SUBSCRIPTION SYSTEM USING A PLURALITY OF TERMINALS

Abstract: In order to permit selective access to a common data bank (20), a plurality of terminals (10a-n) communicate therewith via barge-in data (24T) and subscription (24S) telephone lines. Each terminal includes a basic terminal (31) permitting use of plug-in application (42) and device control (48) modules therewith. The application modules contain programs stored in a memory (44) which enable a computer (30) within the basic terminal to perform specified functions in conjunction with certain subroutines stored in a memory (32a) also within the basic terminal. The device control module enables communication with the data bank. Subscription data identifying the terminals which have access to the data bank is circulated on the subscription barge-in telephone lines, and when a unique code identifying a particular terminal is recognized, the subscription data for that terminal is then permanently stored within a memory (46) in the application module of that terminal. The data to which such terminal has subscribed is retrieved from the data bank by calling a data barge-in telephone line on which such data is circulated, stored in a display memory (34) and displayed on a receiver (12).

Description: DATA ACCESS SYSTEM This invention relates to data access systems using intelligent terminals or home computers, as they are sometimes called. More particularly, this invention per- tains to a data access system wherein one or more of a large number of intelligent terminals may have rapid and selective access to a large library of information within a data bank. The recent proliferation of sophisticated micro- processors has resulted in the development of inexpensive computer systems available to the population at large. This, in turn, has enabled the public to gain access to vast libraries of data of assorted types. For example, information regarding the credit status of any of a large number of credit card customers can be retrieved from a data bank which is continuously updated. Likewise, such systems are used currently to provide information regard¬ ing airline tickets, hotel reservations, etc. There currently exist data banks for retrieving previously pub- lished newspaper and magazine articles, and data banks which provide stock market quotations for selected stocks. In most cases the data is displayed at termi¬ nals which are remote from the data bank and, for obvious reasons, it is highly desirable to be able to connect the individual terminals to the data banks by standard tele¬ phone lines. This in itself can be readily achieved, but there is a problem in providing a large number of sub¬ scriber terminals access by telelphone lines to a single data bank. Today, it is common to use time sharing techniques to provide access to a data bank but this is expensive because of the large amount of equipment which is required, and problems can arise causing excessive delay if too many subscribers attempt to access the data at one time. The object of the present invention is to pro¬ vide a system of the type described wherein a large number of subscribers have rapid access to a data bank at sub¬ stantially less expense than currently available time¬ sharing systems. Another object is to provide a data access sys¬ tem using telephone lines to obtain information from a data bank wherein the increase in number of telephone lines, as the number of users increases, is less than in a two-way telephone communication system. A more specific object is to enable a large number of terminals to gain access to a data bank by direct distance dialing on existing telephone lines with- out the need for direct lines as frequently required in existing time-sharing systems. Briefly, in accordance with the invention, the data bank provides data in the form of a closed loop file which is applied to any of a number of barge-in telephone lines. A user becomes a subscriber to the data bank by transferring into permanent storage at that user's termi¬ nal subscription data containing various identifier codes. Thereafter, the subscriber can retrieve selected text data by dialing a special barge-in telephone line on which the desired text data is circulated. If the user has properly subscribed to that data, the text is then displayed at the user's terminal. The invention is described in detail below with reference to the annexed drawings wherein: Figure 1 is a diagrammatic illustration of the overall system; Figure 2 is a block diagram of a preferred em¬ bodiment of a user's terminal; Figures 3, 4 and 5 show the formats of different types of data applied by the data bank to the barge-in lines; Figure 6 shwos the format of the data stored in' the electrically alterable read only memory of an applica¬ tion module; and Figure 6 is a memory map for a preferred embodi¬ ment of the invention. Figure 1 shows diagrammatically a data access system in accordance with the invention. Each subscriber has a terminal 10a-10n which is connecte ?dd t too a AD ORIGINAL receiver 12a-12n, respectively. These terminals are con¬ nected by standard telephone lines 14a-14n to the tele¬ phone company switching circuits 18. The data which is to be selectively coupled to the terminals 10 for display on the receivers 12 is con¬ tained within a data bank 20. Typically, the data bank 20 may comprise a large computer installation capable of generating on a continuous basis all of the data to which the terminals may wish to subscribe. The data bank 20 may include standard private lines 22 which can be used for the purpose of updating the stored subscription data within the bank. Additionally, and pursuant to the invention, the data bank also is coupled to a series of barge-in telephone lines 24 which are coupled to respective mass calling units 26 within the telephone company switching circuitry 18. Each barge-in line 24 is analogous to a so- called "party line" and may be connected to any one (or more) of many telephone users when a user dials the phone number of the barge-in line. The mass calling units 26 are telephone circuits which permit a large number of lines to call a selected barge-in line at one time. In this way, any user who dials a selected barge-in line will have access to the data on that line even if one or more other subscribers is receiving data from that line. The subscription data may be received from the data bank or, alternatively, from barge-in lines 24S and is used to enable the terminals to subscribe selectively to any of the various services offered by the data bank 20. After subscribing, the text data for a selected service appears on one of the barge-in lines 24T so that the subscription data can be transferred from the data bank 20 to the proper subscribing terminals 10a-10n. The operation of the system is described below reference to an example. At each terminal, the sub¬ scriber operates a keyboard to input data into the system and each terminal includes a serial number which is unique to that terminal and which in effect enables the terminal to operate within the overall system. As explained in further detail below in connec¬ tion with Fig. 2, each of the terminals may include a number of different application modules and device con¬ trol modules. The application modules enable certain types of applications. For example, a "magazine" module may provide the subscriber with the capability of sub¬ scribing to data from a number of publications. A "stock module may provide the capability of receiving quotations on stock prices. In addition to the application modules, a device control module is plugged into the terminal to enable telephone communication with the data bank. After the appropriate application and device control modules have been plugged into the subscriber's terminal, the subscriber may select any one of the appli- cations. For example, if the user wishes to subscribe to one of the publications for which text dat is stored in the data bank, he selects the magazine module and then calls one of the barge-in lines on which there appears a listing of all of the publications to which he may sub- *scribe. If the user decides to subscribe to one of these publications, he notifies the data bank (by mail or tele¬ phone) so that he may then subscribe to the selected pub¬ lications) by having the appropriate subscription data transferred into the memory of his terminal as described below. This subscription data will include the serial - number of the user's terminal, the name of the magazine to which he has subscribed, and the expiration date of his subscription. The subscription data may be transferred from the data bank when it is called by a new . subscriber. It is also contemplated, as an alternative arrangement, that the subscription data (and the subscription data for other new subscribers) may be continuously circulated in the form of a closed loop file on the subscription barge- in line 24S. When the user calls that subscription line, his terminal will recognize his serial number (when it appears) and then transfer the subscription data into the application module of his terminal. Because the sub- scription data appears on a barge-in line, many potential subscribers can call the same subscription line at the same time but, because of the unique identifying serial numbers, only the subscription data specifically intended for any individual subscriber will be transferred into his terminal 10. After the subscription data has been stored in a subscriber terminal 10, the subscriber may obtain the desired text data by dialing the telephone number of the -barge-in line on which that text data has been placed by the data bank 20. Here again, because of the use of barge-in lines, many subscribers (e.g., thousands) may obtain access to the information at one time.. If, for reasons of practicality, a single barge-in line contains data corresponding to magazines other than the ones to which the user has subscribed, the subscriber's terminal will nevertheless accept only the data to which he has already subscribed. The construction of the terminal 10 is shown diagrammatically in Fig. 2. The heart of the system is a microprocessor 30 (for example, Intel Model No. 8080A) contained within a basic terminal 31. The ' microprocessor includes a memory 32 which contains a read only memory (ROM) 32a and a random access memory (RAM) 32b. The data to be displayed generally is fed first to a display RAM 34, and then to a display buffer 36. The display buffer 36 controls a standard character generator 38 which cooperates with a conventional television interface 40 to generate video signals which may be coupled to the television receiver 12. In the preferred embodiment, the display com¬ prises eighteen lines of thirty-three characters. The characters may be alphanumeric or symbols. Typically, each character may be represented by a 6 x 11 matrix as is conventional. A single "page" may thus incude 594 (18 x 33) characters. The display buffer 36 stores a single page of information whereas the display RAM 34 stores three pages of information. In both cases, the data is stored as an eight bit code, the first six bits representing the character code is six bit ASCII and the last two bits representing the color of the character to be displayed. Generally, when the system is used to display subscription data received on the telephone lines, the data is coupled first to the display RAM 34 and then to the display buffer 36; however, display buffer 36 may als receive display data directly from the microprocessor memory 32, from the incoming telephone line, or from the memory within the application module. The operation of the terminal is controlled by means of a keyboard 41 which contains keys corresponding to the characters to be displayed and keys for initiating the various functions of the system as will become more apparent below. The ability to perform specific functions is provided by application modules such as module 42 which is physically and electrically connected to the basic terminal 31 as a plug-in unit. The application module 42 includes, among other things, a ROM 44 and an electricall alterable ROM (EAROM) 46 in which are contained program instructions and subscription data to enable operation of the system. A device control (communications) module 48, which includes a ROM 50 containing program instructions, provides the capability of communication with various different types of input/output devices, in this particu- lar case, conventional telephone lines. As is standard, such access may be provided by means of a data access arrangement (DAA) device 52, which is a commercially available device enabling telephone communication with computers. The basic terminal 31 may receive many separate modules. If, as in the case of the invention, it is desired to communicate by telephone line, it is necessary that there be at least one telephone communications modul BAD ORIGI - ~ - 48. The other modules may be for different types of applications although generally only one application module at a time would be used. Each application module 42 contains specific programs which enable the computer to perform a particu¬ lar function in conjunction with certain basic programs stored within the ROM 32a of the basic terminal 31. An important function of the basic terminal is to generate the desired displays when the stored DISPLAY subroutine of the basic terminal is called for by one of the appli¬ cation programs within a selected module. The basic terminal program will also include INITIALIZATION sub¬ routines and INDEX subroutines (amo'ng others) which are likely to be called by all modules or which identify the application modules plugged into the terminal. The "vendor" (in the example, the magazines to which the terminals subscribe) should have the capability of continuously updating the closed loop files which the data bank applies to the text barge-in lines 24T. For this purpose, each of the vendors may be provided with a basic terminal and a special "vendor" module 50. In this case, the vendor module may provide access to the data bank through the private line 22 (see Fig. 1) fo.? the purpose of updating the stored data within the data bank. Detailed Explanation The invention is explained in detail below by continuing the reference to an example wherein subscri¬ bers may receive data from publications over a telephone line. For purposes of explanation, the system is des- cribed with reference to an arrangement whereby subscrip¬ tion data is received from the barge-in lines 24S although such data may also be selectively retrieved directly from the data bank itself. In describing the invention, the general instructions of the programs for both the basic terminal and magazine (application) module are described. The pro¬ grams required for this example are set forth in full in the annexed Appendices I, Ii and III. Assuming that the magazine module and communica¬ tion module have been plugged into the basic terminal 31 and power turned on, the user may first press the RESET button on the keyboard 41. This causes the program in the basic terminal 31 to check for the modules and to display a list of the modules which are available. For example, the following display may appear on the television receiver. * * * A L P E X 900 P E R S O N A L C O M P U T E R M E N U C O D E A P P L I C A T I O N 1 T E S T D I S P L A Y ' 2 U S E T H E K E Y B O A R D 7 M A G A Z I N E M O D U L E PRESS KEY FOR CODE SELECTION DISPLAY NO. 1 (Available Applications) The basic terminal program for this display in- eludes certain INITIALIZATION subroutines which clear the display RAM 34 and the display buffer 36 among other things. In addition, the INITIALIZATION subroutine calls for an INDEX subroutine which searches for the modules in¬ serted into the basic terminal 31 and then calls a DISPLAY subroutine to display the titles of the inserted modules and to request selection of the desired application. The user may now select a desired application by pressing the key corresponding to the identification code appearing on the display for the desired application (magazine). When that key is pressed, the INDEX sub¬ routine of the basic terminal transfers program control from the basic terminal to the selected module. BAD ORIGINAL The module program first called a MAGAZINE INITIALIZATION subprogram which sets the interrupts to be allowed, causes the display to be erased as before, ■ initializes the keyboard and checks ' for the communication module among other things. After INITIALIZATION, the program calls a MODULE INDEX subroutine. This subroutine calls the DISPLAY sub¬ routine from the basic terminal which then displays the available module functions and asks the user to select a function. For example, display of the magazine module index may be as follows: * * * .M A G A Z I N E M O D U L E I N D E X C O D E A P P L I C A T I O N 1 L I S T C U R R E N T S U B S C R I P T I O N S 2 C A L L F O R A V A I L A B L E P U B L I C A ¬ T I O S 3 C A L L F O R M A G A Z I N E D A T A 4 C A L L T O L O A D N E W S U B S C R I P - T I O N 5 C A L L T O D E L E T E A S U B S C R I P ¬ T I O N P R E S S O N E O F T H E A B O V E C O D E S DISPLAY NO. 2 ' (Magazine Module Index) * * * Data for displaying the module index is stored within the ROM 44 of the module 42 and is fed directly from the module 42 to the display buffer 36, bypassing the display RAM 34. The available functions of the magazine module as shown in Display No. 2 are generally self-explanatory, but each is described in further detail below for the sake of completeness. For the purpose of this explanation, it is assumed that the user wishes to know what publications are available and, therefore, key No. 2 (corresponding to the second listed function "call for available publications" is depressed on the keyboard. This then causes the modul program to display the following message. * * * C A L L F O R A V A I L A B L E P U B L I C A T I O N T H E N U M B E R T O B E D I A L E D I S : 1 2 3 - 4 5 6 7 I F T H E P H O N E N U M B E R I S C O R R E C T P R E S S " R E T U R N " T O S T A R T D I A L I N G. ' T O C H A N G E T H E P H O N E N U M B E R , P R E S S " C " . DISPLAY NO. 3 * * * The phone number may be provided with the appli¬ cation module when delivered by the manufacturer and, for example, may be the phone number of a barge-in line 24 on which is circulated a closed loop file listing all maga¬ zines which are available to subscribers. To call the data bank to obtain this information, the user presses the digits corresponding to the displayed phone number followed by the key marked RETURN. This key transfers program control to a DIAL subroutine stored in the communications module which then dials the selected phone number and returns to the application module program when the number has been dialed and the telephone line is con¬ nected to the subscriber's terminal. The format of the data which appears on the barge-in telephone lines is represented in Figs. 3, 4 and 5. The list of available publications is shown in Fig. 3 which shows that a BOT signal (beginning of tape) is followed by a start of text signal (STX) and then a start of publications list signal (C1). When these characters BAD ORIGINAL have appeared in the proper sequence, the incoming data on the telephone line is then coupled directly into the display RAM 34. In the example under consideration, this may result in the- following display: * * * C U R R E N T L Y A V A I L A B L E P U B L I ¬ C A T I O N S F O R T H E A L P E X A 9 0 0 - 1 / 9 / 7 8 - S U B S C R I P T I O N S A R E F O R 1 Y E A R U N L E S O T H E R W I S E N O T E D - I F A N A S T E R I S K ( * ) P R E S E N T S E N D C H E C K T O : A L P E X S U B S C R I P T I O N S ' C O M M E R C E P A R K D A N B U R Y , C T . 0 6 8 1 0 S P O R T S W E E K L Y $ 1 4 0 W A L L S T R E E T J O UJ R N A L 6 5 T I M E M A G A Z I N E ( * ) 3 5 S T O C K S U M M A R Y 1 7 5 N Y T I M E S S U M M A R Y ( * ) 6 0 T V G U I D E 7 5 P R E S S N E X T P A G E K E Y F O R A D D I T I O N A L S U B S C R I P T I O N S DISPLAY NO. 4 (List of Available Publications) * * * At this stage, the user is now aware of the publications to which he can subscribe. Assuming, for further purposes of the example, that the user elects to subscribe to "Sports Weekly", "New York Times Summary" and n τv Guide", he writes to the vendor (i.e., the data bank) advising it accordingly. The data bank may then place subscription data on a subscription barge-in line 24S in the form of a closed loop file. The format of the sub¬ scription data is shown in Fig. 4, and includes the identifying serial number of the subscriber, the magazine to which he has subscribed and, as to each magazine, the expiration date of his subscription. The user is next advised (e.g., by mail) that his terminal is prepared to receive subscription data which, as explained above, requires that appropriate data be transferred from the data base into the EAROM 46 of the magazine module. When the user is ready to complete the subscrip tion, he returns to the initial magazine module index (Display No. 2) and selects code 4 ("call to load new subscription"). This will cause a display (not shown) instructing the user to dial the indicated subscription telephone line as described previously. As the subscrip¬ tion data (see Fig. 4) flows into the terminal, each ser¬ ial number on the subscription line is compared with the serial number of the subscriber (stored within each modul EAROM). When the serial number compares, the subscriptio data, ' including the magazine name and expiration date, is then transferred into the module EAROM. As part of this procedure, the module program may display the list of magazines being added to the list of subscriptions and, when the search is completed, a com plete list of the updated "current subscriptions" so that the user can check to see that the correct entries have been made. At this stage, the subscriber is now prepared t receive the magazine text data for the magazines to which he has subscribed. For this purpose, he again returns to the initial magazine module index (Display No. 2) and presses code 3 ("call for magazine data"). The application module program first goes through the initialization procedures. It then calls the DISPLAY subroutine and displays the subscription data which has been held in the module EAROM together with instructions for selecting the desired magazine. A typical display of the available magazines is shown below. BADORIGINAL - * * * M A G A Z I N E P G S P H O N E N U M B E R 1 Y T I E S 2 S P O R T S W K L Y 2 9 - 1 - 1 2 3 - 4 5 6 - 7 8 9 0 3 T V G U I D E 2 1 2 - 7 7 5 - 1 2 1 2 E N T E R T H E C O D E ( S ) ( M A X O F 3 ) OF T H E P U B L I C A T I O N S Y O U W I S H T O V I E W ( E X A M P L E 1 , 1 0 , 6 ) T H E N P R E S S " R E T U R N " DISPLAY NO. 5 (Available Magazine Data) * * * Display No. 4 indicates that -there are three available magazines, two of which have indicted phone numbers, which contain the subscription data sought. Assuming that the user wishes to select the New York Times (which includes no phone number) he depresses the key 1 and presses the RETURN button. The module program then searches for a phone number in the module EAROM. In this case, no phone number is present (if the magazine had previously been selected, the phone number would already be stored in EAROM). Accordingly, the program displays a message (not shown) instructing the user to enter the phone number for the selected magazine (the subscriber is notified of the phone numbers for his subscriptions when originally instructed on the subscription procedrues). After the user has entered the telephone number as described previously, the phone number is stored in the module EAROM by calling a "CALL RIGHT BLOCK" subroutine . from the basic terminal program. Next, the message "READY TO DIAL?" may be displayed so that when the user pushes the DIAL key, the terminal will dial the selected tele¬ phone number and connect the basic terminal with the selected magazine data barge-in telephone line 24T. The format of the magazine data appearing on the test barge-in line is shown in Fig. 5. This data includes the name of the magazine, the current date (i.e., the date of data transmission), the time the text was entered in the data bank, the volume numbers on whic the text appears, and the text. The format of the data which is stored in the module EAROM is shown in Fig. 6. The data in Fig. 6 is stored after the user has subscribed to the selected mag zines as described above and after the appropriate tele¬ phone numbers have been entered. After the selected telephone number has been called and the terminal connected through the communica¬ tions module, the module program searches for the selec¬ ted magazine. Since the user is calling a barge-in' sys¬ tem, there will only be a nominal delay in connecting to the telephone line, although some delay will normally be encountered before the selected subscription appears on the line. For example, if the selected magazine data is recirculated every minute, on the average, the subscribe will have to wait thirty seconds before the text he seeks appears on the line. Typically, there may be 612 characters for each page of information to be displayed (including supplemen¬ tal characters used to generate background color). About 120 charactes may be transmitted each second so that approximately five seconds are required to transmit each page. It is further contemplated that if twelve pages of data appear on each closed loop file, slightly more than sixty seconds will normally be required to circulate an entire file. Hence, under the worst of conditions, a subscriber would have to wait no more than about one minute after the telephone connection is made to receive the text data. As the data is fed to the terminal, the module program searches for the selected magazine name. When th data is found, the expiration date (stored in the module - EAROM) is compared with the current date (Fig. 5). If th expiration date is later, the microprocessor 30 couples the subsequent text into the display RAM 34. If the sub¬ scription has expired, the program may cause the message f BAD ORIGINAL A f ~ "subscription expired" to be displayed. When the signal indicating the end of the sub¬ scription is received, the module program causes the com¬ munication module to disconnect the basic terminal from the telephone line. At this point, there will typically be three pages of data stored in the display RAM 34. The content of the display RAM corresponding to page 1 are coupled to the display buffer 36 and, therefore, only that data is displayed. The user may depress a SCROLL button to trans¬ fer continuous data lines from page 2 (and 3) into the display buffer thereby, in effect, permitting the user to "scroll" through the ..contents of the display RAM. The foregoing outlines generally the steps iή- volved for one particular application in first subscribing to the data bank and then receiving the selected text. Other options will also be provided. For example, refer¬ ring again to Display No. 2, if the user presses the INDEX button to return to the magazine module index, he may press key No. 1 to obtain a list of the current subscriptions. The display provided in this case may be as follows: * * * C U R R E N T S U B S C R I P T I O N S M A G A Z I N E E X P D T E # P A G E S C O M M O D R P T 2 / 7 9 2 E X E C U T R P T 6 / 7 9 2 J O N E S R P T A 1 1 / 7 8 1 N Y T I M E S 3 / 7 8 3 S T O C K S U M 2 / 7 9 2 S M I T H R P T B 3 / 7 8 2 P R E S S " I N D E X " T O R E T U R N T 0 I D E X DISPLAY NO. 6 (List of Current Subscriptions) * * * If a user wishes to delete a subscription, key No. 5 will initiate a function similar to "call to load new subscription". The sixth function ("store phone num- ber for a subscription") provides the ability to change telephone numbers should that become necessary or desir¬ able. There may be additional functions to enable the user to store the information received on a tape cassette for subsequent retrieval. When it is desired to record and/or replay the subscription data, it is necessary to plug into the base terminal the appropriate communication module which will permit interfacing with the recording equipment. Fig. 7 is a memory map of a terminal according to a preferred embodiment, including the basic terminal and the various modules, both application and communica¬ tion. Each block includes 1024 bytes and the starting addresses are expressed in hexadecimal. Blocks 8 through ' 45 represent memory within the various modules as indi¬ cated. Slots 1, 2, 3 and 4 represent the ROM of different application modules and slots 1A through 4A are the EAROM (or RAM) of the corresponding application module. For purposes of explanation only, the preferred embodiment of the invention has been described in connec¬ tion with a magazine subscription service. Of course, the invention is not restricted to any type of informa¬ tion and it is contemplated that the data bank may pro¬ vide "data" quite different from the data now provided by data banks. As one further example, the "data" provided may be used to play sophisticated games (e.g. checkers and chess) or games of the type now sold as video games. Hence, as used herein the term "data bank" is intended to include any source of information regardless of the pur- poses for which such information is to be used so long as such information can be transmitted on telephone lines. The term "text data" refers to the information supplied by the data banks and "subscription data" broadly includes any identifying code for the text data to be received so long as it can be used to indicate that a terminal has completed a subscription procedure and is entitled to receive the text data from the data bank. BAD ORIGINAL

Claims: WHAT IS CLAIMED IS: 1. A data retrieval system comprising in combination a data bank, a plurality of text barge-in telephone lines on which text data from said data bank is circulated, a subscription barge-in telephone line on which subscription data for a multiplicity of subscribers is circu¬ lated, and a multiplicity of subscriber terminals, each of which includes data processor means, memory means and display means, each one of said subscriber terminals further including means for transferring the subscription data for said one subscriber terminal only from said subscription barge-in telephone line to said memory means,- and means for selectively causing the text data on at least one of said text barge-in telephone lines to be displayed provided such text data conforms at least in part to the subscription data in said memory means. 2. A data retrieval system according to claim 1 , wherein each subscriber terminal comprises a basic terminal including said data processor an d part of said memory means in which are stored program instructions for controlling the display, at least one application module physically and electrically detachable from said basic terminal and including a second part of said memory means having stored therein pro¬ gram instructions defining the function of the terminal, and a communication module for connecting said termi¬ nal to a selected telephone line. 3. A data retrieval system according to claim 2, wherein the second part of said memory means includes an EAROM for storing the subscription data appearing on said subscrip¬ tion barge-in line. 4. Data retrieval system according to claim 3, wherein each of said basic terminals has a unique identifier code permanently stored in said memory means, said subscription data including the identifier codes of the terminals which are to become subscribers and text identifying signals. 5. A data retrieval system according to claim 1 or 2, further comprising a third barge-in telephone line on which data identifying the services available for subscription is circu¬ lated, and wherein each of said subscriber terminals further includes means for displaying the data appearing on said third barge-in telephone line. 6. For use in a data retrieval system which includes a plurality of text barge-in telephone lines on which text data from a data bank is circulated, a subscriber terminal, comprising data processor means, memory means having stored therein program in¬ structions for operating such data processor means, display means for displaying data under control of said data processor means, means for transferring subscription data unique to the subscriber terminal to said memory means, means for comparing the stored subscription data in said memory means with identifier signals accompanying said text data, and means for selectively causing the text data on at least one of said text barge-in telephone lines to be displayed when said comparing means indicates that the terminal has sub- • scribed to said text data. 7. A data retrieval system according to claim 6, wherein each subscriber terminal comprises BAD ORIGINAL a basic terminal including said data processor means and part of said memory means in which are stored program instructions for controlling the display, at least one application module physically and electrically detachable from said basic terminal and including a second part of said memory means having stored therein program instructions defining the function of the terminal, and a communication module for connecting said termi¬ nal to a selected telephone line. 8. A data retrieval system according to claim 7, wherein the second part of said memory means includes an EAROM for storing the subscription data. 9. Data retrieval system according to claim 8, wherein each of said basic terminals has a unique identifier code permanently stored in said memory means, said subscription data including the identifier codes of the terminals which are to become subscribers and text identifying signals. 10. A method of retrieving data from a data bank, wherein the retrieved data is transmitted via telephone lines and displayed as a terminal, comprising calling a subscription barge-in telephone line on which subscription data for a multiplicity of subscribers are circulated, storing the subscription data corresponding to the calling subscriber at the subscriber's terminal, thereafter calling a text barge-in telephone line on which the text data from said data bank is circulated, comparing an identifying code accompanying the text data appearing on said text barge-in telephone line with the subscription data stored in the terminal, and displaying said text data when the aforesaid comparison indicates that the terminal has subscribed thereto.

Inventors: HASEL L, KIRSCHNER W
Applicants: ALPEX COMPUTER CORP
Application year: 1979
Main classification: G06F3
IPC codes: G06F7, G06F17, G06Q30, H04M11