United States Patent
`
`[191
`
`[11]
`
`4,306,250
`
`Summers et al.
`
`
`
`[45] Dec. 15, 1981
`
`[54] TELEVISION RECEIVER ARRANGEMENT
`HAVING MEANS FOR THE SELECTIVE USE
`OF SEPARATED OR LOCALLY
`GENERATED SYNCHRONIZING SIGNALS
`
`[TF5]
`
`Inventors: Christopher P. Summers, London;
`Richard E. F. Bugs, Croydon; John
`R. Kinghorn, Sutton. all of England
`
`[73] Assignee: U.S. Philips Corporation, New York,
`N.Y.
`
`[21] App1.No.: 179,125
`
`[22] Filed:
`
`Aug. 13, 1930
`
`Related U.S. Application Data
`
`[63]
`
`Continuation of Ser. No. 945.064. Sep. 22. 1978, aban-
`doned.
`
`Foreign Application Priority Data
`[30]
`Sep. 26. 19?? [GB] United Kingdom ............. .. -I(.'032)"l’?
`May 30. ms [on] United Kingdom ............. .. -I-CIJ3-2/78
`
`Int. Cl.’
`[51]
`[52] U.S. Ci,
`[58] Field of Search
`
`
`
`H04N 5/04: H0-1-N 7/08
`.............. .. 358/148; 353/147
`358/12, 14-2, 147, 149;
`340/721, 745. 789, 314
`
`{56}
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`FOREIGN PATENT DOCUMENTS
`461894
`5/1913 Australia.
`i3'i'0535 l0! 1914 United Kingdom .............. .. 358/I42
`OTHER PUBLICATIONS
`
`Wireless World. vol. Bl, No. 14'.-'9, pp. 498-504. Nov.
`1975, Darrington, “Wireless World Teletext Decoder 1
`The Background".
`E.B.U. Review, No. I53. pp. 1453-171. Aug. 1976. Pilz.
`“Techniques for Transmitting Subtitles for Television
`Programmes in Such a Way That Their Display is Op-
`tional“.
`Mullard Technical Information Article 34. Sep. 1976.
`"Broadcast Teletext Specification“, Sep. 1976, pub. by
`BBC, IBA & BREMA.
`
`Primary Exam:'ner—Bernard Konick
`Attorney. Agent. or F1'rm—Thomas A. Briody; William
`J. Streeter; Edward W. Goodman
`
`ABSTRACT
`[57]
`In a television receiver adapted for the display of a
`normal television picture and/or message information
`in which both separated synchronizing signals and lo-
`cally derived synchronizing signals are available, the
`selective use of one or the other of these two forms of
`synchronizing signals. having regard to different dis-
`play circumstances. for the picture and message infor-
`mation display.
`
`353/l49X
`3.288.920 1111966 Baracket
`3,588.35! 6/l9'll Baun .................................. .. 351‘!/149
`
`3 Claims, 1 Drawing Figure
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`U.S. Patent
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`Dec. 15, 1981
`
`4,306,250
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`1
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`4, 306,250
`
`TELEVISION RECEIVER ARRANGELIENT
`HAVING MEANS FOR THE SELECITVE USE OF
`SEPARATED OR LOCALLY GENERATED
`SYNC!-IRONIZING SIGNALS
`
`is a continuation, of application Ser. No.
`This
`945,06#. filed Sept. 22. 1973. Now Abandoned.
`BACKGROUND OF THE INVENTION
`
`This invention relates to television receiver arrange-
`ments of a kind suitable for use in a television transmis-
`sion system of a character in which coded data pulses
`representing alpha-numeric tent or other message infor-
`mation are transmitted in a video signal in at least one
`television line in field-blanking intervals where no pic-
`ture signals representing nonnal picture information are
`present, said television receiver arrangement including
`data selection and acquisition means for extracting se-
`lectively coded data pulses from a received video sig-
`nal, a data store for storing the extracted coded data
`pulses, decoding means for producing from the stored
`coded data pulses a video signal which can be used to
`cause the display on a television screen of the particular
`message inforrnation represented by the stored coded
`data pulses, and oscillator means for producing locally
`generated synchronising signals within the television
`receiver arrangement
`itself, which locally generated
`synchronising signals can be used for the television
`display.
`The television receiver arrangement may include
`suitable television display means, or it may be adapted
`to feed the video signal into a separate television re-
`ceiver.
`A television transmission system of the character
`referred to above is described in United Kingdom pa-
`tent specification No. 1,370,535.
`A television receiver arrangement of the above kind
`is known from Mullard Technical Information Article
`34, dated September, 1976.
`The use of oscillator means within a television re-
`ceiver arrangement of the above kind to produce lo-
`cally generated synchronising signals is also known
`from German Olfenlegungshrifi No. 26 51 635 in which
`the locally generated synchronising signals are pro-
`duced for the television display of stored data in the
`absence of television synchronisation normally received
`(eg. from a broadcast video signal containing synchro-
`nizing signals which can be separated out). The stored
`data which is for display may have been received either
`from a television video signal. or from a normal tele-
`phone transmission line. The television receiver ar-
`rangement described in this German Ofl'cnlegungss-
`chrift is also organised such that it blocks the operation
`of a television synchronising separation stage and in-
`stead producrs locally generated synchronising signals
`when a received television signal falls below a predeter-
`mined threshold level.
`
`SUMMARY OF THE INVENTION
`
`The present invention is based on the premise that in
`a television receiver arrangement of the kind referred to
`in which both separated synchronising signals and lo-
`cally generated synchronising signals can be made
`available, the selective use of one or the other of these
`two forms of synchronising signals, having regard to
`different display circumstances. affords considerable
`advantages in the performance of the arrangement as
`
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`compared with the simple alternative of using the lo-
`cally generated synchronising signals only when the
`separated synchronising signals are not available due to
`the absence or unsuitability of a received television
`signal.
`According to the invention, a television receiver
`arrangement of the kind referred to is characterised in
`that it includes means for causing separated synchronis-
`ing signals to be used for the television display when
`normal television picture display is selected, means for
`causing locally generated synchronising signals to be
`used for the television display when message informa-
`tion display is selected and means for phase-locking the
`locally generated synchronising signals to the separated
`synchronising signals when a suitable video signal
`is
`being received.
`For the purposes of the present specification, a "suit-
`able video signal" is to be understood to be one which
`is not so "noise-corrupted" that coded data pulses
`which are extracted therefrom are likely to result in an
`unintelligible display.
`In a television receiver arrangement according to the
`invention. it has been found that by using the locally
`generated synchronising signals for the television dis-
`play of message information there is the advantage that
`there tends to be less "jitter" in the display, compared
`with using separated synchronising signals. By phase-
`locking the locally generated synchronising signals to
`the separated synchronising signals. whenever possible,
`there is the further advantage that the locally generated
`synchronising signals can then also be used for syn-
`chronisation purposes in the acquisition of coded data
`pulses from an incoming video signal.
`As a modification. means may be provided for inhibit-
`ing the use of the separated synchronising signals for the
`television display when nonnal television picture dis-
`play is selected and for using instead the locally gener-
`ated synchronising signals, if the received video signal
`is not suitable in that
`it is unacceptably “noise-con
`rupted," as aforesaid. This has the advantage that the
`television picture display is unlikely to be degraded any
`further. but that there can now be an intelligible super-
`imposed display on the picture display of any pre-stored
`data, such as channel information as may be generated
`by a television remote control device.
`The invention also extends to a television receiver
`arrangement of the kind referred to and as set forth
`above. embodied in a television transmission system of
`the character referred to. Also. such a television re-
`ceiver arrangement with the aforesaid selective use of
`either separated or locally generated synchronising
`signals can be adapted to cause the display of apha-
`numeric text or other message information concurrently
`with, or as a selectable alternative to normal picture
`infonnation.
`
`DESCRIPTION OF THE DRAWING
`
`In order that the invention may be more fully under-
`stood reference will now be made by way of example to
`the accompanying drawing in which the single FIG-
`URE is a block diagram of a television transrnission
`system of the character referred to embodying a televi-
`sion receiver arrangement according to the invention.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`The drawing shows a television transmission system
`of the character referred to having a television receiver
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`signal V5 is divided into different pages of information.
`and that each page is for display as a whole on the
`screen of the picture tube 9 with the coded data pulses
`representing each page of information being repeated
`periodically with or without updating of the informa-
`tion. It is further assumed that each page of message
`information is identified by means of a unique page
`address code which is included in the coded data pulses
`and defines the page number. A code selector circuit 16
`controls the particular coded data pulses that are ac-
`quired by the data acquisition circuit 15 at any time.
`(This control is indicated by a broad-narrow connection
`representing thv presence of n parallel channels which
`form an :1 bit channel link for carrying it bits of informa-
`tion required for data selection—other groups of paral-
`lel channels forming multi-bit channel links in the televi-
`sion receiver arrangement are represented similarly as
`m. p. a, r, and s numbers of channels and bits of informa-
`tion).
`_
`The acquired coded data pulses are clocked serially
`into the data acquisition circuit 15 by the clock pulse
`output from the clock pulse generator 13. From the data
`acquisition circuit 15. the acquired coded data pulses
`are fed to a data store 17 over an m-bit channel link, m
`bit bytes being required for each character (or other
`item of information) contained in the message irtforma-
`tion. where m=7. for example.
`The data store 17 can store a complete page of mes-
`sage information.
`In a typical Teletext
`transmission,
`each page of message information would contain up to
`2-
`.ows of characters. with each row containing up to
`-EJ characters. Thus.
`in order to identify the different
`characters of a page. it is furthermore assumed that the
`coded data pulses also include an address code for each
`character. this address code employing r bits and being
`fed to the data store 17 from the data acquisition circuit
`15 over an r-bit channel link.
`In view of the restricted transmission time which is
`'
`available for transmitting the coded data pulses repre-
`senting message information, for instance. sufficient
`time to transmit
`the coded data pulses for only one
`character row during a television line in the field-blanlo
`ing interval. character data for a page of message infor-
`mation has to be stored row-by-row in the data store 17
`over a relatively large number of television fields. This
`storing of character data row-by-row in the data store
`17 is under the control of the address codes received
`from the data acquisition circuit 15 over the r-bit chan-
`nel link. Coded data pulses can also be fed into the store
`17 over an s-bit channel link from Viewdata input cir-
`cuits 18, these latter coded data pulses being received
`via a telephone (not shown) from a telephone line 19.
`Another message information source from which the
`data store 17 can receive coded data pulses may be, for
`instance. a video cassette player.
`The television receiver arrangement further includes
`decoding means comprised by a character generator 20
`and a parallel-to-serial convertor 2]. The character
`generator 20 is responsive to the character data stored
`in the data store I".-' to produce character generating
`data which can be used to derive what is effectively a
`new picture signal for displaying the characters repre-
`sented by the stored character data. As mentioned pre-
`viously. different characters can be represented by re-
`spective m-bit bytes. The bits of each byte are fed in
`parallel from the data store 17 to the character genera-
`tor 20 as p-bit bytes. A character format for characters
`to be displayed can be a co-ordinate matrix composed of
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`arrangement for displaying selectively either a televi-
`sion picture which is produced from picture informa-
`tion in a normal broadcast or cable television video
`signal. or alpha-numeric text or other message informa-
`tion which is produced from coded data pulses which
`are transmitted in the video signal in vertical- or field-
`blanking intervals thereof. The possibility can also exist
`for displaying such message information concurrently
`with a television picture, for instance as sub-titles or
`captions which are superimposed on the television pic-
`ture. The television receiver arrangement
`is also
`adapted to receive and display message information
`received from another source. such as Viewdata infor-
`mation as transmitted over a telephone line in the exper-
`imental British Post Office Viewdata System {see Wire-
`less World. February-May, 1977).
`The incoming television video signal VS appears at
`an input lead 1 of the television receiver arrangement
`via its front end 2 which comprises the usual amplify-
`ing, tuning, i.f. and detector circuits. The front end 2 is
`assumed to be coupled to a television transmitter 3 via a
`conventional over-air broadcast or cable transmission
`link 4. The transmitter 3 includes in known manner
`means for producing television picture information.
`means for producing alpha-numeric text or other mes-
`sage information. and further means for generating the
`appropriate composite television video signal contain-
`ing picture signals representative of the picture informa-
`tion. and coded data pulses representative of the mes-
`sage information, together with the usual synchronis-
`ing. equalizing and blanking signals which are necessary
`for the operation of the television receiver arrangement.
`For the nomtal picture display in the television re-
`ceiver arrangement.
`the received video signal V5 is
`applied to a selector circuit 5 which includes a selector
`switch 6. When the switch 6 is closed. the video signal
`V8 is applied to a colour decoder 7 which produces the
`R. G and B component signals for the picture display,
`these component signals being applied via a video inter-
`face circuit 8 to the red. green and blue guns ofa colour
`television picture tube 9. Timebase circuits II] for the
`tube 9 receive the usual line and field synchronising
`pulses LS and F5 from a sync. separator circuit II
`which extracts these synchronising pulses from the
`incoming video signal VS. or from locally generated
`synchronising signals. 3 will be described.
`Coded data pulses representing message information
`in the video signal VS do not affect the picture display
`because they occur in one or more lines in the field-
`blanking interval when there is no picture display. Of St}
`the lines occurring in the field-blanking interval. most
`could be used to transmit coded data pulses represent-
`ing message information. However. in the experimental
`BBC/IBA Teletext System for which the present inven-
`tion was originally conceived. it is proposed at present
`to restrict such use to lines 17/ I B of even fields and lines
`330/331 of odd fields of the 625 line broadcast television
`system used in the United Kingdom. (See “Broadcast
`Teletext Specification“. September 1976, published
`jointly by the British Broadcasting Corporation. Inde-
`pendent Broadcasting Authority and British Radio
`Equipment Manufacturers‘ Association).
`The video signal VS on the input load 1 is also ap-
`plied to data selection and acquisition means comprising
`a data extractor circuit 12, a data clock pulse generator
`13. a data acceptor gate 14 and a data acquisition circuit
`15. It is assumed that the message information repre-
`sented by the coded data pulses contained in the video
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`discrete elements arranged in rows and columns, this
`format being derived from a “read-only" memory
`which serves as the character generator 20 and which
`provides bits of character generating data in rows and
`columns, one row at a time. Since the character generat-
`ing data is required as a modulation of a video signal in
`order to produce selective bright-up of the screen of the
`picture tube 9 to achieve character display, the charac-
`ter generating data is produced serially (as l‘s and 0's)
`by using the convertor 21 to convert each row ofbits of
`data read out from the character generator 20 (e.g.
`n =5) into serial form.
`In order to effect character display on the screen of
`the picture tube 9 using standard line and frame scans,
`the logic of the television receiver arrangement in re-
`spect of character display is so organised that for each
`row of characters to be displayed, all the characters of
`the row are built up television line-by-television line as
`a whole, and the rows of characters are built up in
`succession. It takes a number of television lines to build
`up one row of characters. In the first television line
`character data from the data store 17 to the character
`generator 20 would cause the latter to produce charac-
`ter generating data with respect to the first row of dis-
`crete elements for the first character of the row, then
`with respect to the first row of discrete elements for the
`second character, and so on for the successive charac-
`ters of the row. In the second television line, character
`generating data with respect to the second row of dis-
`crete elements for each character of the row would be
`produced in turn. and so on for the remaining television
`lines concerned.
`The output from the converter 21 is applied to a
`colour coder 22 which produces R’, G’ and B’ compo-
`nent signals for character display,
`these component
`signals being also applied to the video interface circuits
`8. The colour coder 22 can be controlled (in a manner
`not shown) by selected items of the character data in the
`data store 17 to provide a controlled colour display. Of
`course. black-and-white picture and character display is
`also possible, in which event the colour decoder 7 and
`colour coder 22 would be omitted.
`includes, as
`The television receiver arrangement
`aforesaid. as part of the data selection and acquisition
`means, a data acceptor gate 14. The coded data pulses
`extracted from the incoming video signal VS by the
`data extracter circuit 12 are applied to the data acquisi-
`tion circuit 15 via this acceptor gate 14 which is con-
`trolled hy a signal quality arrangement 23. This arrange-
`ment 23 is responsive to apply an inhibiting signal IS to
`the data acceptor gate 14 to inhibit the acceptance for
`storage of coded data pulses when a predetermined
`signal-to-noise ratio in the incoming video signal VS is
`exceeded. The arrangement 23, which may comprise
`the serial combination of an AND-gate, an integrator, a
`threshold detector and a Schmitt trigger circuit, deter-
`mines an acceptable signal-to-noise ratio by comparing
`line synchronizing pulses, separated from the received
`video signal. with locally generated “clean“ line syn-
`chronizing pulses. both of which are applied to the
`AND~gate of the arrangement 23 with the inhibiting
`signal IS appearing at the output of the Schmitt trigger
`circuit. Noise, suflicient to cause break-up of the sepa-
`rated line synchornizing pulses, will cause a similar
`break-up in the output of the AND gate. By selecting a
`suitable threshold in the threshold circuit, the voltage
`output from the integrator will trip the threshold detec-
`tor which thereupon causes the Schmitt trigger circuit
`
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`to generate the inhibiting signal IS. When the separated
`line synchronizing pulses are "clean".
`the resulting
`"clean" pulses from the AND-gate will cause an in-
`crease in the output voltage of the integrator which
`voltage is now above the threshold in the threshold
`detector which then terminates the signal IS from the
`Schmjtt trigger circuit.
`Considering now the selective usage of separated
`synchronising signals and locally generated synchronis-
`ing signals,
`the incoming video signal VS is further
`applied to a sync. pulse separator 24 and to an electronic
`switch 25 (which for the sake of simplicity is repre-
`sented by a mechanical changeover contact having
`fixed terminals 26 and 27 and a changeover contact 28).
`The separated sync. pulses produced by the sync. pulse
`separator 24 are applied to a phase-locked oscillator 29
`which drives a tinting chain 30, and to one input of the
`signal quality arrangement 23. The timing chain 30
`provides appropriate clock and timing pulses to the data
`acquisition circuit 15, the code selector circuit 16, the
`data store 1'7. the Viewdata input circuits 18 and the
`character generator 20. The timing chain 30 also drives
`synchronising pulse generator 31 which produces the
`locally generated synchronising signals in response to
`the output received by it from the timing chain 30.
`Locally generated line sync. pulses are applied via a
`lead 32 to a second input of the signal quality arrange-
`ment 23. Also, these locally generated line sync. pulses
`are combined in a gate 33 with field sync. pulses which
`are produced by the generator 31 on a lead 36. and
`which are synchronised with the incoming field sync.
`pulses supplied by the sync pulse separator 24 via an
`inhibiting gate 36. The output of the gate 33 is applied to
`the switch 25.
`A user control unit 35, which may be a hand-held
`remote control device of any suitable known form,
`controls channel selection and adjustment. etc., at the
`front end 2 and selector switch 5; and also the code
`selector 16 and the Viewdata circuits 18 for the selec-
`tion of either form of message information. When a
`normal picture channel has been selected and the broad-
`cast video signal concerned is being received, a “picture
`on" signal PO produced by the user control unit 35
`causes the switch 25 to assume the position shown with
`contact 28 engaging terminal 26 so that the incoming
`video signal V8 is applied to the sync. separator circuit
`11. As a result, separated synchronising signals are used
`to control the time bases 10.
`When Teletext or Viewdata message information is
`selected, the signal P0 is terminated and the switch 25
`then assumes the position in which Contact 28 engages
`terminal 27 so that now the locally generated synchro-
`nising signals from the pulse generator 31 are applied to
`the sync. separator circuit 11. As a result, the locally
`generated synchronising signals are now used to control
`the time bases 10. in each of these two instances, the
`operation of the time bases 10 is synchronised with the
`incoming video signal VS, in the first instance directly
`and in the second instance because the oscillator 29 is
`
`phase—locked to the incoming video signal VS.
`If the signal quality becomes unacceptable or there is
`no incoming video signal, then the inhibiting signal IS
`from the signal quality arrangement 23 unlocks the
`oscillator 29 to allow it to free-run. and also inhibits the
`application of the field sync. pulses to the generator 31
`by activating the inhibiting gate 36. The locally gener-
`ated synchronising signals are thus still produced but
`are not synchronised with any incoming video signal.
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`When a video signal is present, the signal IS also. of
`course.
`inhibits the acceptor gate 14 to prevent
`the
`reception and storage of noise-corrugated coded data
`pulses.
`As a modification the switch 25 may also be con-
`trolled by the inhibiting signal IS such that even when
`the "picture on" signal P0 is present locally generated
`synchronising signals are selected in preference to sepa-
`rated synchronizing signals when the signal quality is
`sulliciently bad to cause the production of the inhibiting
`signal
`IS. This permits an intelligible superimposed
`display on the picture display of any prestored data.
`such as channel information as may be generated by the
`unit 35.
`We claim:
`
`1. A television receiver arrangement of a kind suit-
`able for use in a television transmission system of a
`character in which coded data pulses representing al-
`pha-numeric text or other message information are
`transmitted in a video signal in at least one television
`line in field-blanking intervals where no picture signals
`representing normal picture information are present,
`said television receiver arrangement including means
`for separating synchornizing signals from said video
`signal, data selection and acquisition means for extract-
`ing selectively coded data pulses from a received video
`signal, a data store for storing the extracted coded data
`pulses, decoding means for producing from the stored
`coded data pulses a video signal which can be used to
`cause the display on a television screen of the particular
`message information represented by the stored coded
`
`l0
`
`I5
`
`20
`
`25
`
`30
`
`35
`
`4,306,250
`
`8
`data pulses, the oscillator means for producing locally
`generated synchronising signals within the television
`receiver arrangement
`itself, which locally generated
`synchronising signals can be used for the television
`display; wherein said television receiver arrangement
`further comprising means for selectively switching be-
`tween 3 normal television picture display and said mes-
`sage information display. means for causing said sepa-
`rated synchronising signals to be used for the television
`display when normal
`television picture display is se-
`lected. means for causing locally generated synchronis-
`ing signals to be used for the television display when
`message information display is selected, means for de-
`tecting a suitable video signal, and means for phase
`locking the locally generated synchronising signals to
`the separated synchronising signals when a suitable
`video signal is being received.
`2. A television receiver arrangement as claimed in
`claim 1. wherein said selectively switching means is
`adapted to cause the display of alpha-numeric text or
`other message information concurrently with. or as a
`selectale alternative to, normal picture infomiation.
`3. A television receiver arrangement as claimed in
`claim 1, which further comprises means for inhibiting
`the use of the separated synchronizing pulses for the
`television display when normal television picture dis-
`play is selected and for using instead the locally gener-
`ated synchronizing signals if the received video signal is
`not suitable.
`C
`I
`I
`I
`I
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`PMC Exhibit 2056
`
`Apple v. PMC
`|PR2016-00755
`
`Page 6
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`45
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`SD
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`55
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`65
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`PMC Exhibit 2056
`Apple v. PMC
`IPR2016-00755
`Page 6