch
`diameter aluminum cable has around 1 dB of attenuation per 100 feet at 181
`MHz; at 1-inch diameter, the attenuation drops to 0.59 dB per 100 feet. The atten(cid:173)
`uation of cable varies with the square root of the frequency. Thus, the attenua(cid:173)
`tion at 216 MHz (within TV channel 13) is twice that of 54 MHz (within TV
`channel 2) since the frequency is four times as great. If channel 2 is attenuated 10
`dB in 1,000 feet, channel 13 will be attenuated 20 dB. Figure 1.1 demonstrates
`this relationship for 1,000 feet of 5/ 8-inch aluminum cable.
`
`1.4
`
`Cable Network Design
`
`Since cable television originally was not a general-purpose communications
`mechanism, but rather a specialized system for transmitting numerous television
`channels in a sealed spectrum, the topology or layout of the network was custom(cid:173)
`ized for maximum efficiency. The topology that has evolved over the years is
`called tree-and-branch architecture. 3
`There are five major parts to a cable system: (1) the headend, (2) the trunk
`cable, (3) the distribution (or feeder) cable in the neighborhood, (4) the drop
`
`4
`
`

`

`10 Chapter 1
`
`Introduction to Cable Television
`
`Upstream band
`
`FM band
`
`,.........,_,
`
`Midband channels
`
`2
`
`3 4
`
`S 6
`
`98 99 14 IS 16 17 18 19 20 21 22 7 8 9
`
`IO 11 12
`
`12
`
`IO
`
`30
`
`so
`
`60
`
`70
`
`80
`
`100
`
`120
`
`130
`
`140
`
`150
`
`160
`
`170
`
`180
`
`190 200
`
`2IO
`
`88
`
`108
`
`Superband channels
`
`Hyperband channels
`
`13 23 24 25 26 27 28 29 30 31 32 33 34 3S 36 37 38 39 40 41 42 43 44 45 46 47 48 49 so 51 52 53
`13
`
`MHz
`
`210
`
`220
`
`230
`
`240
`
`250
`
`260
`
`270
`
`280
`
`290
`
`300
`
`310
`
`320
`
`330
`
`340
`
`350
`
`360
`
`370
`
`380
`
`390
`
`400
`
`Figure 1.2 Cable frequency plan. Numbers above the rectangles are the EIA-542 designations. Historical designations are
`inside the rectangles. Current cable plant bandwidth can exceed 1 GHz.
`
`cable to the home and in-house wiring, and (5) the terminal equipment (set top
`terminals and consumer electronics hardware) .
`Flexible coaxial cable is used to bring the signal to the terminal equipment in
`the home. In the simplest cases, the terminal equipment is the television set or
`VCR. If the TV or VCR does not tune all the channels of interest because it is not
`"cable compatible, " a converter is placed between the cable and the TV or VCR
`tuner.
`Broadcast channels 2 through 13 are not in a continuous band. Other radio
`services occupy the gaps. Cable can reuse these frequencies because its spectrum
`is self-contained within the coaxial environment. The cable converter has a high(cid:173)
`quality broadband tuner and output circuitry that puts the desired cable channel
`on a low-band channel not occupied in the local off-air spectrum. Typically, this is
`channel 2 or 3 and occasionally 4 or 5. The TV or VCR is tuned to this channel
`and behaves as a monitor. Premium programming is typically "scrambled" so
`that it is not clearly visible on an ordinary television receiver. The picture appears
`torn up, and the pieces jump around on the screen in the usual display. The sub(cid:173)
`scriber wishing access to premium programming pays an additional fee and is
`supplied with a descrambler, which is a component of the set top terminal. The
`subscriber who has purchased a product labeled "cable ready " may expect to
`avoid the set top terminal. The requirement to use a set top terminal with a
`descrambler for premium services can be a sore point.
`Figure 1.2 shows the cable frequency plan. Although Figure 1.2 goes up to
`only 400 MHz, cable systems have been built to slightly in excess of 1 GHz with
`more than 150 analog channels. Cable systems with bandwidths of 750 MHz are
`not uncommon, and 550 MHz is typical for upgrades and new construction. The
`home is connected to the cable system by the flexible drop cable, typically 150
`
`5
`
`

`

`Delayed
`AGC
`ATl
`
`Ml
`
`RF in
`
`18.5 The Set Top Terminal 747
`
`Volume
`control
`AT3
`
`Optional
`baseband
`outputs
`
`Audio
`
`Video
`inversion
`
`RF
`modulator
`Video
`
`Channel
`3/4 to TV
`
`On-screen
`display
`
`Out-of-band~--~
`data
`
`Remote control
`receiver
`
`IPPV
`transmitter
`
`Figure 18.10 Modern addressable set top terminal.
`
`Telephone
`
`/
`RF
`interface
`(RF-JPPV)
`
`interface '
`
`Alternates
`
`switched attenuator, which offers, usually, 6 or 10 dB of attenuation during ac(cid:173)
`tive video, and is switched out during horizontal and vertical blanking intervals.
`Operation of the descrambler is described in Section 18.3.1.
`After sync suppression restoration at IF (for the common RF sync suppres(cid:173)
`sion systems), the signal is supplied to video and audio demodulators. At this
`point, the video has had sync suppression removed, but if it is inverted, that still
`must be corrected. The video inversion circuitry handles this task. As in the case
`of sync suppression descrambling, recovered in AT2, video inversion is controlled
`by the controller circuitry, as appropriate to the scrambling system being used.
`Most set top terminals today have an on-screen display (OSD), which is used
`to indicate the channel tuned, time, the program service on that channel, and
`other functions . In ordering pay events, the OSD is normally used. It is becoming
`popular to include electronic program guides in set top terminals, and the OSD
`will also be used for this.
`Audio is normally demodulated to just the composite BTSC stereo signal, as
`described in Chapters 2 and 7. It is not common, but is possible, to include a
`BTSC decoder. It is not likely that a BTSC encoder would be included owing to
`its cost. Volume control is effected at attenuator AT3, which operates on the com(cid:173)
`posite BTSC stereo signal. This does not yield a truly accurate volume control
`
`6
`
`

`

`778 Chapter 19 Consumer Electronics Interface
`
`devices "see" the complete IR emission sequence and respond appropriately, or
`the result may be disappointing.
`Another model of advanced universal remote control includes a clock and a
`timer. The remote control can be positioned so that it simultaneously communi(cid:173)
`cates with both the VCR and the set top terminal. The universal remote control is
`programmed with the VCR control instructions. The remote turns on the VCR at
`the appropriate time, ensures that the VCR is tuned to the output channel of the
`set top terminal, then tunes the set top terminal to the desired channel, and
`finally starts the VCR recording. Consecutive recording of different channels is
`made possible.
`A few models of two-way remote controls have a small screen on the remote
`control that displays signals received from the set top terminal. Titles of songs,
`purchase order forms, interactive games, and other instructions can be viewed.
`
`19.6.2 Electronic Program Guides
`Electronic program guides (EPGs) have been introduced with features that allevi(cid:173)
`ate some of the interface problems. The EPGs are available as stand-alone de(cid:173)
`vices, built into cable set top terminals, or built into TVs or VCRs. Several of these
`devices include one or more infrared light-emitting diodes (LEDs) on short wires
`that are meant to be attached near the remote control window of the VCR, the ca(cid:173)
`ble set top terminal, or the TV. The device with the EPG controls the other devices
`to accomplish the desired result. If the EPG is built into the cable set top terminal,
`the LED controls the VCR so that it turns on and off at the correct times and is
`tuned to the correct channel. If the EPG is built into the VCR, the LED controls the
`channel on the cable set top terminal. Of course, none of these approaches can
`ensure that sufficient blank tape has been put into the VCR!
`A related device, called VCR Plus, uses numeric codes published in printed
`guides (or conveyed electronically in a later version) to the VCR or to a form of
`universal remote control. The codes are decoded using a proprietary algorithm to
`derive the start and stop times and the channel number. Infrared emissions con(cid:173)
`trol the VCR and cable set top terminal.
`
`19.6.3 The TV Integrating Device
`In the mid- l 980s, the research department of a cable operator, American Televi(cid:173)
`sion and Communications in Englewood, Colorado, began development of an ap(cid:173)
`proach the engineers called the TV integrating device (TVID). It was intended to
`be included in a cable set top terminal and to use IR LEDs to control the TV and
`one or more VCRs. It had a built-in EPG and an on-screen display. The goal was to
`provide a simple menu that would allow subscribers to indicate their desires. The
`subscriber would indicate what he or she wanted recorded and what he or she
`wanted to watch. The TVID would take care of switching the descrambler into the
`correct part of the system and turn things on and off at the right time to imple(cid:173)
`ment the subscriber's desires. If a conflict arose, such as wanting to watch a
`
`7
`
`

`

`19.8 Legal Aspects of Cable-ConsumerElectronics Compatibility
`
`779
`
`scrambled channel while recording another scrambled channel, the subscriber
`would be advisedof his or her choices and allowed to act upon them.
`The TVID included a “mood guide,” which gave the subscriber a way ofindi-
`cating his or her mood. Those programs that were appropriate to his or her mood
`would then be displayed for selection to watch or record. The microprocessor
`could keep track of the programs watched and deduce the subscriber’s interests.
`The subscriber would thenbealerted to future programsthatfit his or her previ-
`ous viewing habits. The project reached the early prototype stage but was not
`completed becauseof other priorities.
`
`19.7. Managementof Expectations
`Mostof the subscriber’s problems havesolutions. Some solutions are more com-
`plex than others. The crux of the compatibility problem seems to be the expecta-
`tion that the term “cable ready” brings. To consumers, this means that the TV
`or VCR can be connected to cable andall features and all services are readily
`available. When operation of features is complicated or unexpected results are
`obtained,frustration and angersetin. Ifinstead, expectations were properly man-
`aged andthe subscriber/consumerhad a correct understanding of what was pos-
`sible, the likelihood of disappointment would be reduced. The fundamental
`problem is the managementof expectations.
`
`19.7.1 ComplexityOverload
`
`A major contributorto the difficulties of the consumerelectronics interface is the
`widevariety of choices available in features and functions, the way in which the
`features and functions are operated and controlled, and the diversity of services
`offered by cable operators. The numberof combinations and permutationsisal-
`most infinite. Just the simple matter of entering channel numbers hasseveral
`methods. Some products use an enter button. Others prescribe the way in which
`the digits must be entered. For example, on’some products, requesting channel7
`requires pressing 07. Others can require waiting for a fixed time after entering the
`command. The names for commonfunctions are brand specific. The numberof
`complex features boggles the mind.It may simply not be possible to preserveall
`the product functions and features while offering accessto all the available cable
`services.
`
`19.8
`
`Legal Aspects of Cable-Consumer Electronics Compatibility
`19.8.1 Compatibility Definitions
`The word compatibility should mean that two things work well with each other.
`In the case of compatibility between cable service and consumerelectronics,
`
`|
`
`| ||
`
`||
`
`|
`
`|
`
`aaanaaa
`
`8
`
`

`

`19.3 Connecting Cable, TVs, VCRs, and Set Top Terminals 757
`
`The antenna and cable/converter switch feature (usually operated by remote
`control) switches between two or more inputs to the TV. One input is intended to
`be from the converter and the other directly from the cable (or an antenna) . The
`intention here is to allow the TV's tuner to do the work when nonscrambled
`channels are watched and just use the converter/descrambler's tuner when
`scrambled channels are watched. This feature is similar in function and purpose
`to the auto bypass switch option in converter/descramblers.
`The TV/VCR switch feature on a VCR determines whether the entire cable
`spectrum is presented to the TV or just the channel tuned by the VCR or the tape
`playback.
`
`19.2.4 Consumer Frustration
`The two principal aspects of consumer frustration are the installation and the uti(cid:173)
`lization of consumer electronics products with cable services. Both of these frus(cid:173)
`trations come from the variety of services and features found in these products.
`
`19.3
`
`Connecting Cable, TVs, VCRs, and Set Top Terminals
`
`In 1987, the NCTA Engineering Committee formed a Subcommittee on Consumer
`Interconnection and developed a set of 2 7 diagrams indicating the most likely
`methods of connecting a TV, VCR, and one or more set top terminals along with
`an assortment of switches and signal splitters. Many of these diagrams are also
`found in consumer's manuals that come with new TVs and VCRs. All the inter(cid:173)
`connection schemes have advantages and disadvantages. None solves all of the
`problems. Reviewing some of these diagrams results in a better understanding of
`the complexity of the problem. 4
`
`19.3.1 Basic Cable and Trapped Premium Service Connection
`Figure 19.1 is illustration 12 of the NCTA connection diagram set. The cable is
`connected to the VCR, which is connected to the TV. This diagram is for the basic(cid:173)
`service-only subscriber and the subscriber who has premium services controlled
`by traps. No set top terminal is used. Since less than half of cable subscribers
`have set top terminals and since most subscribers connect more than one TV or
`VCR to cable, the majority of cable connections use this simple configuration.
`
`Advantages
`
`1. Least expensive.
`2. TV and VCR operate as with antenna connections.
`
`9
`
`

`

`758 Chapter 19 Consumer Electronics Interface
`
`Cable set top
`terminal
`
`• 0 I
`
`c::=::=:i
`VCR
`
`Signal
`splitter
`
`A/B
`switch
`
`CJ
`
`CJD
`
`TV with PIP
`
`Matching
`transformer
`
`~
`Remote
`control
`
`Cable input
`
`I c::=::=:i •01
`
`l ~
`
`H
`
`CJ
`
`CJD
`
`Figure 19.1
`
`In-home equipment and simplest connection without set top terminal.
`
`3. Can consecutively record different unscrambled channels automatically.
`4. Can watch one unscrambled channel while recording a different unscram(cid:173)
`bled channel.
`5. PIP works with unscrambled channels when VCR's baseband output is con(cid:173)
`nected to TV's baseband input.
`
`Disadvantages
`
`1. No scrambled services available for either watching or recording.
`2. No interactive services available.
`3. Have to remember to put TV to channel 3 when watching recorded tapes.
`4. Need to use two remote controls or a "universal" remote control.
`5. TV's parental control is inoperative when using VCR's tuner.
`6. Consumer's tuner subject to overload and damage from lightning strikes on
`cable.
`7. Signal leakage possible from inadequately shielded tuners.
`
`10
`
`

`

`19.3 Connecting Cable, TVs, VCRs, and Set Top Terminals 759
`
`Cable input
`
`D
`
`c:io
`
`Figure 19.2 Most common cable connection with set top terminal.
`
`19.3.2 A Simple Start
`Figure 19.2 is illustration 1 of the NCTA connection diagram set. The cable is con(cid:173)
`nected to the set top terminal, which is connected to the VCR, which is connected
`to the TV. This is by far the most popular connection method involving a set top
`terminal because it is the least expensive and simplest to implement and use.
`
`Advantages
`1. Inexpensive and easy to install.
`2. Easy to understand.
`3. Can record scrambled channels.
`
`Disadvantages
`
`1. Can't watch one channel and record a different channel.
`2. Can't consecutively tape different channels automatically because VCR tuner
`does not do channel selection.
`3. Neither the TV tuner nor the VCR tuner has any control.
`(a) TV's parental control, favorite channels, and last channel recall features
`are inoperative. The TV is just tuned to channel 3 (or 4).
`
`11
`
`

`

`760 Chapter 19 Consumer Electronics Interface
`
`(b) VCR's timer, parental control, favorite channels, and last channel recall
`features are inoperative. The VCR is just tuned to channel 3 (or 4).
`4. Need to use three remote controls or a universal remote control to turn on the
`three devices and put the TV and VCR to channel 3 (or 4) .
`5. Makes the TV's picture-in-picture feature useless.
`
`Special Case
`
`1. If the converter/descrambler has an auto bypass switch, then when the con(cid:173)
`verter is turned off, the entire cable spectrum passes through to the VCR, and
`the situation is exactly the same as in Figure 19.1, which is the case where no
`set top terminal is used. When again using a scrambled channel, the sub(cid:173)
`scriber must remember to put the VCR to channel 3 (or 4). If the set top termi(cid:173)
`nal has the channel-mapping feature and the TV or VCR does not, the same
`programming may appear on two different channel numbers. One channel
`number will be found on the set top terminal and the other on the TV or VCR.
`This may be confusing.
`
`19.3.3 Two Set Top Terminal Case
`Figure 19.3 is illustration 2 of the NCTA connection diagram set. The cable signal
`is split and connected to two set top terminals. The left set top terminal is con(cid:173)
`nected to a VCR, which is connected to one input of an A/ B switch, which is con(cid:173)
`nected to the TV. The right set top terminal is connected to the other input of the
`A/B switch.
`This is one of the least popular installations because of its expense and com(cid:173)
`plexity. It would be used by "techies" who want the most flexible system and can
`both visualize how it works and handle multiple remotes with ease. It will be very
`frustrating to others. The dual descrambler feature could be used to simplify both
`the installation and operation of this connection. On-screen displays could fur(cid:173)
`ther assist the subscriber. Despite the flexibility of this connection and the poten(cid:173)
`tial to make it relatively easy to use with on-screen displays, its usage is very
`limited.
`
`Advantages
`
`1. Most flexible.
`2. Can watch any authorized scrambled or unscrambled program.
`3. Can record any (other or same) authorized scrambled or unscrambled
`program.
`4. PIP can be used with both channels if the TV has baseband inputs that are
`connected to the VCR's baseband outputs.
`5. Useful in systems that have both analog scrambling and digital television.
`
`12
`
`

`

`19.3 Connecting Cable, TVs, VCRs, and Set Top Terminals 761
`
`Cable input
`
`3.5 dB
`
`A/B
`
`D
`
`CJO
`
`Figure 19.3 Connection with two set top terminals.
`
`Disadvantages
`1. Can't consecutively tape different channels automatically because VCR tuner
`does not do channel selection.
`2. Expensive hardware and monthly fees.
`3. Complex to install, many cables, many opportunities for signal leakage.
`4. Complex to operate; need to use at least three remote controls.
`5. Neither the TV tuner nor the VCR tuner has any control.
`(a) TV's parental control, favorite channels, and last channel recall features
`are inoperative. The TV is just tuned to channel 3 (or 4) .
`(b) VCR's timer, parental control, favorite channels, and last channel recall
`features are inoperative. The VCR is just tuned to channel 3 (or 4).
`6. Need to use three of four remote controls or a universal remote control.
`7. Most brands of set top terminals will operate simultaneously from one re(cid:173)
`mote control. Consequently, the subscriber may have to operate one terminal
`
`13
`
`

`

`762 Chapter 19 Consumer Electronics Interface
`
`as manual. If the set top terminal supports two control codes, four remote
`controls may be used with this configuration.
`8. If both analog scrambled and digital channels are being used, may need to in(cid:173)
`terchange set top terminals depending on which is to be recorded and which
`is to be watched.
`9. Switch at TV is usually manual, requiring getting out of the chair unless the
`switch is built into the TV and remote controllable.
`10. Splitter cuts signal in half and may introduce noticeable noise.
`
`Special Cases
`
`1. If the left converter/descrambler has an auto bypass switch, then when the
`converter is turned off, the entire cable spectrum passes through to the VCR,
`and the situation is exactly the same as in Figure 19 .1.
`2. If the right converter/descrambler has an auto bypass switch, then when the
`converter is turned off, the entire cable spectrum passes through to the TV,
`and the situation is similar to that shown in Figure 19 .1 but without the VCR.
`3. If the set top terminal has the channel-mapping feature and the TV or VCR
`does not, the same programming may appear on two different channel num(cid:173)
`bers. One channel number will be found on the set top terminal and the other
`on the TV or VCR. This may be confusing.
`
`19.3.4 Minimal Scrambled Channel Usage
`Figure 19 .4 is illustration 5 of the NCTA connection diagram set. The cable signal
`is split into two paths. The left path is connected to a set top terminal, which is
`connected to an A/B switch, which is connected to a TV. The right path is con(cid:173)
`nected to a VCR, which is connected to the other input of the A/B switch.
`This connection could be used by someone who wishes to continue the use
`of the features of their TV and VCR as enjoyed before cable, and only occasionally
`watches, but never records, scrambled channels. This is especially convenient
`for someone with only one scrambled channel or who uses the converter/
`descrambler only for pay per view but doesn't record that programming. The
`right-hand path is identical to Figure 19.1. Alternatively, since the path with
`the converter can be used to watch either scrambled or unscrambled channels,
`the only purpose for the switch is to watch recorded tapes. That could also be
`accomplished with the VCR's baseband output and the TV's baseband input.
`
`Advantages
`
`1. Easy to use if most of the usage is for unscrambled channels.
`2. Can watch any channel while recording any unscrambled channel.
`3. Can consecutively record unscrambled channels automatically.
`
`14
`
`

`

`19.3 Connecting Cable, TVs, VCRs, and Set Top Terminals 763
`
`~
`
`Cable input
`
`3.5 dB
`
`c:=::= •0
`
`A/B
`
`D
`
`CIO
`
`Figure 19.4 Connection for few scrambled channels.
`
`4. Especially easy if only one scrambled channel is taken.
`5. PIP can be made to work as long as the second picture is unscrambled.
`
`Disadvantages
`
`1. Can't record scrambled channels.
`2. On the left side, TV's parental control, favorite channels, and last channel re-
`call features are inoperative. The TV is just tuned to channel 3 (or 4).
`3. Switch must be manually operated unless it is built into the TV.
`4. Need to use three remote controls or a universal remote control.
`5. Splitter cuts signal in half and may introduce noticeable noise.
`
`Special Cases
`
`1. If the converter/descrambler has an auto bypass switch, then when the con(cid:173)
`verter is turned off, the entire cable spectrum passes through to the
`
`15
`
`

`

`764 Chapter 19 Consumer Electronics Interface
`
`...
`
`3.S dB
`
`A/B
`
`[ ]
`
`Cl 0
`
`Figure 19.5 Modified most common connection.
`
`TV, and the situation is similar to that shown in Figure 19.1 but without the
`VCR.
`2. If the set top terminal has the channel-mapping feature and the TV or VCR
`does not, the same programming may appear on two different channel num(cid:173)
`bers. One channel number will be found on the set top terminal and the other
`on the TV or VCR. This may be confusing.
`
`19.3.5 Improved Simple Connection
`Figure 19.5 is illustration 4 of the NCTA connection diagram set. This config(cid:173)
`uration inexpensively overcomes some of the difficulties of Figure 19.2 and espe(cid:173)
`cially makes sense if the TV has a built-in A/B switch.
`
`Advantages
`
`1. Inexpensive and easy to install.
`
`16
`
`

`

`19.3 Connecting Cable, TVs, VCRs, and Set Top Terminals 765
`
`..
`
`2. Easy to understand .
`3. Can record scrambled channels.
`4. PIP feature can be used when one of the channels is always unscrambled and
`the VCR's baseband output is connected to TV's baseband input.
`
`Disadvantages
`
`1. Can't consecutively tape different channels automatically because VCR tuner
`does not do channel selection.
`2. Need to use three remote controls or a universal remote control.
`3. On the left side, neither the TV tuner nor the VCR tuner has any control.
`(a) TV's parental control, favorite channels, and last channel recall features
`are inoperative. The TV is just tuned to channel 3 (or 4).
`(b) VCR's timer, parental control, favorite channels, and last channel recall
`features are inoperative. The VCR is just tuned to channel 3 (or 4).
`4. Switch at TV is usually manual, requiring getting out of the chair unless the
`switch is built into the TV and remote controllable.
`5. Splitter cuts signal in half and may introduce noticeable noise.
`
`Special Cases
`
`1. If the converter/descrambler has an auto bypass switch, then when the con(cid:173)
`verter is turned off, the entire cable spectrum passes through to the VCR, and
`the situation on the left side is exactly the same as in Figure 19.1.
`2. If the set top terminal has the channel-mapping feature and the TV or VCR
`does not, the same programming may appear on two different channel num(cid:173)
`bers. One channel number will be found on the set top terminal and the other
`on the TV or VCR. This may be confusing.
`
`19.3.6 Problematic Connection Example
`Figure 19 .6 is illustration 7 of the NCTA connection diagram set. This figure is al(cid:173)
`most never used with modern set top terminals because they usually require a
`separate frequency for receiving control signals. The VCR would block those
`signals, and the set top terminal would turn itself off after a preset time. Also,
`this configuration would block upstream signals, making impulse pay per view
`(IPPV) and other two-way services impossible.
`
`Advantages
`
`1. Attempts similar functionality to Figure 19 .4 but without the need for the A/B
`switch .
`2. PIP can be used with the second picture unscrambled if the TV has baseband
`inputs connected to baseband outputs from the VCR.
`
`17
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`

`

`766 Chapter 19 Consumer Electronics Interface
`
`Cable input
`
`=
`@
`
`•0
`
`D
`
`C>O
`
`Figure 19.6 Connection with set top terminal difficulties.
`
`Disadvantages
`
`1. Many set top terminals can't be used in this configuration.
`2. Impulse pay per view and other two-way services are impossible.
`3. Can't record scrambled programs.
`4. TV's parental control, favorite channels, and last channel recall features are
`inoperative. The TV is just tuned to channel 3 (or 4).
`5. Need to use three remote channels or a universal remote control.
`6. Converter/descrambler's parental control is inoperative when using VCR's
`channel 3 (or 4) output.
`
`Special Cases
`
`1. If the converter/ descrambler has an auto bypass switch, then when the set
`top terminal is off, the enti