JPS6342908B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a system for digitally transmitting selected items of data and displaying them on the screen of a television receiver. In other words, such a system will be referred to as a teletext system in the following description. More specifically, the invention relates to a receiver for a teletext system. With the increasing importance of information and communication, data banks were created in such a way that they became useful in developing information processing techniques and audiovisual means. Although updating the files storing data makes these systems effective, the cost of maintaining the information currently limits their current use. Teletext systems allow these data to be broadcast from a central processing station that performs the data publication. This centralized organization is similar to that of the newspaper organization, with radio broadcasting approaching newspapers and periodicals. In fact, the teletext system has several features, the main purpose of which is to achieve broadcasting, which allows stored data to be broadcast over an RF channel. The primary means of reception is the television receiver's display screen. This display screen displays pages of text and graphs transmitted in encoded form, such as that shown in French Patent Publication No. 2 313 825, for example. However, Teletext services are transmitted over public or private telephone networks, and Teletext subscribers access data banks containing storage devices that serve as files of information arranged on pages. The keyboard used by the subscriber to select a page allows the subscriber to respond to questions from the file processing unit and the desired page is sent to the subscriber. In television broadcasting, the waiting time for a desired page depends on the transmission capacity handled by the teletext system and the number of pages in the file magazine. This transmission capacity varies considerably depending on whether all television channels are allocated to teletext or only a few blank lines. As an example, for a magazine containing about 50 pages and a transmission capacity of one line per frame, the average latency is on the order of about 15 seconds. In the case of transmission over telephone networks, the central unit responds very quickly, but data transmission occurs at low speeds due to the narrow available frequency band.
It may take several tens of seconds. Regardless of the transmission medium used, the teletext system first selects one page of information from a plurality of pages to be used, then transmits the selected page, and finally transmits the selected page to the television receiver. Including displaying on a screen. On this screen, the images and graphs constructed by the written pages do not have any midtone areas. Furthermore, the use of a television receiver capable of receiving standardized television programs is based on the resolution of a television CRT, for example, approximately 25 characters per column with 40 characters.
Although limited by columns, it makes it possible, on the contrary, to utilize a set of eight colors, for example to embed very clear pages. The alphabet used depends on how letters are written in the country using the Teletext system. In France, one proposed system can be extended to most languages using the Latin alphabet.
It has 126 letters in Latin alphabet. An example of the teletext system is the technical paper entitled "Broadcast Data in Television" published in 1974 in the British technical magazine "GEC Journal of Science and Technology", Volume 4, No. 4, pages 117-124. and British Patent No. 1467240. or
Reference may also be made to the technical paper entitled "ANTIOPE Service Teletext", published May 5, 1975, in the French technical magazine "Radio Broadcasting et Télévision", Vol. 9, No. 40, pages 18-23. The last paper presents the features of the system described above. Furthermore, the aforementioned service pages are compiled into various magazines, and each of these magazines is all periodically broadcast. Each page can be identified by its page number. Some of these pages may include summary text to assist in selecting the desired page using the keyboard. Among the specific functions that a teletext system can perform is the interpolation of text into television images in the form of subtitles in a language selected by the television viewer. Such subtitles may be strictly related to the video or may relate to short pieces of news regarding a given thematic issue. These can be written in rectangular boxes cut into the current video, or erased at the viewer's will. It is clear that the features of this format are related to educational programming. According to one feature of the invention, it is a teletext system for digitally transmitting textual material from any of a number of different services and displaying it on a television screen, the digital transmission being such that successive data packs are This is done in the form of a plurality of data packs in which data from several channels are mixed haphazardly so that they can be associated with any of the different services, said packs having signals constituting a magazine of several pages; In magazines, the data belonging to each page is organized into multiple lines, and the data belonging to each line is preceded by a line flag with a line number, ends with the next line flag, and the line detected after each line flag. The number determines the address in the storage device at which the line data must be stored, and the selection between the different services is determined in a teletext system using a transmission method in which the data for each page of information begins with a page flag. a keyboard means for transmitting necessary control signals including a signal for identifying a desired page and a signal for identifying a desired page; and detecting a desired page by receiving a signal from said keyboard means for identifying a desired page in response to a page flag. comparator circuit means for storing data relating to said desired page in response to an output of said comparator circuit means; character generator means for generating signals for display as characters in a desired format on a screen; said character generator means responsive to an output of said character generator and a control output from said keyboard means; A teletext system is provided comprising a video switching means 14 comprising a matching circuit for sending the output signal of the video signal and adapting the voltage-light characteristics of the cathode ray tube to the control of the composite signal. According to another feature of the invention, the character generator means is configured to transmit a character luminance signal and a primary color R (red) to a matching circuit means.
an additional logic signal as to the presence or absence of V (green) or B (blue), said matching circuit means transmitting the luminance signal to the normal circuitry of the television receiver, said matching circuit means associated with each primary color logic input; a first diode having a cathode connected to an input of an analog amplifier means; and switching means for selectively connecting the output of the primary color amplifier to a corresponding chromaticity input of a television cathode ray tube in response to the keyboard means. , the cathode of said first diode is also connected to the cathodes of a second diode and a third diode, and the anode of the first diode is connected to an associated color input and a first voltage generator delivering a voltage v2. the anode of the second diode is connected to the output of the second voltage generator delivering the voltage v1, and the anode of the second diode is connected to the output of the second voltage generator delivering the voltage v1;
The anode of the diode is connected to the output of a third voltage generator delivering a voltage v3, the third voltage generator having an output also connected to the output of one gate, the output of said gate being , not grounded when the three color inputs receive the logic signal at the same time, grounded in all other cases, voltages v1, v2, v3 are v3>
A teletext system with a relationship of v2>v1 is provided. The invention relates to means provided in the data receiver of each system and making it possible to change the appearance of the text displayed on the television screen, so as to break the monotony of the current display appearance, and the structure of the transmitted signals. . For example, these variations affect character color, background color, blinking of certain characters, changes in character height/width, etc. The character generator that displays characters on the cathode ray tube screen of the television receiver is comprised of non-volatile storage associated with constant-speed recall storage. This non-volatile storage stores all character shape information that can be displayed. The constant retrieval memory stores the character codes, including inter-word spaces and blanks, that form the displayed text. In a constant access memory device, character codes are stored at addresses that correspond to the geographical locations of the associated characters on the displayed page. The display operation consists in successively reading out rows of character codes from the constant-speed recall memory, each read operation of one character corresponding to a character code read from the non-volatile storage in a well-known manner. Produces a scanning readout of the character form of the character. If one character occupies 10 television scan lines, each read operation for a line of character codes from constant-recall storage results in 10 consecutive scans of the character shape from non-volatile storage. . It is clear that this scanning is regulated by a clock controlled from the horizontal sync pulses of the display tube. The signal generated by scanning a single character shape is sent in parallel and converted to serial mode via a shift register, where the shift signal frequency is controlled by a clock controlled from the horizontal synchronizing pulse of the display tube. controlled. The output of this shift register is sampled at another frequency controlled by another clock. The output signal of this shift register is transmitted to the display tube as a luminance signal. Furthermore, in character transmission systems, each character is represented by an octet or 8-bit word, the so-called ASCII code, currently in use. Of the 8 bits of one word, 1
Bits are normally allocated for parity checks.
The other 7 bits give the possibility of creating 128 characters. Of the 128 character creation possibilities, some are assigned to character codes and others to function codes. Furthermore, so-called extended 8-bit words make it possible to double the character creation possibilities by easily changing the meaning of the code following an extended word. Another feature of the invention is that the displayed characters are
They come in a variety of formats that differ in color, size, background, etc., and each format of displayed characters is a telegram expressed by one or more 8-bit words corresponding to the type of character format. The purpose is to provide a text system. According to another feature of the invention, there is provided a system for displaying text on a television screen and transmitting the same digitally;
The sequence of bit words (in addition to the prefix, the page flag followed by the page number, and the line flag possibly followed by the line number) also includes extended 8-bit words followed by format type 8-bit words, and these 8-bit words The word itself is followed by a series of characters to be displayed in the same format as determined by the preceding format type, 8-bit word, and each system receiver has a first constant-speed access memory for storing the encoded characters. In addition to the device, a second constant-speed access memory is provided for storing an 8-bit word of the format type at an address identical to the address of the character belonging to said sequence in the first constant-speed access memory; The read operation from the constant velocity recall memory is performed when the character shape read from the first constant velocity recall memory selects the non-volatile memory of the character generator to be read or is displayed when the character is displayed on the television cathode ray tube. This occurs concurrently with a read operation from a second constant speed access memory having an output to control the brightness or chromaticity of the tube. According to another feature of the invention, an extended 8-bit word is followed by a type 8-bit word that is followed by the last various 8-bit words immediately followed by the first letter 8-bit word of the series to which that type is assigned. On the one hand, received data containing one type component word followed by one extended 8-bit word for each character type component, excluding the component 8-bit words, and being applied to the switching circuit:
An extended 8-bit word followed by a format type 8-bit word is sent serially to buffer storage, while a format type 8
Characters not followed by a bitword 8-bit word or extended 8
bit words to the input of a first constant access memory, and the output of the buffer store is connected to the input of a second constant access memory to transfer content other than the extended 8 bit words to said second constant access memory. The contents of the buffer memory are sent to the constant-speed access memory each time a character belonging to the series of characters is written to the first constant-speed access memory, and the contents of the buffer memory are the format type or the format type component 8-bit word. It is erased when the next extended 8-bit word is received. The device shown in FIG. 1 is identical to that in FIG. 1 of the specification of French Patent Application No. 2,313,825. A number of data sources are switchably connected to the modulation circuit 1 and the transmission antenna 2, such as the data source shown including a data processing circuit 3 connected to a number of control sets 4.1-4.N. Data processing circuit 3
includes a shaping circuit 5 and a storage device 6 having an input connected to the output of the shaping circuit 5, the broadcast output being selectively connected to the modulation circuit 1 and the control output connected to the input of the conversion circuit 7. Ru. Each control set 4.1
-4.N includes a monitor screen 8 and a typesetting typewriter 9 as in 4.1. Each typewriter 9 has a data output connected to the input of circuit 5 and a data input connected to the output of circuit 7. Each control set 4.1-4.N allows the journalist or operator to compose a page on the typewriter 9 while examining on the monitor screen 8 all the features of the final color image, i.e. the size of the characters, blinking and graphic features. do it like this. Each typewriter 9 is similar to a typing machine and includes logic circuitry for organizing and updating documents. The output data from the control sets 4.1-4.N are placed in the circuit 5 according to the standard,
It is stored in the storage device 6. The storage device 6 may be a disk memory in which the sequence of codes to be transmitted corresponding to the language defined in the French technical paper is stored. Therefore, the storage device 6 is
It constitutes a file of pages that are periodically read out and transmitted to the modulation circuit 1 for broadcasting. control set
The operator controlling 4.1-4.N can display on his control screen 8, via the circuit 7, selected pages read from the storage device 6. The embodiment of the device shown in FIG. 1 is well known. These embodiments may be implemented in hardwired logic or programmatically controlled from a computer. As described in the aforementioned French Patent No. 2,313,825, data broadcasting shall be carried out in the play line of the television picture for one television channel. These data are assembled into a data pack containing 32 8-bit words or octets. Each data pack is assigned a prefix indicating the data source address and the number of words contained in the associated data pack. When the length of the data to be transmitted consists of more than 32 8-bit words, it is divided into several data packs and the prefix contains the pack number in addition to other information. There is also an 8-bit word in the prefix that synchronizes the terminal local oscillator of the receiver and another 8-bit word that synchronizes the 8-bit word of each data pack. The total data pack thus transmitted contains 40 8-bit words, each of the 320 bits representing black when the bit value is 0 and white when the bit value is 1. By choosing a receiving frequency that is an odd multiple of the line frequency, possible mutual interference between these digital signals and the video signal can be avoided. In the case of non-return-to-zero modulation, there are 397 breaks in one line resulting in a bit frequency of 6.20MHz. As described in the aforementioned French Patent No. 2,313,825, the computer used as the electronic management unit knows the list of idle lines of the video signal and assigns to these lines various teletext lines similar to those shown in FIG. Insert the data pack received from the editing machine. Various storage devices 6 and modulation circuit 1
Preferably, the connection from the network is constituted by a link such as that described in French Patent No. 2 268 308 entitled "Standardized Communication Interface Device". This link makes it possible to slow down the data flow of the data source constituted by the data storage device when the broadcast device is blocked. When using broadcast networks, it is not directly possible to control the output data flow from the data source by the capacity of the receiver input. To compensate for the lack of feedback control, a simulated receiver similar to the slowest receiver is provided in the management unit. When using other transmission media, the link provides the necessary functionality to properly transmit digital signals. The receiving terminal device shown in FIG. 2 is designed to supplement a general television receiver, and demodulates the data signal transmitted from the station shown in FIG.
These signals are used to write these signals into storage so that they can be re-formatted and then restored to the visible page on the screen of the associated television receiver. The receiving terminal may be a separate unit associated with a conventional television receiver, or it may be an integral part of a suitably designed television receiver. The receiving terminal device shown in FIG. 2, like a general television receiver, transmits an audio signal to a loudspeaker
and a receive-demodulator circuit 10 for transmitting the video signal to a color decoder and scan generator 12 on the other hand. Color signals B1 (blue), V1 (green), and R1
(red) and the luminance signal from the color decoder/scanning generator 12 are not directly transmitted to the cathode ray tube 13, unlike what happens in a typical television receiver, but as explained below. It is transmitted via the video switch 14 which has yet another function. The terminal device shown in FIG. 2 further includes a circuit 10.
and a circuit 15 for separating the data from the video signal, having an input connected to the video output of the device and an output connected to a first selection block 16 similar to the terminal device described in French Patent No. 2,313,825. ing. The output of block 16 is connected to a page selection block and data decoder 17 which has an output connected to the input of page store 18 via link J previously described. The viewer's keyboard 19 has its output connected to the control inputs of blocks 16 and 17, as appropriate. The output of the storage device 18 is the character generator 2
Connected to the 0 input. The signal output of the character generator 20 is the color input R2 (red), V of the video switch 14.
2 (green) and B2 (blue), and also connected to its luminance input. The control output of the keyboard 19 is also connected to the control input of the video switch 14. In circuit 15, a stable oscillator (not shown) generates a 6.20 MHz clock signal as described above. After detection of the line synchronization pulse, when the video signal transmitted from the receiving and demodulating circuit 10 displays a series of dots alternating between black and white at the clock frequency, the oscillator is phase-locked with the received pulse. The output of that oscillator is then utilized as a clock for the received bits. The oscillator is therefore utilized to properly separate the data video from the video signal of existing television programs. The received bits are processed as 8-bit words in circuit 15,
Activate only desired channels and magazines, taking into account service information such as channel number and subscription period. All circuitry for carrying out this process is described in the above-mentioned French Patent No. 2,313,825, in particular with regard to the identification of the desired channel as illustrated in FIG. Assuming the confirmation is positive, the received bit is sent to block 17 via link J. In the described embodiment, the above-mentioned French patent no.
The channel of the device described in issue 2313825 is equivalent to a magazine. It is well known that the various channels of this system are time multiplexed. This channel is therefore for various magazines. As a result, link J transmits the data content of one magazine serially by groups of 8-bit words, but the time interval between two such groups is determined by two reasons. The first originates from the time-multiplexed broadcast mode of the magazine, and the second originates from the transmission mode via link J. The transmission via J from circuit 16 to block 17 is This is possible only when it is ready to receive incoming data. Therefore, the transmission through J takes place in an asynchronous manner. In block 17, the first action is to select the desired page throughout the magazine. As described in the above-mentioned French technical article, a magazine consists of several pages, especially the first page which provides an overview of the magazine. In this magazine, the pages are naturally arranged according to increasing numbers. In broadcasting a magazine, each page of the magazine is not time multiplexed, i.e. the page data is preceded by an 8-bit word representing a page flag followed by a page number, and the next page number is followed by an 8-bit word representing a page flag. followed by another 8-bit word representing another page flag. As a result, in block 17, each page flag is detected, and each time the recognition is positive,
The 8-bit word of the immediately next page number is compared with the page number dialed on the keyboard 19. If the result of the comparison is negative, the 8-bit words already received and the following 8-bit words are
Bit words are counted until the next page flag is detected. If the comparison is positive, the 8-bit words received up to the detection of the next page flag are processed as follows before being transmitted to storage 18. On each page, the characters are arranged in a number of lines. In a series of data 8-bit words, each line is preceded by a line flag followed by an 8-bit word indicating the height of subsequent lines on the page. The line number 8-bit word is utilized to determine one of the addresses of the character to be stored in memory 18. The other address is determined by the position of the 8-bit word within a series of 8-bit words that make up a line, including spaces between the characters. The series of 8-bit words constituting one line includes, in addition to the above-mentioned character words, several 8-bit words representing character features such as color. Those functional 8-bit words or function words are also stored in memory 18 at the addresses of the characters having those characteristics. Thus, in order to obtain the desired page, the magazine reader first dials the appropriate number on the keyboard 19 to obtain a summary of the magazine. From the foregoing, the summary page is selected in block 17. The reader then enters the number of the page he or she wishes to read using the keyboard 19. The data stored in storage 18 provides an electronic geographic representation of the characters within the corresponding page. These data are read out to the character generator 20 using a time base provided in such a way that the storage device 18 can be read completely within one frame period of the television. Character generator 20 receives each character 8-bit word read from storage 18 and
A corresponding character shape is formed from a video signal having two states. One of the above two states is black,
The other state is white. Furthermore, it receives an associated functional 8-bit word indicating, for example, a color and sends out corresponding logic signals R2, V2 and B2. To further clarify how the signals sent from character generator 20 are displayed on screen 13, video switch 14 will be described in more detail with respect to FIG. On the one hand, the video switch 14 switches between a logic signal and an analog signal to be displayed on the cathode ray tube screen 13, i.e.
Text video from character generator 20 or current television video (animated or not)
On the other hand, it is possible to control the switching of signals corresponding to eight color tones, e.g. red, green, blue,
It is possible to determine the character color selected from among yellow, magenta, light blue, white, and black. Video switch 14 also adapts the voltage/light characteristics of the cathode ray tube to control the composite signal.
This adaptation is currently performed at the transmitting station when broadcasting video, and is called gamma correction. However, for composite images whose signals have logical properties, gamma correction cannot be performed at the transmitting station. Therefore, according to the invention, the storage device 1
Means are provided for receiving the signals sent from 8 and adapting the corresponding voltages to the appropriate values required for control of the display tube. For this purpose, the video switch 14 shown in FIG. 3 has two sets of color signal inputs, one R1, one V
1 and B1, the other has R2, V2 and B2 inputs. Furthermore, a luminance input 21 is connected from the associated output of the character generator 20, while the other luminance input 22
are connected from the associated outputs of the color decoder and scan generator 12. Inputs 21 and 22 are connected to the inputs of amplifiers 23 and 24, respectively. Amplifiers 23 and 24 each have a high input impedance and a low output impedance to serve as a voltage source.
has a gain equal to . The signals sent by amplifiers 23 and 24 are conditioned by diodes 25 and 26, respectively, which are powered by a stabilized voltage generator 27. The transmission time constant of those signals is
It is defined by capacitors 28 and 29 according to the input impedances of 0 and 31. keyboard 1
Depending on the position of switch 32, controlled by a control signal coming from input 33 from 9, either amplifier 30 or amplifier 31 is selected, depending on whether the signal is applied to input 21 or 22, respectively. The signal is transmitted via output 34 to the luminance input of display tube 13. Inputs B1, V1 and R1 are each connected to an amplifier 23
and 24, an amplifier 36 which operates as a power supply.
B, 36V and 36R, chromaticity switch 3
5 associated inputs. Chromaticity switch 35 is also controlled by control input 33. Input B2, V
2 and R2 are connected to the inputs of logic signal amplifiers or inverters 37B, 37V and 37R, respectively. The outputs of the logic signal amplifiers 37B, 37V and 37R are connected to the inputs of the logic operator 38, on the one hand, and to the logic signal amplifiers 39B, 39, on the other hand.
Connected to the V and 39R inputs. amplifier 39
The output of B is connected to the cathode of diode 40B, and the anode of diode 40B is first connected to diode 4.
1B, and the second diode 42B.
and finally, via a resistor 44B, to the input of an amplifier 43B that operates as a voltage source. The outputs of amplifiers 39V and 39R are also connected to similar sets of diodes 40V, 41V and 42V.
V and 40R, 41R and 42R, respectively. The anode of the diode 40V is
It is connected to the input of voltage source amplifier 43V via resistor 44V, while the anode of diode 40R is connected to the input of voltage source amplifier 43R via resistor 44R. Further, the cathodes of diodes 40B, 40V and 40R are connected to resistors 46B and 46, respectively.
Adjustable voltage generator 45 via V and 46R
are connected in parallel from the output of diode 41
The cathodes of B, 41V and 41R are connected in parallel from the output of another adjustable voltage generator 47.
The cathodes of diodes 42B, 42V and 42R are connected in parallel on the one hand from the output of the last adjustable voltage generator 48 via a resistor 49 and on the other hand from the output of the logic operator 38. The output of amplifiers 43B, 43V and 43R is 36
B, 36V and 36R outputs as well as the associated inputs of switch 35, respectively. Depending on the state of the control line 33 from the keyboard 19, the switch 35 sends either the signal from the amplifier 43 or the signal from the amplifier 36 from the outputs 50B, 50V and 50R to the display tube 13.
Sends either a signal from resistance 44
R, 44V and 44B are adjustable resistors that operate to compensate for variations in diode characteristics. Next, referring to FIG. 4, the amplifiers 43R, 43
The voltages applied to the respective inputs A, B, C of V and 43B and the inputs R2, V from the voltage generator 20
2 and the logical pulse sent to B2. First assume that at time t1 voltage generator 20 sends out three logic pulses. According to the commonly practiced technique, the arithmetic unit 38 operating as an AND gate or a NOR gate is configured such that the voltage generator 48 is connected to the diodes 42R, 42V and 42B.
The output is turned off allowing a turn-on voltage to be applied through resistor 49 to the output. This voltage has a maximum value denoted v3 and inputs A,
B and C. Assuming switch 35 was properly switched by control input 33, three amplifiers 43R, 43V and 43B
transmits a voltage v3 to the display tube 13 which causes a white point to appear on the screen of the display tube 13. Assume that at time t2, only inputs R2 and V2 receive logic pulses from voltage generator 20, but input B2 receives no pulses. As a result, the output of logic operator 38 is grounded such that diodes 42R, 42V and 42B are turned off. Since the zero voltage applied to input B2 is sent from 39B via two logic inverters 37B and 39B, diode 40B is also turned off, but diode 41B is turned on, and the voltage sent from amplifier 47 to junction C is Transmit v1. The pulses applied to inputs R2 and V2, respectively, are applied to amplifiers 37R and 37R.
9R and amplifiers 37V and 39V, turning on diodes 40R and 40V. Since the voltage of value v2 delivered by amplifier 45 is higher than the voltage of value v1 delivered by amplifier 47, diodes 41R and 41V are turned off and only voltage v2 is applied to junctions A and B. The voltage v2 from the junctions A and B and the voltage v1 from the junction C are the display tube 1.
3 and displays a yellow spot. Two other combinations of pulses produce light blue spots (B and G) and red-purple spots (R and B), respectively. At time t3, only input B2 is input to character generator 20.
Assume that you receive a logic pulse from . The output of logic operator 38 is still connected to ground and connected to diode 4.
Turn off 2R, 42V and 42B. Junction points A and B via diauto 41V and 41R respectively
Since the outputs of amplifiers 39V and 39R are grounded so that voltage v1 from voltage generator 47 is applied to , diodes 40V and 40R are turned off.
On the other hand, diode 40B turns on and transmits voltage v2 from voltage generator 45 to junction C. Voltage v1 from junction points A and B and junction C
The voltage v2 from is transmitted to the display tube 13, which displays a blue spot. During the time between t1 and t2 and between t2 and t3, the output of logic operator 38 is still at ground.
Diodes 40R, 40V and 40B are turned off. 3 diodes 41R, 41V,
and 41B are turned on. Voltage v1 is applied to all junctions A, B and C. A black spot appears on the screen. From the above, it can be said that the switch circuit 14 provides good flexibility in adjusting the color tone. In particular, white is defined by adjusting the voltage v3 from the voltage generator 48, black is defined by adjusting the voltage v1 from the voltage generator 47, and the three primary colors R, G and B are defined by adjusting the voltage generator 45 and the resistor. 46R, 46V and 46B. Instead of using one logical operator 38, several such operations are used, each associated with an adjustable voltage generator so as to be able to apply different shades of brightness according to the user's wishes. It is clear that it is possible to make use of children. It should be noted that link J is preferably of the type described in French Patent No. 2,268,308. This allows asynchronous operation from circuit 16 to circuit 17. Furthermore, the input of link J is
For example, the connection may be made from a wired teletext distribution network using the public telephone network. In the embodiment of the invention which will now be described in detail, storage block 18 and character generator 20 are designed as shown in FIG. Actually, the storage device 18
is composed of two constant-speed access memory devices, RAM memories 51 and 52, as well as a switching circuit 53 and a buffer memory device 54. The input of switching circuit 53 is connected via line 55 from the output of circuit 17 of FIG. 2 which transmits character 8-bit words and line function 8-bit words. The row addressing inputs of storage devices 51 and 52 are connected in parallel from the output of circuit 17 which transmits the row number via line 56. The switching circuit 53 has an output 57 connected to the data input of the storage device 51 and an output 58 connected to the input of the buffer storage device 54 . The output of buffer storage 54 is connected to the data input of storage 52. The data that can be applied to the input of switching circuit 53 via line 55 can be classified into the following groups:
That is, in the simplest case, there is an English character 8-bit word, then an extended 8-bit word plus a character 8-bit word or a normal functional 8-bit word, and finally an extended 8-bit word plus an 8-bit character format type word. Switching circuit 53
includes detection means for recognizing the third group of data, ie, extended 8-bit words + character format type 8-bit words. These means are simple comparators, making it possible to send these bitwords to the output 58, while the first,
A second group of data outputs 57 are sent. By way of example, several types of 8-bit words are illustrated below. The 8-bit word F1 holds the following information when the first 5 bits are in the 1 state, and the 8-bit word F1 holds no information when the first 5 bits are in the O state.
may be provided.

[Table] Therefore, for the 8-bit word 1000100X, this indicates that the following series of characters must be displayed in red on the CRT screen.
For example, the 8-bit word 0110100X indicates that the series of characters must be displayed in blue.
When the fifth bit is 1, it indicates that the 8-bit word is word F1, and when the 7th and 6th bits are 0, the switching circuit 53 can detect the functional 8-bit word.
The meaning of the fourth bit is shown below, and the eighth bit is the parity bit. Similarly, an 8-bit word F2 can be provided in which the bits have the following meanings:

Table: The first bit of 1 indicates that the height of the character should be doubled. A 1 in the second bit indicates that the character width should be doubled. A 1 in the third bit indicates that the background on which the character is displayed should have its color reversed. A 1 in the fourth bit indicates that the character should blink. Therefore, in an 8-bit word 110100X, the height and width of the characters are doubled to indicate that they should be flashed. A 0 in the fifth bit indicates that the 8-bit word is word F2. In a series of 8-bit words applied from line 55 to switching circuit 53, the following series θ, F1,
If θ, F1, a, b, c...... exists, the switching circuit 53 writes the four words θ, F1, θ, F2 into the storage device 54, and then writes the words a, b,
Can understand writing c, ……. circuit 59
By writing the first character word a detected in the memory device 51, the words F1, F from the memory device 54
2 to storage 52 at the same address (the word θ is written from storage 54 to storage 52).
(not transmitted). Circuit 59 is connected to memory 54 by control line 60. Buffer storage 54 is connected to storage 52 by line 61. Reading from storage 54 to storage 52 does not change the contents of storage 54 . Therefore, when writing b to the storage device 51, F1 and F2
is written to the storage device 52 at the same address as b . As a result, the character word is written in the storage device 51 and the format type word is written in the storage device 52 at the corresponding address. The contents of storage device 54 are erased the next time an extended word followed by a type word is written to buffer storage device 54. Other function words may be provided in addition to the function words F1 and F2. For example, F3 allows changing from one letterform to another, then the fifth,
The 7th bit indicates the type word which is also detected by the switching circuit 53, the 6th bit is 0 and the 8th bit is a parity bit. The character generator 20 shown in FIG. 5 is comprised of four nonvolatile memory devices 62-65, a switch 65, a mixing circuit 67, and a monostable circuit 68. Each non-volatile storage device 62-65 has an associated shift register 69-72, respectively, designed to serially transmit bits normally read in parallel from the non-volatile storage device of the character generator. The character shapes are scanned line by line in the storage devices 62-65, each line essentially corresponding to a television picture line. A clock 73 is also provided for controlling read operations from the storage device in accordance with the television video synchronization signal. In Figure 5, some inputs S mean that the TV line synchronization signal is also used to read the associated storage or control the repeat operation.
is also shown. However, to simplify the drawing,
All of the inputs S are not shown. A switch 66 is provided to select one of the registers 69-72 to be connected to the output 74 connected to the mixing circuit 67. This also determines the read operation speed, in other words the sampling rate of the register output. The read output of RAM storage device 51 is connected in parallel to the read address inputs of nonvolatile storage devices 62-65. The parallel read outputs of storage devices 62-65 are connected to parallel inputs of registers 69-72, respectively. The readout output of the RAM storage device 52 is the function word F
It has the same number of wiring lines as the significant bits of 1, F2, and F3. Thus, wires R, G, and B each correspond to the first three bits of F1, and wire H corresponds to F2.
It is shown that the wiring L corresponds to the first bit of F2, the wiring F corresponds to the third bit of F2, and the wiring C corresponds to the fourth bit of F2. Furthermore, since four nonvolatile storage devices are installed, a line M is provided consisting of four wires corresponding to the significant bits of F3, which are assumed to be 2 bits in the above example. Wire H is connected to the control input of clock 73. When the value of H is low, clock 73 operates at normal speed, ie, for each video line, RAM storage 51 is read as well as character lines in non-volatile storage 62-65; 51. For high values of H, the clock speed of clock 73 is reduced by a factor of two. Clock 73, after counting, specifies the address of the line to be read out in character form in non-volatile storage, so that when the value of H is high, each character line is read out twice in succession at the video line frequency. . Therefore, the height of the displayed character will occupy twice as many lines on the screen of the display tube. Its height has doubled. The wiring L actually includes two wirings, one of which is the wiring L1.
controls the bit shift rate of registers 69-72, and the other line L2 controls the advancing rate of horizontal addresses in RAM storage 51 via input L2. Obviously these two speeds are also related to the TV's video line synchronization. When the value of the line L1 is low, the shift speed and sampling speed become normal. For a high value of L1, the shift rate and sampling rate are halved, allowing the same bit to remain in the output cell of each shift register twice as long, so that it can be sampled twice. Therefore, the character point information can be transmitted to the display tube twice on the video line. Therefore, the width is doubled. Since a character then occupies a larger space in the displayed line, it is necessary to halve the progression of the character word in the corresponding line of the storage device 51 via L2. The four wires in line M allow selecting the non-volatile storage device whose output is utilized among the storage devices 62-65. Actually storage device 5
For each read operation from 1, four storage devices 6
It seems that 2-65 are read in parallel. However, switch 66 allows only one connection to circuit 67. For four non-volatile storage devices, each storing one of the four alphanumeric characters, the two bits of word F3 are expected to make it possible to change the language according to the text to be displayed in a simple way. It will be done. When the value on line C is low, the monostable circuit 68 is quiescent, and when the value on line C is high, the monostable circuit 68 is triggered. Monostable circuits may have a speed of about 1 Hz and are used as described above to flash characters. Reference is made to FIG. 6 to explain the purpose of wires R, V (or G), B and F. FIG. 6 shows the circuit 67 along with the output wiring 75 from the monostable circuit 68.
A wire 74 connecting the output of the switch 66 is shown in the figure. It will be recalled first that wire 74 carries a digital signal relating to brightness information.
Therefore, for each character line scan in the non-volatile memory, the parallel -
After serial conversion, the signal transmitted on line 74 takes the form shown by waveform 1 in FIG. When signal 1 is high, the spot is brightened on the picture tube, and when signal 1 is low, the background is not brightened. Wire 74 is connected to the input of a switchable inverter circuit 76 having an output connected to switch 77. The signal output of switch 77 is connected on the one hand to output 21 via a shaping circuit and on the other hand to the first inputs of three AND gates 79, 80 and 81 in parallel. A second input of gate 79 is connected from conductor R, a second input of gate 80 is connected from conductor V (or G), and a second input of gate 81 is connected from conductor B. The output of gate 79 is connected to conductor R2 via shaping circuit 82, and the output of gate 80 is connected to conductor V2 via shaping circuit 83.
The output of 1 passes through a shaping circuit 84 and is connected to conductor B2. A control input of switchable inverter circuit 76 is connected from conductor F, and a control input of switch 77 is connected from conductor 75. Assuming that conductor F and conductor 75 are stationary at a zero state or low value, signal 1 from conductor 74 is applied unchanged to circuit 78 and gates 79-81. The output signal from output 21 of circuit 78 is the third
Shown in detail in the figure. This is processed by the switching circuit 14 shown in FIG. Further, when the conductor V (or G) is in the 1 state or high value, the state 1 of the signal 1 is the gate 7
9 and is applied to the shaping circuit 82 before being processed by the switching circuit 14 of FIG. Therefore,
The red chromaticity signal appears to be similar to the luminance signal that causes characters to appear red. Conductor R and V
When (or G) is at a high value, state 1 of 1 is transmitted, conductors R2 and V2 are at a high value, and color mixing takes place in the picture tube after processing in the switching circuit 14. Therefore, the characters will be displayed in white or one of six predetermined colors using the first three bits of word F1. When conductor F is in a 1 state or high value, the output signal from inverter circuit 76 is inverted with respect to 1 , ie, becomes 1 . This output signal is still processed as signal 1 in gates 79-81, but unlike the previous case, only the outer part of the character corresponding to the state 0 of 1 appears displayed in color. When conductor 75 is periodically transferred to the 1-state, the transmission of signal 1 is interrupted through circuit 77 during those 1-states. As a result, the brightness signal that causes the characters to flash on and off on the display tube is interrupted accordingly. Shaping circuit 78 is also utilized to add a digital synchronization signal to the luminance signal, as shown at S. If there is no format type information, the outputs R, V, B of the storage device 52 are changed so that white characters are displayed on a black background.
It should also be specified that the value becomes high or becomes 1-state. A read operation is performed in RAM storage devices 51 and 52 such that characters are read from non-volatile storage at the same time that the state of the output conductor of storage device 52 is controlled by the type bits of words F1, F2 and F3. is carried out at the same time. Regarding the bit corresponding to "figure" in the word F1, for example, when approaching the non-volatile storage device 62,
A wiring storage device for storing 6-point rectangles is installed, which makes it possible to create figures on the screen by displaying the 6-point rectangles side by side. In fact, the output of the RAM memory 52 is provided with a conductor corresponding to the fourth bit of the word F1, and the word F1 is wired to the wired memory instead of the memory 62 in the same manner as the selection controlled by the conductor M. be able to select. The figure rectangle code is defined in the ACSII code. As an alternative to the teletext mode of operation according to the present invention, the desired operation is to begin each line with a format type word, possibly changing the character format within the line, but preferably reverting to the initial format at the end of each line. The display is therefore resynchronized at the beginning of each line.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a transmitted teletext according to the invention. FIG. 2 is a block diagram of a teletext receiver according to the invention. FIG. 3 is a schematic diagram of a matching circuit for matching the voltage-optical characteristics used in the receiver shown in FIG. 2. FIG. 4 shows waveforms of signals used in the matching circuit shown in FIG. FIG. 5 is a block diagram of the storage circuit and character generator that can be utilized in accordance with the present invention in the teletext receiver shown in FIG. FIG. 6 is a schematic diagram of a mixer circuit used in the receiver shown in FIG. 4.1-4. N... Control device, 1... Modulation circuit, 2... Transmission (transmission) antenna, 3... Data processing circuit, 5... Shaping circuit, 6... Storage device, 7
...Conversion circuit, 8...Monitor screen, 9...
Typewriter.

Claims (1)

[Scope of Claims] 1. A teletext system that transmits data digitally and displays it on a television screen, in which a signal representing the data is divided into a plurality of data packs and broadcast from a broadcasting station. broadcasts data packs from channels that are different data sources in a time multiplexed manner, each data pack having a prefix for selecting data packs from a certain channel, said data being a plurality of data packs. A pack consists of multiple pages that make up one page, and the data pack belonging to each page contains a page flag with a page number, a line flag with a line number, and an extended 8-bit word with a format type of 8-bit word. and a series of 8-bit words comprising a format-type 8-bit word accompanied by a series of coded words identifying a plurality of displayed characters having the format determined by the preceding format-type word. keyboard means 19 for delivering the necessary control signals, including signals for selecting between said different channels and for identifying the desired page; A selection block 16 receives a selection signal and selects a data pack of a desired channel.
a comparison circuit means 17 for detecting a desired page in response to a page flag and receiving a signal identifying the desired page from the keyboard means; and data regarding the desired page in response to an output of the comparison circuit means. and character generator means for generating signals for displaying said desired page as characters in a desired format on a television screen in accordance with the data stored in said storage means. 20; and adapting the voltage-light characteristics of the cathode ray tube to the control of the composite signal by transmitting the output signal of the character generator means to the screen of the television in response to the output of the character generator and the control output from the keyboard means. video switching means 14 including a matching circuit for performing
and wherein said character generator means sends a character luminance signal to a matching circuit and an additional logic signal regarding the presence or absence of a primary color R (red), V (green) or B (blue), said matching circuit means transmitting a luminance signal to a matching circuit. Teletext system, characterized in that the signal is transmitted to the normal circuit of the television receiver, and the brightness and chromaticity are controlled when the characters are displayed on the television picture tube. 2. The matching circuit means includes a first diode having a cathode connected to an input of the analog amplifier means in association with each primary color logic input, and a first diode having a cathode connected to an input of the analog amplifier means in association with each primary color logic input, and a first diode having a cathode connected to an input of the analog amplifier means in response to the keyboard means to match the output of the primary color amplifier to the corresponding one of the television cathode ray tube. switching means for selectively connecting to the chrominance input, the cathode of the first diode also being connected to the cathodes of a second diode and a third diode, and the anode of the first diode being connected to the associated chrominance input; and voltage
The anode of the second diode is connected to the output of the first voltage generator delivering voltage v2, the anode of the second diode is connected to the output of the second voltage generator delivering voltage v1, and the anode of the third diode is connected to the output of the second voltage generator delivering voltage v3. , the third voltage generator having an output that is also connected to the output of a gate, the output of said gate being connected to the output of a third voltage generator that delivers three color inputs simultaneously. 2. The teletext system according to claim 1, wherein the system is not grounded when receiving the logic signal, and is grounded in all other cases, and the voltages v1, v2, and v3 have a relationship of v3>v2>v1. 3. Storage means for storing data relating to said desired page include, in addition to a first ordinary constant access memory 23 for storing coded characters, in a first constant access memory belonging to said series of characters. It includes a second constant speed access memory device 24 that stores a format type 8-bit word at the same address as the address of the character, and the reading operation from the first constant speed access memory device for display is carried out by the first constant speed access memory device 24. The read operation from the second constant-speed access memory 24 is carried out simultaneously with an output signal for selecting the non-volatile memory of the character generator from which the shape of the character read from is to be read. Teletext system according to scope 1.