Note: Descriptions are shown in the official language in which they were submitted.
The pre~ent invention relates to a system for
digitally transmitting and di~playin~ selected item~ of
data on a tele~ision receiver scraen. In short, such a
system wlll be called a "teletext" system i~ the follouing.
~lore particularly, $he invention relates to a teletext
system receiver~
The growing importance of information commu~icatio~
; has resulted in the building of data banks in such a manner
that &uch data banks are usable in developing'infor~ation
processing technics and audiovisual me~. Updating files
whereîn data are stored makes those systems efficient, but
the cost of the information supports presently limit~ th~
pre6~nt field of utllization thereof. A telete~t systeM
makes it possible ~o broadca~t those data from central
processing stations wherei~ data issue is also made. Such
a centr~lized struct~re i5 slmilar to that of ne~spaper
structures a~d radio b oadcastin~ is close to nawspaper
and pcriodical di~tribution.
In fact a t21etext system involve~ several asp~cts,
its main goal ,being to achieve the broadest possible
broadcasri~ of stored data through R~ channel~. A$ the
reception end9 the major mean~ is the television receiver
display screen. It displa~s pages of a text or graphics
~hich ~re tr~ns~itted i~ a~ encoded form as for example
desc~ibed in the United States Patent 4,05~,830 filed
~Jv~,L~L 15, 1977 and invented by Yves Maurice Guinet and Yves ~aurice
Noirel.
~ 2 ~
~lk
~9~i~2
But a teletext service may also be transmitted
through the public or a private telephone networlc throu~
whic~ a teletext subscriber calls a data bank comprising
a memory serving as a file for information arrarlged in pages.
By means of a key board used by the subscriber to sele~t
a page~ the subscriber can answer que~tions fro~ the filc
processing unit and the pages he dcsires are s~nt to him.
In televi.~ion broadcasting5 th0 waiting time for a
desiredpage ~epends on the transmission capacity which the
telete~t system disposes of as well as the number of pages
in the file or ~agazine~ The tra~smission capacity may
con~iderably vary according as a full televlsion channel
is allohed to the teletext system or only some blank lines.
~y ~ay of ~n e~a~ple, ulth a magazine containing about fifty
pages and a transmission capacity of ona line p~r frame9
the ~ean waiting time is of about flfteen seconds
In the case of a transmission through atelephone
net~or~9 the central unit answers very rapidly, but the data
tra~smission is performed at a low rat~ due tv the narrow
frequency band ~idth available and may have a duration of
several tens of seconds.
lY~ate~er is the utilized transmi~sion ~edium, a
teletext system first implies the selection of a page of
info matio~ among a plu~dlity of avallable pages~ the
transmi.ssion of the selected page or pag~s, and, finallyy
-- 3 --
the displ~y Or the selected page on a television screen.
On that screen, the picture~ constituted by the written
page or the grap~ics h~ve no half-tints. Theutillzation
of a televisio~ receiver that can in addition receive
standardized television progranls imposes certain con~traints
resulting from tha television tube resolution, i.e, about
25 rows of 40 characters eachp but o~ the contrary makes
possible in u~ing a set of 8 colors~ for instance, to obtain
very cl~ar page setti.ng. The used alphabets depend on how
character~ are written in the cou~try wherein the teletext
system is utili~ed. In ~rance a proposed sy~tem co~prises
a Lati~ alpnabet o~ 126 ~igns which permit~ t~ ex~end the
system to the most of the languages utili~ing a Latin alphabet.
By way of example of a tele$ext system~ reference may
be made to the technical article entitled "Broa~cast data
i~ television" by A~ Jo Biggs and B.S. Barnaby published
i~ the English technic~l review "GEC Journal of Science ~nd
Technology", vol. 41, No. 4, p.117-1~4, 1974, and te t~e
British Patent 1,467,240. Reference may also be made to the
technical arti~le entitled "~NTIOPETMservice de télétexte"
by B. Marti a~d ~, Mauduit, publ~shed in the ~rench technical
review ~radiodif~usion telévision", 9th year1 No, 409
November-December 1975, 5/5, p.18-23~ In the last mentioned
article~ the features of the previously described system
are indicated, ~urtherrnore in the ~escribed service pa~e~
are assembled in various m~gazine~ each magazine being
Tr~ - Trade r~rk
cyclically broadcast in full. Each page is identi~ied by
its page number. Some o~ -those pages contain sumMarl~s
and appear to help the selectlon o~ the desired page by means
of a keyboard. AMong the special functions that a teletext
systeln may fulfill, one would cite the insortion of a te~t
in a television picture under the forrn of a caption in a
language selected by -the television subscri.ber. Such
captions may either be rigidly associated to tne picture or
relate to short news regarding a predetermined subject matter;
they may ba written in a rectangular box cut-out of a
current picture or dispenser at subscriberls will. ~eatures
of this type are obviously also of interest for educational
progra~ls .
According to a feature of ~h~s invention, thers is
p~ovided a sy~tem for digitally transmitting and displaying
texts on a tele~ision screen,~ wherein the transmitter sta~on
broadcasts, particularly in the for~ of data packs, data
from saveral channels~ the data packs from different channels
being possibly time mult-plexed~ each pac~ comprising a preflx
signal allowing a receiver to accept the data packs of a channel
and to reject other data packs, the set of the data packs of
a channel constituting a magazine made of se~eral pagest
~herein the data pacXs belonging to a page are transmitted
not multiple~ed with data pacXs of another page of the same
2~ magazine, data belonging to a page beginning with a page
1~ 2
flag followed by data indicatin~ the pag9 number, and ending
with the next page flag9 the system receiver comprising a
keyboard making it pos~ible to indicate the number of the
desired page~ a circuit for recognizing the page Pl~gs
which energi2ed a comparator circuit cornparing the data that
im~ediately follow any page flag ~ith the number indicated
on the keyboard, data being, ~hen the compari~on i5 positive~
~ent to a memory that stores the character ~ata, a character
generator being capable of di~playing on the screen of a
tçlevision receiver tube~ the characters from data read out
from the said memory.
According to ~nother feature of this invention~ there
is provided a telete~t syste~ wherein the data b~longing
to sach page are grouped in rows (or page lines), the data
belonging to each row bein~ preceded by a row flag followed
by a row ~umber, and ending with the ne~t ~ow flag, thP row
number detected after e~ch row flag determining the address
at which the row dat~ must be stored in the said memory.
According to anoth~r feature~ fro~ the character data
the character ~enerator deliver~ to a matching circuit the
character l-l~;n~nce signals, and in addi~ion logic pulses
each concerning the presence or the absence of a basic color
R (red) 9 Y (green~ or B (blue)~ the sa~d matching circuit
transferring the luminance signal to conventional circuits
f the television receiver, the said matching circuit comprising
~ ~ ~9~
associated with each basic color logic input a first
diode whose anode is connected to the input of an analog
amplifler ~hose output is con~ectad to the correspQnding
chrominance ~elevision tube input, the anode of the first
dlode being, in addition9 connected to the anodes of a
s~co~d and a third diode, the first ~lode cathode being
connected from the associat~d color in~ut and the output
of a first voltage ~enerator delivering a volta~e v2~ the
second diode ca*hode being connected frorn the output of
a second voltage generator deli~eri~ a voltage vl, and the
third diode ca~hode belng connected from the o~tput of a
third Yoltage generator:delivering a voltage v3~ the third
generator outp~t b~ing in addition connected to the output
of a gate whose output is not grounded when the thre~ color
inpu~s together receive logic pulse~ and grounded in any
other casej with ~3~ Y2 ~ Vl 7 the value~ of vl, v2 and v3
being selected appropriately.
This înv~ntion also r~lates to an arrange~nt of
the transmitted signals and means provided în each system
. 20 data receiver,for m~ki n~ it possible to vary the appearance
of texts displayed on a television screen so as *o break off
the monotony of the current display appearancesO For in~tance,
those varlations may affect the cnaracter color, background
color, flashing on and off for certain characters9 changes
2~ in character height an~/or wid'h, etc~
It is to be remembered that a character generator
for displaying characters on a television receiver cathode
ray tube screen comprise3 a permanent memory as~ociated to
~ ra~dom access ~lemory. The permane~t mernory stores the
shape information ~or every character which can be
displayed. '~he random acces6 memory stores the character
codes~ including the spacings or blank~ between worde forming
the text to be displayed. In the random access memory the
character codes are stored at addres3es which correspond
to ~he geographic positions of the associ~ted characters
' in the page to be displayed. The display operation consists
~n a sequential read-out of the ro~s of character codes from
the random access memory, each read operation for ~ character
ca~sing in a known manner the scAnning read-out of the character
shape of the character corresponding to the read character
code, from the permanent memoryu Should a character occupy
ten television scanning lines, each read operation for a row
of character codes from the random access memory results in
ten s~ccessive sc~n;ngs of the character shapes frol~ the
permanent memo,~ry. Obviously sC~nn;ngs are controlled by
clocks which are controlled from the display tube line
synchronization. The signals resulting from the scanning
o~ the shape of a character ar2 parallel delivered~ then
' convert~d into serial mode th-ou~h a sni~t register wherein
the shift signal freouency is controlled ~y a clock that is
-- 8 --
controlled frorn the display tube line sync. The output
o* the shi~t register is sampled at another :~requency
controlled by anothe~ clock and the shi~t register output
signal is transmitted toward the tube as a luminance signal.
Furthermore in charac~er transmission sy~tems wherein
each character is represented by an octet, i.e. an eight-
bit word, the so-caLled ~SCII code is currently in use.
Among the eight bits ol a word, one bit is normally assigned
to parity check. The 7 other bits provide 12~ character
possibilities Among those 128 possibilities some are
assigned to character codes and other ones to function codes.
In addition, a so-called escape eight-bit word makes it
possibls in practice to double those possibilities in currently
changing the ~eaning of codes follo~ing an escape word.
15 - ~nother purpose of the present invention is to
provide a te?ete~t system wherein the displayed characters
may be of va~ious types that are dlfferent each from the
other in the shape, color, si2e, bac~ground, and so on, each
t~pe of displayea character being identified by means of
one or several ei~lt-blt words corresponding to the character
type identlty.
According to another fea~ure of the present invention9
there is provided a system for digitally trans~itting and
displayi~ tex~s on a television screen wherein the sequence
f the trarsmitted eight - bit words co~prises (in addition to
_ g _
prefixes, pa~e flags followed by pa~e numbers~ and row
flags poss.ibly followed by row numbers) e~c~pe ~ight-bit
words followed by type identity eight bit words~ themselves
followed by a sequence of characters to ~e displayed in the
same type the identity of which is detern~ined by the
precedin~ type identity eight-bit words9 each system receiver
cornprisin~, in addition to ~ first conventional random
m~mory
access/storing the coded ch~racters, a second random ~cce6s
memory storing the type identity eight~bit words at the same
2ddresses as the addresses of the characters belonging to
the said se~uence in the first random access memory9 read
operation from the first random access memory f~r display
purpo~e being parformed as the same time as read operation
from the ~aco~d random access memory whos~ output signal
selects a character generator permanent memory from which
the ~hape of characters read out from the first ra~dom access
memory is to be read out, and/or controls the l~l~;nAnce and/or
chrominance in the display tube at the time the characters
are displayed~on the television tube.
According to another feature o~ this invention~ the
type identity eight-bit words f~llowing an escape eight-bit
word comprise an identity component eight-bit word followed
by an escape eight-bit word per ch~racter identity
component~ save ~he last identity compo~ent eight-bi+
word that is directly follo~ed by the f~rst character eight-
_ 10 -
01 bit word of a sequence of characters which the type is assigned
02 to, the received data being applied to a switching circuit
03 delivering, on the one hand, the escape eight-bit words followed
04 by type identity eight-bit words serially to a buffer memory and,
05 on the other hand, character eight-bit words or escape eight-bit
06 words not followed by type identity eight-bit words to the input
07 of the first random access memory, buffer memory output being
08 connected to second random access memory input and deliverying
09 its contents save escape eight-bit words, to said second random
access memory each time a character belonging to said sequence is
11 written into the first random access memory, the contents of the
12 buffer memory being erased when receiving a next escape eight-bit
13 word followed by a type identity or type component identity
14 eight-bit word.
More particularly, the invention is a teletext system
16 for digitally transmitting and displaying text material from any
17 of many different services on a television screen. The digital
18 transmission is in the form of data packs randomly intermixed
19 from several channels, whereby successive data packs may relate
to any of the completely different services. ~ach of the packs
21 have signals constituting a mazagine of several pages, wherein
22 the data belonging to each page are grouped in rows (or page
23 lines), the data belonging to each row being preceded by a row
24 flag followed by a row number, and ending with the next row
flag~ The row number detected after each row flag determines the
26 address at which the row data must be stored in the memory. The
27 data for each page of information begins with a page flag. The
28 system is comprised of keyboard apparatus for identifying a
29 desired page~ whereby signals from the keyboard select between
i, .~
~96~
01 different services. A comparator circuit is responsive to page
02 flags and detects the desired page responsive to operation of the
03 keyboard apparatus. A memory responsive to the comparator
04 apparatus stores data relative to the desired page. A character
05 generator displays the desired page on a television screen
06 responsive to the data stored in the memory apparatus.
07 The invention is also a receiver or a teletext system
08 for digitally transmitting and displaying texts on a television
09 screen, wherein a transmitter station broadcasts signals
represen-ting the text. The signals are in the form of data
11 packs, sent over several channels. The data packs from different
12 channels are randomly time multiplexed. Each of the data packs
13 include the transmission in sequence of eight-bit words
14 comprising page flags followed by page numbers and row flags
followed by row numbers, escape eight-bi~ words followed by type
16 identity eight-bit words, type identity eight-bit words, followed
17 by a sequence of coded words identifying characters which are to
18 be displayed in the same type which is identified by the identity
19 words determined by the preceding type identity words. The words
receiver is comprised of a first random access memory for storing
21 the coded character words at certain addresses, and second random
22 access memory for storing the type identity words at the same
23 certain addresses as the addresses of corresponding character
24 words stored in the first random access memory. Apparatus is
included for reading the words stored in the first random access
26 memory and at the same time as the read out of the words stored
27 in the second random access memory, Accordingly a character and
28 at type identity are simultaneously selected. Permanent memory
29 - lla -
6~LZ
01 apparatus is responsive to the read out of the second random
02 access memory Eor giving the shape of the characters read ou-t
03 from the first random accessory memory.
04 The invention is also a teletext system wherein the
05 display characters may be oE various types that are different
06 from each other as in the shape, color, size, and background,
07 each type of character displayed being identified by at least one
08 eight-bit word corresponding to the character type followed by an
09 escape eight-bit word. Each system receiver includes a first
random access memory for storing encoded information characters,
11 second random access memory for storing the type identi-ty
12 eight-bit words at the same addresses as the addresses of the
13 information characters, and apparatus for simultaneously reading
14 the first and second access memory for a display at the same time
of the encoded information characters with a selected type of
16 character shape, and a buffer memory. Switching apparatus
17 serially applies the received data escape eight-bit words
18 followed by type identity eight-bit words to the buffer memory
19 and character eight-bit words Gr escape eight-bit words not
followed by type identity eight-bit words to the input of the
21 first random acccess memory. The buffer memory output is
22 connected to the second random access memory input and delivers
23 its contents, except for escape eight-bit words, to the second
24 random access memory each time a character belonging to the
sequence is written into the first random access memory. The
26 contents of the buffer memory is erased when the next escape
27 eight-bit word is followed by a type or type component identity
28 eight-bit word is received.
29 - llb -
01 The above mentioned features of the present invention,
02 a~ well as other features thereof will appear more clearly in the
03 following description of an embodiment, the said description
04 being made in conjunctin with accompanying drawings, wherein:
~05 Fig. 1 is a block diagram of a teletext transmitter
~06 according to this invention,
07 Fig. 2 is a block diagram of a teletext receiver
08 according to this invention,
09 Fig. 3 is a schematic diagram of a matching circuit for
11
12
13
14
16
17
18
1 9
21
22
23
24
~6
27
28
29 - llc -
z
01 matching the voltage/light characteristics utilized in the
02 receiver shown in Fig. 2,
03 Fig. 4 illustrates waveforms of signals used in the
04 matching circuit shown in Fig. 3,
05 Fig. 5 is a block diagram of memory circuits and
06 character generator usable according to this invention in ~he
07 teletext receiver shown in Fig. 2, and
08 Fig. 6 is a schematic diagram of a mixer circuit
09 utili~ed in the receiver shown in Fig. 5.
The assembly shown in Fig. 1 is similar to that shown
11 in Fig. 1 o the description of the already mentioned U.S.
12 Patent 4,058,830. To a modulator circuit 1 and a transmission
13 antenna 2 there are switchably connected a number of data
14 sources, such as the data source shown which comprises a data
processing circuit 3, connected to a number of control sets
16 4.1-4.n. Data procèssing circuit 3 includes a shaping circuit
17 5, and a memory 6 whose input is connected to the output of
18 circuit 5 and whose broadcast output may selectively be
19 connected to modulator circuitry 1 while its control output is
connected to the input of a conversion circuit 7. Each control
21 set 4.1-4.n includes, as shown at 4.1, a moni-tor screen 8 and a
22 composing typewriter 9. Each typewriter 9 has a data output
23 connected to the input of the circuit 5 and a data input
24 connected to the output of the circuit 7.
- 12 -
``l?
01 Each control set 4.1-4~n allows a journalist or other
02 operator to compose pages by means of the typewri~er 9 while
03 checking on the monitor screen 8 every characteristic of the
04 Einal color picture, e.g. the character size, flashings on and
05 off and graphic particularities. Each typewriter 9 is similar
06 to a typing machine and includes logic circuitry for composing
07 and updating the documents. Output data from sets 4.1-4.n are
08 put, in accordance with given standards, in circuit 5, then
09 stored in the memory 6. Memory 6 may be a disk memory wherein
there are stored the sequences of codes to be transmitted
ll corresponding to the language determined in the abov~-mentioned
12 French technical article. Thus memory 6 constitutes a file of
13 pages that are periodically read out and ~ransmitted to the
14 modulator circuitry l to be broadcast. An operator controlling
a set 4.1-4.n can also have displayed on his control screen 8 a
16 selected page read out from memory 6 through circuit 7.
17 Embodiments of the equipment shown in Fig. l are
18 known. They can either be embodied in a wired logic form or in
l9 a programmed form controlled frcm a computer.
The assumption may be made that, as in the already
21 mentioned U.S. Patent No. 4,058,830, a data broadcast is
22 made on a television channel in the idle lines of the
23 television picture. rrhose data are assembled in data packs
24 including up to 32 eight-bit words or octets. To each data
- 13 -
..~.. ~
01 pack -there is assigned a prefix indicating the data source
02 address and the number of words contained in the concerned data
03 pack. When the length of data to be transmitted compri es more
04 than 32 eight-bit words, it is shared among several data packs
05 and the prefix contains the pack number in addition to other
06 information. Within the prefix also included are 2 eight-bit
07 words for synchronizing the receiver terminal local oscillator
08 and another eight-bit word for synchronizing the said eight-bit
09 words in each data pack. Thus a full transmitted data pack
includes 40 8-bit words wherein each of the 320 bits represents
11 a black when the bit value is 0 and white when it is 1.
12 Possible interferences between these digital signals and the
13 proper video signal is reduced by selecting a repetition
14 frequency that is an odd multiple of the line frequency. There
are 397 periods in a line which results in a bit frequency of
16 6.20 MHz, with a non-return-to-zero modulation.
17 As described in the already mentioned U.S. Patent
18 No. 4,058,830, a computer used as an electronic control unit
19 knows the list of the idle lines in a picture signal and
inserts into those lines the data packs it receives from the
21 various telete~t editors, similar to that shown in Fig. 1.
22 Connections from the various memories 6 and modulator
23 circuitry 1 are preferably constituted of links, such as
24 the link described in the French paten-~ 2,268,308
- 14 -
!7
~s~
entitled ~Standardized colllrnunication interface device~'.
Such a link makes it possible to slow down the data flow
of a data source consti~uted by a data memory, when the
broadcast system is blocked. When using a broadcasting
~etwork, it is not possible ~o control directly the output
data flow from a source deri~ed from the receiver input
capacity; to overcome this lack o~ feedback control~ a
~imulated receiverS similar to ~he slowest receiver7 is
prov~ded in the cont~ol unit. When using other transrnission
media the said link provide~ thc funct~ons needed for a
correct trans~ission o~ the digital signals.
Reception terminal shown ln Fig. 2 is designed to
supplement a conve~tional television receiv~r and is used
to demodulate the data ~ignals transmitted f~om the station
shown in Fig. 1, to resh&pe them~ *he~ to write them into
a store sc that it is possible to restore a vlsible page
on the associated television receiver screen. Reception
term~al ma~ ~ a separate unit assoclated to a con~entional
~ele~ision recei~er or a portion integrated in an accordingly
designed ~elev~sion recelver.
The receive terminal shown in Fig~ 2 comprises, like
a conventional television receiver, a reception-demodulation
clrcuit 10 delivering~ on the one hand, audio signals to a
loud-speaker 11 and, on the other hand, video signals to a
color decoder and scanning generator 12, Color signals B1
_ 15 _
~9~2
01 (blue), Vl ~green) and Rl (red) as well as ll~m;n~nce signal
02 Erom the generator 12 are not transmitted, contrary -to what
03 occurs in a conven-tional television receiver, directly to tube
04 13, but through a video switch 14 that has still another
05 function as will be hereinafter described.
06 Furthermore the receive terminal shown in Fig. 1
07 comprises a circui-t 15 separating data from -the video signal,
08 the input of the circuit 15 being connected to the video output
09 of the circuit 10 and output of the circuit 15 being connected
to a first selection block 16, similar to that of the terminal
11 equipment described in the already mentioned U.S. Patent
12 4,058,830. The output of block 16 is connected through an
13 above mentioned link J to a page selection block and a data
14 decoder 17, whose outpu~ is connected to the input of a page
memory 18. A viewer keyboard 19 has its outputs suitably
~16 connected to control inputs of selection block 16 and decoder
17 17. The output of memory 18 is connected to the input of a
18 character generator 20. Signal outputs of character generator
1~ 20 are connected to color inputs R2 (red), V2 tgreen) and B2
(blue) of the video switch 14 as well as to a luminance input
21 thereof. A con-trol output of -the keyboard 19 is also connected
22 to a control input of the video switch 140
23 In the circuit 15, a stable oscillator, not shown,
24 generates a clock signal at 6.20 MHz, as mentioned above.
- 16 -
~L~L8~i1Z
01 When, after the detection of a line synchronization pulse, a
'2 video signal transmi-tted froxn circuit 10 presents a sequence of
~3 alternative white and black points at that clock requency, the
04 said oscillator is phase locked with the received pulses. The
05 oscillator output is then used as a clock for the received
06 bits. Thus that oscillator is utilize~ to correctly separa-te
07 the video data signal from a current television video program
08 signal. Received bits are processed as eight-bit words in
09 circui~ 15 and service information, such as channel number and
subscription period, are taken therein into account to make
11 only the desired channel or magazine valid. All the circui-try
12 performing such a process are described in the already
13 mentioned U.S. Patent 4,058,830, and particularly regarding the
14 validation of the desired channel described in Fig. 6 thereof.
Assuming the validation is positive, received bits
16 are sent to block 17 through link J. In practice, in the
17 embodiment described, a channel of a system described in the
18 already mentioned U.S. Patent No. 4,058,830 is equivalent to a
19 magazine. It is known that the various channels of such a
system are time multiplexed; so it is for the various
21 magazines. As a result link J transmits the data contents
22 of a magazine serially per groups of 8-bit words, but
23 with intervals between those groups due to two
~4 - 17 -
9~
reasons, the first one o~ which results from the tim~
multiplexed broadcasting mode of ~he magazlnas and the
other one results from the transmission mode through link J,
~he transmi~sion thr3ugh J from 16 to 17 being only possible
~hen block 17 is ready to receive data. Thus transmission
~ink 3 i~ performed in a~ asynchronous manner.
In block 7 a flrst operation is to select the de~ired
page t~rough the magazineO Indeed~ as de~cribed i~ the
already mentioncd ~rench ~echnical ar~icle, a magazine is
composed of ~everal pages wit~ particularly a ~irst page
indicatin~ the magazine summaryO In the maga~i~e the pages
are naturally ordere~ according to increasing numeral~. It
is also to be noted that in the broadcast of a maga~i~e
the pages thareof are not time multiplexed~ i.e. page data
ara preceded by a 8-bi~ word repre~enting a page flag~
followed by the page nu~ber, and are followed by another ~-bit
word representing another page flag followed ~y the next
page number. As a ~esult, in block 17 there is performed
the detection o~ each page flag, then eac~ time a reco~nition
is posi~ive the compal~ison of the immediately following page
number 8-bit word 1~ith the page number indicated by the
keyboard 19. 1~nen the result of th~ comparison is negativey
the already received 8-bit words and ths following ones are
destroyed up to t1le dete~tion of the next page flag. When
the result of the comparison is positi~e~ ~ne 8-words recei~d
_ 18 -
up to the detection of the next page flag are transmitted
to memory 18~ after having been processed a~ ~ollows. I~
each page the char~cters are ordered in rows. In the
9equence of data 8-bit word4, each row is preceded by a row
flag followed by an 8-bit word lndicating the height of
the followin~ row in the pa~e. The ro~ number 8-bit ~ord
is used to determine one of~ the addresses of the character~
to be sto~ed in the memory 18. The other address is
determined by the posi~ion of the character 8-bit word in
the ~equence of character 8-bi~ wGrds constituting a row,
includin~ bla~ks between characters, It must be noted that
the s~quence of 8-bit words co~stituting a row includes,
in addition to the proper character words~ so.~e 8~bit words
indicati~g character partic~lars, such as the color. These
function 8-bit words are also stored in the memory 18 at
the address of the characters they characterise.
Thus~ ~or o~t~;T~;ne the p~ge that he requires, a magazinc
viewer ~irst keys the r~quired number on the keyboard 19
for consulting 'the magazine summary. From the above lt
will be underslood that this results in the summary page being
selected in blocl~ 17. ~hen the ~iewsr composes on keyboard
19 the numbe~ of the page he wishes to read.
It will be noted thac the data stored in the memo~y
18 provide an electronic ~eo~raphic representation of the
characters in the corresponding page~ These data are read
19 _
o~ o
out to the character ger1erator 20 usinO~ a ti~e basis
provlded in such a rnanner as to rnake it pos~ible for the
me~ory 18 to be read completely in a telaYision frame periodO
C~arac-ter generator 20 receives eacn character 8-bit word
read out from the ~emory 18 and builds the corre~ponding
letter shapa from a video signal havi~g two conditions9
one conditio~ being black and the othsr whi-te. In addition~
it receive~ the associated functi~n 8-bit word indicating
for insta~ce the color and delivers the correspo~ding
lo logic signals R2~ V2 and B2.
To make clearer how signals delivered froln generator
20 are d~splaysd on screen 13, video switch 14 ~ll now be
described in detail in conjunction with ~ig~ 3. Vldeo
~witch 14 ma~es~o3sible, on the one hand~ control of the
swltching o~ logic and analog signal~ to be displayed on
tube screen 13~ ei~her corresponding to a text picture froin
20~ or a current televl~ion picture from 12 elther animated
or not~ and, on the o~ner hand, to determine the character
color selected among 8 shades, i.e. for in~tance, red~
green, blue, yello~, .~agenta, cyan~ ~hite and blackO
Video s~itch 14 a~so perPorms an adap-tation o~ the
Yoltage/light characteristics of the tube to the control of
the synthe~ized si~als. Such an adaptation is currently
perPormed in the tran~misslon station, when broadcasting
pictures, belng 'hen known as the gamma-correctionO But with
- 20 -
synthesized plctures whe~ein signals have a logic nat~re,
no gamma-correct~on can be made at ~he transmission
station, Accordingly7 according to the present invention,
ther~ i~ provided means for receiving the signals deli~ered
from memory 18 and for adapting the corresponding voltages
to suitable values needed for the control of the display
tube.
For tha~ purpo~e, ~ideo switch 14, shown in Fig~ 3~
has two set~ of color signals inputs, i.e. on the one hand,
R1, ~1 and B19 and, on the other handt R2, V2 an~ B2.
Furthsrmore, a l~minance input 21 is connected ~rom the
associate.d output of 20 while ano~her lun~inance input 22 is
connected ~rom the associated output of 120 Inputs 21 and
22 ar~ respectiv~ly conn2cted to inputs of amplifiers 23
and 24. Each amplifier 23 or 24 has a gain equal to 1 with
a high input impedance and a low output in~pedance so as to be
a voltage source. Signals delivered from 23 and 24 are
respectivel-~ adju~ed ~y diodes 25 a~d 26 supplied by a stable
voltage genera~or 27. Transfer time constants for these
input signals are dete~nined by capacitors 2B and 29 according
to the input impedances of the ampli~iers 30 and 31. Dep~nding
on the position of a ~witch 32 co~trolled by a con~rol signal
from ~he keyboard 19. via input 337 either a signal ~rom
amplifier 30 or a signal from/a~plifier 31, ~especti~ely
corresponding to either signal applied to 21 or signal applied
, "
z
to 22~ is tran~mitted~ via output 34~ to the l~ n~nce
input of tube 13.
The i.nputs Bl, V1 and Rl are respectively connected
to the associated i~puts of a chrominance switch 35, through
amplifiers 36B~ 36~ and 36R which operate as voltage
60urces, like a~plifie~ 23 and 24. A chrominance switch 35
is also controlled by the control input 33. The inputs
B29 V2 and R2 are respectively connected to the inputs of
logic si~nal amplifier~ or lnverters 37~9 37V and 37R. The
outputs of in~erters 37B, 37V and 37R are respectively
connected, on the one hand, to the inputs of a lo~ic cper~tor
38 ~nd, on the other hand, to the inputs of logic signal
amplifie~s 39B, 3~V and 39R. The output of amplifier 39B
i~ connected to the cathode of a diode 40B whose anods is
connected, firs*9 to the anode of a diode 41B~ second, to
the anode of a diode 42B andt ~inally, to the input of an
am~lifie~ 43B, operating as a voltage ~ource, through a
resistor 44B. Outputs of amplifiers 39V and 39B are also
r~sp~ctively connected to similar sets of diode3 40Y9 41V
and 42V~ and 40R~ 41R and 42R. The anode of diode 40V is
con~ected to the i~put of a ~oltage source ampli~ier 43V,
via a resisto~ 44V, while the anode of diode 40R is con~ected
to the input of a voltage source amplifier 43R, via a
resistor 44R. ~urthermore the cathodcs of diodes 40B9 40V
and 40R are parallel connected from the output of an adjustable
- 22 _
voltage generator 459 through adjustable re~istors 46~,
46V and 46R respectively. The cathodes of diodes 41B,
~lV and ll1R are parallel connected from the output of
another adjl-stable voltage generator 47. The cathodes
of diodes 42B7 42V and 42~ are paral].el connected f~om the
output of a last adjustable voltage generator 48, through
a ~esistor 49, on the one hand, and from the output of
logic operator 38, on t~e other hand. The output~ of
an)plifiers 43B, 43V and ~3R are raspectively connected~ as
outputs of 36B, 36Y and 36R~ to associa~ed inputs of.s~itch 35.
Depending on the condition of the control wire 33 ~rom the
keyboard t9, the switch 35 delivers ~rom outputs 503~ 50V
and 50R to the tube 13, either signals from the a~nplifiers
43, or fron~ the ampli~iers 36. Resistances 44R, 44V and
44B are ad3ustable resistors ssrvi~g to correct diode
characterlstic variations.
Now with ref~rence to Fig. 4, the voltages applied
to respecti~e inputs ~, B and C of the ampliflers ~3R,
4,V and 43B wil~' be considered versus logic pulses delivered
from the generator 20 to the input~ ~2, V2 and B2.
~irst,Lhe assumption is made that, at ti~e tl, the
generator 20 delivers three logic pulses. The logic operator
38, operating as an A~-D gate or a NOR ga~e, accordi.ng to the
technology in use, tnen has its o~tput off, which allows the
~oliage generato~ 4~ to ap~ly, through the resistor 49, a
- 23 -
turning-on voltage to the dioda~ 42R, l~2V and l~2B7 that
voltage having t~e highest value, i~dicated by v3~ and being
transmitted to the illputs A, B and C. Assu~ing that tha
switch 35 has been correctly switched by the si~lal on
inp~t 33, the three amplifiers 43R, 43V and 43B transmit
those voltages v3 to tube 13 which eauses a white spot to
~ppear on the screen of tube 13.
At a time t2, ~he a~sumption i~ made tha-t only the
inputs R2 and V2 receive logic pulses from the generator
20, but the in~ut B2 receives no pul~e. A3 a result
thereof the output of logic operator 38 is grounded so that
the diodes 42~, 42V and ~2B are off. Through th~ two legic
in~erters 37B and 39B~ the zero voltage applied to the
lnput B2 is delivered from amplifier 39B so that the diode
40B i~ also off while-the diode 41~ is on and transmits to
the junction point C the voltage vl delivered from the
amplifier 47, Pulses appliad re~pectively to inputs R2 and
V2 are transmitt~d thrvu2h amplifie~ 37n and 33R9 and
amplifiers 37V~a~d 39V, which tU~l diodes 40R and 40V on.
Since a volta~e of value v2 delivered from the amplifier
45 is higher than a voltage of valu~ vl delivared fro~
genara~or 47, diodes 41R and 41V are off and only voltage
v2 is applied to junction points A and B~ Voltages v2 from
A and ~, and voltage vl from C are tra~smitted to t~be 13
uhich dis?lays a yellow spo-t. The other t~o com~inations
- 24 ~
of pulses re~ult in a cyan spot (B and G) and a magenta
spot ~R and B)~ respectiv~ly.
At time ~3, the agsumption is ~ade that only the
input B2 receives a logic puls~ from the generator 20.
The output of logic operator 38 is still grou~lded turning
diodes 4ZR, 1~2V and 42B off~ Diodes 40Y and I~OR are off9
because the outpu~s of ampli~iers 39V and 39R are grounded
so that a voltage v1 from the generator 47 is applied,
via diodes 41V and 41R~ to junction points A and ~9
respectively. On the other hand, the diode 40B is on and
transmits the ~oltage ~2 from the amp~ifier 45 to juncticn
point C. Voltages v1 from points A and ~, and voltage
- ~2 from point C are tra~s~itced to tube 13 which di~plays
a blue spot.
Between ti~es t1 and t29 or betwee~ times t2 and t3,
the ou$put o~ operator 3~ i~ still groundedO The diodes
40R, 40Y and 40B ar~ off, Onl~ the three dlo~es 41R9 41V
and 41B are on~ The voltage v1 is applied t~ all the junction
points A, B and C. A black spot a~psars on the ~creen~
It will be understood from the above that the switch
circuit 14 provides a good Lle~ibilit~ in adjusting the
colors. Particularly9 white is defined by ~djusting the
voltag~ v3 from the generator ~89 black is definad by
a~justi~g the v~l~age ~1 from the generator 479 and the basic
colors R9 G and B are defined by adjustlng the generator ~5
and the resistors 46R? 46V and ~6B~
- 25 -
It would obviously be possible, instead of using
a ~ogic operator 38, ~o utilize -~everal such operAtors,
- each being associated to an adjustable ~oltag~ ~enerator9
so as to permit the adaptation o~ the lt~min~nce o~ the
variou~ shad~s according to user's wishes.
It is to be noted that the link J is preferably of
the type described in French Patent No. 2~268,308. Such
a link makes possible an asynchronous operatlon from
selection block 1~ to decoder 170 Furthermore, as an
~lternative~ the input of the link J may be connected from
a wired telete~t di~tribution network~ for instance~
utilizing the public telephone network~
In an embodiment of this in~ention which will now
be described in dstail~ the mer~ory bloc~ 18 and the character
generato~ 20 are designed as sho~n in ~ig, 5. In practice
the memory 18 comprises two random access mem~ries (~AM)
51 and 52~ as well-a~ a switching circuit 53 and a bu~fer
memory 5~. The input of the switching circuit 53 is
connected, vi~ a liIle 559 from the OUtp'lt of` circui-~ 17,
Fig. 2y that delivers the character 8-bit words and the row
function 8-bit words. Row addressing inputs in the memories
51 and 52 are parallel connected~ via line 56, from the
output of the ci~cu-it 17 which delivers the row numbers.
The switchin~ circuit 53 has an output 57 which is connected
to the data input of memory 5f and an output 58 which is
- 26 _
~9~
connected to the input of the buffer memory 5~. Tha
output of the buffer memory 54 is connected to the data
input of the rnernory 52.
Data for application to the input o~ ~witchin~
circuit 53, via line 55, ~ay be grouped in the foll~wing
families: first~ in the simplest ca9e, an alphanumeric
character 8-bit ~ord, then an escape 8~bit word plus
either a character 8-bit word or a conventional functlon
8-bit word, and finaily an escape 8-bit word plu5 a
character type identity 8-bit word. The switching circuit
53 includes detection ~eans for reco~nizillg third family
data - escape 8-bit word plus character type identity 8-bit
wo~d -, t~ose ~nea~s being possibly sirnple comparators, and
: m~k; ng it possible to send them to output 58 while flrst
17 and seco~d family data are sent to output 57.
By way of exam~le, some types of identity 8-bit
~ords will now be ill~strated An 8-bit word ~1 may be
provided w~erein the five first bits c~rr~, when they are
în the l~conditio~ the followin~ information, but, when
they are in the,0-condition, no informat~on.
1st bit Znd bit 3rd bit 4th bit 5th bit 6th bit 7th bit
~ed Gre~n Blue Graphic 1 0 0
8th bit
,
Thus, ~ith a 8-bit word 1000100X, it indica tes that
the se~uence of the characters following it must be displayed
-- 27 --
%
in red o~ the tube ~cree~. By ~ay of exa~ple~ with a
8-bit word 01 lOlOOX, it indicates that thc ~equence must
be di~played in cyan. When the 5th bit i~ 1, it indicates
that the 8-bit word is a word ~1; when 6th and 7th bits
are 0, switching circuit 53 can detect the function 8-bit
wo~ds, the meaning of the 1~th bit will be described i~ the
followingt t~e 8th bit is a parity bito
:i~ In a sam~ manner~ a 8-bit word F2 ~ay be provided
wherein the bits have the followin~ meanings.
. 1st bit 2nd bit 3rd bit 4th bit 5th bit 6th b.it 7th bit
Height W'idth Ground ~lashing 0 0 0
8th bit
X
When the 1st bit is 19 it lndicates tha-t the character
hei~ht ls to be doubled, whe~ the 2nd bit is 1, it
indicates that th~ character width is to be doubled; when
the 3rd bit is 1, it indicates that the ground onto which the
character is to be displayed must ha~e its color reversed;
when th~ 4th bi~t is 1~ it indicates that th0 character must
be ~lashed on and o~f~ Thus, with a 8-bit word 1 lOlOOX,
it indicates that height and width of the charac ters must
be doubl ad and they must be ~lashed on and off~ The 5th bit
bèing 0 indicates that th2 8-bit wor~ is a word F2.
in
Now it is possible to understand that, when/the
sequence of` 8-bit words applied from li~ 55 to switching
~ 28 --
... .. . . . . ..
circuit 539 there ~3 the following serie~: ~ F1 ~ F1 a b c . . .;
switchin~ circuit 53 will write the four word~ ~ F1 ~ ~1
into memory S4~ then words a b c ..., into ~emory 51,
Writing of fir~t character word a into memory 51 which is
detected in circuit 59 initiates writing at the same
address into memory 52 of words ~1 and F2 from memory 54
(words 0 being not transmitted ~rom memory 51~ to memory 52~o
Clrcuit 59 is connected ~y control line 60 to memory 5~
Buffer memory 54 is connected to RA~ memory 52 by line 61.
Read out from memvry 54 to memory 52 does not
alter the co~tents of memory 54-. Thus~ when writing b
into memory 51~ ~1 and ~2 are written at th~ sa~e addres~
a~ b into mamo~y 52. Ag a conclusion at corresponding
addresses cnaracter ~ord 5 are written in'o ~2mo~y 51 and
type identity words are ~ritte~ into memory 52. The
contents of memory 54 are erased at the next writin~ into
bu~fer memory 54 of an escape word followed by an identity
word,
In addit~on io function words ~1 and ~2, othar function
words ~ay also b~ provided, as for instance ~3 ma~ing it
possible to change from a character shape to another
character ,shape, taken together the 5th and 7th bits then
indicate an i.dentity word which ls detected in switching
circuit 53~ the 6th bit being O and the 8th bit being ~till
a parity bit.
- 29 _
The characte~ generator 20, shown in ~ig~ 5,
comprises four permanent memories 62-~5; a switch 65, a
mixing circuit 67 ~nd a monostable circuit 63~ Each
perman~nt memory 62-65 is associated respectively wlth
a shift register 69-72 designed for delivering serially
the bits conventionally read in parallel ~roma character
generator permanent memory. It is to be remelnb~red that
the scanning of character shape is performed in memories
62-65 line per line 7 each basically corresponding to a
television p~cture line. A clock 73 is also provided which
con*rols read o~er~tions from memories in accordance wi~h
television picture line synchronization signals. In
~i~. 5, some inputs S are also indlcated wnich mea~ that
television line synchronization si~nals are also used -for
rea~ing the concerned memories or controlling repetiti~e
operatio~s; howeYer9 to simplify the drawing, all the
~nputs S are not indicated.
Swltch 66 is provided ~or selec~ing one of the
registers 69-7~ that is to be connected to its output 74
connected to mi~ing circui-t 67; it also d0termines the read-
out operation rate9 or in other words the sampll~g rate of
register outputs~
The read-out output of R~ memory 51 is parallel
connected to read-out address ir.puts of permanent ~emories
~5 62-65. Parallel read-out output~ of memories 62-65 are
- 30 -
respecti~ely connected to parallel inputs of register4
69-72,
The read-out output of RAM memory 52 has as ma~y
wi.~es a~ significant bits i~ function word~ ~1, F2 and F3,
Thus these are indicated wires R,G~ B respectively
corresponding to the ~irst 3 bits o~ F1, wire ~ corresponding
to the first bit of F2, wire L co~responding to the second
bit of F2, wira F corre~ponding to the third bit of ~2
and ~ire C corr~sponding to the fourth bit of F2 t In
addition, there is provided a line M comprislng four wires
correspondi~g to the significant bits of r`3, which are in
the de~c~ibed example assumed to be two bi-ts s~nce four
permanent memories are provided.
~ire H ~ connected to ~ control input of the clock
73~ ~en H i8 low, the clock 73 operates at a normal rateS
i.e. for each picture line RA~I memory 51 is read as well
as a character ~h~pe line in the permanent memories 62_65,
that line corresponding to the address read o~t from 51.
When H is high~'the clock rate of clock 73 ~s di~ided by
two. As the clock 73 designates, after counting, the address
of the line to be read in the character shapes of the
permanenl memories, when ~ is high~ cach character shape line
i5 successlvely read twice at the picture line frequ~ncyO
Thus the height o~ ths displayed character occupies twice
as mally lines on ths tube sc~en. Its heigh-t i3 doubledO
- 3~ -
z
~ire L indeed lncludes t~o wires, one L1 controllin~
the bit shift rate in re~i~ters 69-72, the other L2
controlling th~ horizontal address progress rate in RAM
meMory 51, via input L2. Obviously these two rates are
also related to the television picture line synchronization.
~en wire ~ i~ low, the shift rate and the sampli~lg rate
are no~mal. When wire L is high~ the shift rate and the
sampl~ng rate are both divided by two 60 that the same bit
stays twice as long in the output cell of each shift
regi~ter and th0refore can be sampled twice. Thus
information relating to a c~aracter point can be sent twice
to the displ~y tube in the picture line~ Accordingly the
; width is doubled. As a character then occupies a wide~
place in t~a displayed row, it i8 necessar~ throu~h input
L2, to reduce by two the progress of the character word3
i~ the corre~po~dlng row in memory 510
The four wires of line M make possible the selection
of the parmanent memory whose output is utilized amo~g the
memorics 62_650 Indeed a~ each read-out operation ~ro~ the
memory 51, the ,four memories 62_55 ars read-out in parallel~
However, the switch 66 allo~s only one co~ection with the
circuit 67. With four permanent memories wherein there are
respectively storad four alphabets, it appears that two bits
of words ~3 permit in a simple man~er the language to be
changed depending on the texts to be displaye~.
- 32 -
When wire C is low~ the monostable circuit 68
is at rest~ when the wir~ C is high, the monostabl~
circuit is triggered on. The monostable circui~ rate may be
of about about 1 Hz and is used as described hereabove
for flashing characters on and of~.
~eference will now be made to ~ig~ 6 for describing
the purpose3 of wires ~, V (or G), B and ~. In ~ig. 6~
there are s~i~l shown the wire 74 connecting the output
of the switch 65 to the clrcuit 67, as well as the output
wire 7~ from the monostable circuit 68. First lt is
to be remem~ered that the wire 74 carries digital si~nals
relating to the lu~inance information. Thust with each
character shape line scann; ng in a parma~ent memor~, after
the parallel-serlal.conversion in the corr~sponding shift
register, the ~ignal transmitted by 74 ~s shaped as
indicated b~ the ~-ave form 1~ ~ig. 6. When signal 1 is hi.gh,
a spot i~ lit on the tube~ when signal 1 is low, the back-
ground doe~ no* light. The wire 74 i9 co~nected to the
input of a switchable in~erter circuit 75 ~hose output is
connected to a,s-~itch 77. ~he sig~al output of the switch 77
is connected, on the one hand, to the output 21 through a
shaping c~rcui' 78 and9 on the other hand, in parallel to
first lnputs of three ~D gates 73, 80 and 81. A second
input of gate 79 is connected to wire R, a second input of
gate ~0 is connected to wire R (or G), and a second input of
33 -
gate 81 is connected to wire B. The outout of gate 7
is connac-ted to wire R2 through a shap:Lng circuit 82,
the output of` the gate 80 is connected to the wire Y2
through a shaping circuit S3~ and the outpu-t of the gate ~1
is connected to -the wire B2 through a shaping circuit 8!~.
The control input of ths switchable in~er~er circuit 76
is connacted to the wire ~ while the control input of the
switch 77 is co~nected to the wire 75.
Assuming that the wires ~ and 75 are at rest in the
0-condition or 1oW9 the slgnal 1 fro-m w~re 74 is applied
without change to the circuit 78 and the gates 79-81.
From tha output 21 of circuit 78, the output signal is
processed in tha switching circuit 14, Fig. 2, shown in
detail in Fig. 3. In-addition ass~min~ that the wire R
ls (or G) îs in the 1-condition or high~ conditions 1 of
signal 1 are transmitted through gate 79 and applied to
shaping circuit 82 be~ore being processed in switchlng
circuit 14, Fig. 2. Thu3 it appear~ tnat the red chrominanca
signal is simllar to the 11l~;n~nce signal that causes the
character to ba displayed in rad. Whan wiras R and Y (or G)
are high, conditions 1 of 1 are transmitted and wires ~2
and V2 b~come high, the color mix belng performad in the
tube after p.rocessing ln switching circuit 14~ Tha result
is thus obtained tqat characters may be displayed in whi-te
or as one of 3iX predatermlned colors by using the ~rs-t
three bits of the word ~1.
_ 3~ _
æ
When the wi.re ~ is in the 1-condition or high, the
output signal from 76 is re~ersed with respect to 1,
i.e. 1. Such an outpu ~ signal is still processed in gates
79-819 as signal 1, but contrary ~o the previous described
case, only the part~ outside of the characters correspo~ding
to conditions 0 of 1 appear.displayed in color.
When the wire 75 is pariodically turned to the
; 1-condition, the transmission of signal 1 is interrup~ed
through the clrcuit 77 during these l-conditions. As a
.. . ...... . . .
~ 10 result the lllm;n~nce si~nal is accordingly interrupted
: which causes the character to flash on ~d off on the display~
Tha shaping circuit 78 is also utili~ed for adding
~he digital synchronization signal to the lll~;n~nce signal~
as indicated by S.
~lso to be noted that9 with no type-identity
in~ormation, the outputs ~VB of memory 52 are high or in
tha l-conditlon~ so as to display white characters on a
black bac~ground~
Read-out opera~ions are ob~iousl~ performed at the
same time in th~e ~ 1 memories 51 and 52 so as to read
characters ~rom perm~nent memories at the same time as the
conditions of the output wires of memory 52 are controlled
by identi~y bi~ in words F1, F2 and .~3.
With respect to the bit corresponding to a Graphic
in word ~1, it must be understood that there i~ provided,
- 3~ -
for instance close to the per~lanent ~emory 62, a wired
memory whsrein there are 9 ~ored .six-point rectangles
making it possible, by di~playlng them side by side~
for graphic~ to be ~roduced on the screen. In practice,
the output of the RAM rnemory ~2 has a wire corresponding
to the 11th bit of F1, which permits the wired memory
to be selected instead of the ~emory 62 in a similar manner
to the selection controlled by the wire M, Graphic
rectangle cudes are provided in the ~CSII code"
In an alternative method of operation of the
teletext system ~ccording to this invention9 it is pre.erred
to begin each row with a type identity word, the character
type being possibly ch~nged within the row, but returning
to tne initial ~pe at the end of each row, Thus the
display is resy~chronized at the beg-nnin~ of each row.
t
- 35 -
,
