`
`PMC Exhibit 2115
`
`Apple v. PMC
`|PR2016-01520
`
`Page 1
`
`PMC Exhibit 2115
`Apple v. PMC
`IPR2016-01520
`Page 1
`
`
`
`. I w1reess
`world ..
`
`I
`
`_Electronics, Television, Radio, Audio
`
`FEBRUARY 1977
`
`Vol83 No1494
`
`Contents
`
`31 Attitudes to mobile radio
`32 -~Viewdata by S. Fedida
`37
`:ransient 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
`44 Circuit ideas
`46 "Telecomms industry needs reorganization"
`47 Nickel cadmium cells by K. C. Johnson
`48 Announcements
`49 Logic design - 2 by B. Holdsworth and L. Zissos
`54 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 -
`Kennedy
`66 Transistor arrays - Circards 32 by J. Carruthers, J. H. Evans,
`-- T. Kinsler and P. Williams
`6b 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
`
`3 by G. R..
`
`Front cover shows a gr&up of
`silica optical fibres made! by
`Standard TelecommunicatioJj
`Laboratories for use in opticaf
`communication systems.
`·
`Photographer Paul Brierley
`
`IN OUR NEXT ISSUE
`
`rhythm
`Electronic
`accompaniment. Con(cid:173)
`structional design
`for a
`"rhythm section" which
`controls the musical timing
`of sources giving percus(cid:173)
`sion sounds and can be
`used with an electronic
`organ.
`
`Interference from ama(cid:173)
`teur stations with tele(cid:173)
`VISIOn, sound and audio
`equipment - how bad is it?
`Results of a RSGB survey
`that attempts to assess the
`situation fairly.
`
`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.
`
`l:.__i!
`
`\ . J
`
`Current issue price 35p, back issues (if available) 50p, at Retail and Trade Counter, Paris Garden,
`London SELBy post, current issue 55p, back issues (if available) 50p,order and payment to Room 11,
`J)orset House. London SEI 9LU.
`'Editorial & Advcrtisiri); offices: Dor»et Hou:;c. St<~mford Street. London SEI 9i:U.
`Telephones: Editorial 0 I 26 I 8620: Advertising 01-26 I 8339 .
`Tclegrams.Tclc,. Wiworld Bisnespres 25 I 37. London. C<1blcs. "Ethaworld, London SE 1.''
`Subscription rates: 1 year: £7.00 UK <ma overseas ($18.20 USA ancl Canada). Student rate: I year, £3.50
`UK and overseas ($9.10 USA and Canada).
`·
`Distribution: 40 Bowling Green Lane. London EC I R ONE. Telephone 01-837 3636.
`·Subscription>: Oakfield House. Perrymount Rd. Haywards Heat11. Sussex RH 16 3D H. Telephone
`ICY I.P.C. Business Press Ltd, 1977-
`0444 59188. Subscribers are requested to notify a change ot' address.
`
`1 ib~a I
`
`!nW<,~I~ Bu!011U~
`p._,,!I<H•l'll
`
`PMC Exhibit 2115
`Apple v. PMC
`IPR2016-01520
`Page 2
`
`
`
`32
`
`VIE'WDATA
`
`Wireless World, February 1977
`
`The Post Office's textual information and communications
`system: 1
`- backgro~nd and introduc~ion
`
`(
`
`by S. Fedida, B.Sc.(Eng.), M.Sc., F. I.E. E., A.C.G.I. 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(cid:173)
`play. It differs from teletext which is a
`specific sv.stem of broadcasting tex(cid:173)
`tual
`information
`interleaved with
`pictorial information: the two systems
`are complementary rather than com(cid:173)
`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 accessing a
`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(cid:173)
`ity.
`Many private c<i>mputer networks
`have also been installed world wide to
`provide business and scientific com(cid:173)
`puter facilities on in-house bases.
`Viewdata on the other hand belongs to
`a family of computer~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 ~ave to be
`specifically tailored to this class of users
`who may well have, and indeed will
`have, considerable expertise and intel-
`
`Viewdata index displayed on a com(cid:173)
`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
`information- retrieval and other pur(cid:173)
`poses, but have neither time nor indeed
`the inclination to .submit to the usually
`tiresome computer protocol. (The pro(cid:173)
`tocol is the set of rules and instructions
`which govern access to computers. and
`the use of their programmes.)
`·
`·
`Several attempts have been made in
`the recent past to bring computer-based
`information to the people.
`
`The Reston experiment. A well docu(cid:173)
`mented attempt
`is
`the Reston
`experiment2 in Virginia USA, using the
`Mitre Corporation interactive television
`system TICCIT which stands for
`"time-shared, interactive, computer(cid:173)
`controlled information television" uti-
`
`·[ising 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(cid:173)
`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
`the rate of 60 times a second.
`The individual selection of informa(cid:173)
`tion frames is carried out using a
`telephone connection from the user to
`the computer centre, together with the
`push-button set o'n 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 2115
`Apple v. PMC
`IPR2016-01520
`Page 3
`
`
`
`Wireless World, February 1977
`
`coded on line 480 or 481 (for even and
`odd frames) of the tv scan. A coupler/
`decoder at the user end examines this
`address and connects the video recorder
`to cable for the duration of the follow(cid:173)
`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
`service3 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 service to the
`home user and the small busines~. 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 user that the latter needs
`no special computer training whatever.
`It is believed that this system closed
`down after an irttial one-year experi~
`mental period.
`
`DIALS (calculation by telephone). This
`system4 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
`instructiohs being keyed on the push(cid:173)
`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(cid:173)
`tion.
`The calculation facilities offered by
`DIALS are fairly complex. They include
`the simple arithmetic operati0ns +,
`-, X, +, {/ and also basic facilities
`such
`as
`trigonometric
`functions,
`logarithms and so forth. It is 'also
`possible to input an algebraic expres(cid:173)
`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(cid:173)
`phone keyboards cannot be used with(cid:173)
`out substantial modifications to trans(cid:173)
`mit the required instructions. This is
`
`J
`
`J
`J
`J
`]
`
`J
`
`J
`
`J
`
`:F 13
`l 2xd 6
`
`(Blue)
`
`I J+/1 9 -#
`
`I (A 1 1 I
`I 'i L I ,.,
`I X 1 7 1
`
`.*,
`
`!Red)
`
`) 0
`
`2
`
`.R 5
`
`8
`
`+ 0
`
`Fig. 1. Overlay template attached to
`push-btltton telephone used in DIALS
`calculation service
`
`overcome by superimposing a remova(cid:173)
`ble template on to the dial and using
`groups of numbers and symbols for
`each of the required calculation sym(cid:173)
`bols. A diagram of the overlay is shown
`in Fig. l. For example, an expression
`such as
`"4X(3+5)-6.2"
`is transmitted as
`4*7*1~*05*2*86*52**~
`The end group of symbols **::; signifies
`the "go" instruction (instructing the
`computer to go ahead with the compu~
`tation).
`Trigonometric and logarithmic func(cid:173)
`tions are transmitted as a number
`preceded by F and followed by the
`argument in brackets, e.g. log10(X) is
`transmitted as F2(X), while library
`programmes are given .a number pre(cid:173)
`ceded by L, e.g. the integrating function
`is L36.
`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 iri a number of ways to be
`described later.
`/
`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 no'
`doubt added to the difficulties.
`
`Bell Picturephone computer access
`system. As part of the development of
`Picturephone in the USA, means were.
`developed to display computer generat(cid:173)
`ed information on the Picturephone
`station set.5
`. Picturephone is a Bell
`Telephone development which provides
`face to face communication between
`a t~o way
`telephone subscribers -
`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(cid:173)
`phone connection is also required. A
`typical local arrangement is shown in
`Fig. 2.
`Given an environment which has
`already been designed and established
`
`'
`
`~:
`
`33.
`
`to support Picturephone, 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 <lata.
`set (equivalent to a modem in UK
`· terminology) was developed to provide
`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~·,
`phone,station 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(cid:173)
`nalling) as in the previo\ls 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 'and'
`stored therein. It is converted irt the'·
`data set to a video signal which is then·.
`transmitted to the Picturephone statidl1'
`as if it were a standard Picturephone .
`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 30:
`times per second.
`.·
`Clearly this technical solution to the:
`retrieval and display of computer based
`information is satisfactory in an en vir:·
`onment where the Picturephone is'
`already established as a viable com(cid:173)
`munication service, and its develop-'
`ment might then have followed the lines
`of Viewdata in terms of protocol, extra
`facilities etc., had it be~n persevered
`with.
`Viewed however, as a means of
`providing simply a new information and
`communications service to the general
`public, its association with Picture(cid:173)
`phone delayed and indeed hindered its
`proper development and timely intro(cid:173)
`duction, since it depended on the
`establishment of a w.ideband Picture(cid:173)
`phone capability across the country ,to
`. achieve the penetration needed to make
`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 197017(
`more or less concurrently with the
`systems mentioned earlier. As with
`these systems there was the notion that
`there was an important potentiaf fot
`applying computer-based
`infor;nation
`systems to the public service area, buf
`that, while technologically there were
`no insuperable hurdles to overcome, .
`nevertheless there were fundamental·
`problems that had to be resolved before'
`practical and e(;onomically. viable sy.s:'
`terns could be designed and engineere<i,
`· ·
`to be usable by the general public.
`
`•· American Standard Code for Information
`Interchange.
`
`PMC Exhibit 2115
`Apple v. PMC
`IPR2016-01520
`Page 4
`
`
`
`34
`
`Wireless World, February 1977
`
`Fig. 2. (above). Basic local
`arrangement used in the
`Picturephone system '
`developed by Bell
`Telephone; (right)
`Picturephone computer
`access system
`
`Voiceband
`data (Ink
`
`Computer
`
`Data*
`set
`20203
`
`1--...:.....---1 Data *
`
`set
`20203
`
`Display
`data
`set
`
`Standard
`Picturephone
`loop
`
`+
`
`Data
`set
`403E2
`
`*Required if the
`display data set
`is remote from
`the computer
`
`In common with all these systems,
`Viewdata set out to solve these prob(cid:173)
`lems. As was to be expected, each
`solution turned out to be somewhat
`different, partly to adapt to a different
`environment, but also because of dif(cid:173)
`ferent design philosophies. These prob(cid:173)
`·
`lems are in the following areas:
`a the terminal
`• the transmission sys.tem
`a the computer relationship
`,a tlie system potential
`
`The terminal.. The terminal used to
`communicate with the computer clearly
`luis · to be a ·low-priced, attractivefy
`styled and reliable piece of electronics.
`to ensure a wide market penetration
`with the general public.
`·
`. The push-button telephone. is clearly
`such a terminal. Indeed in the standar(cid:173)
`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
`'many users 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 voict.
`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(cid:173)
`pread use in the computer field for some
`years, but their cost is still well'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 2115
`Apple v. PMC
`IPR2016-01520
`Page 5
`
`
`
`Wireless World, February 1977
`
`modifications, rriay 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(cid:173)
`phone (s.ee 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 a<;.lapters 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(cid:173)
`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(cid:173)
`ever, requires the use of the teleph?ne
`
`Fig. 3. (below). Displayed index from
`which the user self!cts the topic he
`requires. Fig. 4 (right). Index to maga(cid:173)
`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.
`the
`Alternative systems based on
`"frame grabbing" principle and trans(cid:173)
`mitting the whole data base contin(cid:173)
`uously over a tv br<;~adcast channel on
`cable or off air are also possible and
`indeed could 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(cid:173)
`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 information6.
`The absence of a return channel to
`the information source obviously
`implies that the system is not interac(cid:173)
`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(cid:173)
`ation is required to support a broad
`range of additional services as provided
`by Viewdata, then the telephone trans(cid:173)
`mission medium is the best availaole.
`This is why Viewdata has been
`implemented as an "intelligent" com(cid:173)
`munications medium using the tele(cid:173)
`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(cid:173)
`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(cid:173)
`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(cid:173)
`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 designs,.hardware logic
`• systems. But whereas we do not expect
`the user of !l piece of logic hardware to
`be able to design it, in the computer field
`there is not a great deal of distinc,:tion
`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 scho'ol 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(cid:173)
`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 . a-re ·-particularly
`relevant to 'the situation prevailipg 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
`.Viewdata 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 slightly.below par
`as regards educational standards. It is
`rather a question of specialised training,
`which few people outside the ranks of
`
`I
`'"
`
`J
`J
`l
`
`]
`]
`]
`J
`]
`J
`]
`]
`]
`J
`]
`]
`
`PMC Exhibit 2115
`Apple v. PMC
`IPR2016-01520
`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 en'!bled to
`instruct the machine (computer) to do
`all that the designers intended them to
`do.
`The first objective is
`to get the
`machine to the people, and when this
`has achieved a high degree of penetra(cid:173)
`tion, then is the time to refine it to
`attempt to meet the needs of those who
`may want to do more with the machin'e
`than most people.
`
`The computer dialogue. How then is it
`possible to overcome the very consider(cid:173)
`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(cid:173)
`derstand" what the user wants. The
`usual method of communicating with.
`computers is to design a special pro(cid:173)
`gramming language which the user has
`to learn and which the computer is
`programmed to "understand." This
`works adequately in conventional com(cid:173)
`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(cid:173)
`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 is the 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(cid:173)
`mation on offer is very limited, the
`whole index may be displayed on one
`frame only.
`In Viewdata the information is sub(cid:173)
`divided in a tree structure. The top of
`
`1 ndex- page 3
`
`I
`
`33
`
`34
`
`35
`
`page 30
`
`31
`
`32
`
`I
`I
`
`News, etc.
`
`I
`
`-1. .,.
`
`I
`
`322 323 324
`
`Entertainment
`
`page 320 . 321
`
`page
`
`3230
`
`What's on
`
`I .
`I
`I I
`
`3232
`
`3233
`
`3234
`
`I 3231
`I
`. I 32301
`I
`
`page 32300
`
`32304
`32302
`32303
`
`Week 8/8/-17/8
`
`323004
`323002
`323000
`page
`323001
`323003
`I
`Friday
`
`is
`in Vie-wdata
`Fig. 5. Information
`sub-divided in a tree structure. This
`gives an example of main topics (at the
`top) being sub-divided down to sub(cid:173)
`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 ievels, 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 number.s
`being a
`correspondingly large
`number of digits
`
`WirPIPss Wnrlil. FPhruarv 1977
`
`ing to an easily understood classifica(cid:173)
`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(cid:173)
`ticable to offer such a complex index in
`dne 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 dowh, 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 and
`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.
`First ihe 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 ~he means of the
`general public.
`It is for all these reasons that the
`index selection was chosen. With this
`arrangement the whole system is kept'
`basically simple and easy to understand.
`(To be continued)
`
`References
`I. 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 1971.
`2. In Touch Services, Comptding. November
`1973, report by Pamela Evans.
`4. DIALS (Calculation by Telephone),
`Yoshijuki Mirna and Toshiaki Shibagama,
`Japan Telecommtmications Review 197().
`5. P. S. Warwick and G. W. Phipps, The
`Picturephone System, Computer Access,
`BSTJ, Vol. 50, No 2, February 19'7'1.
`·
`6. S. Fedida, Viewdata - An Interactive
`Information Me,dium for the General Public
`using the Telephone Networks. 6th Interna(cid:173)
`tional Broadcasting Convention, 20-24 Sep(cid:173)
`tember 1976.
`
`PMC Exhibit 2115
`Apple v. PMC
`IPR2016-01520
`Page 7
`
`