TRANSMISSION OF TELETEXT PAGES TO SELECTED RECEIVERS

Abstract: A method for transmitting teletext signals from a transmitter to a plurality of receivers wherein a plurality of successive and numbered teletext pages are transmitted currently. In addition to the teletext pages determined for all the receivers, it is possible to transmit a plurality of pages which are determined to be received only by one or more selected receivers. Each of these receivers has been allocated a digital address and comprises a store for storing teletext pages. Control signals are transmitted to the selected receiver or receivers on a given teletext page, said control signals comprising addresses of the selected receiver or receivers as well as information on the point or points of time at which teletext pages determined for said receivers will subsequently be transmitted. Then the pages determined for said receivers are transmitted, and said pages are received by said receivers and stored in the store of each receiver.

Description: Transmission of teletext pages to selected receivers The invention concerns a method of transmitting teletext signals from a transmitter to a plurality of receivers, wherein a plurality of successive and numbered teletext pages are transmitted continuously. In addition to the teletext pages determined for all receivers, it is pos¬ sible to transmit a plurality of pages which are deter¬ mined to be received only by one or more selected re¬ ceivers. A digital address is allocated to each of these receivers which comprises a store for storing teletext pages. The invention moreover concerns a sequence of a plurality of such successive and numbered teletext pages as well as an apparatus for receiving such teletext sig¬ nals. Finally, the invention concerns the use of teletext signals for transmitting pages determined to be received only by one or more selected users. It is generally known to broadcast text via existing tele¬ vision transmitters in the form of so-called teletext. There is an international protocol for transmission of teletext signals. It is possible to transmit text pages, each of which can contain up to 32 rows of text of 40 characters each. Generally and therefore also below, the text lines are called "rows" to distinguish them from the lines of the usual television image. Only 24 of the 32 rows of text are intended to be displayed on the screen of the television receiver. A plurality (generally 2) of rows are modulated in a binary coded form into their respective ones of the lines of the television image within the so- called image blanking interval. This interval substanti- ally comprises the top 25 lines of the television image. This television signal, which also contains teletext in¬ formation in addition to the ordinary image information, is transmitted from a television transmitter and can then be received by television receivers. However, the teletext information is only accessible to the television receivers which contain a teletext decoder capable of capturing and storing the row of text concerned for each line of tele- text information. Such a decoder is usually adapted to store and capture one page of teletext information at a time. This page can then be displayed on the screen of the television receiver, either on a self-coloured background or with the normal television image as the background. The teletext information is usually transmitted continu¬ ously as a constantly repeated sequence, which is also called a teletext loop. The loop can maximally comprise 8 so-called magazines, each of which comprises 100 pages. Special characters are provided at the front of each row, which i.a. control colour, background colour and the like. Corresponding check sum characters capable of correcting single bit errors are provided at the end of each row. A plurality of subpages transmitted successively may be associated with each page. This means that the first sub- page is transmitted at the first run of the loop, the next subpage at the next run of the loop, and so on. Thus, if there are n subpages, n runs of the teletext loop are re- quired before all n subpages have been transmitted. The teletext information in the loop is usually trans¬ mitted in sequence, so that the maximum of 8 magazines of 100 pages of 32 rows are run continuously in the teletext loop. Since each row is unambiguously identified by maga¬ zine number and page number, the rows may be transmitted in arbitrary order, if so desired. It is not necessary to transmit empty magazines, pages or rows. It should be noted that it is possible to replace the information on a given side for each run. Thus, with this system it is possible to give the viewers of a TV station access to up to 800 pages with information of general interest. All viewers having a teletext decoder have access to the same information. US patent specification 4 866 770 discloses a system enab¬ ling transmission of information from e.g. the head quar¬ ters of a company to its branch offices employees. Various forms of information may be involved, including teletext information. The system enables transmission of certain items of information to all receivers, while other items of information are transmitted only to individually ad¬ dressable receivers. Furthermore, the information may be encrypted, so that only the receivers provided with a de- cryption unit are capable of viewing the information. It is also described that the receivers may be provided with a storage unit, e.g. in the form of a video recorder which can be remote-controlled by means of a control signal from the transmitter. Thus, a video recording can e.g. be transmitted at night and automatically be stored on the video recorder for viewing the following day. However, this is a system which is used specifically for this purpose. For example, a non-public satellite may offer to the companies private communications between various branch offices by using the satellite connection of the company. This entails that a system of transmitter stations, satellites, etc. is to be constructed for the purpose. Of course, the costs of this system are to be paid by the users, and the system is therefore primarily of interest to users having a great need for exchange of information between various branch offices. Furthermore, this system uses direct transmission on indi¬ vidually addressed teletext pages, which means that a given page is e.g. allocated to a specific receiver which then constantly occupies this page. This has an extremely limiting effect on the capacity of the system. The invention provides a system capable of operating as an extension of an already existing teletext system. Thus, the system enables transmission of teletext information to selected users without huge transmission equipment invest¬ ments, etc. having to be made. At the transmission end, only equipment capable of editing the desired message and optionally coding equipment have to be added. At the re¬ ception end, the users who are to be able to receive the special information are merely to buy a receiver box. Thus, at quite low costs it will be possible to transmit information to selected receivers in the area covered by "the TV station in question. Furthermore, a much more flexible utilization of spare capacity in the teletext system is obtained, since infor¬ mation for a specific receiver only occupies a teletext page for a short time, and then the page is available to other receivers. This is achieved according to the invention by a method of the type mentioned in the opening paragraph, wherein con- trol signals to the selected receiver or receivers are transmitted on a given teletext page, said control signals comprising addresses of the selected receiver or receivers as well as information on the point or points of time at which teletext pages determined for said receivers will subsequently be transmitted. Then the pages determined for said receivers are transmitted, and these pages are re- σeived by said receivers and stored in the store of each receiver. It will hereby be possible to transfer a teletext page to one ore more specific receivers merely by transmitting it in a single run of the teletext loop, the decoder con¬ cerned having been informed beforehand that it is to cap¬ ture the page concerned and store it in its store. Then the page is present in the store of the receiver and can then be output from this and be displayed on the televi¬ sion screen, as required. Thus, the page concerned is not to be transmitted continuously from the transmitter sta¬ tion. When an information page is to be transmitted to a re¬ ceiver, the system can thus merely choose a random spare teletext page, state this on the index page and transmit the information. The teletext page in question is thus available for other information and/or other receivers immediately thereafter. When, the specific pages are additionally transmitted with a uniform character and background colour, e.g. black text on a black background, as stated in claim 2, unauthorized viewers are prevented from viewing the teletext page con¬ cerned, even if they should be capable of capturing it by the single run of the loop. In the receivers which are to receive the message, the colour of the characters and/or the background are then merely changed, thereby making the text visible. To improve the certainty that unauthorized viewers will not be able to view the messages intended to be received only by selected receivers, the messages, as stated in claim 3, may be encrypted so that the text will be visible only if the decoder is provided with a corresponding de- crypting unit. When, as stated in claim 4, a receiver is moreover pro¬ vided with a modem and a telephone connection, it will be possible to request from the receiver that specific infor¬ mation be transmitted to precisely this receiver. Thus, the receiver concerned will be informed by the transmitter by means of control signals at the first opportunity that the page concerned will now be trans¬ mitted so that it can be received and stored in the re¬ ceiver. When, as stated in claim 5, receivers are provided with magnetic card readers, it will be possible that the trans¬ mitter can require entry of a specific magnetic card prior to transmitting a given item of information to the re¬ ceiver concerned. This can be utilized e.g. if reception of certain items of information is to be paid for, or if only users possessing a specific authorization code are allowed to receive the pages concerned. When, as stated in claim 6, the teletext pages received and stored in a receiver are utilized for further trans- mission via another TV transmitter or optionally a closed network, it will be possible that a company can e.g. re¬ ceive specific pages, as described above, and then trans¬ mit these as normal teletext to a plurality of receivers located at different positions in the company. It is thus possible to transmit a specific page from the first trans¬ mitter to the first receiver, which then transmits the page concerned via the second transmitter to a specific one of the receivers which can receive the signals from this. As mentioned, the invention also concerns a sequence or teletext loop of a plurality of consecutive and numbered teletext pages. When, as stated in claim 7, at least one of the pages in the sequence comprises control signals for the selected receiver or receivers, the advantages des¬ cribed above are obtained. Where transmission of a large number of teletext pages to a specific receiver is needed, it is possible to permit the pages concerned to occupy a whole run of the sequence or the teletext loop, as described in claim 8. A large amount of information can hereby be transmitted more quickly to a specific receiver, while, on the other hand, the access time to a specific teletext page is increased for the ordinary users. In a specific embodiment, which is described in claim 9, the teletext loop can be stopped completely, a specific page number being then transmitted a large number of times successively to the same receiver. At each transmission of the page concerned, this contains new information, and each of the pages thus transported is stored in the re¬ ceiver concerned. An apparatus for receiving the signals described above is stated in claim 10. Further, as stated in claim 11, the apparatus may be adapted to change the colour of the characters and/or the background on the pages received, and, as stated in claim 12, it may be adapted to decrypt information which has been encrypted prior to transmission from the transmitter. As described in claims 13 and 14, the apparatus may more¬ over comprise a modem which can be coupled to a telephone connection, as well as a magnetic card reader. As des¬ cribed in claim 15, the apparatus may be adapted for out- putting the stored teletext information as an ordinary TV signal. It will hereby be possible to view the desired in¬ formation without the connected television set being pro¬ vided with a normal teletext decoder. Finally, the invention concerns the use of the teletext signals described above for transmitting teletext pages determined for all receivers as well as pages determined to be received only by one or more selected receivers. This use is described in claim 16. The invention will be explained more fully by the follow¬ ing description of embodiments, which just serve as examp¬ les, with reference to the drawing, in which fig. 1 shows a system for broadcasting of teletext, with a TV transmitter and one of many TV receivers as well as a receiver box according to the invention with connected TV receiver, fig. 2 shows a receiver box according to the invention, fig. 3 shows a data store at the TV transmitter with re¬ cords of one teletext page each, a teletext loop compris- ing the pages which are broadcast sequentially and conti¬ nuously by the TV transmitter, as well as a data store in the receiver box with records of one teletext page each, and fig. 4 shows a system comprising several TV transmitters. Fig. 1 shows i.a. a generally known system for broadcast¬ ing of teletext. A store 1 contains teletext information, in which teletext pages are stored as records in a regis- ter. Each of the pages contains up to 32 lines of text having 40 characters each. Generally and below the said lines are called "rows" to distinguish them from the lines of the TV image. A teletext generator 2 gets a plurality (generally two) of rows in the store for each TV image and modulates each row - in binary form - into one of the lines of the TV image in the so-called image blanking in¬ terval. This interval substantially comprises the top 25 lines of the TV image. These lines are outside the active portion of the screen of the picture tube when the TV re¬ ceiver is correctly set. The TV signal, which now contains the teletext information in addition to video information (the image), is trans¬ mitted by the transmitter 3 and received by the TV re¬ ceiver 4. This may contain a teletext decoder 5, which captures and stores the row of text concerned for each line of teletext information. The decoder 5 is usually adapted to store and capture one page of teletext informa¬ tion at a time. This page can be displayed on the screen of the TV receiver 4, either on a self-coloured (black) background, or with the ordinary TV image as the back¬ ground. In addition, fig. 1 shows a TV receiver 7 connected to a receiver box 6 according to the invention. The TV antenna 10 is connected to the receiver box 6, which passes on the antenna signal to the antenna input 9 of the TV receiver 7. In addition, the receiver box is connected to a tele¬ phone line 8 via an incorporated modem, so that it can transmit and receive data via the telephone line in an otherwise known manner. Fig. 2 shows the structure of a receiver box according to the invention. The receiver box has an antenna input 20 connecting it to a TV antenna or a cable installation or the like, said box receiving TV signals with teletext through said input. The receiver box can supply TV signals with teletext on an output 21. The signal from the antenna input 20 goes to a TV tuner 22. The demodulated video sig¬ nal 23 passes from the tuner to a teletext decoder 24. The signal 23 is also conveyed to a modulator 25, from which - modulated on a carrier wave - it can be transmitted on the output 21. The teletext decoder 24 captures and stores one page of teletext information at a time. The tuner 22, the teletext decoder 24 and the modulator 25 are components which are known per se from TV receivers or videotape recorders. Via a so-called pass-through-connection 37 the antenna connection 28 is moreover conveyed directly from the antenna input 20 to the output 21 without being demodu- lated. This enables the connected TV receiver to receive all TV programs as usual, without the tuner 22 having to be tuned on the channel concerned. A microcomputer 26, consisting of at least a CPU (comput- ing unit) 27, a program store 28, a keyboard and/or remote control unit 29 and a data store 30, controls the function of the receiver box and handles teletext data received via the teletext decoder 24. Via the command connection 31 the CPU can control the teletext decoder 24 and the modulator 25 as well as the other units of the receiver box, of which a modem 33, a printer 35 and a card reader 36 are shown as examples. Through the modem 33 and a telephone line 34 the CPU can communicate with remote units, e.g. the unit supplying the teletext information which the re- ceiver box receives and stores. If e.g. the receiver box detects an error in the received text, it can call the transmitter to request retransmission. The modem 33 can also be used for calling data bases or other data sup¬ pliers, requesting supply of data as teletext via a TV transmitter. The printer 35 can give information or docu¬ mentation to the user of the receiver box. Through the card reader the receiver box can "receive electronic pay¬ ment" for services supplied through teletext or through a video decoder (not shown) in the receiver box, or the user's identification permitting him to receive given in- formation. Teletext data and text data can be transmitted between the units of the receiver box through the data connection 32 controlled by the microcomputer 26. For direct transmission of teletext data from the teletext decoder 24 to the modulator 25 (i.e. for direct display of teletext) there is provided a data connection 39 where teletext data are transmitted as so-called RGB signals, i.e. a form of video signal. A so-called data gate 40 is provided for communication with peripheral devices, e.g. for transmission of stored data in another manner than as a video signal or TV image. This gate may be used e.g. for passing on the stored data for retransmission as teletext via another TV transmitter. Fig. 3 shows the contents of a teletext loop. The name loop refers to the phenomenon that the teletext informa¬ tion is generally broadcast via the TV transmitter se¬ quentially and continuously, and therefore timewise con¬ stitutes a loop which is repeated indefinitely - with or without changes in the contents - as long as the teletext is active. As mentioned before in the explanation of fig. 1, transmission takes place with a plurality of rows (ge¬ nerally two) in each TV image. If desired, the rows may be transmitted in arbitrary order, since each of them carries a complete address with magazine and page numbers, but ordinarily the rows are transmitted numerically and page by page, magazine by magazine, from page 100 to page 899. Each transmission of these pages is called "a run of the teletext loop". The teletext information 50 to be transmitted is stored in a register 51 in which the individual records are here shown as whole teletext pages. 52 designates the shown symbolic representation of the entire teletext loop which contains the pages 100 to 899, divided into 8 magazines of 100 pages each. It is shown by way of example that the pages 540 and 541 comprise 3 subpages each. They are therefore shown in the register 51 as triple records. During transmission the subpages 540/1 and 541/1 are transmitted in the first run of the loop 52, subpages 540/2 and 541/2 in the second run, and so forth. When all the subpages of a given page have been transmitted, the procedure is recommenced with subpage 1 of said page. The data store in the receiver box includes a register 56 which can contain teletext rows. However, the records of the register are here shown as pages 57. As explained more fully elsewhere in this description, the receiver box can receive instructions contained in the transmitted teletext informatio . It is shown by way of example that page 430 (53) contains instructions for the receiver box. According to the inven¬ tion, the receiver box can be programmed to receive e.g. page 430 constantly and to respond to the instructions contained in this, which also specify the individual re¬ ceiver boxes to which the instructions relate. In this example the instruction is contemplated to be that the receiver box considered here is to store pages 540/1 to 541/3, a total of six pages, cf. 57, for subsequent dis¬ play on the connected TV set. The receiver box then cap¬ tures and stores pages 540 and 541 and stores them in the register 56 in this and the subsequent two runs of the loop 52. The instructions contained on the page concerned (here 430) may be of many different kinds. As another example it may be mentioned that the page may contain encryption keys enabling the receiver box to decrypt the text received, before or after it has been stored. As a third example it may be mentioned that the page concerned may contain in¬ structions on how to edit the teletext information re¬ ceived before it is transmitted to the connected TV re¬ ceiver. This may e.g. involve division into pages, selec- tion of colours for signs and background, etc. An example of the use of the invention may be transmission of messages to the staff of a company at their private addresses. Such transmissions might replace or supplement a staff magazine, technical or administrative instructions or the like. Since the messages arrive at the receivers very quickly, also urgent messages or messages which must necessarily be topical can be transmitted in this manner. A TV station broadcasting teletext can distribute said messages in the area covered by it, provided that the staff of the company have a TV set and sufficiently good reception conditions. Apart from the teletext installa¬ tions already existing at the TV station, it is only ne- cessary to provide devices and programs for administering and possibly encrypting the information to be broadcast and arrange it suitably in the store of the teletext ge¬ nerator of the TV station, cf. fig. 1, pos. 1. Of course, also a receiver box is needed for each of the TV receivers of the staff, cf. fig. 1, pos. 6. The initial costs are thus low. Practically no transmis¬ sion costs are involved, because spare capacity in the • teletext system of the TV station is utilized, and because the TV transmitter is already in operation most of the time. The other operating expenses are mostly on admini- stration of the system and on editing the messages; this work would also have to be performed if the messages were to be transmitted through other media. Therefore, the use of the invention described here involves considerable economic advantages. Another example of a use of the invention may be broad¬ casting of teletext via a system of TV transmitters broad¬ casting a common program (e.g. nationwide) from a central source alternating with individual programs (e.g. regional programs). Both common (nationwide) teletext pages and in¬ dividual (regional) teletext pages are to be broadcast simultaneously via each transmitter. All teletext pages are to be administered and broadcast from a central source, which may optionally be the same central source producing the common TV program. However, the common program is interrupted on each TV transmitter when this is to broadcast an individual pro- gram, and there is then no transmission connection for the teletext pages from the central source, because these are only present on the individual TV transmitter as part of the video signal in the common program. Using the invention, both the common and all the indivi¬ dual teletext messages can be distributed from the central source, there being installed on each of the TV transmit¬ ters of the system a special version of the receiver box of the invention, which, using the method of the inven- tion, is caused to store partly the common teletext infor¬ mation and partly the individual teletext information to be broadcast via the TV transmitter concerned. The contents of teletext pages in the store of the re- ceiver box are transferred via a data interface 40, cf. fig. 2, to a store in a teletext generator, cf. fig. 1, pos. 1. Then both the common and the individual teletext pages can be broadcast from the store together with the individual TV program. A third example of a use of the invention may be transmis¬ sion of larger amounts of data from a data base to a user of the data base. An order may be given by the user to the voice response system of the data base from the user's telephone apparatus with keyboard and 2-tone signalling, or from the keyboard 29 of the receiver box via the modem 33 and the telephone line 34. When the order has been given, the telephone connection can be interrupted, and the data base can tt-^ϊ. transmit the desired information via a data line to - as apparatus providing the store 1 at the TV station with da * a. Then, as described elsewhere in this application, the information can be transmitted to the user's receiver box, in which it is stored for later display on the user's TV receiver. This use of the invention entails that the user has access to information from data bases without other investments in equipment than the receiver box, which is much cheaper than e.g. a PC installation. Furthermore, telephone time is saved, since the user's telephone line is occupied only when the order is given. Fig. 4 shows one TV transmitter 60 of a system of TV transmitters broadcasting a common program (e.g. nation¬ wide) from a central source 61, 62, alternating with in- dividual programs (e.g. regional programs) from a local source 63. Both common (nationwide) teletext pages and individual (regional) teletext pages are to be broadcast simultaneously by each transmitter. All teletext pages are to be administered and broadcast from a central source 64, which may optionally be positioned at the same location as the central source 61 producing the common TV program. A teletext generator 65 receives the teletext information from the store 64 on its data input 66 and the video sig¬ nal from the source 61 on its video input 67. As mentioned above, the teletext generator 65 modulates the teletext information into some of the lines of the video signal and passes on the modulated signal to the TV transmitter 62. The common TV program including teletext is transmitted via a special connection 68 (e.g. a radio chain connec¬ tion) to a regional TV station, including i.a. the re- ceiver 69 and the transmitter 60. Prior to the receiver 69, the received signal is applied to a receiver box 70 according to the invention; as described before, this re¬ ceiver box can be programmed to select the teletext signal and supply it at its data gate 71, cf. fig. 2, pos. 40. By means of suitable devices, here symbolized by the double switch 72, the TV transmitter of the regional station can be provided either (in position I of the switch 72) with the common TV signal including teletext received from the transmitter 62, or (in position II of the switch 72) with a signal from the teletext generator 73 composed of the regional video signal from the source 63, which the tele¬ text generator 73 receives on its video input 74, and the common teletext signal which the teletext generator 73 receives on its data input 75. This remedies the drawbacks, mentioned elsewhere in this application, that the common program on each regional TV transmitter is interrupted when an individual program is to be broadcast, and that there is then no transmission connection for the teletext pages from the central source, since these are only present on the individual TV trans¬ mitter as part of the video signal in the common program.

Claims: P a t e n t C l a i m s : 1. A method of transmitting teletext signals from a transmitter to a plurality of receivers, wherein a plura¬ lity of consecutive and numbered teletext pages are trans¬ mitted currently, and wherein, in addition to teletext pages determined for all the receivers, it is possible to transmit a plurality of pages which are determined to be received only by one or more selected receivers, a digital address being allocated to each of said receivers which comprises a store for storing teletext pages, c h a ¬ r a c t e r i z e d in that control signals are transmit¬ ted to the selected receiver or receivers on a given tele- text page, said control signals comprising addresses on the selected receiver or receivers as well as information on the point or points of time at which teletext pages determined for said receivers will subsequently be trans¬ mitted; that the pages determined for said receivers are then transmitted, and that said pages are received by said receivers and stored in the store of each receiver. 2. A method according to claim 1, wherein the teletext signals contain information on the colour which the cha- racters of a given teletext page and its background, res¬ pectively, are to have when displayed on said receivers, c h a r a c t e r i z e d in that the teletext pages determined to be received only by one or more selected receivers are transmitted with the information that the characters and background of the pages are to be displayed with the same colour, and that said control signals com¬ prise messages to the selected receivers to change the colour of characters and/or background, and that the re¬ ceiver then changes the colour accordingly when displaying said pages so that the characters become visible. 3. A method according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the information on the teletext pages determined to be received only by one or more se¬ lected receivers are encrypted prior to transmission in an otherwise known manner; that said control signals for the selected receivers contain information on how to recreate the information, and that when received in the selected receivers the information is recreated by decryption. 4. A method according to claims 1-3, c h a r a c t e r ¬ i z e d in that a request is transmitted from a receiver via a modem and a telephone connection to the transmitter to transmit one or more given teletext pages, and that " these are then transmitted to the receiver concerned. 5. A method according to claim 4, wherein at least some of the selected receivers are provided with a magnetic card reader, c h a r a c t e r i z e d in that prior to transmission of a given teletext page the transmitter re- quests proof of the right of the receiver to receive the information concerned by means of said control signals; that the receiver then transmits said proof to the trans¬ mitter via said modem and telephone connection after a correct magnetic card has been entered into the magnetic card reader, and that the transmitter then transmits the teletext page to the receiver concerned. 6. A method according to claims 1-5, c h a r a c t e r ¬ i z e d in that the teletext pages stored in the store of one or more receivers are transmitted as teletext signals via a further TV transmitter or a closed network connected to the receiver concerned. 7. A sequence of a plurality of successive and numbered teletext pages for transmission from a transmitter to a plurality of receivers, wherein, in addition to the tele- text pages determined for all the receivers, it is pos¬ sible to transmit pages determined to be received only by one or more selected receivers, a digital address being allocated to each of these receivers, c h a r a c t e r - i z e d in that at least one of the pages in the sequence comprises control signals for the selected receiver or re¬ ceivers, said control signals comprising addresses of the receiver or receivers as well as information on the page number or numbers of the sequence or one or more subse- quent sequences on which teletext pages determined for said receivers will be transmitted. 8. A sequence according to claim 7, c h a r a c t e r ¬ i z e d in that all the pages of the sequence are deter- mined to be received only by one or more selected re¬ ceivers. 9. A sequence according to claim 8, c h a r a c t e r ¬ i z e d in that it just comprises a single page, that it is transmitted a plurality of successive times, and that it contains new information at each transmission so that a large number of pages can rapidly be transmitted to one or more selected receivers. 10. An apparatus for receiving teletext signals from a transmitter transmitting sequences of successive and num¬ bered teletext pages, a digital address being allocated to said apparatus which is adapted to store a plurality of the received pages, c h a r a c t e r i z e d in that the apparatus is adapted to receive control signals comprising the address of the apparatus and, in response to these control signals, to receive and store a plurality of tele¬ text pages determined to be received by said apparatus. 11. An apparatus according to claim 10, wherein the tele¬ text signals contain information on the colour which the characters of a given teletext page and its background, respectively, are to have when being displayed, c h a ¬ r a c t e r i z e d in that it is adapted to change the colour of either characters or background of the pages determined to be received by said apparatus in response to received control signals. 12. An apparatus according to claim 10 or 11, wherein the information on the pages determined to be received by se- lected receivers is encrypted, c h a r a c t e r i z e d in that it comprises means to recreate the transmitted information by decryption in response to received control signals. 13. An apparatus according to claims 10-12, c h a r a c ¬ t e r i z e d in that it moreover comprises a modem de¬ signed to transmit a request to the transmitter via a telephone connection to transmit one or more given tele¬ text pages. 14. An apparatus according to claim 13, c h a r a c ¬ t e r i z e d in that it moreover comprises a magnetic card reader, and that it is adapted to transmit a signal to the transmitter via said modem and telephone connection after entry of a correct magnetic card into the magnetic card reader. 15. An apparatus according to claims 10-14, c h a r a c ¬ t e r i z e d in that it is adapted to output a random one of the stored teletext pages, and that the output can at least take place in the form of a normal TV signal. 16. Use of teletext signals transmitted from a transmitter to a plurality of receivers, wherein a plurality of suc- cessive and numbered teletext pages are transmitted cur¬ rently, and wherein each of some receivers has been allo- cated a digital address and comprises a store for storing teletext pages, for transmitting pages determined to be received only by one or more selected receivers in addi¬ tion to the teletext pages determined for all the re- ceivers, control signals being transmitted on a given teletext page to the selected receiver or receivers, said control signals comprising addresses of the receiver or receivers as well as information on the point or points of time at which teletext pages determined for said receivers will subsequently be transmitted, following which the pages determined for said receivers are transmitted from the transmitter to said receivers and stored in the store of each receiver.

Inventors: JENSEN ERIK, VIND ERIK, JENSEN, ERIK, VIND, ERIK
Applicants: JENSEN ERIK, VIND ERIK, JENSEN, ERIK, VIND, ERIK
Application year: 1993
Main classification: H04N7
IPC codes: H04N1, H04N7