CH650887A5 - Circuit arrangement for an information system and method of data transmission using it - Google Patents

Description

The invention relates to a circuit arrangement for an information system which transmits information in digitally coded form as a teletext signal in one or more television channels via cable or wirelessly, comprising a television or a television monitor for displaying the information with a program selection device and an RF part for the selection and demodulation of a television signal and a method for data transmission with this circuit.

The problem for largely inexperienced users at airports, exhibition grounds, training centers and other large companies is that there is a lot of information at a large number of terminals (several hundred) in a simple manner and in the shortest possible time (with dialog steps and information in less than a second) (several thousand "information pictures") to have access.

For this purpose, two different solutions are known from practice. Firstly, the use5

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Common display terminals and connection of each terminal to a central computer via modems and standard telephone dialing lines or direct lines. On the other hand, the use of conventional television monitors and connection of each monitor to a crossbar distributor via its own line (usually coax cable). A so-called digital video distributor is connected to the central computer for each image to be displayed, the output signals of which can be switched to the monitor lines via a crossbar distributor.

The first solution is common in IT systems. The planned screen text system offers newer, cheaper solutions. It is problematic and not common here that the high data rate of over 10,000 bit / s required for short access times and, because of the large distances that may be present, require very complex modems. In addition, the simultaneous access of, for example, several hundred users can no longer be managed by an inexpensive computer system. The second solution is currently e.g. common at airports to display departure times and other. The video signals of all the images to be displayed are available at the input of the crossbar distributor and can be selected in a very short time and switched through to a monitor. Since a complex digital video converter and an input channel of the crossbar distributor is required for each picture and each monitor also needs its own output channel of the crossbar distributor and a separate RF line there, this solution is no longer for systems with many pictures or many terminals practical.

Approaches for a possible third solution are offered by the new form of communication, teletext, which is intended as a pure distribution service for information, but does not allow the participant to interact with the central office and only to disseminate text content of general interest such as current news, time, sports results, etc. serves during the broadcast of television programs. In this case, characters and graphic elements are transmitted in unused lines of the vertical blanking interval of the television signal in coded form, which are then processed with an additional device in the home television for image reproduction. The best-known example of this system type is the British test system Teletext. There, in the unused lines 17, 18, 330 and 331 of each television picture, the information of up to one hundred pictures (“text pages”) is transmitted cyclically one after the other, each of which has twenty-four lines of text with forty characters each. The user selects the desired text page based on an overview with a two-digit number, which then appears on his screen after twenty-four seconds at the latest. For this purpose, the signals arriving via the antenna or the cable in the HF part of the television set are converted into video signals in an additional device, and the text is reproduced on the screen of the television set.

The waiting time can be reduced considerably if a complete television channel is only available with teletext signals and so instead of four lines, over six hundred lines per frame can be used for transmission. Such an extension of teletext is described in "Electronic Text Communication" Springer Verlag, Berlin 1978, pages 70 to 84 under the title "Cable Text and Cable Text Retrieval", Kaiser W. as a variant of the communication type "Cable Text" (without return channel), which the desired enables fast access times. From the technical concept, however, teletext is limited to an insufficient number of different images and with regard to the display options.

As a dialog form, only the retrieval of pictures by entering the complete picture number is provided, a transmission and evaluation of control characters is not possible.

Based on this, it is an object of the invention to use circuit components known per se to create a circuit arrangement with which the possibilities of communication via terminals, televisions and monitors can be expanded considerably. In particular, the addressing options and thus the number of different images and the display options should be expandable. In addition, this circuit arrangement should allow the use of control characters and enable numerous other forms of dialogue, some of which the subscriber cannot distinguish from interactive dialogues with a return channel. In addition, it should be possible to implement targeted information transfer to individual devices.

According to the invention, the characterizing features of claim 1 are provided to achieve this object.

The invention further relates to a method for data transmission with the circuit according to claim 1 and characterized as in claim 3. Appropriate further developments of this method are the subject of claims 4 to 13.

The advantage of the invention is in particular

that with already available components of teletext and professional screen text, an improvement and expansion of the possibilities with regard to the speed of data transmission, storage and image reproduction is achieved. These improvements are mainly achieved by using a professional on-screen text decoder instead of a teletext decoder for evaluating the transmitted data and storing and reproducing them on a screen, which enables the display in a more complex form than teletext allows, and the allows the processing of control characters. Since the screen text decoder cannot process the high data rate of approx. 7 Mbit / s, a commercially available teletext demodulator is used for this. A circuit for address evaluation compares part of the transmitted data (the address part) with the number of the image to be displayed, which is stored in the address preset memory. If there is a match, the following data of a block of e.g. 40 bytes passed on to a silo memory, which is read out by the screen text decoder at a significantly reduced data rate. The number of addressable picture numbers can be expanded by also using and evaluating the time of transmission for addressing. For example, the data of the picture 4812 are only transmitted in the television lines 48, 148, 248 etc. and are identified there with the picture number 12 (possible with two-digit teletext). This ensures that a sufficient time interval (e.g. a hundred television lines) is maintained between the transmission of two data blocks of an image for slow further processing.

The addressing options can also be expanded in that the address can also contain non-numeric bit combinations. The dialog options can be expanded in a variety of ways. In the case of information systems in "Menu technology", alternative entries for selection are shown in a picture, e.g. are designated with digits. After entering these digits, a new picture appears, which requires further selection or already contains the desired information. This dialog technique is also possible without a return channel with the circuit arrangement described in that the address default memory e.g. is set to address 0000 by pressing a start button (picture 0000 is e.g. an overview picture with several offered alternatives) and

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that a new valid image address is created based on a button print. For example, when entering a 4, the address 4000, when entering an 8 in the next dialog step, the address 4800, etc. In order not to limit the number of dialog steps to the number of digits in the picture number (e.g. 4), a picture (e.g. 4812) can only contain commands that the address default memory, for example Load with the address A 000 and initiate the retrieval of this picture.

Another possibility is that an assignment table identified by control characters is transmitted in an image (e.g. 4812), whereby the circuit then causes that e.g. a 3 e.g. The picture number 5923 and any other picture number from the table are loaded into the address default memory etc., etc. This also enables computer-aided teaching systems without a return channel, in which the student is shown different follow-up teaching units depending on his inputs (solution, answers).

Animations of pictures etc. Extensions are also possible. For example, by evaluating control character strings that contain several picture numbers and information on the time intervals between the calls of these pictures.

The aforementioned tasks can be performed by the circuit arrangement for address evaluation, but e.g. also from a microprocessor of the on-screen text decoder. All described parts of the circuit arrangement can be installed in the housing of a television set.

An exemplary embodiment is described below and illustrated by a sketch:

The figure schematically shows a circuit summarizing the circuit arrangement of the individual components known per se. In the basic version, the terminal consists of a professional screen text device, which is composed of a color television set 1 and a screen text decoder 2. The terminal is connected via the antenna input 3 to the program selection and HF part 4 of the color television set 1 to a cable network 5. The channel is selected using the selection keypad on the program selection and RF section 4. Of the existing channels, one channel is reserved for data transmission. Switching to other channels, e.g. TV programs or TV broadcasting can be prevented at the terminal. One from the channel to the

Video signal outgoing data transmission is passed on to a teletext demodulator 6 connected to the color television set 1 or its program selection and HF part 4 and converted there into a binary signal. The video-5 signal, which is transmitted on a television line (64, us), contains an address or picture number at the beginning and then encoded data for this picture. A circuit for an address evaluation 7 compares a part of the transmitted data (the address part) with the number of the image to be displayed, which is stored in a downstream io address preset memory 8. If the address or picture number corresponds to the picture number determined from the dialog carried out via the dialog keyboard 10, the subsequent data of a block (e.g. 40 bytes) are passed on to a silo memory 9 connected downstream of the address evaluation device 7. This data transfer from the address evaluation 7 into the silo memory 9 takes place at a speed or data rate of approx. 7 Mbit / s, but from the silo memory 9 to the screen text decoder 2 or from it with a greatly reduced data rate of approx. 140,000 bit / s is read out or processed. Only a professional screen text decoder is suitable for this (the usual data rate for standard screen text is approx. 1200 bit / s). The screen text decoder 2 can also generate signals for controlling a large display 11 and / or a printer 12 in the case of appropriately labeled images. In order to keep the silo memory 9 small, it is necessary that the information for an image is not transmitted in a coherent data block, but rather that the transmission is distributed in small blocks over a period of several milliseconds.

The individual components can be installed in a television set and used as a terminal e.g. can be rented for exhibition stands. Some public terminals have an additional 35 printers.

From a technical point of view, the circuit arrangement or the system connected with it is a pure distribution system without a return channel. Because of the high transmission rate and thus the high number of quasi-simultaneously available images, the user can access a dialog that cannot be distinguished from interactive operation.

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1 sheet of drawings

Claims (13)

650 887 1. Circuit arrangement for an information system which transmits information in digitally coded form as a video text signal in one or more television channels via cable or wirelessly, comprising a television or a television monitor for reproducing the information with a program selection device and an HF part for the selection and demodulation of a television signal, characterized by the arrangement of the following components: a) a teletext demodulator (6) is connected to the television set (1) and synchronizes and regenerates the received digital signals, b) a circuit for address evaluation (7) is connected to the teletext demodulator (6), c) the address evaluation (7) is followed by an address preset memory (8), in which certain parts of a bit sequence to be transmitted containing the code for a picture number or picture address are continuously checked to determine whether these parts correspond to the picture number or picture address specified in the address output memory , d) a silo memory (9) is connected downstream of the address evaluation (7) correspondingly connected to the address default memory (8), in which, with a positive result from b) and c), subsequent data and the quantity of which is defined are temporarily stored, e) the silo memory (9) is followed by a screen text decoder (2) corresponding to the television (1) and a printer (12), in which the data arriving from the silo memory with a reduced transmission rate is sent for further processing. 2. Circuit arrangement according to claim 1, characterized in that when transmitting a video signal without HF modulation (as a BAS signal) the teletext demodulator (6) is connected directly to the cable network (5). 2nd PATENT CLAIMS 3. A method for data transmission with the circuit arrangement according to claim 1, characterized in that data belonging to an image are transmitted in succession in individual blocks of fixed length, the block length corresponding to the size of the silo memory (9) and the time interval between two to the same image associated data blocks is so large that the slower transmission of the data to the screen text decoder (2) takes place during this time and the frequency of transmission of all blocks belonging to an image is determined by the desired maximum waiting time for this image. 4. The method according to claim 3, characterized in that the address default memory (8) either from a dialog keyboard (10) or other devices, e.g. the screen text decoder (2), data are supplied and the address code contains digits as well as other characters. 5. The method according to any one of claims 3 and 4, characterized in that in the address evaluation (7) only parts of an address given in the address preset memory (8) are compared with the transmitted picture number or picture address, and other parts thereof with the number of a television line or certain bit positions of this picture number or picture address. 6. The method according to any one of claims 3 to 5, characterized in that the address preset memory (8) is set to zero in all places of the address by a signal and that thereafter the individual digits in the address preset memory (8) by a dialog keyboard (10) or be overwritten from left to right or vice versa in another device, whereby a valid picture number or picture address is created after each entry of a position. 7. The method according to any one of claims 3 to 6, characterized in that the address evaluation (7) belonging to a predetermined picture number or picture address Checks data for a given control character and loads the subsequent characters into the address default memory (8). 8. The method according to any one of claims 3 to 7, characterized in that the address preset memory (8) stores several picture numbers or picture addresses in succession and that the address evaluation (7) checks the data belonging to the given picture number for a certain control character string and the subsequent characters in loads its extended memory and then successively initiates the reception of all associated images. 9. The method according to any one of claims 3 to 8, characterized in that the address preset memory (8) stores a plurality of picture numbers or picture addresses as an assignment table and that the address evaluation (7) checks data belonging to the given picture number or picture address for a specific control character string and the subsequent ones Loads characters into their extended memory and then, if a character is specified by the dialog keyboard (10), takes an image number or image address for these characters from the assignment table and initiates the reception of the associated image. 10. The method according to any one of claims 3 to 9, characterized in that the address evaluation (7) checks the data belonging to the predetermined picture number or picture address for further control characters, and then further functions, e.g. triggers the switch to another television channel for the reproduction of television images transmitted there. 11. The method according to any one of claims 3 to 10, characterized in that the address evaluation (7) contains a one-time predetermined device number and that it checks the data belonging to the given picture number or picture address for a certain control character and compares the following characters with the given device number, and further characters and commands related to this picture number or data belonging to the image address can only be used if the comparison result is positive. 12. The method according to any one of claims 3 to 11, characterized in that the functions of the address evaluation (7) are taken over by a microprocessor of the screen text decoder (2). 13. The method according to any one of claims 3 to 12, characterized in that the functions in the extended address memory (8) are taken over by the microprocessor of the screen text decoder (2) and this only loads one address into the address memory (8).