PMC Exhibit 2066
`PMC Exhibit 2066
`Apple v. PMC
`Apple v. PMC
`|PR2016—OO753
`IPR2016-00753
`Page 1
`Page 1
`
`

`
`Electronics, Television, Radio,‘ Audio
`FEBRUARY1977
`voles No1494
`
`Contents
`
`3.1 Attitudes to mobile radio
`32.-«Viewdata by S. Fedida
`37
`transient intermodulation in amplifiers by Bert Sundqvist
`39 H.F. predictions
`\\
`40 News of the month
`Unique optical link
`Television “sound” for the deaf
`Band II ferrite rod aerials
`Circuit ideas
`“Telecomms industry needs reorganization”
`Nickel cadmium cells by K. C. Johnson
`Announcements
`Logic design — 2 by B. Hoidsworth and L. Zissos
`Letters to the editor
`‘
`WARC 1979 and official secrecy
`Aural sensitivity to phase
`Advanced pre-amplifier design
`57 Electronic systems by W. E. Anderton
`59 Further notes on the Wireless World teletext decoder by J. F.
`Daniels
`<
`61 Literature received
`62 Weather satellite picture facsimile machine — 3 by G. R. .
`Kennedy
`’
`V
`66 Transistor arrays — Circards 32 by J. Carruthers, J. H. Evans,
`’" T. Kinsler and P. Williams
`62> Mystery Soviet over-the-horizon tests
`69 Digital angle modulation -—— 2 by R. Thompson and D. R.
`Clouting
`75 Electronica 76
`'
`76 Sixty years ago
`77 Characteristics and load lines -—— 4 by S. W. Amos
`80 World of amateur radio
`81 New products '
`123 APPOINTMENTS VACANT
`136 INDEX TO ADVERTISERS
`
`Current issue price 351:, back_ issues (if available) 50 . at Retail and Trade’ Counter, Paris Garden.
`London SE1. By past. current issue 551). back issues (i available) 50p,_order and payment to Room 11,
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`_
`Telephones: Editorial 0| 261 8620: Advertising Ol~26l 8339.
`.
`TclegralnsTelcx. Wiwnrld Bisnespres 25l37.London. Cables. “Eihaworlcl. London SE1."
`Subscription rates: 1 year: £7.00 UK and overseas ($18.20 USA and Lianada). Student rate: l year. £3.50
`UK and overseas ($9.10 USA and Canada).
`‘
`*
`_
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`V 0444 59188. Subscribers are requested to notify a change of address
`C3
`l.P.C. Business Press Ltd. 1977-
`
`' Vsewdata
`blitkei csdmi
`
`a
`t
`Front cover shows 2: gm '
`by
`silica optical
`fibres mad
`Standard Telecommunication
`Laboratories for use in*op_tical
`communication systems.
`Photographer Paul Brierley
`
`IN OUR NEXT ISSUE ..
`
`.
`
`rhythm
`Electronic
`Con-
`accompaniment.
`structional design for.
`a
`"rhythm section" which
`controls the musical timing
`of sources giving percus-
`sion sounds and can be
`used with an electronic
`organ.
`
`Interference from ama-
`teur stations with tele-
`vision‘,
`sound and audio
`equipment — how bad is it?
`Results of a RSGB survey
`that attempts to assess the_
`situation fairly.
`
`7 Television test generator.
`Construction of a laboratory
`instrument giving cross‘-
`hatch, dot matrix,
`colour
`bar and ‘grey scale patterns’.
`Simple design based on ‘
`t.t.l. integrated circuits.
`
`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 2
`
`

`
`‘is:
`
`i
`
`Wireless World. February 1977
`
`i/IEWDATA
`The Post O-ff,ic,e,’s__t_extual
`information and communications
`system:
`1 _— background. and introduction
`
`. py s. Fedida, l§.Sc.(Eng.),‘M.Sc., F.|.E.E., A.Cl.G.l. Post office Research centre
`
`Viewdata is a system for disseminat-
`ing, and retrieving computer based
`information, using the domestic
`telephone line for communication and
`the domestic television set for dis-
`play. It differs from teletext which is a
`specific system of broadcasting tex-
`tual
`information interleaved with
`pictorial information: the two systems
`are complementary rather than com-
`petitive. This article looks at earlier
`systems of accessing computer data
`banks
`from remote points using
`telephone lines and then introduces
`the Viewdata system now on pilot
`trial in the UK.
`‘
`'
`
`Essentially the concept of accessinga
`computer data bank from a remote
`point using telephone lines is not new.
`The technique was demonstrated in the
`mid-60s by Dr Sutherland of
`the
`Massachusetts Institute of Technology,
`and has been used increasingly ever
`since, but mainly by the professional
`computer user.
`Indeed. networks of
`computers ' have been "installed in
`various parts of the world for
`this
`purpose
`and for
`the purpose of
`‘computation. In the~US an ambitious
`computer network ARPANET has been
`in operation for some years and has
`been extended to provide world wide‘
`coverage.
`In Europe a new system
`EURONET" is
`in process of being
`implemented to provide a computer
`network for scientific and technical
`information in the European Commun-
`ity.
`,
`,Many private computer networks
`have also been installed world wide to
`provide business and scientific_com-
`puter facilities on in—house bases.
`Viewdata on the other hand belongs to
`a family of(:ompuLer—based information
`systems which are intended for the
`general public, i.e. users who have no
`computer training whatever and indeed
`who do not intend to undergo such
`training.
`. Systems of these kinds have to be
`specifically tailored to this class of users
`who may well have, and indeed_will
`have, considerable expertise and intel-
`
`index. displayed on a com-
`Viewdatci
`mercial teletext/Viewdata receiver.
`
`lectual ability but not necessarily in the
`intricacies and minutiae of computer
`programming.
`In general
`they are
`anxious to use the capabilities of
`computers both for the purpose of
`informationvretrieval and other pur-
`poses, but have neither time nor indeed
`the inclination to‘ submit to the usually
`tiresome computer protocol. (The pro-
`tocol is the set of rules and instructions
`which govern access to computersand
`the use of their programmes.)
`Several attempts have been made in
`the recent past to bring computcr—based
`information to the people.
`
`The Reston experiment. A well docu-
`mented attempt
`is
`the Reston
`experiment2 in Virginia USA, using the
`Mitre Corporation interactive television
`system TICCIT which stands for
`“time—sharecl,‘ interactive, computer-
`controlled information television” uti-
`
`'lising a standard television receiver as a
`display.
`Essentially the system requires that
`the user be connected to a cable
`television network, over which are
`transmitted a number of still tv frames,
`60 different frames per second. Thus
`assuming an information cycle time of
`10 seconds,
`i.e. each user accesses, a
`different frame every 10 seconds, the
`system can support 600 users simultan-
`eously on a dedicated tv channel, each
`user
`receiving his own selection of
`information.
`Associated with the user television
`receiver is a video tape recorder, which
`takes a recording of the frame intended
`for the user and plays it back to the tv at
`thexrate of 60 times a second.
`The individual selection of informa-
`tion frames is carried out using a
`telephone connection from the user to
`the computer centre, together with the’
`'push_—button set on the telephone with -
`which the user may key the number of
`the frame required. When this is done
`the computer
`transmits this frame
`followed by a user address, which is
`
`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 3
`
`

`
`Wireless World, February 1977
`coded on line 480 or 481 (for even and
`odd frames) of the tv scan. A couplerl
`decoder at the user end examines this
`address and connects the video recorder
`to cable for the duration of the follow-
`ing frame,
`thus capturing the frame
`selected.
`The home equipment needed in this
`system is not only a tv set but also a
`video tape recorder and a special
`adapter, while the communications
`medium consists of a wideband cable
`and a telephone connection.
`
`In-Touch. This computer information
`service’ was launched in Seattle,
`Washington in 1973 with the backing of
`the Seattle First National Bank for the
`purpose of providing a number of
`financial and budgeting servicerto/the
`home user and the small business. It
`uses the push-button telephone, to send
`‘instructions to the computer, which
`then provides a voice response. Thus
`the terminal equipment is minimal. The
`main problem of course is to so organise
`the service that the obvious limitations
`of
`the terminal equipment both in
`transmitting and receiving information
`are effectively overcome. The other
`problem noted by the originators of the
`scheme, and somewhat related to the
`above but clearly much more complex,
`is to so arrange the dialogue between _
`computer and userthat the latter needs
`no special computer training whatever.
`It
`is believed that this system closed
`down after an intial one-year experi-
`mental period.
`
`DIALS (calculation by telephone). This i
`system“ was developed by NTT (Nippon
`Telegraph and Telephone Co.),
`the
`public telephone administration in
`Japan, to provide a calculation service
`to telephone subscribers, on an on-line,
`real-time basis. The public service was
`initiated in 1970/71. In this case also the_
`push-button telephone is used as a
`transmit and receive terminal, outgoing
`instructions being keyed on the push-
`button keypad and transmitted to‘ the
`computer as a sequence of audio tones.
`The computer response is a voice signal
`which gives the result of the computa-
`tion.
`-
`The calculation facilities offered by
`DIALS are fairly complex. They include
`the simple arithmetic operations +,
`—, X,
`-2,
`and also basic facilities
`such
`as
`trigonometric
`functions,
`logarithms and so forth.
`It
`is ‘also
`possible to input an algebraic expres-
`sion with dummy arguments which is
`memorised by the computer. This is
`then followed by sets of arguments
`supplied by the’ user on which the
`computer operates. Finally it is possible
`to call some library programmes, for
`example for statistical work, compound
`interest and the like.
`.
`Clearly the standard 12-button tele-
`phone keyboards cannot be used with-
`out substantial modifications to trans-
`mit the required instructions. This is
`
`33.
`
`to support Picturcphone, it is clearly,‘
`possible to enhance the video facility by_'
`providing the option of displaying
`computer-based information as an
`alternative to the normal‘ pictorial
`information. To do this a display data.
`set (equivalent
`to a modem‘ in UK‘
`* terminology) was developed to provide j
`computer access to Picturephone users.
`Essentially this data set, which is sited
`‘ at the exchange, acts as an interface
`between the computer and the Picture-2’:
`phvonesstation at the user’s premises.
`Instructions to the computer are sent
`by the customer to the exchange using
`the push-button telephone (m.f. sig-
`nalling) as in the previous systems. This
`is converted by the display data set to
`ASCII* characters and transmitted to
`the computer along a narrow-band data '
`line. which could be a standard voice
`circuit. The computer response, which
`is a string of ASCII characters,
`is.
`received by the display data set ‘andf
`stored therein.
`It
`is converted in the,"
`data set to a video signal which is the
`transmitted to the Picturephone statioh
`‘ as if it were a standard Picturephonei‘,
`signal. Since there is no storage at the"
`subscriber's end this information needs
`to be sent repeatedly, television fashion;
`to keep the display ‘refreshed, at 30f
`times per second.
`Clearly this technical solution to the-
`retrieval and display of computer based.‘
`information is satisfactory in an envir-f
`onrnent where the Picturephone is"
`already established as a viable "com-_
`munication service, and its develop-"
`ment might then have followed the lines
`of Viewdata in terms of protocol, extra
`facilities etc., had it been persevered
`with.
`
`Viewed however, as a means of:
`providing simply a new information and
`communications service to the general
`public,
`its association with Picture-
`phone delayed and indeed hindered its
`proper development and timely intro-
`duction, since it depended on the‘
`establishment of awideband Picture-
`phone capability across the countryflto
`\ achieve the penetration needed to make V
`the service economically viable and
`truly available to the general public.
`,
`
`_:_
`
`-
`
`‘
`Development of-Viewdata
`The Viewdata concept began in the Post
`Office Research Department in 1970/71;,‘ _
`more or
`less concurrently with the
`systems mentioned earlier. As with’
`these systems there was the notion that
`there was an important potential foij
`applying computer-based information
`systems to the public service area, buff
`that, while technologically there were
`no insuperable hurdles to overcome, ’
`nevertheless there were fundamental’;
`problems that had to be resolved before
`practical and economicallyvviable sys-J
`tems could be designed and engineered,
`to be usable by the general public. -
`'i
`
`" American Standard Code for Information
`lnterc hange.
`
`. H
`(Red)
`
`‘
`
`(Blue)
`
`1. Overlay template attached to
`Fig.
`push-button telephone used in DIALS
`calculation service
`V
`
`'
`
`overcome by superimposing a remova-
`ble template on to the dial and using
`groups of numbers and symbols for
`each of the required calculation sym-
`bols. A diagram of the overlay is shown
`in Fig. 1. For example, an expression
`such as
`“4 ><(3 +5)—G.2"
`is transmitted as
`4*7*l$*05*2*86*52**:
`The end group of symbols **: signifies
`the “go" instruction (instructing the
`computer to go ahead withthe compu-
`tation).
`A
`*
`Trigonometric and logarithmic func-
`tions are transmitted as a number
`preceded by F and followed by the
`argument in brackets, e.g.
`log,D(X) is
`transmitted as F2(X), while library
`programmes are given .a number pre-
`ceded by L, eg. the integrating function
`is L36.
`‘
`7
`.
`The use of the template has been
`explained at some length to indicate the
`complexity introduced in a system of
`this kind, if one is limited to using just
`the 12 buttons of the telephone push-
`button set. This complication is avoided
`in Viewdata in a number of ways to be
`described later.
`,
`4’
`The use of a voice response system for
`imparting the kind of
`information
`mentioned above is obviously fraught
`with pitfalls, and the complexity of the
`coding needed to pass instructions nos
`doubt added to the difficulties.
`
`Bell Picturephone computer access
`system. As part of the development of
`Pi(:turephone in the USA, means Were.
`devéloped to display computer generat-
`ed information on the Picturephone
`station set.5. Picturephone is a Bell
`Telephone development which provides
`face to face communication between
`telephone subscribers — a two way
`video telephone. Special
`lines (Video
`access lines) must be installed to
`transmit Picturephone information to
`the subscribers. These consist of two
`pairs of
`lines equalized to transmit
`satisfactorily, at
`least
`in the initial
`stages, a bit
`rate of 6.312 Mbit per
`second.
`In addition the normal
`tele-
`' phone connection is also required. A
`typical local arrangement is shown in
`Fig. 2.
`Given an environment which has
`already been designed and established
`
`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 4
`
`

`
`cusToMER's
`PREMISES
`
`LOCAL CENTRAL ~
`OFFICE
`
`Telephone
`switch
`
`Wireless World, February 1977
`
`2-wire
`telephone
`trunks
`
`Picturephone
`trunks
`
`_
`_
`Fig. 2. (above). Baszc local
`arrangement used in the
`Picturephone system "
`developed by Bell
`Telephone; (right)
`Picturephone computer
`access system
`
`4
`
`Voice-band
`data link
`
`‘Standard
`Picturephone
`loop
`
`Computer
`
`-if Required i1’Lh'e
`display data set
`is remote from
`the computer
`
`Picture-phone
`switch
`
`L.___.__
`
`‘
`
`In ‘common with all these systems,
`Viewdata set out to solve these protr
`lems. As was to be expected, each
`solution turned out to be somewhat
`different, partly to adapt to a different
`environment, butalso because of dif-
`ferent design philosophies. These pr0l')~
`lems are in the following areas:
`'
`'
`Q the terminal
`(the transmission system
`0 the computer relationship
`9 the system potential
`
`The terminal. The terminal used to
`communicate with the computer clearly
`‘has’ to he a ‘low~priced, attractively
`styled and reliable piece of electronics.
`to ensure a wide market penetration
`with the general public.
`'
`,
`The push-button telephonelis clearly
`I such axterminal. Indeed in the standar-
`disation of m.f. telephone systems, this
`' possibility has been kept firmly in view,
`and has resulted in ‘proposals for
`_enhanced push-button sets containing
`_16 keys.
`
`While the push-button telephone is a
`suitable transmission terminal,
`for
`ignyiusers it has obvious limitations
`for the more advanced applications,
`Indeed attempts at squeezing a large
`alphabet from the, limited number of
`keys only leads, to confusion and‘
`irritation on the part of the user. As a
`receiving terminal it requires that the
`'-computer response be a voice response.“
`Here also this could well be acceptable
`some time, but
`it suffers from very
`serious limitations. Where the amount
`of information is fairly limited, e.g. one
`or
`two items of
`information, voice
`response is probably acceptable to’
`many users. Even then,
`the fleeting
`nature of the voice response hinders
`comprehension very seriously and
`messages need to be repeated several
`times to allow full understanding, the
`taking of notes etc.
`.
`Two of the systems described above
`used the pushbutton telephone, but the
`extent and versatility of the service
`planned for Viewdata made the push-
`
`button telephone associated with >VOiC£
`response quite unsuitable for a good
`general purpose information system
`capable of growing to meet the needs of
`the users.
`The alternative to a voice response
`system is the visual display. This is
`easier to implement and vastly cheaper
`as far as the computer is concerned and
`to the user it offers unparalleled scope
`in comprehension and in the range of
`information that can be put over. It can
`lend itself to multilingual and graphical
`information" fairly readily. One of the
`important aspects of Viewdata is the
`possibility of implementing a wide
`range of information services across
`multi—national boundaries.
`Visual displays have been in wides-
`pread use in the computer field for some
`years, but their cost is still we1l‘above
`that considered acceptable to the mass
`market. It is therefore not surprising
`that many information systems have
`sought to capitalise on the domestic
`television display’, which, with suitable
`
`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 5
`
`

`
`Wireless World, February 1977
`
`modifications, may be adapted to
`become the ideal information terminal
`for home use. It also has considerable
`attractions in the form of a dedicated
`communication station for office use —
`what we have called the Viewdata-
`phone (see below).
`Ideally an unmodified tv set, with an
`adapter box capable of transforming it
`into a computer terminal,
`is the best
`approach, and while this is technically
`quite feasible for Viewdata, where
`transmission data rates are low, and
`colour is not an essential facility, it is
`,much less suitable for teletext. In the
`last—mentioned case and where a colour
`display is required in Viewdata (and
`there is no doubt that the addition of
`colour gives considerable visual _
`appeal), a built-in adapter is preferable.
`It is hoped that tv sets with integral
`adapters, and external adapters for
`existing tv sets, will be available on the
`market quite soon.
`
`The transmission system. Initially the
`major impetus to the development of
`information systems for the home was
`provided by the availability of spare
`bandwidth in cable tv systems. Clearly
`this makes sense, since the spare
`bandwidth is available at marginal cost,
`the main use being to convey television
`programmes. Hence in countries where
`cable tv networks are fairly extensive,
`such as the USA and Canada,
`the
`emphasis has been on using this
`medium for the transmission of infor-
`mation.
`The Reston [experiment mentioned
`above is an example of such a system
`and clearly provides a great deal of
`information, e.g. pictures, which Cannot
`be easily accommodated with narrow
`band systems such as those depending
`on telephone lines. This system, how-
`ever, requires the use of the telephone
`
`Fig. 3. (below). Displayed index from
`which the user selects the topic he
`requires. Fig. 4 (right). Index to maga-
`zine 3 as listed on the Fig. 3 display,
`showing the progressive nature of the
`Viewdata index.
`
`network as well, to provide the selection
`means and thus lose‘ the advantage of
`marginal costing of unused bandwidth
`of the tv cable installation.
`Alternative systems based on the
`“frame grabbing” principle and trans-
`mitting the whole data base contin-
`uously over a tv broadcast channel on '
`cable or off air are also possibleand
`indeed (‘.m1ld become very attractive. In
`these systems the page selection is
`carried out at the receiving point and
`hence they do not require a return
`communications channel.. Properly
`designed they are capable of transmit-
`ting a great deal more information than
`the Reston system, provided pictorial
`information is not required. A single tv
`channel, for example, could provide the
`equivalent
`of
`30,000
`pages
`of
`alphanumeric information“.
`The absence of a return channel to
`the information Source obviously
`implies that the system is not interac-
`tive, i.e. the user cannot respond to the
`information provided, or generate
`information himself. Thus the system is
`completely passive and cannot provide
`services requiring user interaction.
`Where spare tv channels are not
`available, either off-air or in a cable tv
`environment, or when interactive oper-
`ation is required to support a broad
`range of additional services as provided
`by Viewdata, then the telephone trans-
`mission medium is the best available.
`This is why Viewdata has been
`implemented as an “intelligent" com-
`munications mcdium using the tele-
`phone system. In order to impose the
`minimum of constraints on the rapid
`build up of
`the service and ensure
`rugged and reliable operation, only the
`current well—proven transmission per-
`formance of the telephone network is
`postulated; as indeed is the exi_sting
`telephone switching environment. Thus
`the current experimental Viewdata
`system on pilot trial uses 1200 bits per
`second for computer to terminal and 75
`bits in the reverse direction. As deve-
`lopments and enhancements take place
`in this area,
`they will be gradually
`introduced in Viewdata with the aim of
`improving performance and reducing
`costs.
`
`35
`
`The computer relationship. In Viewdata
`as in the other systems noted earlier, the
`problem of how to enable users with no
`special computer training to access and
`instruct a computer loomed large,
`mainly because computer programming
`had developed from the very beginning, '
`and with very few exceptions, into an
`increasingly complex set of routines.
`These demanded a great deal of con-
`centration, attention to detail and
`constant and continuous practice to be
`mastered effectively.
`In a sense the computer programmer’
`is a designer of a logic system, who uses ‘
`logical
`instructions instead of using
`logical circuit interconnections like his’
`colleague who designshardware logic
`systems. But whereas we do not expect
`the user of a piece of logic hardware to
`be able to design it, in the computer field
`there is not a great deal of distinction
`between the design programmer and
`the user programmer. This is in part due
`to the extraordinary flexibility of the
`computer. Dedicated and trained users
`are able to modify a programme or if
`necessary write new ones to suit their
`specific applications.
`To quote from the originators of
`In-Touch, “There is the problem of how
`to communicate with someone who
`only had a high school education or
`less”. “How do you get them to operate
`a computer error free?” “Having done
`that you must program the computer to
`respond satisfactorily to the communi-
`cation by that customer. You also have
`to configure the hardware (and the
`software) consistent with customers
`who are not sophisticated and therefore
`do not expect anything to break.”
`These comments are particularly"
`relevant to the situation prevailing in
`Viewdata and some of
`the above
`systems, where the range of services
`extend far beyond the provision of a
`simple set of
`information. But
`in
`.\/iewdata the designers of the system
`have taken a substantially. more
`enlightened view. They do not
`look
`down on the user as being “naive",
`“unsophisticated” or slightlybelow par
`as regards educational standards. It is
`rather a question of specialised training,
`which few people outside the ranks of
`
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`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 6
`
`

`
`36
`
`those who do computer programming
`as a full
`time occupation have the
`‘ opportunity or even the willingness to
`acquire.
`A clear distinction is drawn between
`computer programmers who design
`programmes and computer users who
`use them and are thus enabled to
`instruct the machine (computer) to do
`all that the designers intended them to
`do.
`the
`to get
`. The first objective is
`machine tothe people, and when this
`has achieved a high degree of penetra-
`tion, then is the time to refine it to
`attempt to meet the needs of those who
`may want to do more with the machine
`than most people.
`\
`
`The computer dialogue. How then is it
`possible to overcome the very consider-
`able problem of ensuring adequate
`communications between user and
`computer? The key is in the dialogue
`between the two.
`The computer must first of all “un-
`derstand” what
`the user wants. The
`usual method of communicating with’
`computers is to design a special pro-
`gramming language which the user has
`to learn and which the computer is
`programmed to “understand.” This
`works adequately in conventional com—_
`puter programming but is clearly far too
`complicated in this application. Another
`approach is to use a prompting system:
`the computer offers a number of choices
`from which the user selects the one
`most appropriate to his requirements.
`This clearly limits the user's freedom
`but nevertheless avoids many of the
`problems connected with formal com-
`puter languages.
`The simplest of these dialogues is an
`index from which the user selects the
`topic he requires (see Figure 3). This of
`course isthe technique used in teletext.
`But the index in Viewdata is progressive
`(see Fig. 4), unlike that
`in ‘ teletext,
`where since the total amount of infor-
`mation on offer
`is very limited,
`the
`whole index may be displayed on one
`frame only.
`In Viewdata the information is sub-
`divided in a tree structure. The top of
`
`Index— D396 3
`
`page
`
`320 . 321
`
`322
`
`323
`
`324
`
`Entertainment
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`
`information in Vie‘wdata is
`5.
`Fig,
`sub—divided in a tree structure. This
`gives an example of main topics (at the
`top) being sub-divided down to sub-
`topics (at the bottom).
`
`the tree is a list ‘of main topics, each of
`which is then subdivided into sub-topics
`all
`the way ‘ down to the piece of
`information required. (See Fig. 5.) Some
`of the branches in Viewdata may extend
`down to perhaps 8 to 10 levels, thus
`implying a choice from several hundred
`million pages.
`The reason for the difference is to do
`with the scope and depth of treatment
`of the information supplied. Whereas in
`teletext the content of a magazine of
`which only one is transmitted at present
`is 100 pages, in the proposed Viewdata
`system a small
`local system might
`contain as many as 50,000 to 100,000
`pages of
`information. Clearly it
`is
`therefore necessary to subdivide this
`into a number of sub-sections, accord-
`
`Fig. 6. Some
`information is
`presented in
`considerable detail,
`with page numbers
`being a
`correspondingly large
`.
`.
`number of digits
`
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`mg to an easily understood classifica-
`tion which enables the user to find the
`bit he wants quickly and simply.
`Some of the information is given in
`great detail and the corresponding page
`number could have 6, 7 or even 8 digits
`(see Fig. 6). It would clearly be imprac-
`ticable to offer such a complex‘ index in
`one lump. Hence the selection system
`chosen.
`At every selection step the user only
`needs to key a single digit to move to the
`next
`level down,
`thus considerably
`simplfying and speeding up the whole
`operation.
`.
`Other selection or retrieval systems
`are, of course, possible. For example, it
`would be possible to print
`the total
`computer index and have it available
`like a directory to all users. This entails
`the additional expense in printing and
`distribution, presents serious updating
`problems and may confuse many users.
`By incorporating the index in the
`system this is made self-contained an
`flexible.
`~
`'
`A fundamentally different approach
`to the step by step index is that used in
`many information retrieval systems.
`This is
`the use of “key-words.” An
`example of the use of keywords would
`be to key “football results". There are
`several problems associated with a
`selection by keywords. These are fairly
`easy to resolve in computer data bases
`intended for the professional, but not so
`easy for a public service.
`H
`First the keyword approach requires
`a “thesaurus,” a dictionary of terms
`used together with their synonyms
`which are meaningful to the computer,
`Secondly,
`the user would require a
`much more complex keyboard than the
`basic keyboard normally provided.
`Thirdly the use of keywords involves
`the computer in what could be a
`considerable search, and hence would
`cause the computer costs to escalate
`probably, beyond the means of the
`general public.
`these reasons that the
`It is for all
`index selection was chosen. With this
`arrangement the whole system is kept‘
`basically simple and easy to understand.
`(To be continued)
`
`References
`l. The Euronet Project, by G. W. P. Davies,
`Proceedings of the European Computing
`Conference, London, September 1975.
`2. The Reston, Virginia, Test of the Mitre
`Corporation, interactive Television System.
`The Mitre Corporation, Washington, Report
`MTP352, May 197].
`2. in Touch Services, Computing. November
`1973, report by Pamela Evans.
`4. DIALS (Calculation by Telephone),
`Yoshijuki Mima and Toshiaki Shibagama,
`Japan Telecommunications Review 1970.
`5, P. 5. Warwick and G. W. Phipps, The
`Picturephone System, Computer Access,
`BSTJ, Vol. 50, No 2, February 1971.
`f
`6. S. Fedida, Viewdata — An Interactive
`Information Medium for the General Public
`using the Telephone Networks. 6th Interna-
`tional Broadcasting Convention, 20-24 Sep-
`tember l976.
`—
`
`PMC Exhibit 2066
`Apple v. PMC
`IPR2016-00753
`Page 7