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`PMC Exhibit 2117
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`IPR2016-01520
`Page 1
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`\
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`f
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`PMC Exhibit 2117
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`

`

`l
`
`l '
`
`wireless
`world
`
`Electronics, Television, Radio, Audio
`
`APRIL 1977
`
`Vol 83
`
`No 1496
`
`Contents
`35 Time, gentlemen, please
`36 NRDC surround-sound system by M. A. Gerzon
`39 News
`40 Characteristics and load lines - 5 by S. W. Amos
`44 Wireless World amateur radio station
`45 Sensitive metal detector by D. E. O'N. Waddington
`48 H.F. predictions·
`53 New of the month
`Bullock's boardroom and the engineer
`Britain pioneered the integrated circuit"
`Vmos devices "middle of this year"
`57 Education by radio in Honduras by M. K. Bates
`60 Literature received. 100 years ago
`61 Circuit i4eas
`Simple noise generator
`Variable band-pass filter
`Ripple eliminator
`·65 Viewdata- 3 by S. Fedida
`70 World of amateur radio
`73 Electronic rhythm unit - 2 by A. Battaiotto and G. Ronzi
`76 Letters to the editor
`The Warden Report
`Current dumping amplifier
`. Advanced pre-amplifier design
`79 Broadcast stereo coder by T. Brook
`83 Power semiconductors by M. R. Sagin
`93 New products
`96 Just for the record by A. D. Foster
`APPOINTMENTS VACANT
`INDEX TO ADVERTISERS
`
`the
`Front cover, showing
`medium wave aerial at Radio(cid:173)
`landia, Comayagua, Honduras,
`introduces the article on edu(cid:173)
`cation by radio in that country
`(page 57).
`Photographer Paul Brierley
`
`.IN OUR NEXT ISSUE
`
`Electrolytic capacitor tester.
`Enables the value of an electro(cid:173)
`lytic capacitor to be measured
`automatically and
`the
`result
`displayed directly by meter.
`Leakage is also indicated.
`
`Two-stage linear amplifier. A
`discussion of
`the design of
`solid~state 50W and 300W
`linear amplifiers for the h.f. band
`(1 .6-30MHz).
`
`look
`'80s, a
`the
`in
`Radio
`forward to sound receiver design
`and the ideal set of the future by
`the BBC's chief engineer of radio
`broadcasting.
`
`Current issue price 35p, back issues (if availa-ble) 50p, at Retail and Trade Counter, Paris Garden,
`London SE!. By post, current issue 55p, back. issues (if available) 50p, order and payment to Room 1.1.
`Dorset House, London SEl 9LU.
`;·Editorial & Advertising offices: Dorset Hou,c. Stamford Street. London SEJ 9LU.
`Telephones: Editoriol 01-261 8620: Advertising 01·261 8339.
`Telegrams/Telex. ·Wiworld Bisncspres 25137 London. Cables. '"Ethaworld. I...O"ndon SE I.
`Subscription rates: 1 year: £7.00 UJ< ana overseas ($18.20 USA and Canada). Student rate: ·I year, £3.50
`UK and overseas ($9.10 USA and Canada).
`Distribution: 40 Bowling Green Lane. London EClR ONE. Telephone 01·837 36:36.
`Subscriptions: Oakfield House. Pcrrymount Rd. Haywards Heath. Sussex RH 16 3D H. Telephone
`0444 59188. Subscribers are requested to notify a change of address. © I.P.C. Business Press Ltd, J97i"
`Page ii
`
`ISSN 0043 6062
`
`1 ib~a 1
`
`!nft'"•r•onll Bus•ne~l
`P•e1< AH~(•arn
`
`., .. no•••l•,..,.
`
`·~-AOICII_._
`
`PMC Exhibit 2117
`Apple v. PMC
`IPR2016-01520
`Page 2
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`

`

`....
`
`l
`
`l
`~
`
`Wireless World, Apri11977
`
`VIEWDATA
`
`65
`
`3 - Operation of thesystem: terminals and codes
`
`by S. Fedida, B.Sc. (Eng), M.Sc., F.I.E.E:, 'A.C.G.I. Post Office Research Centre
`
`Part 1 of this series, in the February
`issue, gave an introduction to View(cid:173)
`data, with mentions of earlier sys(cid:173)
`tems. Part 2, in the March issue, dealt
`mainly with applications. This article
`,now describes the overall arrange(cid:173)
`ment of the system, the codes used
`and the Viewdata terminal.
`
`Fig. I gives an oven~fl view of a Viewdata
`connection. The home terminal, shown
`at the bottom left hand side, comprises a
`domestic television set, a telephone
`instrument, a Viewdata adaptor and a
`keypad. The actual assembly is shown
`in Fig. 2. Two types of keypads proposed
`are shown in Figs. 3 and 4. The basic
`keypad is Fig. 3; this provides the ten
`numerals, *and ;; symbols and keys for
`automatic dialling, if installed. Fig. 4 is
`an alphanumeric keypad. This contains
`in addition to the above, the complete
`upper case alphabet, punctuation marks
`and symbols like £,%,/, arithmetic and
`algebraic symbols and cursor· control
`characters. A typical Viewdata terminal
`for the office, the Viewdataphone, is
`shown schematically at the bottom
`right hand side of Fig. 1. This consists
`of a Viewdata
`terminal and a
`self-contained telephone instrument. A
`typical Viewdataphone was shown in
`the March issue. The Viewdata com(cid:173)
`puter is shown at the top of Fig. 1,
`notionally connected to a variety of
`data banks, either direct or through the·
`switched telephone network.
`' As mentioned in the February issue·
`communication between the terminal
`and the Viewdata computer is at a rate
`of 1200 bits/s from computer to termin(cid:173)
`al and 75 bits/sin the opposite direction.
`More details of this arrangement will be
`given later.
`In order to establish a connection to
`the Viewdata computer the user dials
`the telephone number of the computer
`as for a normal telephone call. When the
`connection is established the computer
`generates a high pitched tone (fre-
`.'quency 1300Hz) which is heard in the
`telephone receiver. The user then
`presses a button marked "data" on the
`telephone set, which switches the
`telephone line from the telephone set to
`a modem (modulator-demodulator).
`The telephone receiver is then set by the
`
`side of the cradle. Once contact is
`estabiished, the computer transmits a
`first frame, which requires the user to
`enter a user number. When this has
`been done Viewdata offers the first
`index (shown in the February issue, p.
`32).
`The .;;tction is now transferred to .. ine
`keypad. On this the user keys-in his user
`number and any further responses.
`Suppose the user wishes to obtain
`information about entertainment acti(cid:173)
`vities for a given day of the week. Th~
`
`Fig. 1 .. Overall picture of connections in
`Viewdata, showing the telephone
`system at the top and the home and
`office terminal at the bottom.
`
`user may enter the entertainment'page
`direct by keying *3230;:;. An example of
`one of the pages in the entertainment
`sequence was Fig. 6 in the February
`issue. In later models of the terminal,
`tise is made of the calling key on the
`keypad. This calls the Viewdata com(cid:173)
`puter automatically and switches over
`to the modem without the user's
`intervention. The keypad may then be
`used as previously.
`· The design philosophy of Viewdata
`which has been dealt with in the first
`
`.--~Data
`banks
`
`Strowger,
`crossbar
`or TXE
`exchanges
`
`Page 65
`
`Other
`customers
`
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`IPR2016-01520
`Page 3
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`

`

`66
`
`two parts of this article referred to the
`need to keep the cost of Viewdata down
`to very low levels, both on the terminal
`side and on the computer usage side.
`Indeed, unless the cost of using the
`computer facility is kept substantially
`below that of using current computer
`time-sharing systems, the whole project
`may not become viable: This therefore .
`postulates the use of a distributed
`computer system, so arranged that the.
`majority of users may have access to a
`nearby computer centre, at the cost of a
`local telephone call for the connection
`plus a correspondingly modest charge
`for the use of the computer and the
`information provided.
`The resulting network is typically as
`shown in Fig. 5. Users are within a local.
`call distance of their computer centres,
`shown as rectangles. A cluster of local
`computer centres is grouped under the
`control of a regional .centre for the
`purpose of data gathering a:nd distribu(cid:173)
`tion. A national data centre controls the
`operation of the whole system and
`distributes to each regional centre new
`·information, news and data updates.
`Regional centres also accept informa(cid:173)
`tion of regional or local interest and
`distribute this to the local centres.
`
`The Viewdata terminal
`'Display format. The display format of
`Viewdata is ,identical with that of
`teletext, i.e. a page consists of 24 rows of
`40 characters each, each character
`being generated by a 5 x 7 matrix with
`upper and lower case, character round(cid:173)
`ing, graphics symbols and colour. Thus:
`a great deal of the electronics in a
`terminal may be common to Viewdata
`and teletext, the differences being
`primarily concerned. with. the aoditiori:..
`·a! functions needed in Viewdata, the
`different modes of transmission appli(cid:173)
`cable to these two systems and the
`different contraints appertaining to the
`different communications media
`involved.
`In the case of Viewdata the data
`enters the terminal via the telephone
`line at relatively low speed, and, as the
`probability of data corruption is quite
`low, little is needed for the purpose of
`error detection and correction. Indeed,
`extensive Viewdata tests have been
`
`Wireless World, Aprill977
`
`except for the actual codes transmitted
`over the line, where a slight change is
`made to comply with International
`Standards Organization recommenda(cid:173)
`tions.
`The table of codes used for Viewdata
`is shown in Figs. 6, 7 and 8. Fig. 6 shows
`the joint Viewdata and teletext codes
`for alphanumeric characters only. This
`differs from earlier versions in the
`following characters:
`
`Column
`5
`5
`5
`5
`6
`7
`7
`7
`7
`
`Row
`11
`12
`13
`15
`0
`11
`12
`13
`14
`
`was
`[
`\
`J
`
`Is now
`<-·
`1;2
`
`-?
`~
`
`\4
`II
`3,4
`
`Note: The top, left-pointing, arrow is used as
`an assignment statement; the lower, right(cid:173)
`pointing, arrow means "go to"; and the sign ;;
`is used as a terminator and for special
`functions. Note also that the arithmetic
`operator X (multiply) used in Viewdata is
`shown as x (lower case x), while the minus
`sign(-) is code 2/13 and the exponentiation
`sign is code 5/14 shown as t.
`'
`Fig. 4. More elaborate, alphanumeric,
`..-keypad with a variety of other symbols.
`
`~ Fig. 5. A distributed Viewdata network,
`showing local computers, regional
`centres and national data centre.
`
`.& Fig. 2. Home terminal for Viewdata,
`with television set, telephone (right)
`and keypad on the table.
`
`.t. Fig." 3. Basic keypad used in a Viewdata
`terminal,providing ten numerals and a
`few other keys.
`
`carried out over the past two years from
`a large number of centres in the UK and
`on the Continent. In all these tests the
`public switched telephone network was
`used to connect up to the experimental
`Viewdata system based at Martlesham,
`near Ipswich, and transmission diffi(cid:173)
`culties have been very rare.
`The character codes used for View(cid:173)
`data and teletext are also identical,
`
`Regional data, news
`
`Regional
`centre
`
`Local
`r---"'--'--,computer 3
`
`local
`r-----"--L-,computer 2
`
`Local
`computer .1
`
`Regional clusters
`100,000 customers each
`
`local
`computer 2
`
`· Local
`computer 3
`
`Page 66
`
`PMC Exhibit 2117
`Apple v. PMC
`IPR2016-01520
`Page 4
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`

`

`Wireless World, Apri11977
`
`0
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`
`(NUL)
`
`(OLE)
`
`alpha"
`red
`
`alpha"
`green
`
`alpha"
`yellow
`
`graphics
`red
`
`graphics
`green
`
`graphics
`·yellow
`
`0
`
`1
`
`2
`
`3
`
`4
`
`4
`5
`6
`7
`
`8
`9
`10
`
`11
`12
`13
`
`0
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`0 0 1
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`0 1 0
`0 1 1
`1 0 0
`1 1 0
`
`'"
`
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`1 0 0 0
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`-
`
`1 0 0 1
`
`5
`
`6
`
`7
`
`6
`
`9
`
`alpha"
`blue
`
`·gra·phics
`blue
`
`alpha"
`magenta
`
`graphics
`magenta
`
`alpha"
`cyan
`
`alpha"
`white
`
`flash
`
`steady
`
`graphics
`cyan
`
`graphics
`white
`
`conceal
`display
`
`contiguous
`graphics
`
`1 0 1 0
`
`10
`
`end box
`
`graphics
`
`.1 0 1 1
`
`11
`
`start box
`
`(ESC)
`
`1 1 00
`
`12
`
`1 1 0 1
`
`13
`
`1 1 1 0
`
`14
`
`15
`
`normal
`height
`
`double
`height
`
`(SO)
`
`black
`background
`
`new
`background
`
`hold
`graphics
`
`'
`
`··~j
`
`ai ~
`~ C3
`~ ~
`~ ~
`~ il
`~ ll
`~ ~
`~ ll
`f:B ~
`~ ~
`separated ~ ~
`~ ~
`~ ~
`~ ll
`~ i!
`~ ~
`
`rele-ase
`graphics
`
`~ =
`-~ ~
`~ ll
`~ il
`-!I!:
`ll
`Ei ~
`~ ~
`El II
`~ r.l
`iii
`~ li
`~ il
`~ I
`
`(51)
`_,
`Fig. 7. Codes for graphics used in· teletext.
`
`1 1 1 1
`
`,,
`I Bits I b7b6 b5b4 b3b2b1 ~ 0
`
`0
`
`0
`0
`0
`
`b7
`bs
`bs
`
`w
`
`0000
`
`0
`
`NUL
`
`0 0 0 1
`
`0 0 1 0
`
`0.0 1 1
`
`1
`
`2
`
`3
`
`0
`
`1
`
`0
`1
`
`1
`
`1
`0
`
`1
`
`..
`
`·-
`
`... ···-·
`
`_,
`
`1
`
`0
`
`0
`
`0
`
`1
`
`1
`
`1
`0
`
`1
`
`1
`
`2a
`
`3a
`
`4a
`
`5a
`
`5a
`
`0
`
`1
`
`~
`~
`~
`
`alpha 0
`red
`
`green
`
`yellow
`
`graphics
`red
`
`graphics
`green
`
`graphics
`yellow
`
`1
`
`7a
`
`r:;_:j •
`~
`lie
`
`Fig. 7 shows the graphics and control
`characters use in teletext, as at Sep(cid:173)
`tember 1976*, the conventions being as
`before, that is:
`l. All character rows start in the
`"steady", "alphanumeric white" and
`"unboxed" condition without control
`characters.
`2. Control characters shown are dis(cid:173)
`played as spaces, but control whether
`alphanumeric or graphic characters are
`-displayed and. what colour is used.
`3. Alphanumeric characters in columns
`4 and 5, i.e. all of the upper case letters
`and a few others, may be displayed next
`to graphic symbols without an inter(cid:173)
`vening space.
`While the intervening space conven(cid:173)
`tion following a control character is
`essential in teletext, it has been accept(cid:173)
`ed in Viewdata for the sake of unifor(cid:173)
`mity, although it is not really essential
`and imposes undesirable constraints on
`the page format.
`Additional control characters have
`recently been added to teletext to
`provide enhanced display facilities. The
`"intervening space" convention is
`somewhat modified and made less
`onerous, although not all its undesirable
`effects are eliminated.
`The new control characters, which
`may be applied equally in Viewdata are
`in four groups:
`Contiguous/separate graphics.-Codes-i79
`and 1110 in teletext, 5a/9 and 5a/l0 in
`Viewdata. This provides the choice of
`graphics symbols filling the whole of a
`character rectangle, or only six discrete and
`·separate dots.
`Normal height/double height. Codes 0112
`and 0/13 in teletext, 4a/12 and 4a/13 in
`Viewdata. This provides for the optional
`display of alphanumeric characters in the
`standard size, i.e. within the normal char-
`
`'Broadcast T'eietext Specification. Published
`jointly by the Broadcasting Corporation, Indepen(cid:173)
`dent Broadcast~ng Authority and British Radio
`Equipment Manufacturers Association.
`
`ffi ~
`oc, ~ C3
`DC2 ~ ~ alpha 0
`oc3 . ~ ~ alpha"
`DC4 ~ il alpha"
`~ lj alpha"
`~ ~ alpha"
`~ ll alpha"
`white
`f:B ~ flash
`~ ~ steady
`~ ~ end box
`ESC ~ ~ start box
`~ ~ normal
`~ ll double
`cursor ~ i!
`~ ~
`Fig. 8. Control and graphics codes used in Viewdata.
`
`0 1 0 0
`
`0 1 0 1
`
`0 1 1 0
`
`0 1 1 1
`
`1 0 0 0
`
`1 0 0 1
`
`4
`
`5
`
`6
`
`7
`
`6
`
`9
`
`ENQ
`
`BS
`
`CAN
`
`HT
`
`1 0 1 0
`
`10
`
`LF
`
`1 0 1 1
`
`11
`
`1 1 0 0
`
`1 1 0 1
`
`12
`
`13
`
`VT
`-
`
`FF
`
`CR
`
`1 1 1 0
`
`14
`
`1 1 1 1
`
`15
`
`home
`IS2
`
`blue
`
`magenta
`
`cyan
`
`height
`
`height
`
`~ =
`i;
`ll
`il
`ll'
`~
`~
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`~
`~
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`il
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`
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`~
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`rt
`~
`~
`
`graphics
`blue
`
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`magenta
`
`graphics
`cyan
`
`graphics
`white
`
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`display
`
`cor.tiguous
`graphics
`
`separated
`graphics
`
`black
`background
`
`new
`background
`
`hold
`graphics
`I release
`graphtcs
`
`Page 67
`
`PMC Exhibit 2117
`Apple v. PMC
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`Page 5
`
`

`

`68
`
`acter rectangle or stretched vertically to
`double height, the ·width of each character
`and the intervening spaces between char(cid:173)
`acters remaining the s~me.
`
`Black background/new background. The
`background colour of the character rectangle'
`is normally black. Whenever the new
`background control character l/13 in tele(cid:173)
`text or 5a/l3 in Viewdata occurs, the display
`colour then obtaining is adopted as the new
`background colour.
`Hold graphics/Release graphics. Codes 1/14
`
`and l/15 in teletext, 5a/14 and 5a/15 in
`Viewdata. This allows a limited range of
`abrupt display colour changes in a row
`whereas normally there is at least one space
`between rectangles with different display
`·
`colours in the same row.
`
`The graphics and control characters
`in Viewdata are show in Fig 8, but
`before these are looked at in detail, the.
`use of a cursor in Viewdata should first
`be_ explained.
`
`Wireless World, April 1977
`
`Cursor. The cursor in Viewdata is a
`symbol which shows up on the display
`as a bright rectangle, filling 1the space of
`an upper case alphabetic character. It
`may be switched on and off, as required.
`by a switch on the terminal or on the
`keypad, or by remote control from the
`computer. It may also be moved any(cid:173)
`where over the display either manually
`by using special keys on the keypad or
`by remote control from the computer.
`The cursor has many functions.
`
`r r
`I Elits I b7 b6 bs b4 b3 b2 b1
`
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`bs
`bs
`
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`
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`
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`
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`
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`
`0001
`
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`
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`
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`
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`
`0
`
`1
`
`2
`
`3
`
`4
`
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`
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`
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`
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`
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`
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`
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`
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`
`.-
`
`alphan
`red
`
`alpha"
`green
`alpha"
`yellow
`
`alphan
`blue
`
`Q
`
`graphics
`red
`R graphics
`green
`s graphics
`yellow
`
`T
`
`.,.. Fig: 9. Complete
`set of Viewdata
`codes. columns
`2a, 3a, 6a and 7a
`for graphics and
`columns 4a.and
`5aforthe
`controls.
`
`1
`
`?a
`
`w
`~
`~
`
`7
`
`p
`
`q
`
`r
`
`s
`
`t
`
`- ~
`a ~
`EC
`b
`•C ~
`d ~
`e ~
`f ~
`!l:l
`g
`h Ei
`li
`j ~
`k ~
`-!iii
`l
`m ~
`fl
`!I
`
`n
`
`0
`
`i
`
`= il
`ll
`~
`~
`~
`~
`~
`~
`i
`li
`il
`I
`
`'f Fig. 10. Block
`diagrams of (a) a
`Viewdata
`terminal and (b)
`a teletext
`terminal,
`showing video
`connections to
`the television set.
`
`u
`
`y
`
`w
`
`X
`
`y
`
`z
`
`Y4
`
`II
`
`%
`
`-.
`I
`
`alp han
`magenta.
`
`alpha"
`cyan
`
`alpha"
`white
`
`flash
`
`steady
`
`graphics
`blue
`u graphics
`magenta
`v graphics
`cyan
`w graphics
`white
`
`X
`
`y
`
`conceal
`display
`
`contiguous
`graphics
`
`end box
`
`z
`
`separated
`graphics
`
`normal
`height
`
`height
`
`v,
`
`black
`background
`
`background
`
`start box -
`double - new
`
`graphics
`
`t hold
`n release
`
`graphics
`
`~ 0 ~ @
`C3
`~ 1
`A
`~ 2 ~ B
`m 3 ~ c
`il D
`g:j
`13
`~ 5
`~ 6 ~ F
`~ 7 ~ G
`~ 8 ~ H
`~ 9 ~ I
`~ . ~ J
`.
`~ . ~ K
`•
`il L
`~ <
`~
`= ~ M
`~
`> ~ N
`~
`·? ~ 0
`
`0/o
`
`8.
`
`I
`
`(
`
`)
`
`*
`
`+
`
`•
`
`
`-.
`
`I
`
`0 1 1 0
`
`0 1-1 1
`
`1 0 0 0
`
`.1 0 0 1
`
`6
`
`7
`
`8
`
`9
`
`'
`
`i
`
`BS
`
`CAN
`
`HT
`
`1 0 1 0
`
`10
`
`LF
`
`1 0 1 1
`
`11
`
`VT
`
`ESC
`
`1 1 0 0
`
`'1 1 01
`
`12
`
`13
`
`FF
`
`CR
`
`1 1 1 0
`
`14
`
`1 1 1 1
`
`15
`
`cursor
`home
`
`outputs
`
`Electronic
`video
`change-over
`·switches
`
`VIEWDATA
`DECODER
`UNIT
`INTERFACE BOARD
`~1;······-~rwitch control,. .... ________ . .
`(a)
`
`Page 68
`
`(b)
`
`PMC Exhibit 2117
`Apple v. PMC
`IPR2016-01520
`Page 6
`
`

`

`Wireless World, April1977
`
`(b)
`
`VIEWDATA
`DECODER UNIT
`
`Line input
`
`Basically it gives a visual indication of
`the position on the screen at which the
`next character sent by the computer
`will be displayed. When the computer
`sends a new page of information to the·
`terminal, it first sends a code which
`returns the cursor, whether visible or
`not on the display, to the "home"
`position which is at the top left-hand
`side of the display. Thereafter, as each
`character is entered, the cursor is
`moved one character position to the
`right. The position of the cursor,
`whether this is switched on or off, is
`recorded by two counters, a character
`counter and a row counter, which
`maintain at all times a knowledge of the.
`'position at which the next character is
`to be displayed (and entered on
`memory). Thus we talk of the cursor as
`it it were a real entity, whether or not it
`is displayed.
`By moving the cursor by means of the
`controls available (see below), the
`computer may position it to where the
`next character is to be entered. Thus it is' '
`,not necessary to send a series of spaces
`where one or more blank lines are
`required, or where a row of characters is
`shorter than the full length of the line,
`The cursor also enables the computer to
`overwrite a portion of a display without
`having to first erase and retransmit the
`whole page.
`The cursor may also be used at- the
`terminal for editing purposes, e.g. when
`composing messages or doing calcula(cid:173)
`tions, or to point at a feature of the
`display it is desired to manipulate. In
`this context the cursor is a powerful .
`communication channel between com-
`
`Fig. 11. Block diagrams of (a) a teletext
`terminal and (b) a Viewdata terminal,
`showing rf. (u.h.f.) connections to the
`television set.
`
`puter and user which resembles a
`pointer (but more about this later).
`Control characters in columns 0 and 1
`must comply with IS07 for line tran's(cid:173)
`mission and so far 15 have been
`allocated. Additional characters in the
`same columns may be allocated in
`future as more facilities are included. ·
`The control characters wmcri nave so
`far been allocated in the experimental
`system undergoing pilot trials are:
`
`Col/ Name Function
`row
`0/1
`0/5
`
`0110 .LF
`
`0/12 FF
`
`·NUL None-used for timing purposes· ·
`ENQ Code sent oy coinputerto
`.terminal to initiate automatic·
`terminal identification .
`0/8 BS Back-space. Moves cursor one
`character position to left
`0/9 HT Horizontal tao. Moves cursor.
`-one s:l).aracter position to pght
`Line feed. Moves cursor one line·
`position down
`0/11 VT Vertical tab. Moves cursor one
`line position up
`Form feed. Erases screen and
`moves cursor to top left hand
`side of screen (position 1)
`0/13 CR CarriageTeturn. Moves cursor to·
`first p_(lsition on same line
`Combinations
`of these char-.
`acters will be •
`used to switch
`on .tape recor-.·
`ders and hard·· ·
`copy devices
`remotely
`
`1/1
`
`112
`
`13
`
`DC1
`
`DC2
`
`Device
`control I
`Device
`control2
`DC3 Device.
`control3
`
`Page 69
`
`69
`
`114 DC4 Device control4. Used to switch
`off both tape recorder and hard
`copy unit
`l/8 CAN CanceL Used to delete line of
`character. This code is used only
`from terminal to computer
`119 ESC. Escape. Used .to indicate to
`terminal that the character
`following is from another set of
`control codes (in this case the
`control code set 2a to 7a of
`colours or graphics) ·
`l/10 IS2 Home. Returns cursor to
`character position 1 on screen
`(top left hand side)
`
`Graphics characters. The graphics and
`colour control characters for Viewdata
`are shown in Fig. 8 columns 2a, 3a, 6a, 7a
`for graphics and 4a and 5a for the
`controls. For line transmission the
`control characters of 4a and 5a are
`always preceded with ESC (code 1/11).
`On receipt of this code the terminal
`reverses the polarity of bit 7 from 1 to 0,
`thus restoring compatibility with tele(cid:173)
`text and places the characters in store.
`The graphics characters in columns
`2a, 3a, 6a and 7a are fully compatible
`with teletext and are treated 'in the same
`way when displayed. The complete set
`of Viewdata codes is shown in Fig. 9.
`
`Block diagram of terminal. A block
`diagram of a Viewdata terminal is
`shown in Fig 10 (b). This shows the
`interconnection between the Viewdata
`decoder and the video amplifier of the
`colour tv receiver. An interface board
`contains the electronic switch which
`provides
`the changeover from
`tv ,
`.reception to Viewdata. The input to the
`Viewdata decoder unit is, of course, the
`·telephone line. By contrast Fig 10 (a)'
`shows the teletext decoder connections
`(Wireless World, December 1975, pp·.
`563-566). The input to the teletext
`decoder is obtained from the i.f. input.
`Fig 11 shows a similar set of conn-ec(cid:173)
`tions where the entry to the television
`set for display purposes is the aerial'
`socket of the tv receiver. In Viewdata
`only (b) a u.h.f. modulator has to be
`added~ whereas-forteietext (a) an'
`additional tuner and i.f. strip must be'
`provided. Hence the considerably
`greater attraction of a built-in decoder
`in the case of teletext.
`(To be continued)
`
`The journal you like
`Wireless World's average circulation
`·last year was up 4,604 copies to 69,220
`per month, according to the Audit
`Bureau of Circulations. Overseas
`readers, in countries from the USSR and
`USA to the Falklands and Seychelles,
`bought 21,000 of tl!ese.,Qn average, for
`the past eight years 200 more' readers
`have joined our circulation each month.
`
`PMC Exhibit 2117
`Apple v. PMC
`IPR2016-01520
`Page 7
`
`