Patent Publication Number: US-7913275-B2

Title: Method and apparatus for switching targeted advertisements at a set top terminal

Description:
CROSS REFERENCE TO RELATED APPLICATIONS: 
     This application is a divisional of application Ser. No. 08/735,549 filed Oct. 23, 1996, now U.S. Pat. No. 6,738,978 entitled “Method And Apparatus For Targeted Advertising” (As Amended), which is a divisional of application Ser. No. 08/160,280, filed Dec. 2, 1993, now issued U.S. Pat. No. 5,600,364, entitled “Network Controller for Cable Television Delivery Systems”, all of which are herein incorporated by reference. The following other continuation-in-part applications are also incorporated herein by reference:
         Ser. No. 08/160,281, filed Dec. 2, 1993, now issued U.S. Pat. No. 5,798,785, entitled “Reprogrammable Terminal For Suggesting Programs Offered On A Television Program Delivery System;”   Ser. No. 08/160,282, filed Dec. 2, 1993, now issued U.S. Pat. No. 5,659,350, entitled “An Operations Center For A Television Program Packaging And Delivery System;”   Ser. No. 08/160,193, filed Dec. 2, 1993, now issued U.S. Pat. No. 5,734,853, entitled “Set Top Terminal For Cable Television Delivery Systems;”   Ser. No. 08/160,194, filed Dec. 2, 1993, now issued U.S. Pat. No. 5,990,927, entitled “Advanced Set Top Terminal For Cable Television Delivery Systems;”   Ser. No. 08/160,283, now issued U.S. Pat. No. 5,682,195, entitled “Digital Cable Headend For Cable Television Delivery System.”       

    
    
     TECHNICAL FIELD 
     The invention relates to television entertainment systems for providing television programming to consumer homes. More particularly, the invention relates to a network controller that monitors, controls and manages a television program delivery network from a cable headend. 
     BACKGROUND OF THE INVENTION 
     Advances in television entertainment have been primarily driven by breakthroughs in technology. In 1939, advances on Vladmir Zworykin&#39;s picture tube provided the stimulus for NBC to begin its first regular broadcasts. In 1975, advances in satellite technology provided consumers with increased programming to homes. 
     Many of these technology breakthroughs have produced inconvenient systems for consumers. One example is the ubiquitous three remote control home, having a separate and unique remote control for the TV, cable box and VCR. More recently, technology has provided cable users in certain parts of the country with 100 channels of programming. This increased program capacity is beyond the ability of many consumers to use effectively. No method of managing the program choices has been provided to consumers. 
     Consumers are demanding that future advances in television entertainment, particularly programs and program choices, be presented to the consumer in a user friendly manner. Consumer preferences, instead of technological breakthroughs, will drive the television entertainment market for at least the next 20 years. As computer vendors have experienced a switch from marketing new technology in computer hardware to marketing better useability, interfaces and service, the television entertainment industry will also experience a switch from new technology driving the market to consumer useability driving the market. 
     Consumers want products incorporating new technology that are useful, and will no longer purchase new technology for the sake of novelty or status. Technological advances in sophisticated hardware are beginning to surpass the capability of the average consumer to use the new technology. Careful engineering must be done to make entertainment products incorporating new technology useful and desired by consumers. 
     In order for new television entertainment products to be successful, the products must satisfy consumer demands. TV consumers wish to go from limited viewing choices to a variety of choices, from no control of programming to complete control. Consumers wish to advance from cumbersome and inconvenient television to easy and convenient television and keep costs down. Consumers do not wish to pay for one hundred channels when due to lack of programming information, they seldom, if ever, watch programming on many of these channels. Viewers wish their programming to be customized and targeted to their needs and tastes. 
     The concepts of interactive television, high definition television and 300 channel cable systems in consumer homes will not sell if they are not packaged, delivered and presented in a useable fashion to consumers. Consumers are already being bombarded with programming options, numerous “free” cable channels, subscription cable channels and pay-per-view choices. Any further increase in TV entertainment choices, without a user friendly presentation and approach, will likely bewilder viewers with a mind-numbing array of choices. 
     The TV industry has traditionally marketed and sold its programs to consumers in bulk, such as continuous feed broadcast and long-term subscriptions to movie channels. The TV industry is unable to sell its programming in large quantities on a unit per unit basis, such as the ordering of one program. Consumers prefer a unit sales approach because it keeps costs down and allows the consumer to be more selective in their viewing. 
     In today&#39;s television world, networks manage the program lineup for individual channels. Each network analyzes ratings for television shows and determines the appropriate schedule or program lineup to gain market share and revenue from advertising. Program ratings are determined using a test group of viewers and statistical analysis methods. Since each channel is in competition with every other channel, there is no coordinated effort to organize television programming in a manner that primarily suits the viewers. 
     Advertising has become equally annoying, with viewers being “forced” to watch television commercials for goods and services that are neither needed nor desired. As a result, consumers have become impatient and dissatisfied with today&#39;s television delivery systems. Equally problematic, these television delivery systems do not have the capabilities or features necessary to operate in the digital environment. Consequently, advances in digital technology call for a new television program delivery system that is capable of satisfying varying consumer and viewer needs. 
     Existing cable headends are unequipped for the transition to a digital system. These cable headends have no means for monitoring and controlling the large numbers of program signals and advertisements that will eventually be passed on to both consumers and viewers. These cable headends are unequipped to manage account and billing information for set top terminals without relying on telephone lines. In addition, these cable headends have no means for targeting advertisements to particular consumers and viewers. 
     What is needed is a network controller capable of modifying program control information received from an external source. 
     What is needed is a network controller capable of targeting video to viewers. 
     What is needed is a network controller capable of targeting television commercials to specific consumers and viewers. 
     What is needed is a network controller capable of gathering information on programs watched by viewers. 
     The present invention is addressed to fulfill these needs. 
     SUMMARY OF INVENTION 
     A system and method for switching targeted advertisements is described herein. In one embodiment one primary advertisement is assigned to a first channel, where the first channel carries a program. At least one alternate advertisement is assigned to one or more alternate channels. Selected set top terminals switch to one or more of the alternate channels to display alternate advertisements, where the selection of the alternate channel is based on information related to users of the set top terminals. 
     The present invention utilizes a network controller for a television delivery system. The network controller is the central component that provides monitoring and control of set top terminals in a television delivery system. The network controller is a component of a digital cable television delivery system. The network controller of the present invention provides much greater capability and flexibility than existing cable headend control equipment. 
     The network controller of the preferred embodiment performs all its cable network monitoring and control of set top terminals within the cable headend. The cable headend receives and processes digitally compressed program signals before the signals are relayed to each set top terminal. Each cable headend site is equipped with multiple satellite receiver dishes and a signal processor. 
     As an intermediary between the set top terminals and the program delivery system&#39;s operations center (or other remote site), the cable headend relies on the network controller to perform key cable system operations. In particular, the network controller accommodates regional programming needs by working with other cable headend components. The network controller also performs the system control functions for the cable system. 
     The primary function of the network controller is to manage the configuration of set top terminals and process signals received from the set top terminals. In the preferred embodiment, the network controller monitors, among other things, automatic poll-back responses from the set top terminals remotely located at each subscribers&#39; home. The polling and automatic report-back cycle occurs frequently enough to allow the network controller to maintain accurate account and billing information as well as monitor authorized channel access. 
     In the simplest embodiment, information to be sent to the network controller will be stored in RAM within each subscriber&#39;s set top terminal and will be retrieved only upon polling by the network controller. Retrieval may, for example, occur on a daily, weekly or monthly basis. The network controller allows the system to maintain complete information on all programs watched using a particular set top terminal. 
     The network controller is also able to respond to the immediate needs of a set top terminal, or a group of set top terminals. The network controller can modify a program signal received from the program delivery system&#39;s operations center before the program signal is transmitted to the set top terminal. Therefore, the network controller enables the delivery system to adapt to the specific requirements of individual set top terminals when information on these requirements cannot be provided to the operations center in advance. In other words, the network controller is able to perform “on the fly programming” changes. With this capability, the network controller can handle sophisticated local programming needs such as interactive television services, split screen video, and selection of different foreign languages for the same video. In addition, the network controller controls and monitors all compressors and decompressors in the system. 
     The network controller makes use of a number of software routines that assist the network controller to perform its major functions. One of the major routines assists the network controller to modify the program control information so that changes and additions in programming and advertisements can be accommodated. Such changes and additions include set top terminal access authorizations and deauthorizations. 
     A set top terminal data gathering routine allows the network controller to schedule and perform polling of all set top terminals operating in the system. The software also provides the network controller with a means of processing status reports received from set top terminals in response to polling requests. 
     A video targeting routine makes use of a viewer&#39;s demographic information and viewing habits to determine those advertisements that are of most interest to that particular viewer. In so doing, the routine generates packages of advertisements targeted towards each viewer. 
     An additional routine correlates the programs accessed with pricing information to generate billing reports that can be sent to a given set top terminal over the cable distribution network. Aside from this routine, the network controller accommodates other methods of billing and account maintenance, such as through the use of remote billing sites. 
     The present invention is not only able to operate in the digital environment but also introduces many new features to television program delivery and cable headend control. 
     The present invention provides for several methods for targeting advertising to at least one subscriber. In one embodiment, programs watched data are gathered from a subscriber and then the programs watched data is analyzed to determine the frequency of programs watched by the subscriber. The analyzed programs watched data are correlated with categories of advertisements, such that each advertisement category includes at least one advertisement. An advertisement is then selected from the correlated categories and transmitted for display to the subscriber. 
     These and other objects and advantages of the invention will become obvious to those skilled in the art upon review of the following description, the attached drawings and appended claims. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of the primary components of the television delivery system. 
         FIG. 2  is an overview of the television delivery system operations. 
         FIG. 2A  is a schematic of a marketing information interface. 
         FIG. 3  is a schematic of the operation of the primary components of the system. 
         FIG. 4  is a diagram of the primary components of the cable headend. 
         FIG. 5  is a diagram of the cable headend showing the primary components of the network controller. 
         FIG. 6   a  is a schematic of a basic cable headend having network controller components. 
         FIG. 6   b  is a schematic of an alternative embodiment of  FIG. 6   a.    
         FIG. 7  is a detailed diagram of the components of the cable headend. 
         FIG. 8   a  is a drawing of a broadcast television menu screen to be displayed on a set top terminal. 
         FIG. 8   b  is a drawing of a hit movie menu screen to be displayed on a set top terminal. 
         FIG. 8   c  is a drawing of a hit movie description menu screen to be displayed on a set top terminal. 
         FIG. 9   a  is a diagram for out-of-band two-way data transmission for a digital/analog headend. 
         FIG. 9   b  is a diagram for in-band two-way data transmission for a digital/analog headend. 
         FIG. 10   a  is a diagram of the polling request message format. 
         FIG. 10   b  is a diagram of the polling response message format with an expanded view of the programs accessed block field. 
         FIG. 11  is a diagram of the network controller CPU and its relational components. 
         FIG. 12  is diagram of the network control database structure. 
         FIG. 13  is a diagram of the relationship between the major software routines. 
         FIG. 14  is a block diagram of the software flow chart for the Modifying PCI routine. 
         FIG. 15  is a block diagram of the software flow chart for the Polling Cycle routine. 
         FIG. 16  is a diagram of a sample programs watched matrix. 
         FIG. 17  is a block diagram of the software flow chart for the Basic Advertisement Targeting routine. 
         FIG. 18  is a block diagram of the subroutine flow chart for processing programs watched matrices through correlation algorithms. 
         FIG. 19  is a diagram of the subroutine flow chart for determining final groupings of set top terminals. 
         FIG. 20   a  is a diagram showing a sample assignment of advertising channels to set top terminal groups watching particular categories of programs. 
         FIG. 20   b  is a diagram assigning available bandwidth for multiple advertising channels. 
         FIG. 21  is a diagram of the software flow chart for an alternative to the Basic Advertisement Targeting routine. 
         FIG. 22  is a diagram of the software flow chart for the Account/Billing routine. 
         FIG. 23  is a diagram of an embodiment that uses remote statistical and billing sites. 
         FIG. 24   a  is a schematic of a set top terminal. 
         FIG. 24   b  is another schematic of a set top terminal. 
         FIG. 24   c  is yet another schematic of a set top terminal. 
         FIG. 24   d  is still another schematic of a set top terminal. 
         FIG. 25  is a flow chart of the progression of primary menus in the menu driven system of the set top terminal. 
         FIG. 26  is a drawing of basic menus according to an embodiment of the invention. 
         FIGS. 27   a  and  27   b  are drawings of introductory menus. 
         FIGS. 28   a ,  28   b ,  28   c  and  28   d  are drawings of home menus. 
         FIG. 29  is a drawing of an alternative home menu. 
         FIGS. 30   a ,  30   b ,  30   c ,  30   d ,  30   e ,  30   f  and  30   g  are drawings of major menus. 
         FIG. 31  is a drawing of hit movie description menu. 
         FIGS. 32   a  and  32   b  are drawings of hit movie notification submenus. 
         FIGS. 33   a  and  33   b  are drawings of menus related to promotion of high definition television programming. 
         FIGS. 34   a ,  34   b , and  34   c  are drawings of interactive television promotional menus, for Levels A-C. 
         FIGS. 35   a ,  35   b ,  35   c ,  35   d , and  35   e  are drawings of submenus for interactive television services, Level A. 
         FIGS. 36   a ,  36   b ,  36   c ,  36   d , and  36   e  are drawings of on-line service menus. 
         FIGS. 37   a ,  37   b , and  37   c  are drawings of menus for digital audio services. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A. Television Program Delivery System Description 
     1. Introduction 
       FIG. 1  shows the present invention as part of an expanded cable television program delivery system  200  that dramatically increases programming capacity using compressed transmission of television program signals. Developments in digital bandwidth compression technology now allow much greater throughput of television program signals over existing or slightly modified transmission media. The program delivery system  200  shown provides subscribers with a user friendly interface to operate and exploit a six-fold or more increase in current program delivery capability. 
     Subscribers are able to access an expanded television program package and view selected programs through a menu-driven access scheme that allows each subscriber to select individual programs by sequencing a series of menus. The menus are sequenced by the subscriber using simple alpha-numeric and iconic character access or moving a cursor or highlight bar on the TV screen to access desired programs by simply pressing a single button, rather than recalling from memory and pressing the actual two or more digit numeric number assigned to a selection. Thus, with the press of a single button, the subscriber can advance from one menu to the next. In this fashion, the subscriber can sequence the menus and select a program from any given menu. The programs are grouped by category so that similar program offerings are found on the same menu. 
     2. Major System Components 
     In its most basic form, the system uses a program delivery system  200  in conjunction with a conventional concatenated cable television system  210 . The program delivery system  200  generally includes (i) at least one operations center  202 , where program packaging and control information are created and then assembled in the form of digital data, (ii) a digital compression system, where the digital data is compressed, combined/multiplexed, encoded, and mapped into digital signals for satellite transmission to the cable headend  208 , and (iii) a set of in-home decompressors. The program delivery system  200  transports the digital signals to the cable headend  208  where the signals are transmitted through a concatenated cable television system  210 . Within the cable headend  208 , the received signals may be decoded, demultiplexed, managed by a local central distribution and switching mechanism, combined and then transmitted to the set top terminal  220  located in each subscriber&#39;s home over the cable system  210 . Although concatenated cable systems  210  are the most prevalent transmission media to the home, telephone lines, cellular networks, fiberoptics, Personal Communication Networks and similar technology for transmitting to the home can be used interchangeably with this program delivery system  200 . 
     The delivery system  200  has a reception region  207  with an in-home decompression capability. This capability is performed by a decompressor housed within a set top terminal  220  in each subscriber&#39;s home. The decompressor remains transparent from the subscriber&#39;s point of view and allows any of the compressed signals to be demultiplexed and individually extracted from the composite data stream and then individually decompressed upon selection by the subscriber. The decompressed video signals are converted into analog signals for television display. Such analog signals include NTSC formatted signals for use by a standard television. Control signals are likewise extracted and decompressed and then either executed immediately or placed in local storage such as a RAM. Multiple sets of decompression hardware may be used to decompress video and control signals. The set top terminal  220  may then overlay or combine different signals to form the desired display on the subscriber&#39;s television. Graphics on video or picture-on-picture are examples of such a display. 
     Although a single digital compression standard (e.g., MPEG) may be used for both the program delivery system  200  and the concatenated cable system  210 , the compression technique used may differ between the two systems. When the compression standards differ between the two media, the signals received by the cable headend  208  must be decompressed before transmission from the headend  208  to the set top terminals  220 . Subsequently, the cable headend  208  must recompress and transmit the signals to the set top terminal  220 , which would then decompress the signals using a specific decompression algorithm. 
     The video signals and program control signals received by the set top terminal  220  correspond to specific television programs and menu selections that each subscriber may access through a subscriber interface. The subscriber interface is a device with buttons located on the set top terminal  220  or on a portable remote control  900 . In the preferred system embodiment, the subscriber interface is a combined alpha-character, numeric and iconic remote control device  900 , which provides direct or menu-driven program access. The preferred subscriber interface also contains cursor movement and go buttons as well as alpha, numeric and iconic buttons. This subscriber interface and menu arrangement enables the subscriber to sequence through menus by choosing from among several menu options that are displayed on the television screen. In addition, a user may bypass several menu screens and immediately choose a program by selecting the appropriate alpha-character, numeric or iconic combinations on the subscriber interface. In the preferred embodiment, the set top terminal  220  generates the menus that are displayed on the television by creating arrays of particular menu templates, and the set top terminal  220  displays a specific menu or submenu option for each available video signal. 
     3. Operations Center and Digital Compression System 
     The operations center  202  performs two primary services, packaging television programs and generating the program control information signal. At the operations center  202 , television programs are received from external program sources in both analog and digital form.  FIG. 2  shows an embodiment of the operations center receiving signals from various external sources  212 . Examples of the external program sources are sporting events, children&#39;s programs, specialty channels, news or any other program source that can provide audio or visual signals. Once the programs are received from the external program sources, the operations center  202  digitizes (and preferably compresses) any program signals received in analog form. The operations center  202  may also maintain an internal storage of programs. The internally stored programs may be in analog or digital form and stored on permanent or volatile memory sources, including magnetic tape or RAM. Subsequent to receiving programming, the operations center  202  packages the programs into the groups and categories which provide the optimal marketing of the programs to subscribers. For example, the operations center  202  may package the same programs into different categories and menus for weekday, prime-time viewing and Saturday afternoon viewing. Also, the operations center  202  packages the television programs in a manner that enables both the various menus to easily represent the programs and the subscribers to easily access the programs through the menus. 
     The packaging of the digital signals is typically performed at the operations center  202  by computer assisted packaging equipment (CAP). The CAP system normally includes at least one computer monitor, keyboard, mouse, and standard video editing equipment. A programmer packages the signals by entering certain information into the CAP. This information includes the date, time slot, and program category of the various programs. The programmer and the CAP utilize demographic data and ratings in performing the packaging tasks. 
     Extracts of customer purchases will be provided to the Operations Center  202 . These extracts of information will be formatted and correlated with customer demographics for marketing purposes by the Marketing Information Interface (MII)  702 . The MII  702  is shown in  FIG. 2   a . The Marketing Information Interface (MII)  702  subroutine interfaces the processing and editing subroutines with marketing data. This interface regularly receives programs watched information from billing sites  720 , cable headends  208 , or set top terminals  220 . In addition, other marketing information  722  such as the demographics of viewers during certain time periods may be received by the MII  702 . The MII  702  also uses algorithms  724  to analyze the program watched information and marketing data  720 ,  722 , and provides the analyzed information to the processing and editing subroutines. 
     The process program line-up subroutine  730  uses information from the MII  704  and Packager Data Entry Interface (PDEI)  700  to develop a program line-up. Algorithms are used to assign programs in time slots. 
     The operations center  202  may also “insert” directions for filling local available program time in the packaged signal to enable local cable and television companies to fill the program time with local advertising and/or local programming. Consequently, the local cable headends are not constrained to show only programs transmitted from the operations center  202 . 
     After the programmer selects the various programs from a pool of available programs and inputs the requisite information, the programmer, with assistance from the CAP, can select the price and allocate transponder space for the various programs. After the process is complete, the CAP displays draft menus or program schedules that correspond to the entries of the programmer. The CAP may also graphically display allocation of transponder space. The programmer may edit the menus and transponder allocation several times until satisfied with the programming schedule. During the editing, the programmer may direct the exact location of any program name on a menu with simple commands to the CAP. 
     The packaging process also accounts for any groupings by satellite transponder which are necessary. The operations center  202  may send different groups of programs to different cable headends  208  and/or set top terminals  220 . One way the operations center  202  may accomplish this task is to send different program packages to each transponder. Each transponder, or set of transponders, then relays a specific program package to specific cable headends  208  and/or set top terminals  220 . The allocation of transponder space is an important task performed by the operations center  202 . 
     The operations center  202  may also “insert” directions for filling local available program time in the packaged signal to enable local cable and television companies to fill the program time with local advertising and/or local programming. Consequently, the local cable headends  208  are not constrained to show only programs transmitted from the operations center  202 . New set top converters will incorporate both digital and analog channels. Therefore, the cable headend  208  may combine analog signals with the digital signals prior to transmitting the program signals to the set top terminals  220 . 
     After the CAP packages the programs, it creates a program control information signal to be delivered with the program package to the cable headend  208  and/or set top terminal  220 . The program control information signal contains a description of the contents of the program package, commands to be sent to the cable headend  208  and/or set top terminal  220 , and other information relevant to the signal transmission. 
     In addition to packaging the signal, the operations center  202  employs digital compression techniques to increase existing satellite transponder capacity by at least a 4:1 ratio, resulting in a four-fold increase in program delivery capability. A number of digital compression algorithms currently exist which can achieve the resultant increase in capacity and improved signal quality desired for the system. The algorithms generally use one or more of three basic digital compression techniques: (1) within-frame (intraframe) compression, (2) frame-to-frame (interframe) compression, and (3) within carrier compression. Specifically, in the preferred embodiment, the MPEG 2 compression method is used. After digital compression, the signals are combined (multiplexed) and encoded. The combined signal is subsequently transmitted to various uplink sites  204 . 
     There may be a single uplink site  204  or multiple uplink sites (represented by  204 ′, shown in phantom in  FIG. 1 ) for each operation center  202 . The uplink sites  204  may either be located in the same geographical place or may be located remotely from the operations center  202 . Once the composite signal is transmitted to the uplink sites  204 , the signal may be multiplexed with other signals, modulated, upconverted and amplified for transmission over satellite. Multiple cable headends  208  may receive such transmissions. 
     In addition to multiple uplinks, the delivery system  200  may also contain multiple operations centers. The preferred method for using multiple operations centers is to designate one of the operations centers as a master operations center and to designate the remaining operations centers as slave operations centers. In this configuration, the master operations center coordinates various functions among the slave operations centers such as synchronization of simultaneous transmissions and distributes the operations workload efficiently. 
     4. Cable Headend 
     After the operations center  202  has compressed and encoded the program signals and transmitted the signals to the satellite, the cable headend  208  receives and further processes the signals before they are relayed to each set top terminal  220 . Each cable headend site is generally equipped with multiple satellite receiver dishes. Each dish is capable of handling multiple transponder signals from a single satellite and sometimes from multiple satellites. 
     As an intermediary between the set top terminals  220  and the operations center  202  (or other remote site), the cable headend  208  performs two primary functions. First, the cable headend  208  acts as a distribution center, or signal processor, by relaying the program signal to the set top terminal  220  in each subscriber&#39;s home. In addition, the cable headend  208  acts as a network controller  214  by receiving information from each set top terminal  220  and passing such information on to an information gathering site such as the operations center  202 . 
       FIG. 3  shows an embodiment where the cable headend  208  and the subscriber&#39;s home are linked by certain communications media  216 . In this particular embodiment, analog signals, digitally compressed signals, other digital signals and up-stream/interactivity signals are sent and received over the media  216 . The cable headend  208  provides such signaling capabilities in its dual roles as a signal processor  209  and network controller  214 . 
     As a signal processor  209 , the cable headend  208  prepares the program signals that are received by the cable headend  208  for transmission to each set top terminal  220 . In the preferred system, the signal processor  209  re-routes or demultiplexes and recombines the signals and digital information received from the operations center  202  and allocates different portions of the signal to different frequency ranges. Cable headends  208  which offer different subscribers different program offerings may allocate the program signals from the operations center  202  in various manners to accommodate different viewers. The signal processor  209  may also incorporate local programming and/or local advertisements into the program signal and forward the revised signal to the set top terminals  220 . To accommodate this local programming availability, the signal processor  209  must combine the local signal in digital or analog form with the operations center program signals. If the local cable system uses a compression standard that is different than the one used by the operations center  202 , the signal processor  209  must also decompress and recompress incoming signals so they may be properly formatted for transmission to the set top terminals  220 . This process becomes less important as standards develop (i.e., MPEG 2). In addition, the signal processor  209  performs any necessary signal decryption and/or encryption. 
     As a network controller  214 , the cable headend  208  performs the system control functions for the system. The primary function of the network controller  214  is to manage the configuration of the set top terminals  220  and process signals received from the set top terminals  220 . In the preferred embodiment, the network controller  214  monitors, among other things, automatic poll-back responses from the set top terminals  220  remotely located at each subscribers&#39; home. The polling and automatic report-back cycle occurs frequently enough to allow the network controller  214  to maintain accurate account and billing information as well as monitor authorized channel access. In the simplest embodiment, information to be sent to the network controller  214  will be stored in RAM within each subscriber&#39;s set top terminal  220  and will be retrieved only upon polling by the network controller  214 . Retrieval may, for example, occur on a daily, weekly or monthly basis. The network controller  214  allows the system to maintain complete information on all programs watched using a particular set top terminal  220 . 
     The network controller  214  is also able to respond to the immediate needs of a set top terminal  220  by modifying a program control information signal received from the operations center  202 . Therefore, the network controller  214  enables the delivery system to adapt to the specific requirements of individual set top terminals  220  when the requirements cannot be provided to the operations center  202  in advance. In other words, the network controller  214  is able to perform “on the fly programming” changes. With this capability, the network controller  214  can handle sophisticated local programming needs such as, for example, interactive television services, split screen video, and selection of different foreign languages for the same video. In addition, the network controller  214  controls and monitors all compressors and decompressors in the system. 
     The delivery system  200  and digital compression of the preferred embodiment provides a one-way path from the operations center  202  to the cable headend  208 . Status and billing information is sent from the set top terminal  220  to the network controller  214  at the cable headend  208  and not directly to the operations center  202 . Thus, program monitoring and selection control will take place only at the cable headend  208  by the local cable company and its decentralized network controllers  214  (i.e., decentralized relative to the operations center  202 , which is central to the program delivery system  200 ). The local cable company will in turn be in communication with the operations center  202  or a regional control center (not shown) which accumulates return data from the set top terminal  220  for statistical or billing purposes. In alternative system embodiments, the operations center  202  and the statistical and billing sites are collocated. Further, telephone lines with modems are used to transfer information from the set top terminal  220  to the statistical and billing sites. 
     5. Set Top Terminal 
     The set top terminal  220  is the portion of the delivery system  200  that resides in the home of a subscriber. The set top terminal  220  is usually located above or below the subscriber&#39;s television, but it may be placed anywhere in or near the subscriber&#39;s home as long as it is within the range of the subscriber&#39;s remote control device  900 . In some aspects, the set top terminal  220  may resemble converter boxes already used by many cable systems. For instance, each set top terminal  220  may include a variety of error detection, decryption, and coding techniques such as anti-taping encoding. However, it will become apparent from the discussion below that the set top terminal  220  is able to perform many functions that an ordinary converter box cannot perform. 
     The set top terminal  220  has a plurality of input and output ports to enable it to communicate with other local and remote devices. The set top terminal  220  has an input port that receives information from the cable headend  208 . In addition, the unit has at least two output ports which provide communications from the set top terminal  220  to a television and a VCR. Certain menu selections may cause the set top terminal  220  to send control signals directly to the VCR to automatically program or operate the VCR. Also, the set top terminal  220  contains a phone jack which can be used for maintenance, trouble shooting, reprogramming and additional customer features. The set top terminal  220  may also contain stereo/audio output terminals and a satellite dish input port. 
     Functionally, the set top terminal  220  is the last component in the delivery system chain. The set top terminal  220  receives compressed program and control signals from the cable headend  208  (or, in some cases, directly from the operations center  202 ). After the set top terminal  220  receives the individually compressed program and control signals, the signals are demultiplexed, decompressed, converted to analog signals (if necessary) and either placed in local storage (from which the menu template may be created), executed immediately, or sent directly to the television screen. 
     After processing certain signals received from the cable headend  208 , the set top terminal  220  is able to store menu templates for creating menus that are displayed on a subscriber&#39;s television by using an array of menu templates. Before a menu can be constructed, menu templates must be created and sent to the set top terminal  220  for storage. A microprocessor uses the control signals received from the operations center  202  or cable headend  208  to generate the menu templates for storage. Each menu template may be stored in volatile memory in the set top terminal  220 . When the set top terminal receives template information it demultiplexes the program control signals received from the cable headend  208  into four primary parts: video, graphics, program logic and text. Each menu template represents a different portion of a whole menu, such as a menu background, television logo, cursor highlight overlay, or other miscellaneous components needed to build a menu. The menu templates may be deleted or altered using control signals received from the operations center  202  or cable headend  208 . 
     Once the menu templates have been stored in memory, the set top terminal  220  can generate the appropriate menus. In the preferred embodiment, the basic menu format information is stored in memory located within the set top terminal  220  so that the microprocessor may locally access the information from the set top terminal instead of from an incoming signal. The microprocessor next generates the appropriate menus from the menu templates and the other menu information stored in memory. The set top terminal  220  then displays specific menus on the subscriber&#39;s television screen that correspond to the inputs the subscriber selects. 
     If the subscriber selects a specific program from a menu, the set top terminal  220  determines on which channel the program is being shown, demultiplexes and extracts the single channel transmitted from the cable headend  208 . The set top terminal  220  then decompresses the channel and, if necessary, converts the program signal to an analog NTSC signal to enable the subscriber to view the selected program. The set top terminal  220  can be equipped to decompress more than one program signal, but this would unnecessarily add to the cost of the unit since a subscriber will generally only view one program at a time. However, two or three decompressors may be desirable to provide picture-on-picture capability, control signal decompression, enhanced channel switching or like features. 
     In addition to menu information, the set top terminal  220  may also store text transmitted from the cable headend  208  or the operations center  202 . The text may inform the subscriber about upcoming events, billing and account status, new subscriptions, or other relevant information. The text will be stored in an appropriate memory location depending on the frequency and the duration of the use of the textual message. 
     Also, optional upgrades are available to enhance the performance of a subscriber&#39;s set top terminal  220 . These upgrades may consist of a cartridge or computer card (not shown) that is inserted into an expansion slot in the set top terminal  220  or may consist of a feature offered by the cable headend  208  or operations center  202  to which the user may subscribe. Available upgrades may include on line data base services, interactive multi-media services, access to digital radio channels, and other services. 
     In the simplest embodiment, available converter boxes such as those manufactured by General Instruments or Scientific Atlanta, may be modified and upgraded to perform the functions of a set top terminal  220 . The preferred upgrade is a circuit card with a microprocessor which is electronically connected to or inserted into the converter box. 
     6. Remote Control Device 
     The primary conduit for communication between the subscriber and the set top terminal  220  is through the subscriber interface, preferably a remote control device  900 . Through this interface, the subscriber may select desired programming through the system&#39;s menu-driven scheme or by directly accessing a specific channel by entering the actual channel number. Using the interface, the subscriber can navigate through a series of informative program selection menus. By using menu-driven, iconic or alpha-character access, the subscriber can access desired programs by simply pressing a single button rather than recalling from memory and pressing the actual channel number to make a selection. The subscriber can access regular broadcast and basic cable television stations by using either the numeric keys on the remote control  900  (pressing the corresponding channel number), or one of the menu icon selection options. 
     In addition to enabling the subscriber to easily interact with the cable system  200 , the physical characteristics of the subscriber interface  900  should also add to the user friendliness of the system. The remote control  900  should easily fit in the palm of the user&#39;s hand. The buttons of the preferred remote control  900  contain pictorial symbols that are easily identifiable by the subscriber. Also, buttons that perform similar functions may be color coordinated and consist of distinguishing textures to increase the user friendliness of the system. 
     7. Menu-Driven Program Selection 
     The menu-driven scheme provides the subscriber with one-step access to all major menus, ranging from hit movies to sport specials to specialty programs. From any of the major menus, the subscriber can in turn access submenus and minor menus by cursor or alpha-character access. 
     There are two different types of menus utilized by the preferred embodiment, the Program Selection menus and the During Program menus. The first series of menus, Program Selection menus, consists of an Introductory, a Home, Major menus, and Submenus. The second series of menus, During Program menus, consists of two primary types, Hidden menus and the Program Overlay menus. 
     Immediately after the subscriber turns on the set top terminal  220 , the Introductory menu welcomes the subscriber to the system. The Introductory menu may display important announcements from the local cable franchise, advertisements from the cable provider, or other types of messages. In addition, the Introductory menu can inform the subscriber if the cable headend  208  has sent a personal message to the subscriber&#39;s particular set top terminal  220 . 
     After the Introductory menu has been displayed the subscriber may advance to the next level of menus, namely the Home menu. In the preferred embodiment, after a certain period of time, the cable system will advance the subscriber by default to the Home menu. From the Home menu, the subscriber is able to access all of the programming options. The subscriber may either select a program directly by entering the appropriate channel number from the remote control  900 , or the subscriber may sequence through incremental levels of menu options starting from the Home menu. The Home menu lists categories that correspond to the first level of menus called Major menus. 
     If the subscriber chooses to sequence through subsequent menus, the subscriber will be forwarded to the Major menu that corresponds to the chosen category from the Home menu. The Major menus further refine a subscriber&#39;s search and help guide the subscriber to the selection of his choice. 
     From the Major menus, the subscriber may access several submenus. From each submenu, the subscriber may access other submenus until the subscriber finds a desired television program. Similar to the Major menu, each successive level of Submenus further refines the subscriber&#39;s search. The system also enables the subscriber to skip certain menus or submenus and directly access a specific menu or television program by entering the appropriate commands on the remote control  900 . 
     The During program menus (including Hidden Menus and Program Overlay Menus) are displayed by the set top terminal  220  only after the subscriber has selected a television program. In order to avoid disturbing the subscriber, the set top terminal  220  does not display the Hidden Menus until the subscriber selects the appropriate option to display a Hidden Menu. The Hidden Menus contain options that are relevant to the program selected by the viewer. For example, a Hidden Menu may contain options that enable a subscriber to enter an interactive mode or escape from the selected program. 
     Program Overlay Menus are similar to Hidden Menus because they occur during a program and are related to the program being viewed. However, the Program Overlay Menus are displayed concurrently with the program selected by the subscriber. Most Program Overlay Menus are small enough on the screen to allow the subscriber to continue viewing the selected program comfortably. 
     B. Network Controller Description 
     1. Monitoring and Control of Set Top Terminals 
       FIG. 4  shows the network controller  214  of the present invention as part of a digital cable headend  208  operating in an expanded cable television program delivery system, indicated generally at  200 . The network controller  214  monitors program selections at subscribers&#39; homes, maintains accurate account and billing information and authorizes both subscriber channel access and particular set top terminals  220  to operate in the system. 
     The network controller  214  performs its monitoring and control capability by working with other system components housed, in part, within the cable headend  208 . These cable headend components include a cable headend receiver  203  and a signal processor  209 . As shown in the  FIG. 4 , digital RF program signals  205  are received and processed for further distribution to a subscriber&#39;s home through a set top terminal  220 . The program signals  205  are digitally compressed and multiplexed signals that may be processed at the cable headend  208  or simply passed through to the cable distribution network. In the embodiment shown in  FIG. 4 , the program signals  205  are received by the cable headend receiver  203  and transmitted to the signal processor  209 . 
     The signal processor  209  prepares the program signals  205  that are received by the cable headend  208  for transmission to each set top terminal  220 . In the preferred system, the network controller  214  supervises and, in some cases, instructs the signal processor  209  in routing the signals to subscribers. In this way, the network controller  214  and signal processor  209  work with one another to perform basic control functions in the cable television system  200 . Typically, this work is accomplished by the transfer of control information, represented at  211 , between the network controller  214  and the signal processor  209 . 
     Although it is preferred that the signal processor  209  and network controller  214  be co-located at the cable headend  208 , the network controller  214  may be remotely located from the cable headend  208 , as long as it remains in communication with the signal processor  209  in order to exchange control information  211 . 
     In many instances, the program signals  205  received from the operations center  202  must be modified prior to being sent to the set top terminals  220 . These modifications to the program control information  211  are made by the network controller  214  working in conjunction with the signal processor  209  to send a set top terminal control information stream (STTCIS). From the signal processor  209 , the network controller  214  receives the program signals  205 , which include cable franchise specific information added by the operations center  202 . The network controller  214  modifies the program signals  205 , if necessary, and communicates the new information back to the signal processor  209 . The signal processor  209  then forwards the information to the set top terminal  220  in the form of the STTCIS, arrow  215 . In most instances, the network controller  214  will modify the program signals  205  by adding additional information; however, the program signals  205  can be passed through the cable headend  208  to the set top terminal  220  without any modification. 
     The signal processor  209  and network controller  214  are both capable of handling the addition of simple local availabilities (e.g., local advertisements) into the signal sent to the set top terminal  220 . The network controller  214  is also capable of handling more sophisticated local programming needs such as targeting video commercials, infomercials, interactive programming and certain data services. The network controller  214  receives all electronic signals sent by the set top terminal  220 , including those sent in response to interactive service requests and some data service requests. The network controller  214  coordinates the necessary switching and access to allow the subscriber to enjoy these services. 
     The network controller  214  has the capability of performing “on the fly programming” changes, assisting in (i) masking portions of subscriber&#39;s television screens (split screen video), (ii) selecting different audio signals for the same video (foreign languages), and (iii) interactive features. In addition, the network controller can create programming changes. For last minute changes to programming (such as for a local emergency or important regional events), an operator using the network controller  214  can modify the program signals  209  “on the fly” and change menus available to the subscriber. This accommodates short notice changes to program packaging that cannot be handled by the operations center  202  in advance. 
     In order to accommodate split screen techniques for promo and demo video (which will be described later), undesired video portions of the television or menu screen may be masked. The network controller  214  can send the necessary control information to inform the set top terminal  220  to mask portions of a specific channel&#39;s video. For example, a video channel with a split screen showing four separate videos would require a three-fourths mask to focus the viewer on the featured video clip. 
     Tiered programming allows different users to view different video even though they are “tuned” to the same channel. For example, the network controller  214  may know the demographics of its subscribers through a database generated, in part, from prior subscriber choices, an interactive selection, or other means. Using the demographics information, the network controller  214  may target commercials to the correct audience by showing different commercials to subscriber&#39;s with different demographics. Information on programs watched may also be used to target commercials. Even though subscribers will believe they are “tuned” to one channel, they will be switched to a different channel for the tiered video and targeted commercial. Alternatively, individual subscribers may be offered a menu with the option of several commercials from which to choose. 
     To accommodate foreign speaking subscribers, multiple audio channels for television programming may be provided. The subscriber may be shown menus of programs available in the subscriber&#39;s native language. The function of choosing the correct audio to correspond to the selected language may be handled by either the set top terminal  220  or the network controller  214  depending upon the configuration. Local programming in several languages or additional audio channels for a foreign language translation of a popular television program may be provided by the network controller  214 . Using a picture-on-picture feature, sign language may be similarly made available to certain set top terminals  220  for the deaf. The sign language video may be transmitted to the set top terminal  220  on a separate channel. Also, a text overlay for the deaf may be easily produced on the lower part of the screen. The control signals for producing the text overlay may be handled by the network controller  214 . 
     In other embodiments, the network controller  214  can act as a central computer and provide intra-set top terminal interactive games, inter-set top terminal interactive games, computer bulletin board type services, message services (Electronic mail), etc. For example, a subscriber may play war games with six of his (anonymous) fellow subscribers each in their own home each operating a separate tank. The network controller  214  gathers the players using set top terminal  220  communications and acts as the referee. The network controller software “plays” the game and generates the video control signals to be transmitted to the set top terminals  220 . From the video control signals, the set top terminal generates a view of the playing field and shows movement of the tanks. Using a similar method, a bulletin board or message system can be set up to discuss a particular program such as “Twin Peaks Whodunit” for enthusiasts with set top terminals  220 . 
     2. Monitoring and Control of Cable Headend Signal Processor 
       FIG. 5  shows the network controller&#39;s major components and how these components relate with other components of the cable system  200 . The network controller&#39;s internal components include a network controller CPU  224 , databases  226 , control receiver  228 , local memory  230  and telephone modem  232 . The network controller&#39;s CPU  224  and databases  226  may be accessed through an operator control station, which may include peripherals such as a computer workstation, CRT display, and printer, represented by the workstation  234 . 
     Information required to operate the network controller  214  will be stored in databases  226  and local memory  230  (e.g., either in RAM, ROM, or magnetic or optical Read/Write devices) at the cable headend  208  as well as in memory (RAM and/or ROM) within each subscriber&#39;s set top terminal  220 . In the preferred embodiment, two-way communications between the network controller  214  and set top terminal  220  will occur over cable lines. Many other methods of communication, including those which do not require cables or wires, may be used with the present invention. Using two-way communication, interactive television programming can be accommodated through the network controller  214 . In addition, the preferred network controller  214  will be able to access set top terminals  220  via phone lines for trouble shooting, special features or sophisticated reprogramming. 
     The network controller CPU  224  controls the interface, depicted at  211 , between the network controller  214  and the signal processor  209 . This interface  211  allows control information to flow or transfer between the two cable headend  208  components. Standard RS-232 or RS-422 links, an IEEE-488 bus or other interface media may be used. During standard operation, program control information is passed through this interface  211  to the network controller CPU  224  from the signal processor  209  (i.e., the program control information having been sent to the signal processor  209  over satellite from the operations center  202  with the RF program signals  205 , not shown in  FIG. 5 ). The network controller CPU  224  processes the program control information based on data stored in the network control databases. This processing includes modifying the program control information to accommodate regional programming needs. 
     After processing, the network controller CPU  224  passes the program control information, including any modifications, back to the signal processor  209  for distribution over the cable system  200 , via the cable distribution network  236 . In this fashion, the network controller  214  provides programming and network control instructions to the set top terminals  220  through the signal processor  209 . 
     The processing of program control information by the network controller CPU  224  can also make use of any data received by the network controller&#39;s control receiver  228 . The control receiver  228  is a microprocessor-based device that receives “status reports” directly from the set top terminals  220 . The status reports received by the control receiver  228  generally include information that allows the network controller  214  to track, among other things, a subscriber&#39;s program access history, as described below. The control receiver  228  can store the status reports internally in a local storage or memory device and transfer them to the network controller CPU  224 . Typically, the control receiver  228  is interfaced with the network controller CPU  224  using standard RS-232 or RS-422 links, an IEEE-488 bus or the like. 
     In the preferred embodiment, the network controller CPU  224  scans the control receiver  228  at a predetermined rate (e.g., once every few seconds) to initiate the status report transfer. Upon transfer, the network controller CPU  224  adds the data and control information in the status reports to the network control databases  226  by: checking for changes in previously received status information, processing the new information and updating the corresponding parameters in the network control databases  226 . The network controller  214  processes the information stored in its databases with any program control information relayed through the signal processor  209  from the delivery system&#39;s operations center  202 . This processing capability allows the network controller  214  to modify prior control signals and create new ones. The network controller  214  transfers both modified and unmodified control signals, along with any local combined program signals  205 , to the signal processor  209  to be combined with others program signals  205  for distribution over the cable system  200 . 
     3. Modifying the Program Control Information Signal 
     Tables A-C, described below, provide an example of some information that can be sent in the program control information signal to the set top terminals  220 . The program control information signal generated by the operations center  202  provides data on the scheduling and description of programs. The program control information signal may be sent through the network controller  214  or, in an alternate configuration, directly to the set top terminal  220  for display to the subscriber. In the preferred embodiment, the program control information signal is stored and modified by the network controller  214  and sent to the set top terminal  220  in the form of a set top terminal control information stream (STTCIS). This configuration can accommodate, among other things, differences in individual cable systems and possible differences in set top terminal  220  devices. 
     The set top terminal  220  integrates either the program control signal or the set top terminal control information stream together with data stored in the memory of the set top terminal  220 , to generate on-screen menu displays for assisting the subscriber in choosing programs for viewing. (Throughout the description the term “program control information” is being used to indicate control information coming from the cable headend  208  to the set top terminal  220 , whether it is sent directly from the operations center  202 , processed by the network controller  214  and then forwarded to the set top box (STTCIS), or transmitted over telephone lines.) 
     The types of information that can be sent using the program control signal includes: number of program categories, names of program categories, what channels are assigned to a specific category (such as specialty channels), names of channels, names of programs on each channel, program start times, length of programs, description of programs, menu assignment for each program, pricing, whether there is a sample video clip for advertisement for the program, and any other program, menu or product information. In addition, the program control information signal may be used periodically to reprogram or reconfigure a set top terminal  220  or group of set top terminals  220  (described in detail in co-pending patent application Ser. No. 08/160,281, now issued U.S. Pat. No. 5,798,785 entitled, REPROGRAMMABLE TERMINAL FOR SUGGESTING PROGRAMS OFFERED ON A TELEVISION PROGRAM DELIVERY SYSTEM, filed by the same assignee incorporated herein by reference). 
     The goal of the menu driven program selection system  200  used with the present invention is to allow the subscriber to choose a program by touring through a series of menus utilizing a remote control  900  ( FIG. 3 ) or similar device providing cursor movement. The final choice in the series of menus will identify one particular channel and one time for activation of that channel. Armed with a channel and activation time, the set top terminal  220  can display the selected program on the television for the viewer. To achieve this goal one embodiment of the present invention assigns an intelligent alpha-numeric code to each program. This alpha-numeric code identifies the category of the program, the menu in which the program should be displayed, its transmission time(s), and the position on the menu that the program should be displayed. 
     In this embodiment, the program control information, including menu codes, is sent continuously from the operations center  202  to the network controller  214 , and ultimately to the set top terminal  220 . For example, four hours worth of programming information can be sent via the program control information signal continuously using the information shown in Tables A-C. 
     Table A shows the basic programming information that may be sent to the set top terminal  220 . The program descriptions shown are coded abbreviations. For example, C for comedy, N for news, S for sports, A for cartoons, and TX for text. If there is a textual description for a program, such as a movie, the description may be given following that program&#39;s coded description or may be communicated following the four hours&#39; worth of programming information. As is shown in the coded listing, program descriptions for programs greater than a half hour in length need not be repeated (each half hour). The video description code informs the set top terminal  220  of whether there is still or live video available to advertise the program. 
     For example, a sporting program may be assigned a code of B35-010194-1600-3.25-Michigan St. vs. USC. The letter B would assign the program to category B, sports. The second alpha-numeric character number 3 would assign the program to the third menu of the sports category. The third character of the code, number 5, assigns the program to the fifth program slot on the third menu. The next six characters, Jan. 1, 1994, represent the date. The following four characters, 1600 represent the start time which is followed by the length of the program and the program name. This entry represents a sports show, a college football game, which will be aired at 4:00 PM on New Years day 1994. 
     
       
         
           
               
               
               
               
               
               
             
               
                 TABLE A 
               
               
                   
               
               
                   
                   
                 *Program 
                   
                   
                   
               
               
                   
                 *Program Name 
                 Length 
                 *Menu code 
                 *Description 
                 *Video 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 12:00 PM 
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 Cheers 
                 .5 
                 E24 
                 C 
                 N 
               
               
                 2 
                 Terminator 
                 2.0 
                 A33 
                 Tx 
                 S 
               
               
                 3 
                 Prime Time 
                 1.0 
                 D14 
                 N 
                 N 
               
               
                 4 
                 Football Special 
                 .5 
                 B24 
                 S 
                 N 
               
               
                 • 
               
               
                 • 
               
               
                 • 
               
               
                 • 
               
            
           
           
               
            
               
                 12:30 PM 
               
            
           
           
               
               
               
               
               
               
            
               
                 1 
                 Simpsons 
                 .5 
                 E14 &amp; C13 
                 C 
                 S 
               
               
                 4 
                 Football Game 
                 3.0 
                 B13 
                 S 
                 N 
               
               
                 • 
               
               
                 • 
               
               
                 • 
               
               
                   
               
            
           
         
       
     
     In the 12:30 Channel 1 entry of Table A, two menu codes are shown. By allowing two menu codes, programs that may fit under two different category descriptions may be shown in both menus to the subscriber. With this minimal amount of information being communicated to the set top terminal  220  on a regular basis, the terminal is able to determine the proper menu location for each program and the proper time and channel to activate for the subscriber after his menu selection. 
     Table B shows an example Events Table that may be downloaded to a set top terminal  220  using the Event Data file, which contains information about events and pricing. As shown in the table, the three columns of the Events Table identify the field number, the field itself and the type of information downloaded in the Event Data file. The first column contains the field numbers 1 through 11. The middle column contains the corresponding field parameters, including the event type, event ID, global channel ID, price, start time, end time, start date, end date, P-icon, name and description. The third column contains corresponding field type information. As shown in this field type information typically consists of an unsigned integer; hours, minutes and seconds; months, day and year; and ASCII character identifier. 
     
       
         
           
               
               
               
             
               
                 TABLE B 
               
               
                   
               
               
                 Field # 
                 Field 
                 Type 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 1 
                 Event Type 
                 Unsigned Int 
               
               
                   
                 1 = YCTV ™ 
               
               
                   
                 2 = Pay-per-view 
               
               
                   
                 3 = Reg. TV 
               
               
                 2 
                 Event ID 
                 Unsigned Int 
               
               
                 3 
                 Global Channel ID 
                 Unsigned Int 
               
               
                 4 
                 Price (in Cents) 
                 Unsigned Int 
               
               
                 5 
                 Start Time 
                 HH:MM:SS 
               
               
                 6 
                 End Time 
                 HH:MM:SS 
               
               
                 7 
                 Start Date 
                 MM/DD/YY 
               
               
                 8 
                 End Date 
                 MM/DD/YY 
               
               
                 9 
                 P-Icon 
                 ASCIIZ 
               
               
                 10 
                 Name 
                 ASCIIZ 
               
               
                 11 
                 Description 
                 ASCIIZ 
               
               
                   
               
            
           
         
       
     
     Table C shows an example Event Data file. In particular, Table C shows two data streams corresponding to two event types. The first data stream identifies a YCTV™ event in the first field. The second field designates the event ID, which is 1234 in this example. The third field includes the global channel ID number two. The fourth field indicates the cost of 50 cents for this event. The fifth and sixth fields indicate the respective start and end times of 3:00 a.m. to 3:00 p.m., respectively. The seventh and eighth fields show the corresponding start and end date, designated as Aug. 25, 1993 and Aug. 27, 1993, respectively. Field nine indicates the P icon set to PBS.PCX graphics file. Finally, fields ten and eleven indicate the name and description of the event selected, which in this case is Sesame Street and Barney. The second data stream in the Event.Dat example shown in Table C includes analogous information for Terminator IV, which is designated in field one as a pay-per-view event. 
     
       
         
           
               
             
               
                 TABLE C 
               
               
                   
               
               
                 Event Data Example 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
            
               
                 1{grave over ( )}1234{grave over ( )}2{grave over ( )}50{grave over ( )}03:00:00{grave over ( )}15:00:00{grave over ( )}08/25/93{grave over ( )}08/27/93{grave over ( )}pbs.pcx{grave over ( )}Sesame 
               
               
                 Street &amp; Barney&#39;s Sesame Street and Barney Abstract 
               
               
                 2{grave over ( )}1234{grave over ( )}2{grave over ( )}50{grave over ( )}20:00:00{grave over ( )}22:00:00{grave over ( )}08/25/93{grave over ( )}08/25/93{grave over ( )}t4.pcx{grave over ( )}Terminator 
               
               
                 4{grave over ( )}Terminator 4 Abstract 
               
               
                   
               
            
           
         
       
     
     The program control information signal and STTCIS can be formatted in a variety of ways and the on-screen menus can be produced using different methods. For instance, if the program control information signal carries no menu format information, the menu format for creating the menus can be fixed in ROM at the set top terminal  220 . This method allows the program control information signal to carry less information but has the least flexibility since the menu formats cannot be changed without physically swapping the ROM holding the menu format information. 
     In the preferred embodiment, the menu format information is stored at the set top terminal  220  in temporary memory, either in a RAM or EPROM. This configuration provides the desired flexibility in the menu format while still limiting the amount of information needed to be communicated through the program control information signal. New menu format information would be sent using the program control information signal or the STTCIS to the set top terminals  220  each time there was a change to a menu. 
     In the simplest embodiment, the menus remain fixed and only the text changes. Thus, the program control information signal can be limited to primarily text and a text generator can be employed in the set top terminal  220 . This simple embodiment keeps the cost of the set top terminal  220  low and limits the bandwidth necessary for the program control information. Another simple embodiment uses a separate channel full-time (large bandwidth) just for the menu information. 
     4. Processing the Program Control Information Signal 
       FIGS. 6   a  and  6   b  show a more detailed schematic of the components of the cable headend  208 , focusing on the interplay between the network controller  214  and the signal processor&#39;s  209  major hardware components. The network controller  214  uses, among other components, the signal processor  209  to implement its monitoring and control capabilities. Although the network controller  214  of the present invention will work with nearly any cable headend signal processing equipment, it is preferred that the signal processing equipment be modern equipment capable of handling digitally compressed video. 
       FIG. 6   a  depicts an embodiment of the basic signal processing capabilities of the cable headend  208  and shows connections to components of the network controller  214 . As shown in the figure, RF cable signals  205  are received at the headend  208  through a bank of integrated receiver demodulators (IRDs)  240 . Each IRD  240  includes customary RF processing equipment, including a low noise amplifier, a demodulator and other filtering devices (not shown). As each RF feed is fed through the individual IRDs  240 , the signals are manipulated and transferred to the demultiplexer and other signal processing equipment for further processing. The demultiplexer  242  splits each cable TV signal into its respective video and audio signal components. In addition, the demultiplexer  242  extracts data from the cable television signals and inputs such data to the control CPU  244 . 
     The control CPU  244  exchanges control information with the network controller  214 , as shown at  211 . This control information is exchanged between the signal processor&#39;s control CPU  244  and the network controller CPU  224 . In particular, the network controller  214  and signal processor  209  pass control information through the interface linking the two CPUs in order to perform any modifications to the program control information signal. The network controller CPU  224  oversees such modifications, accessing various network control databases  226  for guidance in instructing the signal processor&#39;s control CPU  244 . The instructions provided by the network controller  214  in turn guide the signal processor  209  in combining and/or adding programming signals and advertisements for transmission to the set top terminals  220 . 
     The local insertion component  246  of the signal processor  209  allows the control CPU  244  to execute the instructions received from the network controller  214  and insert any local programming and advertisements. Once such regional programming and advertisements have been inserted, the local insertion component  246  passes the various signals to a multiplexer  248  that combines the various programming and advertising signals. The output of the multiplexer  248  is transferred to RF modulator  250  that disseminates the composite video and audio signals to the set top terminals  220 . The data extracted from the cable television signals by the demultiplexer  242 , which is also sent to the control CPU  244 , is transmitted to the set top terminal  220  using a separate RF modulator  252 . 
     The network controller  214  accommodates two-way RF data communications with the set top terminals  220 . Upstream data transmissions from the set top terminals  220  are received by the network controller&#39;s control receiver  228 . These upstream data transmission capabilities are described in detail below. 
       FIG. 6   b  diagrams another embodiment of a basic cable headend  208  having a network controller  214  and more sophisticated signal processing equipment. Again, RF cable television signals  205  are fed into a bank of IRDs  240  as described above. These signals  205  are demultiplexed into individual video and audio signal components, with data being extracted and sent to the control CPU  244 . The individual video and audio signal components are fed into a digital logic circuit  256  that is flexible enough to select individual video and audio signals for repackaging. The network controller  214  oversees such repackaging by: (i) receiving the program control information from the control CPU  244 , (ii) modifying or manipulating the signal as necessary, and (iii) transferring the modified program control information signal back to the control CPU  244 . 
     With instructions from the network controller  214 , the control CPU  244  may insert local avails into the digital logic system  256  and execute the various selections of individual video and audio signals for subsequent transmission to the set top terminals  220 . Once individual video and audio signals have been selected and all local insertions have been made, the outputs of the digital logic circuitry  256  are transferred to a serializer  258  which recombines all the signals into a serialized format. The serially-formatted signals are in turn transferred to RF modulators  250  for distribution over the cable network  200 . The selection and recombining components of the signal processing equipment are described in greater detail in a co-pending patent application Ser. No. 08/160,283, now issued U.S. Pat. No. 5,682,195, entitled DIGITAL CABLE HEADEND FOR CABLE TELEVISION DELIVERY SYSTEM, incorporated herein by reference; however, such sophisticated combining circuitry is not necessary for the operation of the network controller  214 . Rather, a simpler signal processing system may readily be used. 
     In the embodiments diagrammed in  FIGS. 6   a  and  6   b , the signal processor  209  may, acting alone or in conjunction with control instructions from the network controller  214 , incorporate local programming and/or local advertisements into the program signals and forward the revised signal to the set top terminals  220 . To accommodate this local programming availability, the signal processor  209  must combine the local signal in digital or analog form with the program signals  205  received from operations center  202 . If a local cable system  200  uses a compression algorithm or standard that is different than the one used by the operations center  202 , the signal processor  209  must also decompress and recompress incoming signals so they may be properly formatted for transmission to the set top terminals  220 . In addition, the signal processor  209  performs any necessary signal decryption and/or encryption. 
       FIG. 7  diagrams an alternative embodiment of a digital/analog cable headend  208 . In particular, this embodiment includes decompression and recompression capabilities, showing the types of signal processing components that the network controller  214  may control. As shown in  FIG. 7 , the cable headend  208  receiver front-end, indicated at  260 , demodulates the received transponder signals  205 , which may contain four, six, eight or more audio/video channels of information, into a digital bit stream of multiplexed digitized MPEG or MPEG 2 format video. The signal processor  209  receives the multiplexed signals and initially performs any demultiplexing required to process the received signals. The demultiplexers  242  separate the multiplexed signals into separate individual MPEG or MPEG 2 format digital channels. Depending on the transponder signal received, the demultiplexer  242  may have four, six, eight or more cross connects to the combiner  264 . The outputs of the demultiplexers  242  are selectively enabled by the control CPU  244 . Those outputs of the multiplexer  248  that are enabled are then input to the combiner. 
     Decrypting may be necessary and can be conducted by a separate decrypting device  262  included as part of the signal processor&#39;s internal components. The signal processor&#39;s control CPU  244  may be controlled by a remote site (such as a national site) via a modem or similar connection  266 . Therefore, the remote site is able to control the output of the demultiplexers  242 . Alternatively, instead of enabling the outputs of the demultiplexers  242 , the inputs of the combiner  264  may be selected by the control CPU  244 . By enabling or selecting multiplexer  248  outputs, the control CPU  244  is able to control which television programs are combined and transmitted to the viewers. 
     The combiner  264  combines the enabled or selected outputs of the demultiplexers  242  into the proper format and outputs the signals through a compressor  268 , and an encryptor  270  (if desired), to a digital modulator  272 . The modulator  272  outputs a modulated RF carrier combined with other carriers onto the cable distribution network  236 . The set top converter terminals  220  in subscribers&#39; homes select and demodulate a particular channel selected by the user. As selections are made, the set top terminal  220  stores the programs accessed in its local storage for later transmission to the network controller  214  at the cable headend  208 . 
     5. Changing Menu Content by Modifying the Program Control Information Signal 
       FIGS. 8   a  through  8   c  are sample menu screens produced by a set top terminal  220  using the program control information signal.  FIG. 8   a  shows a menu which enables the viewer to select a program category from among a choice of eight program categories  1048 .  FIG. 8   b  shows a menu  1050  for the viewer to select a hit movie from among ten hit movies  1052 .  FIG. 8   c  depicts a menu  1054  which provides information about a movie and enables a viewer to order the movie for viewing. 
       FIGS. 8   a  through  8   c  show text generated by a set top terminal  220 . This text is generated using information received via the program control information signal by a text generator (not shown) in the set top terminal unit  220 . Those portions of the text that generally remain unchanged for a period of weeks or months may be stored in EEPROM or other local storage. For example, the text “HIT MOVIES from”  1056  will consistently appear on each hit movies&#39; major menu. This text may be stored on EEPROM or other local storage. Further, text such as that which appears at the lower center part of the screen “PRESS HERE TO RETURN TO CABLE TV”  1058  appears many times throughout the menu sequence. This text may also be stored locally at the set top terminal  220 . 
     Text which changes on a regular basis, such as the movie titles  1052  (or other program selections), will be transmitted to the set top terminal  220  by either the operations center  202  or the cable headend  208 . In this manner, the cable headend  208  may change the program selections available on any menu by modifying the program control information signal sent by the operations center  202  and transmitting the change. 
     It is preferred that the text, e.g.,  1048 ,  1052 ,  1056 , etc., be generated by the set top terminal  220  separately from the graphics because the text can be stored locally in a more compact manner requiring less storage space at the set top terminal  220 . In addition, it allows for easy communication of text changes from the operations center  202  or cable headend  208  to the set top terminal  220 . 
       FIGS. 8   a  through  8   c  show the use of day, date and time information  1060  on menus. This information may be obtained in a variety of ways. The day, date, and time information  1060  may be sent from the operations center  202 , the cable headend  208  (signal processor  209  or network controller  214 ), the uplink site  204 , or generated by the set top terminal unit  220  internally. Each manner of generating the day, date, and time information  1060  has advantages and disadvantages which may change given the particular embodiment and costs. 
     In the preferred embodiment, the day, date, and time  1060  are generated at a central location such as the operations center  202  and are adjusted for regional changes in time at the cable headend  208 . In particular, the network controller  214  modifies the PCI signal to accommodate regional day, date and time information and changes and additions in regional programming and advertisements. These modifications are automatically processed by the network controller CPU  224  upon initiation of the Modifying PCI software routine, as described below. In an alternate embodiment, the network controller&#39;s control station operator can manually enter programming, advertising and menu modifications. 
     6. Receiving Information from Set top Terminals 
     The network controller  214  is equipped to receive information from the set top terminals  220  on a regular or random basis.  FIGS. 9   a  and  9   b  diagram separate embodiments for upstream data transmission for a digital/analog cable headend  208 . In particular,  FIG. 9   a  diagrams an out-of-band two-way data transmission system  280  wherein satellite feeds  282  are received at the cable headend  208  by a number of satellite receivers  284  and digital signal processing equipment  286 . The satellite receivers  284  are used for analog transmissions and the digital signal processing equipment  286  is used to process digital programming signals. The analog signal paths allow analog cable television programming signals to be received by the set of satellite receivers  284  and to be passed to a series of modulators and scramblers  288  the output of the modulators and scramblers  288  is sent to an RF combiner  290 . 
     A data transmitter (Data Tx)  292  makes use of the control information transferred to the signal processing equipment from the network controller  214 . This data transmitter inserts data into the RF combiner  290 . Through the use of a separate data transmitter, any downstream data transmissions may be sent to a set top terminal  220  on an out-of-band frequency (i.e., out of the frequency band used for video signal transmissions). 
     Digital signals are also input to the RF combiner  290  from the digital signal processing equipment  286 . These digital signals are typically assigned to separate frequency bands. Once the data, analog and digital signals have been combined using the RF combiner  290 , the composite signals are further processed at the cable headend  208  for distribution over the cable network. This further processing involves using a diplex filter  294  that accommodates two-way RF communications over the cable distribution network. 
     The diplex filter  294  requires that the various sets of signals be translated to different frequency bands. Typically, services to the home are sent in a downstream band, which begins at 54 MHz and extends today to typically 550 MHz. Other systems that use a maximum frequency less than or greater than 550 MHz, however, may readily be accommodated by the embodiment shown in  FIG. 9   a . Downstream services may include TV channels, FM radio, digital/audio signals and various control and information data streams. 
     Upstream transmissions from the set top terminal  220  are typically sent in the frequency band between 5 and 50 MHz. Other frequency limits may, however, be employed in special cases. For example, the industry is currently experiencing movement toward using 5 to 42 MHz for upstream services. 
     Although the diplex filter  294  is not an inherently bi-directional device, it may be made bi-directional by splitting the spectrum between downstream and upstream signals, as described above. The diplex filter  294  effectively becomes bi-directional by passing high-band signals in the downstream direction and passing low-band signals in the upstream direction. For downstream transmission capability, all signals in the high-band of 50 to 550 MHz are passed to a fiber/coax translation point, indicated generally at  300 . 
     At the fiber/coax translation point  300 , optical energy is relayed to the various optical nodes  304 . This distribution of optical energy typically involves splitting the optical energy among the nodes  304  and transporting the energy downstream on one or more downstream fibers. In addition, electrical energy signals are sent over coaxial cables, through a series of amplifiers  306  along the cable for distribution to individual subscribers. Individual subscribers simply tap into the amplifiers along the coaxial cable in order to receive programming and downstream data signals. 
     Upstream data transmission are sent to the cable headend  208  from each optical node  300  over fiber and input into the cable headend&#39;s RF combiner  308 . Upstream transmissions over cable are accommodated using carrier frequencies in the lower frequency band. These upstream data transmissions over the coaxial cable are passed through the diplex filter  294 , which filters out all high-band frequencies and passes all low-band frequencies. Subsequently, the diplex filter  294  transfers such low-band frequencies to the RF combiner  308 . The RF combiner  308  combines all upstream data transmissions from the set top terminals  220  and inputs these combined data signals into the network controller  214  for later processing. 
       FIG. 9   b  shows an alternative embodiment to  FIG. 9   a . In particular,  FIG. 9   b  shows the same overall configuration as the embodiment above (and is commonly numbered) although downstream data transmissions from headend  208  to the set top terminals  220  are accomplished through in-band two-way data transmission. Thus, the primary difference between the diagrams shown in  FIGS. 9   a  and  9   b  is that the latter embodiment uses a method of inserting data into the downstream programming signals themselves for distribution to the set top terminals  220  in the cable network. 
     Basically, the data placed on the programming signals using a set of data inserters  312  that are electrically connected to each modulator and scrambler component  288 . In this way, data can be inserted in-band along with video and audio signals, thereby modulating the data on the same respective carrier frequencies used by the video and audio signals. The inserted data is thus combined with video and audio signals and input into the RF combiner  290  for downstream distribution. As described above, digital signals are also combined using the RF combiner  290  and disseminated over the cable network. Upstream transmissions are accomplished as described above in conjunction with the discussion for  FIG. 9   a.    
     Upstream information received from the set top terminals  220  typically includes, for example, program access data gathered at each set top terminal  220 . Such information may be communicated to the network controller  214  through a variety of methods including any of the following methods: (1) cyclic polling, (2) random access, and (3) telephone modems. Cyclic polling and random access methods make use of the two-way RF system diagrammed in  FIGS. 9   a  and  9   b , described above. 
     As described below, the preferred embodiment employs a cyclic polling method. Although various polling schemes will work with the present invention, a roll-call polling scheme is preferred over other schemes such as hub polling or token-passing since roll-call polling provides the greatest degree of centralized control. 
     Using this preferred method, program access information is stored at each set top terminal  220  until it is polled by the network controller  214  for information retrieval using a polling request message format  920  as shown in  FIG. 10   a . This frame format  920  may include such program control information as shown in Tables A-C above, typically consisting of six fields: (1) a leading flag  922  at the beginning of the message, (2) an address field  924 , (3) a subscriber region designation  926 , (4) a set top terminal identifier  928  that includes a polling command/response (or P/F) bit  930 , (5) an information field  932 , and (6) a trailing flag  934  at the end of the message. 
     The eight-bit flag sequence that appears at the beginning and end of a frame,  922  and  934 , respectively, is used to establish and maintain synchronization. Such a sequence typically consists of a “01111110” bit-stream. The address field  924  designates a 4-bit address for a given set top terminal  220 . The subscriber region designation  926  is a 4-bit field that indicates the geographical region in which the subscriber&#39;s set top terminal  220  is housed. The set top terminal identifier  928  is a 16-bit field that uniquely identifies each set top terminal  220  with 15-bit designation followed by an appended P/F bit  930 . Although field size is provided by this example, a variety of sizes can be used with the present invention. 
     The P/F bit  930  is used to command a polling response from the set top terminal  220  addressed, as described below. The frame format  920  also provides a variable-length information field  932  for other data transmissions, such as information on system updates. The frame format  920  ends with an 8-bit flag  934  (or trailing flag) that is identical in format to the leading flag  922 , as set forth above. Other frame formats will be apparent to one skilled in the art and can be easily adapted for use with the system. 
     Using any such polling request message format  920 , the network controller  214  interrogates each set top terminal  220  sequentially, one by one. In this type of access strategy, the network controller  214  is designated as the central controller of the cable distribution network  200  and is responsible for control of the communications links between itself and the set top terminals  220 . This control includes issuing commands to the set top terminals  220  and receiving responses back from the set top terminals  220 . 
     Basically, the network controller  214  instructs the signal processor  209  to transmit to each set top terminal  220  a polling request, which asks whether a set top terminal  220  has any information to transmit. The set top terminals  220  are identified by the unique address and set top terminal identifier  928 . It is preferred that the set top terminal  220  transmit information and messages to the network controller  214  only when given permission by the network controller  214  to do so. 
     Where, for example, specialty programs have been accessed since the previous poll, the set top terminal  220  is given permission to transmit a polling response in the form of a status report that includes any such access information. The network controller&#39;s control receiver  228  is tasked with the receipt of set top terminal  220  polling responses or status reports. These status reports generally include information that allows the network controller  214  to track a subscriber&#39;s program access history. As described above, the control receiver can store the status reports locally and/or transfer them to the network controller CPU  224 . 
     The network controller CPU  224  immediately processes each polling response as it is received from each set top terminal  220 . The network controller CPU  224  updates pertinent databases  226  with the received information, and then sends another polling request to the next set top terminal  220  on its list. A set top terminal  220  with no information to transmit so indicates in a reply to the network controller  214 . Once all set top terminals  220  have been given permission to transmit status reports, a cycle is complete and a new cycle begins. 
     Through a polling cycle, the network controller  214  acquires the information needed to operate the system  200 . During the cycle, the network controller  214  sends signals to the set top terminals  220  to authorize both their operation and access to specific channels. If, for example, a subscriber has failed to pay a recent bill, the network controller  214  can deauthorize the subscriber&#39;s set top terminal  220 . Likewise, when a subscriber orders a program or channel, the network controller  214  checks the subscriber&#39;s account for good standing by reading the proper database file. After the check, the network controller  214  then either authorizes or deauthorizes access by the set top terminal  220  using the data transmitted in a modified program control information signal. As a result, the cycle requires a series of requests and responses to operate. 
       FIG. 10   b  shows an example frame format  920 ′ for the status reports received from the set top terminals  220  during the polling cycle. This frame format is substantially identical to the polling request message format  920  ( FIG. 10   a ), and includes: (1) a leading flag at the beginning of the message, (2) an address field, (3) a subscriber region designation, (4) a set top terminal identifier that includes a polling command/response (or P/F) bit, (5) an information field, and (6) a trailing flag at the end of the message, each designated by a common number with respect to  FIG. 10   a , but with the prime indicator (′) added. 
     Again, the information field  932 ′ remains variable in length so that the status of an indeterminate number of programs accessed, as represented at  933 ′, can be included in the frame. In this way, the control message length of the polling request message is minimal since the network controller  214  does not transmit such access information. After a polling response by a given set top terminal  220 , however, the control message length increases in proportion to the number of programs accessed. 
     During transmission, the P/F bit  930 ,  930 ′ is used to carry out the polling function. In particular, the P/F bit  930  is set to a “1” position to command a polling response from the set top terminal  220  whose address is identified in the frame  928 . The set top terminal  220  addressed must respond to the command with the same P/F bit  930 ′ also set to the “1” position. The response will include the number of programs accessed and their corresponding event identification numbers as shown in  FIG. 10   b  at  933 ′. In cases where the set top terminal  220  has not accessed any programs since the previous polling cycle, the set top terminal  220  responds with the P/F bit  930 ′ set to “1” and the programs access block denoting zero programs accessed. 
     The second method for the network controller  214  to receive information from the set top terminals  220  is through the use of a random access scheme. In an alternate embodiment that uses this method, individual set top terminals  220  can send control-related messages to the network controller  214  without being polled. This scheme is particularly useful in networks where subscriber regions include potentially large numbers of subscribers. High concentrations of subscribers may be found, for example, in large metropolitan areas. In such cases, the polling cycle can be replaced with a more sophisticated random access strategy such as carrier-sense multiple access with collision detection (CSMA/CD). In this scheme, each set top terminal  220  must “listen” before it transmits and then does so only if it senses an idle medium. When the return link to the network controller  214  is silent, a given set top terminal  220  can transmit its messages. Any messages sent from a set top terminal  220  to the network controller  214  would set the P/F bit  930 ′ to a “0” position to indicate that the message is not in response to any command or polling request. In addition to CSMA/CD, other random access schemes can be used with the system, such as CDSL. 
     The third method for the network controller  214  to receive information from the set top terminals  220  is through the use of telephone modems. In an alternate embodiment, the set top terminals  220  communicate program access information and orders to the network controller  214  using telephone modems. In this embodiment, the set top terminals  220  are equipped with a modem port to facilitate such operation. Thus, communications between a given set top terminal  220  and the network controller  214  can be established over telephone lines when cable traffic or other primary traffic is congested. The preferred method of using telephone modems is in combination with a control or “hit” signal from the network controller  214 . A group (or region) of set top terminals  220  is “hit” simultaneously by the network controller  214  via the cable. Only those set top terminals  220  within the group that have data for the network controller  214  call the network controller  214  by modem. The network controller  214  is equipped with a bank of modems (organized to roll-over telephone calls) to answer the incoming calls. 
     Among the three methods discussed for the network controller  214  to receive information from the set top terminals  220 , the use of the cyclic polling scheme depicted in  FIGS. 10   a  and  10   b , is preferred. Polling is preferred because it allows the network controller  214  to conduct and control communications with set top terminals  220  over the cable network in an orderly fashion. In particular, the network controller  214  can schedule data retrieval by polling the set top terminals  220  one by one. A random access method, on the other hand, does not allow the network controller  214  to maintain such orderly communications. Instead, the network controller  214  receives data from the set top terminals  220  at random, depending on when the cable medium is idle. This random reception of data lessens the degree of control that the network controller  214  has over set top terminal transmissions. Likewise, the third method, which uses telephone modems, is less desirable than the polling method since the use of modems does not allow for upstream interactivity over the cable medium. 
     7. Processing Information Received from Set top Terminals 
     Regardless of the scheme used by the set top terminals  220  to access the network controller  214 , any polling responses and upstream interactivity is received by the network controller&#39;s control receiver  228  as shown in  FIG. 11 , depicting the components of the control receiver  228 , which includes a demodulator  310  and demultiplexer  313  to demodulate and demultiplex transmissions received from any set top terminal  220  in the cable distribution network  200 . As described above, the control receiver  228  transfers, through a control buffer  315 , the received information to the network controller CPU  224  for processing. 
     Processing is accomplished by the network controller CPU  224 . Operator instructions are input to the network controller CPU  224  through the operator control station  234  that includes, for example, a computer/workstation with a CRT display, printer and other peripherals. Multiple operator control stations  234  can be used to assist in control operations. 
     Regional operator control stations (not specifically shown, but substantially identical to stations  234 ) may be used and may include multiple operator control stations each assigned to a particular subscriber region corresponding to a geographic region where set top terminals  220  are located. Thus, each regional operator control station is assigned to a subscriber region, providing monitoring and control capabilities over such regions. All regional program control information is transferred to the network controller CPU  224  for processing, as in the case where a single control station  234  is used. Likewise, during this processing, portions of the network control databases  226  may also be updated. 
     No set number of databases  226  are required for the network controller  214  to perform its operations, and a single temporary database may be used. In the preferred embodiment, however, the network controller  214  uses several databases (indicated at  226 ) that are accessed during network control operations. These databases  226  are identified in  FIG. 11  and include: (1) the Viewer Profile database  314 , (2) the Account/Billing database  316 , (3) the Program Library database  318 , (4) the Program Scheduling database  320 , (5) the Advertisement Library database  322 , and (6) the Advertisement Scheduling database  324 . 
       FIG. 12  shows one example of a network controller&#39;s basic database structure including the databases identified in the preceding paragraph. The data stored in these databases is not simply raw data. Rather data may be processed, correlated and appropriately indexed to create a true relational database  226 . 
     As shown in  FIG. 12 , the Viewer Profile database  314  includes: (i) a Set top ID File, (ii) a Subscriber Region File, (iii) a Customer ID File and (iv) a Viewer Log File, the latter three files being indicated generally as a file group  332 . The Set top ID File  330 , common to each of the databases comprising the network controller&#39;s database  226 , contains set top converter records with each record representing a unique set top terminal  220 . Examples of information stored in this file includes set top terminal type, software version and set top terminal identification/serial number. The Set top ID File  330  contains the key data that links each relational database with one another, as described below. 
     The Subscriber Region File, part of file group  332 , includes information such as headend  208  assignment, regional operator control workstation assignment and a designation for the subscriber&#39;s geographical area. The Customer ID and Viewer Log Files, part of file group  332 , include the subscriber&#39;s personal information, such as name, address and telephone number, and information on the subscriptions to cable services for each customer as well as a personal profile for each viewer, respectively. 
     The personal profile consists of demographic information that may be gathered in a number of ways. The set top terminal  220  builds the personal profile for each viewer and stores the information in a memory file by viewer name. To build a personal profile in the preferred system, the viewer answers a series of questions presented on a series of menu screens. These personal profile screens request the viewer to input information such as name, sex, age, place of birth, place of lower school education, employment type, level of education, amount of television program viewing per week, and the number of shows in particular categories that the viewer watches in a given week such as, sports, movies, documentaries, sitcoms, etc. Any demographic information which will assist the set top terminal  220  in targeting advertisements to the viewer may be used. 
     In addition to gathering demographics at the set top terminal  220 , the personal profile can be compiled using other methods. For instance, the information can be gathered using questionnaires sent by mail and subsequently entered in the Viewer Profile Database  314  by the network controller&#39;s control station operator. 
     As an alternative to gathering demographic data, a simulated profile can be generated using an algorithm similar to that described below that analyzes access history and viewing habits. Using test information generated from a statistically significant number of viewers, the simulated profile algorithm estimates the viewer&#39;s age, education, sex and other relevant information. The analysis requires reviewing the viewer&#39;s programs watched and statistically comparing the viewer&#39;s programs watched with the test group. Also, the algorithm can place the subscriber or viewer in a viewer category. This analysis is transparent from the subscriber&#39;s point of view and attempts to accurately profile the viewer. Various viewers or viewer categories can later be targeted with different advertisements. 
     The Account/Billing database  316  includes (i) the Set top ID File  330 , and (ii) an Account History File, and (iii) a Billing File, the latter two files indicated at  338 . The Set top ID File, as described above, contains information unique to each subscriber, including set top terminal type, software version and set top terminal identification/serial number. The Account History and Billing Files contain information concerning each subscriber&#39;s past bills and account record and information on the most recent bill, including data from which the next billing report can be generated, respectively. 
     The Program Library database  318  include (i) the Set top ID File  330 , and (ii) a Programs File, (iii) a Preview File, (iv) a Program Category File, (v) a Price Category File and (vi) Service File, the latter five files identified at  344 . As usual, the Set top ID File identifies each set top terminal  220  by identification number. The Programs File contains information on every program offering in the system, including name, length and type of program. The Preview File contains information on previews for specialty programs stored in the Programs File. The Program Category File contains a set of categories into which each program may be placed, such as movies, sports, science fiction and news. The Price Category File contains information on pricing for various categories of programs, grouping programs and services into categories by price. The Service File maintains information on the various cable services available in the system  200 . 
     The Program Scheduling database  320  includes (i) the Set top ID File  330 , and (ii) an Access History File, (iii) a Programs Watched Matrices File and (iv) a Program Scheduling Library, the latter three files indicated at  350 . The Access History File contains information on the programs that the set top terminal  220  has accessed and the Programs Watched Matrices contains information on the number of programs watched in a given program category during different times of day. Relative to the Programs Watched Matrices file, a programs watched matrix is shown in  FIG. 16  and further described below. The Program Scheduling File contains information on the times of day and the corresponding programs that are being offered for viewing at each subscriber location. 
     The Advertisement Library database  322  includes (i) the Set top ID File  330 , and (ii) an Advertisements File, and (iii) an Advertisement Category File, the latter two files being indicated at  354 . The Advertisements File contains information on every advertisement in the system, including name, length and type of advertisement, and the Advertisement Category File contains a set of categories into which each advertisement can be placed 
     The Advertisement Scheduling database  324  includes (i) the Set top ID File  330 , and (ii) an Advertisement Selection File, and (iii) an Advertisement Targeting File, the latter two files identified at  358 . The Advertisement Selection File contains information on the advertisements that have been offered to each subscriber and keeps track of the ones that have been selected. The Advertisement Targeting File contains information on the advertisements and advertisement categories that have been chosen by the system as being of the most interest to a specific subscriber. 
     The network control databases  314 ,  316 ,  318 ,  320 ,  322 ,  324  comprising the database  226  are relational databases generally keyed to information in a single file. Specifically, the relational key is a set top terminal  220  identification number stored in Set top Terminal ID File  330 , as shown in  FIG. 11 . This set top terminal identification number allows the database files that correspond to a particular subscriber to be linked together by a common reference. In other words, the databases are structured such that subscribers are referenced in each database file by a unique set top terminal identification number. In this way, each database may be accessed based on set top terminal identification number alone. Thus, using a subscriber&#39;s set top terminal identification number, the network controller CPU  224  can access and process information pertaining to that subscriber from any of the above described database files. In configurations where multiple set top terminals  220  are allocated to a single customer (or household), a unique subscriber identification number may be added to the database  226  to group the set top terminals  220  by customer. With the set top terminal identification as a relational key, many additional databases may be created that correlate and store pieces of subscriber-specific information from the six databases and underlying files. 
     8. Overview of Software Routines 
       FIG. 13  shows the major software routines initiated and executed by the network controller CPU  224 . These routines are: (1) the Modifying PCI routine  370 , (2) the Polling Cycle routine  372 , (3) the Advertisement Targeting routine, and (4) the Account/Billing routine  376 . Together, these routines, along with the operator entry and update functions  380 ,  382 , respectively, enable the network controller  214  to perform its major functions. 
     The Modifying PCI routine  370  is the software that enables the network controller  214  to modify the program control information (PCI) signal received from the signal processor  209 . This software routine generally allows the network controller CPU  224  to modify the PCI signal content so that changes and additions in programming and advertisements can be accommodated. Such changes and additions include access authorizations and deauthorizations in the form of authorization and deauthorization messages, respectively. 
     The Polling Cycle routine  372  is the software sequence that interactively executes the network controller&#39;s polling cycle allowing the network controller  214  to schedule and perform polling of all set top terminals  220  operating in the system  200 . The software also provides the network controller  214  with a means of processing status reports received from set top terminals  220  in response to polling requests. For a random access system (not depicted), the software of this routine  372  would be changed. 
     The Advertisement Targeting routine  374  is the software that generates packages of television commercials and advertisements geared towards particular viewers and makes use of a viewer&#39;s demographic information and viewing habits to determine those advertisements that are of most interest to that particular viewer. In so doing, the routine  374  outputs packages of advertisements targeted towards each viewer. 
     The Account/Billing routine  376  is the software that the network controller CPU  224  runs to generate billing reports for each set top terminal  220 . In general, the routine  376  correlates the programs accessed with pricing information to generate each report. 
     9. Modifying PCI Routine 
       FIG. 14  shows a software flow diagram for the network controller&#39;s Modifying PCI routine  370 . The Modifying PCI routine (or sequence) is initiated, block  384 , automatically by the network controller CPU  224  upon receipt of the program control information (PCI) signal from the signal processor  209 . Once the network controller  214  receives the PCI signal, the network controller CPU  224  begins processing the signal by reading the PCI data carried by the signal, block  386 . 
     After reading the PCI data, the network controller CPU  224  “calls” other routines to interactively process data and continue the modification process for each set top terminal  220 . First, the network controller CPU  224  calls the Polling Cycle routine  372 , at block  388 , in order to request data retrieval of the information stored at individual set top terminals  220 . Such information includes data on the programs accessed and those ordered for later viewing. As polling responses are received from the set top terminals  220 , the network controller CPU  224  next calls, block  390 , the Advertisement Targeting routine  374 , which generally arranges groupings of commercials for different subscribers based, in part, on viewer demographic information and program access history. 
     The network controller CPU  224  next calls  392  the Account/Billing routine to begin processing all programming and channel access requests. The Account/Billing routine determines, among other things, whether the subscriber&#39;s account is in good standing, verifying that past bills have been paid and that access authorization is warranted. Upon completion of this verification process, a verification message will be sent to the network controller&#39;s operator control station  234  indicating that access should be granted. 
     In the preferred embodiment, an access authorization code may automatically be processed by the network controller CPU  224  and appended to the PCI signal originally received from the signal processor  209 . This modified PCI signal and access authorization code will then be transferred back to the signal processor  209  for transmission to the set top terminals  220 . 
     With continued reference to  FIG. 14 , in an alternate embodiment that uses the Modifying PCI Routine  370 , at blocks  394  and  396 , the operator manually enters any changes in programming and menu content, along with access authorizations, into the program scheduling database  320 . The manual entry of programming and menu content in this embodiment, blocks  394 ,  396 , requires that the operator access the database information generated and updated by the other routines and make necessary changes in the program scheduling database. The network controller CPU  224  reads this updated database information, generates a modified PCI signal, and sends, block  398 , the signal to the signal processor  209 . 
     If a subscriber account is delinquent, access to any new programs or channels ordered will not be authorized. Instead, the network controller CPU  224  will deny authorization and generate a deauthorization message to be included in the PCI signal that will be returned to the signal processor  209  for transmission to the set top terminals  220 . Alternatively, the network controller CPU  224  generates a delinquency message that is transferred to the CRT display at the network controller&#39;s operator control station  234 . Upon reviewing the message, the operator may then manually enter message text to be included in the PCI signal that informs the subscriber of a delinquent account. 
     10. Polling Cycle Routine 
       FIG. 15  shows a software flow diagram for the network controller&#39;s Polling Cycle routine  372 , which iteratively executes the network controller&#39;s polling cycle. The number of iterations correspond to the number of set top terminals  220  being polled. The network controller CPU  224  initiates the Polling Cycle sequence periodically on a predetermined basis, block  400 . Typically, this period is set by the operator at the network controller&#39;s operator control station  234  at once per day, although other periods (e.g., multiple times per day or once per week) can be used. 
     Upon initiation of the sequence  400 , as depicted at function block  402 , the network controller CPU  224  reads the Set top Terminal ID File  330  and begins generating, block  404 , a polling request frame (shown in  FIG. 10   a  and described herein above) for the first set top terminal  220  identified in the file  330 . Once the necessary polling request information is complete, the frame is transferred to the signal processor CPU  244  through the interface between the signal processor  209  and network controller  214 . After transfer to the signal processor  209 , the frames may be transmitted to the set top terminals  220 , block  406 . Meanwhile, the network controller&#39;s control receiver  228  awaits the corresponding response. 
     Upon receipt of a polling response, as depicted at block  408 , the network controller CPU  224  reads the received information from the control buffer  315 . The network controller  214  reads the information field of the polling response frame format, as described above. The network controller CPU  224  processes, indexes and stores the data in an appropriate format, updating the corresponding database files with the information received, block  410 . The processing and indexing of the raw data into a relational database  226  is important to the ability of the network controller  214  to quickly take actions such as targeting commercials without lengthy processing time. The polling routine subsequently returns to the Set Top Terminal ID File  330 , as shown at decision block  412 , to continue the polling cycle for the next set top terminal  220  identified in the file  330 . When the routine  372  sequences through the last set top terminal  220 , the cycle is complete and the routine  372  ceases until the next polling period. 
     Most often, the files that require updates during the polling cycle are the Access History File and the Programs Watched Matrices File, both indicated generally at  350  in  FIG. 12 , and the Account History File  338 . For example,  FIG. 16  shows an example of a 30-day programs watched matrix, denoted  351 , for one set top terminal  220  (not shown in  FIG. 16 ). The matrix  351  is divided into six rows, corresponding to six four-hour time slots. The columns of the matrix  351  are divided, as necessary, by the program categories available for viewing. Each entry in the matrix  351  denotes the number of programs watched in a particular program category and time period. 
     After the status report is received on each set top terminal  220 , the polling response routine (see  FIGS. 10   a  and  10   b ) determines which time slot and category of program numbers in the matrix  351  need to be increased. Thus, entries in the matrix  351  are updated upon receipt of each set top terminal&#39;s polling status report, thereby maintaining a running total of the programs watched. For example, during the 0800-1200 time period, the matrix  351  shows that this set top terminal  220  has been used to watch ten movies during the past month. Preferably the program watched identifying information is stored in addition to the running totals in the Programs Watched Matrices file. Use of programs watched matrices is further described in the following section describing the Advertisement Targeting routine. 
     11. Basic Advertisement Targeting Routine 
       FIG. 17  shows the seven primary functions of the basic advertisement targeting routine  374 . The function of this routine is to target video for set top terminals  220  based on historical viewing data and other data that is available at the network controller  214 . Advertisements that may be targeted include video, commercials and infomericals, with infomericals being time varying video segments (e.g., thirty seconds, fifteen minutes). 
     When initiated, block  420 , the first subroutine, identified at function block  422 , accesses the programs watched matrices (exemplified by matrix  351 ) stored in the Programs Watched Matrices file in the Program Scheduling database  320 . The subroutine uses a unique set top terminal ID to access a specific matrix for one set top terminal  220 . These matrices are maintained and updated by the polling response routine. 
     The second subroutine, function block  424 , which develops other matrices based on other available information, is an optional subroutine not required for the functioning of the system. For groups of set top terminals  220  or for each individual set top terminal  220 , matrices may be developed based on the demographic information, billing information, pricing information, age information and other information which may be stored in the network controller  214  databases. 
     The third subroutine, block  426 , processes all matrices through a set of correlation algorithms. In particular, this subroutine  426  takes matrices developed in the first two subroutines and processes the matrices until reaching a final matrix. 
       FIG. 18  diagrams an embodiment of this matrices processing subroutine  426  which is called by the advertisement targeting sequence shown in  FIG. 17 . As shown in  FIG. 18 , the subroutine  426  is initiated  427  and then accesses or queries, block  428 , the programs watched file and gathers information regarding either an individual subscriber or a node of subscribers. The software can gather the programs watched information in this way for individual subscribers or a set of subscribers. 
     Once the programs watched information has been gathered from the databases, the routine  426  selects and groups, function block  430 , programs watched based on program categories and time slots. The software initially takes each program category (e.g., sports, news, movies, etc.) and establishes the number of programs watched for a given time slot. The time slots may be set to any length of time, including, for example, one, two, three or four hour timeframes. The software will loop through such a counting process for each group and timeslot and then proceed to build a programs watched matrix, block  432 , based on the program categories and time slots. Essentially, all programs watched in a particular category and time slot will be entered into the programs watched matrix. Once the matrix has been built, the subroutine  426  will process the matrix for a given subscriber or node of subscribers through the correlation algorithms. 
     A number of correlation algorithms may be used to weight each selected program category group. For example, as shown at block  434 , a sum of squares algorithm may be used to determine the weighting. Once the groups have been weighted, the weighted groups will be correlated, as at block  436 , with various advertisements stored in the network control databases. The software can then select a set of the most heavily weighted advertisements for transmission to individual subscribers or sets of subscribers in a cable distribution network node. Having determined the weightings of each group and prioritizing the groups accordingly, the subroutine returns  438  to the advertisement targeting sequence  374  of  FIG. 17 . 
     Referring back to  FIG. 17 , the fourth subroutine, as represented at function block  428 , uses the final matrix developed by the correlation and weighing algorithm described above, to select a grouping (or selective filter) for each set top terminal  220 . The final groupings of advertisement that may be sent to the set top terminals  220  or node of set top terminals  220  may use a subroutine as diagramed in  FIG. 19 . 
     The subroutine  428  depicted in  FIG. 19  is called or initiated by the advertisement targeting sequence  374  of  FIG. 17  in order to determine the final groupings. Basically, this subroutine selects a set of commercials that will be used in the chosen groupings, function block  444 . This selection process typically involves advertisements from various advertisement categories (from a number of advertisers which have purchased “air time”). Each advertisement will subsequently be assigned a number of times that it will be shown in a given timeframe, block  446 . This frequency of display may be based on various factors, including the number of requests and cost paid by the respective advertisers to have the commercial displayed. Such factors are used in the next step of the subroutine, block  448 , which assigns a weighting to specific commercials or advertisements in each advertisement category or group. These weightings are used to prioritize the advertisements that will be sent to individual set top terminals  220  or nodes of set top terminals  220 . 
     Once the advertisements have been weighted, the software executes its correlation algorithm,  450 , using selected criteria (i.e., the various factors used to weight the advertisements) as well as the output of each programs watched matrix. Any number of correlation algorithms and weighting algorithms may be used with the software, including the sum of squares weighting algorithm described above. 
     The results from the correlation algorithm subsequently determine the advertisements and programming material that is sent to the signal processor  209  for distribution over the cable network, as represented at block  452 . Once the subroutine  428  completes these steps, the network controller CPU  224  updates the account and billing database based on the ads that are sent to the signal processor  209  for subscriber viewing, as shown at block  454 . These billing database updates allow the advertisers to track the costs and frequency of the advertisements targeted to specific set top terminals  220  or nodes of set top terminals  220 . Following the updates, the subroutine returns to the advertisement targeting sequence shown in  FIG. 17 , block  456 . 
     Referring to  FIG. 20   a , set top groupings (A through E)  460  are shown. The number of set top groupings available is determined by the bandwidth available to transmit commercials. The bandwidth of the system will limit the number of commercials which are available at the set top terminal  220  at any given time. 
     Referring back to  FIG. 17 , the fifth subroutine, represented at function block  466 , prepares set top group information for transmission to the set top terminals  220 . This subroutine  466  modifies the PCI signal and includes set top group information in the information field of the frame format given earlier. The various methods for transmitting the group information to the set top terminals  220  are described below. 
     The sixth subroutine, block  468 , selects the target video and is the last decision making process in targeting a commercial for a viewer and, can be performed by either the set top terminal  220  or the network controller  214 . In the preferred embodiment, the set top terminal  220  performs this last step by correlating (or matching) the program being watched by the viewer with the set top group information that has been previously transmitted by the network controller  214 , and the targeted video is then displayed, as shown at block  470 .  FIG. 20   a  shows an exemplary table matching set top terminal groups  460  and program category being watched  470  with a specific channel (continuously) showing commercials. The commercial channels are shown in  FIG. 20   b  at  474  and are assigned Roman numerals I through X, for example. The number of set top groupings and channels showing commercials can vary.  FIG. 20   b  shows a division of available bandwidth to carry ten videos, ten commercial channels. In this example, the channels  474  are numbered 101-110. 
     The network controller  214  will transmit group information to a set top terminal shown as row names  460  on  FIG. 20   a . The network controller  214  will also transmit data which informs the set top terminal  220  which of the multiple commercial channels  474  is assigned to a television program category shown as Columns  470  on  FIG. 20   a . Each set top terminal  220  only requires the data related to that set top terminal&#39;s assigned group (or row). For example, in  FIG. 20   a , the set top terminal in group A (row A) is provided with data on the commercial channel which are assigned for sports programs as I, children&#39;s programs as IV and movie category as III. In this manner, each set top terminal  220  is only required to store information related to its own grouping. Therefore, a set top terminal  220  which is in group A only needs to store the information related to group A, which is found in row A of  FIG. 20   a . This information includes one commercial channel assignment for each of the eight program categories. Using this information, the set top terminal  220  first determines the category of the television program currently being watched and then is able to quickly determine which channel to switch the viewer when an advertisement availability occurs during the program. 
     The network controller  214  can also perform the step of correlating program category watched  470  and set top terminal grouping  460  to select the target video. In order for the network controller  214  to perform this function, it must have information on the program currently being watched by the viewer. To obtain this information in a polling system, set top polling must occur on a real-time basis (i.e., 10 minutes). 
     During the target commercial selection process, the set top terminal programming will default to the existing commercial during a program if it is missing any of the information needed to determine which of the continuously playing commercial channels to show. In alternative embodiments, the default that is shown on the regular programming channel will correlate with one of the assigned set top groupings and program categories.  FIG. 20   a  shows, at  478 , that the default has been assigned to set top terminal grouping C for program categories “children” and “entertainment.” The three preferred methods to transmit targeted commercials to a set top terminal  220  are: (1) the Additional Bandwidth method (or individual video access); (2) the Multiple Channel method, and (3) the Split Screen method. Each method has certain advantages and disadvantages. The Additional Bandwidth method allows the most flexibility by more specifically targeting commercials before the commercials are transmitted to a set top terminal  220 . However, it requires a great deal of available bandwidth in the delivery system. This is difficult with a cable system  200  but possible when a telephone or personal communications system is used to transmit the commercials to the set top terminal  220 . 
     The Additional Bandwidth method allows the network controller  214  to run through a set top terminal&#39;s specific correlation algorithms and target specific commercials from hundreds for each set top terminal  220 . This method allows for the greatest customizing of targeting and allows for a greater selection of commercials to be shown. Only after a commercial advertisement is selected by the network controller  214  for the specific set top terminal  220  does transmission of the commercial occur. 
     The Multiple Channel method requires a set top terminal  220  “transparently” to change channels during a scheduled advertisement from the channel of the currently viewed program to the channel which is carrying the targeted commercial. Although this channel changing method may be transparent to the viewer, it creates difficulty in terms of timing and synchronizing the commercials to begin and end during an advertisement availability occurring in the normally scheduled program. The channel changing is done within the set top terminal  220  using the existing tuner(s). The hardware required to accommodate such transparent channel switching capabilities are shown in  FIGS. 24   a , and  24   b .  FIG. 24   a  shows the set top terminal hardware components which accommodate channel switching within a single 6 MHz channel bandwidth. These components include a tuner  603 , a demodulator  606 , a demultiplexer  609 , a multiplexer  604 , a decompressor  622 , a microprocessor  602 , and local memory M. The tuner  603  operates by tuning to a specific 6 MHz bandwidth which includes the displayed video and a number of channels carrying advertisements. The demodulator  606  processes these signals and sends them to the demultiplexor  609 , which converts the received signal into separate program and advertisement signals. During this processing, the microprocessor  602  coordinates the demultiplexing of the programming signals. Once the video signal pauses for a commercial break, the microprocessor  602  instructs the multiplexer  604  to select the advertisement or advertisements for decompression and subsequent display on the subscriber&#39;s television. This hardware configuration allows the set top terminal  220  to switch between channels within the 6 MHz bandwidth and display various advertisements for viewing, regardless of the video currently being watched by the subscriber. 
     Where a targeted advertisement falls outside the tuned 6 MHz bandwidth containing the video that the subscriber is currently watching, the hardware configuration shown in  FIG. 24   b  is used. In this configuration, the microprocessor  602  instructs the tuner  603  to return to another 6 MHz channel bandwidth, as represented by bi-directional arrow A. 
     Working together, the microprocessor  602  and tuner  603  allow targeted advertisements, which have been transmitted in another 6 MHz bandwidth, to be tuned with minimal acquisition time and delay. In particular, this configuration allows the set top terminal  220  to tune outside a given 6 MHz bandwidth (to another 6 MHz bandwidth) in order to select a targeted advertisement for display. This alternative embodiment may require the use of a full screen mask in order to minimize any annoying screen rolling during the tuning process. The masking is intended to cover any glitches which would otherwise be displayed during the acquisition time (e.g., 0.5 seconds) for returning to another 6 MHz channel bandwidth. 
     Where the acquisition time or delay becomes unreasonable, an alternative embodiment can include the use of two tuners similar to the configuration shown in  FIG. 24   c . This alternative configuration using two tuners, trades an increased cost for lower acquisition times. In set top terminals  220  equipped with two tuners, the terminal can use the second tuner to tune the channel showing the commercial. (Set top terminals with two tuners are described in detail in co-pending patent application, Ser. No. 08/160,194, now issued U.S. Pat. No. 5,990,927, entitled, ADVANCED SET TOP TERMINAL FOR CABLE TELEVISION DELIVERY SYSTEMS, incorporated herein by reference. Again, the channel changing is transparent to the viewer who believes the same channel is continuously being shown. The Multiple Channel method has the disadvantage of requiring that sufficient additional channels be available (by less bandwidth than Available Bandwidth method). Those skilled in the art will recognize a number of other configurations of set top terminal hardware that will accommodate a transparent channel switching feature. 
     The Split Screen method transmits multiple commercials on a single channel using a split screen technique; commercials being pre-recorded and prepared prior to transmitting to the set top terminal  220 . Although many commercials can be transmitted on a single channel, in the preferred form of the split screen method, only four commercials are shown. As the number of commercials increases the size and the amount of video information transmitted for each commercial decreases proportionately (i.e., 6, 8, 12, etc.). Using split screen methodology, either a masking technique or a scaling and repositioning of video technique must be used at the set top terminal  220  to show the ad. The masking and repositioning-scaling techniques are further defined in co-pending application Ser. No. 08/160,193, now issued U.S. Pat. No. 5,734,853, entitled, SET TOP TERMINAL FOR CABLE TELEVISION DELIVERY SYSTEMS, owned by the assignee of the present invention and incorporated herein by reference. The scaling and repositioning technique produces better quality commercials, but requires expensive equipment at the set top terminal  220 . The set top terminal  220  will perform audio switching with the split screen method to amplify the correct audio. 
     12. Alternatives to Basic Advertisement Targeting Routine 
       FIG. 21  shows a software program flow  490  that is an alternative to the network controller&#39;s Basic Advertisement Targeting routine  374 , depicted in  FIG. 17 . The alternative program  490  allows each set top terminal  220  to be individually targeted with specific advertisements and is initiated automatically, block  492 , by the network controller CPU  224  upon receipt of each polling response from a set top terminal  220 . Thus, once the network controller  214  receives program access information from a set top terminal  220 , the network controller CPU  224  begins the process of selecting a package of advertisements that is based on, among other things, that subscriber&#39;s demographic information and viewing history. 
     Upon receipt of a polling response from a set top terminal  220 , the network controller CPU  224  reads the set top terminal identifier,  494 , and the programs accessed,  496 , from the polling response (or status report) (depicted in  FIG. 10   b ). The network controller  214  writes information on the programs accessed to the Program Scheduling database  320 , updating the Access History File which contains listings of all programs accessed within the past week, month or year. 
     With continued reference to  FIG. 21 , the network controller CPU  224  then calls a subroutine that sorts the programs accessed by program category, block  498 . In turn, the program categories are sorted,  500 , based on the number of times that programs appearing in each particular category are accessed. In so doing, this sorting subroutine determines and ranks those programs and program categories that are most frequently viewed by that set top terminal  220 . 
     The subroutine can iteratively produce rankings for different time slots in a given day. In this way, different rankings can accommodate different viewing preferences during those time slots for a single set top terminal  220 . For example, where rankings for eight three-hour time slots are desired, the subroutine determines a ranking of programs and program categories for each three-hour viewing period. Thus, a different ranking may be produced, for instance, for a morning time slot and an evening time slot. All rankings of programs and program categories for that set top terminal  220  are written to the Viewer Profile database  314 , updating the Viewer Log File, as at function block  502 . 
     Next, the network controller CPU  224  calls a subroutine that correlates the updated Viewer Log File with the Advertisement Categories File in the Advertisement Library database  322 , block  504 . By correlating these two files with one another, the subroutine assigns or correlates various categories of television commercials to each ranking of programs and program categories in the Viewer Log File. The categories of television commercials and advertisements that may be so assigned are found in the Advertisement Categories File indicated generally at  354  as part of the library  322  and may include: (1) Household Goods/Products, (2) Home Improvement and Maintenance, (3) Personal Hygiene, (4) Entertainment Items and Events, (5) Sporting Goods and Events, (6) Motor Vehicles and Related Products, (7) Foodstuffs and Beverages, and (8) Miscellaneous. Where, for example, the viewer has watched a sporting event, the Sporting Goods and Events, Home Improvement and Maintenance, and Foodstuffs and Beverages categories may be assigned to that particular sporting event/program and Sports program category. 
     Once the programs and program categories ranked in the Viewer Log File are correlated with the advertisement categories in the Advertisement Categories File, the routine calls a sorting subroutine that ranks the groups of advertising categories correlated based on other information in the database files. In the preferred system, this ranking is primarily based on data in the updated Access History File and the updated Viewer Log File, as shown at function block  506 . By using data on the viewer&#39;s past program selections and demographic information, the subroutine ranks the correlated categories of advertisements according to those likely to be of most interest to that viewer. 
     After the advertisement categories have been sorted and ranked, the routine selects the top three advertisement categories as the targeted categories for a given time slot and viewer, block  508 . Individual advertisements are then chosen from the Advertisements File, with all selections made from the targeted categories,  510 . The advertisements that are selected are written to the Advertisement Targeting File from where advertising packages can be generated, function  512 , for transmission to the set top terminal  220 . Such packages are generated by the network controller CPU  224 , which accesses the Advertisement Targeting File and includes the targeted advertisements in the PCI signal. The entire routine is repeated for each set top terminal  220  and, alternatively, each viewer. 
     13. Account/Billing Routine 
       FIG. 22  shows a software flow diagram for the network controller&#39;s Account/Billing routine  376 , initiated automatically at block  520  by the network controller CPU  224  upon receipt of each polling response from a set top terminal  220 . Upon receipt of such a response, the network controller CPU  224  identifies the set top terminal identifier from the polling response, block  522 . The program access block in the polling response is also read, function  524 , and the Access History File is updated with the received information, function  526 . The routine then calls a subroutine that correlates the updated information in the Access History File with the Price Category File in the Program Library database, block  528 . Once all programs accessed since the last polling cycle are assigned to a price category, the pricing information from each category is written to the Account History File, updating the file at  530 . The network controller CPU  224  generates a billing report for each set top terminal  220  based on the updated account history, function  532 . This billing report can be sent to the set top terminals  220  in a polling request. Specifically, in one embodiment, the information field of the frame format described in  FIG. 9   a  is used to provide the set top terminal  220  with billing information. 
     Account information for each set top terminal  220  can be viewed through a monthly account review menu. The account information necessary to create the monthly account review menus may be stored either in the memory of the set top terminal  220  or at a remote location that communicates with the set top terminal  220 . In the simplest embodiment, the set top terminal  220  records a subscriber&#39;s selections locally and calculates the monthly account review based upon the subscriber&#39;s selections which require the payment of fees. This monthly account information is stored locally and sent to the network controller  214  upon polling. 
     The Account/Billing routine is capable of processing account and billing information generated in other embodiments. For example, in an alternate embodiment, the subscriber&#39;s viewing selections and billing information may be continuously maintained at the network controller  214  or a remote site connected via communication lines to the cable headend  208 . The network controller  214  or the remote site must regularly transmit the monthly account information to the set top terminal  220 . 
     Each embodiment, such as local billing storage at the set top terminal  220 , billing by the network controller  214  or billing by a remote site, has advantages and disadvantages. If the account information and processing is done locally at the set top terminal  220 , each set top terminal  220  must be provided with the memory and necessary processing capability to maintain the account. This greatly increases the cost of a set top terminal  220 . If the account information is maintained remotely, the remote site must remain in regular contact with the set top terminal  220  in order to provide the subscriber with billing information. To accommodate homes with multiple viewers two or more set top terminals  220  may be placed on a single bill or two accounts may be created for one set top terminal  220 . 
       FIG. 23  shows another embodiment in which billing may be accomplished through the use of remote statistical and billing sites (SBS). In this arrangement, statistical and billing information from individual communities of set top terminals  1750  is communicated through cable headend sites to regional statistical and billing sites  1730  (SBS). A regional SBS may serve several cable headend sites, shown at  1732 . The regional SBS  1730  calculates billing and statistical information and passes necessary billing information back downstream through the network controller  214  at the cable headend  208  to an appropriate single set top terminal  220  in a subscriber&#39;s home. In addition, the regional SBS  1730  communicates the billing and statistical information received on program viewer choices to the central SBS  1740 . 
     The central SBS  1740  accumulates the data received from a number of regional statistical and billing sites and calculates national statistical and billing information. In the preferred embodiment, the regional SBS  1730  prints and mails bills to subscribers. The central SBS  1740  can calculate program ratings, shares and HUTS (homes using televisions) for the nation and by region. With information from interactive TV programs, sophisticated statistical information may be gathered through the network controllers of the cable headends. 
     This arrangement for billing and statistical information provides the operators of the system with the advantages of distributive processing. 
     Remote billing sites may serve regions of the country by having each cable headend  208  in a region of the country connected to one regional billing site. The information from the regional billing sites may then be communicated on a less frequent basis to the operations center  202  or a central billing location. This method of distributed processing of billing enables the central billing location to receive fewer communications and be more efficient. In addition, the communication links between the cable headend&#39;s network controller  214  and regional sites will be of shorter distance than communication links to the operations center  202  from the cable headends  208 . This should result in a cost savings to the system operator. 
     Regional statistical and billing may, however, be eliminated and all communications from the cable headend  208  may proceed to the Central SBS  1740 . In fact, the Central SBS  1740  can be collocated with the operations center  202  and all functions performed at one central location. If the cable program packaging and delivery system  202  is established in just one locale, the network controller  214  can perform all the statistical and billing procedures. 
     C. Targeted Advertising Using Menu System 
     C.1. Menu Structure 
       FIG. 25  shows a series of menus having a normal or standard format for a variety of alternative embodiments of the invention. An Introductory menu screen  1000  that is displayed upon power up, and that contains important messages, followed by a Home menu  1010  with major programming categories is the basis upon which many alternative embodiments of the menu driven selection process can be built. 
     Skipping a sequence or level of the menu structure is possible and perhaps desired in certain instances. In simple alternate embodiments it is possible to combine the Home menu  1010  and the Introductory menu  1000  into one menu that performs both functions. It will be obvious to one skilled in the art that the specific functions of the Home menu  1010  and the Introductory menu  1000  may be exchanged or shared in a number of ways. It is also possible to allow a user to skip directly from the Introductory menu  1000  to a submenu  1050 . This can be accomplished most easily with a separate direct access remote control  900  button. Generally, a user will access a television program through execution of a submenu  1050 . 
     The During program menus  1200  are enacted by the set top terminal  220  only after the user has selected a television program. These menus provide the user with additional functionality and/or additional information while he is viewing a selected program. The During program menus  1200  sequence can be further subdivided into at least two types of menus, Hidden Menus  1380  and Program Overlay Menus  1390 . 
     To avoid disturbing a user during viewing of a program, the Hidden Menus  1380  are not shown to the user but instead “reside” at the set top terminal  220  microprocessor. The Hidden Menus  1380  do not effect the selected program audio. The microprocessor awaits a button entry either from the remote control  900  or the set top terminal  220  buttons before executing or displaying any Hidden Menu options. The Hidden Menus  1380  provide the user with additional functions such as entering an interactive mode or escaping from a selected program. 
     Program Overlay Menus  1390  are similar to Hidden Menus  1380  in that they occur during a program. However, the Program Overlay Menus  1390  are overlayed onto portions of the television screen and not hidden. The Program Overlay Menus  1390  allow the user to continue to watch the selected television program with audio but place additional information on portions of the television screen. Most overlays cover small portions of the screen allowing the user to continue to comfortably view the program selection. Other Overlays that are by their nature more important than the program being viewed will overlay onto greater portions of the screen. In an embodiment, some Program Overlay Menus  1390  reduce or scale down the entire program video screen and redirect the video to a portion of the screen. 
       FIG. 26  shows an embodiment for user selection of television programming. The Introductory menu  1000  followed by the Home menu  1010  is the preferred sequence of on-screen displays. In the embodiment shown in  26 , the Home menu  1010  provides a choice often major menus  1022 ,  1024 ,  1026 ,  1028 ,  1030 ,  1032 ,  1034 ,  1036 ,  1038  and  1040 . Upon selection of a major menu  1020  from the Home menu  1010 , the program proceeds to the major menu  1020  offering further viewer selections. Each major menu  1020  may be customized to target the expected viewership. Depending on the number of available program choices, the major menus  1020  either breakdown the major category into sub-categories or provide the user with access to further information on a particular program. 
     For example, the major menu  1024  for children&#39;s programming provides a list of subcategories  1053  from which the user selects. Upon selection of a subcategory, a submenu  1054 ,  1055  listing program choices within that sub-category is shown to the user. Upon selection of a particular programming choice within the submenu  1055 , the user is then provided with a second submenu  1059  describing the program that the user has selected. From this menu, the user may now confirm the program choice and receive a confirmation submenu  1061  from the set top terminal  220  software. 
     Since the system utilizes digital signals in compressed format, High Definition Television programming can also be accommodated through the menu system. In addition, since the set top terminal  220  has two way communication with the cable headend, interactive television programming is possible, with return signals generated by the set top terminal  220 . Similarly, the system can support “movies on demand” where a user communicates through the set top terminal  220  with an automated facility to order movies stored at the facility. 
     Using this on-screen menu approach to program selection, there is nearly an unlimited number of menus that can be shown to the user. The memory capability of the set top terminal  220  and the quantity of information that is sent via the program control information signal are the only limits on the number of menus and amount of information that can be displayed to the user. The approach of using a series of menus in a simple tree sequence is both easy for the user to use and simply implemented by the set top terminal  220  and the remote control  900  with cursor movement. A user interface software programmer will find many obvious variations from the preferred embodiment shown. 
       FIGS. 27   a  and  27   b  show examples of Introductory menu screens that are displayed on the user&#39;s television. The embodiment shown in  FIG. 27   a  welcomes the user to the cable system and offers the user three options, for example. The user may choose regular cable television (channels 2 through 39), videos on demand (e.g., movies), or instructions on the use of the remote control  900 . Other basic program options are possible on the Introductory menu screen  1000 . For example, instead of, or in addition to, the remote control  900  instructions, a system “help” feature can be offered on the Introductory menu  1000 . 
       FIG. 27   b  shows an alternate embodiment for the Introductory menu screen  1000 . In the upper left-hand corner of the menu, is a small window  1002  that may be customized to the user. The user may be given the option of showing the current time in this window. In the upper right-hand corner a second customized window  1004  is available in which the user may show the day and date. The windows  1002  and  1004  may also be customized for users to show military time, European date, phase of the moon, quote of the day, or other informational messages, including promotionals, infomercials and advertisements. The windows  1002  and  1004  may be customized by users using on-screen menu displays following the Introductory menu  1000 , or informational messages may be provided by a remote site such as the operations center  202 . 
     In an embodiment, the user is given the capability of accessing basic channels such as regular broadcast television and standard cable television channels directly from the Introductory menu  1000  by entering the channel number. The user is also given the capability of directly accessing his account with the cable television company. Further, in the embodiment, the user may directly access a major menu  1020  and bypass the Home menu  1010 . If the user is familiar with the programming choices available on the major menus  1020 , he may select an icon button, or a lettered key (alpha key) from the remote control  900  and directly access the desired major menu  1020 . If any key entry other than those expected by the set top terminal  220  software program is made, the Home menu  1010  is placed on the television screen. If, after a period of time, no selections are made from the Introductory menu  1000 , the program may default to the Home menu  1010 . 
       FIGS. 28   a ,  28   b ,  28   c , and  28   d  are examples of Home menus  1010  that may be used in the set top terminal  220  software.  FIGS. 28   a - 28   d  all employ multiple window techniques to make the menu user friendly and offer a significant number of choices. A channel line up and the major menus  1020  may both appear on the Home menu  1010 . 
     In  FIG. 28   a , the Home menu  1010  displays both the standard channel line up and the video on demand icons for selection by the user.  FIG. 28   a  also shows various levels of subscription programming, including a “Basic” cable package and a “Basic Plus” package. Each of the choices of subscription programming preferably is assigned a different color. This increases the user friendliness of the present invention. 
     In  FIGS. 28   b - 28   d , the left half of the screen is used to list the channel number and network abbreviation of the most popularly watched networks. The right half of the screen offers access to a variety of major menus  1020  listed by category names. 
       FIG. 28   b  shows an embodiment in which only eight major menus  1020  are utilized. By pressing the alpha-numeric or icon key corresponding to the category of programs the user desires, the appropriate major menu  1020  is accessed. In addition, the user may employ an on-screen cursor to select any option shown in the menu. To move the cursor, the user may use either the cursor movement keys on the remote control  900  or similar keys located at the top of the set top terminal  220 . 
       FIG. 28   c  shows how additional major menus  1020  can be displayed on the Home menu  1010 . When there is no longer room available for additional major menu  1020  choices on the Home menu  1010 , the user may access a second screen of the Home menu  1010 . For example, in  FIG. 28   c , if additional major menus  1020  “J” through “Z” existed, the user would access those menus by highlighting and selecting the J through Z menu option (or press the buttons J-Z on the remote control  900 ). After selecting J through Z, the second or extended Home menu  1010  would appear on the user&#39;s television set. This menu would then list options J through Z separately by name. The Home menu  1010  may have many extended Home menu screens. However, any more than a few extended Home menu screens may confuse the average user. 
     The Home menu  1010  of  FIG. 28   d  adds an additional feature at the bottom of the television screen  1011 . This option allows the user to see only those program selections that are available on broadcast television.  FIGS. 28   a - 28   d  are but a few of the numerous variations available for the Home menu  1010 . 
     Additionally, as shown in  FIG. 29 , in an alternate embodiment, the Home menu  1010  (or menu which would normally follow the Introductory menu  1000 ) can be simply the standard cable channel line-up. Offering the standard cable line-up on a separate menu may make selection easier for users with small television screens. 
       FIGS. 30   a  and  30   b  are examples of major menus  1020 . In particular,  FIGS. 30   a  and  30   b  show a major menu  1040  whose category is hit movies. 
     The hit movie category is a list of recently released movies which have been found to be popular among movie goers. This movie list may be changed once or twice a week to keep in line with new movie releases. Again, multi-window and customized window techniques are utilized to make the menu as user friendly as possible. 
       FIG. 30   a  shows an embodiment of the hit movies menu  1040 . The hit movies menu icon along with the hit movies category letter A are displayed. The current date and time are displayed at the top of the screen over a menu background. Ten movie selections are displayed in the center of the screen  1009 , each in a box that may be highlighted when selected. In the lower left part of the screen, a logo window  1512  is available as well as two other option choices  1011 , Movie Library and Return to Cable TV. In an alternate embodiment, the return to Cable TV option is changed to return to the Home menu  1010  (or return to other viewing choices). 
     In  FIG. 30   b , the left upper window  1002  displays current time and the right upper window  1004  displays a message. This menu provides a list of eight movie titles and their rating. A user who desires further information on any particular movie may select the movie using the cursor movement buttons and press the “go” button on the remote control  900  or set top terminal  220 . 
     In the major menu  1020  example of  FIG. 30   b , the customized windows  1002  and  1004  in the upper corners may remain constant from menu to menu. The name of the menu and category are at the top and center of the menu screen  1039 . To make the menu aesthetically pleasing, the instructions are given across the center of the screen and choices in large legible type are provided. Additionally, at the bottom of most menu screens  1011 , the user is given the option of returning to regular TV or returning to the Home menu  1010 . 
       FIGS. 30   c - 30   g  show alternative embodiments of major menus  1020  for the Home menu  1010  shown in  FIG. 28   a .  FIGS. 30   c - 30   g  show various major menus directed to the type of subscription services available (basic service  1420 , basic plus  1422 , economy package  1424 , ala carte and premium channels  1426 ). These menus also provide promotional or advertising information, the cost for the particular subscription service, or other video inserted by the operations center  202 , the cable headend  208 , or the set top terminal  220 , for example.  FIG. 30   g  shows a major menu for the Learning Channel  1428 , one of the individual channels shown in the Home menu of  FIG. 28   a.    
     The above menus may be grouped in similar colors or shades of colors. For example, the basic subscription service could have a light pink color. As the subscription services increase in terms of the number of channels available, the color shading may increase correspondingly. Therefore, the premium subscription service (ala carte service) would have a dark red color, contrasting with the light pink color of the basic subscription service. 
     In  FIG. 30   b , the movie titled Terminator 4 is highlighted, signifying that the user has chosen this program option from the hit movie major menu.  FIG. 31  shows a submenu  1050  which would follow the selection of Terminator 4 on the hit movie major menu. In  FIG. 31   a , the banner across the top of the screen  1502  remains constant from major menu  1020  to program description submenu  1050 . For the comfort of the user, the left upper window  1002  remains the same and shows the current time. The upper right-hand corner  1004  carries a message stating the next start time for the movie selected. 
     C.2. Notification 
       FIGS. 32   a  and  32   b  are notification submenus informing the user that a program selection is about to begin (e.g., counting down until start time). Using these submenus, the set top terminal  220  warns the user prior to switching away from the program being viewed to a prior selected program. These notification submenus are provided to the user approximately one or more minutes before the set top terminal  220  changes the viewing channel. 
     Both notification submenu  1127  examples allow the user to cancel the program order. In  FIG. 32   a , the user is notified in the center of the screen that the chosen program may be canceled within the first five minutes. In  FIG. 32   b  the user may press escape to cancel the order without charge. The notification submenu  1127  of  FIG. 32   b  informs the user of the start time at the upper portion  1103  of the screen. 
     The notification submenu of  FIG. 32   b  is an example of a simple three-window menu. A strip window at the top of the screen  1103  notifies the user of the program selected and the amount of time before the program begins. The center window is a large video window  1556  for displaying the program. At the bottom of the screen the submenu carries another strip menu  1105  that informs the user to escape from the program selection without charge by pressing escape. 
     Using a notification submenu  1127  may allow the operations center  202  or the cable headend  208  to display other videos for the user to view until the start time of the chosen program. The other videos include short video clips from the chosen program, promotionals, infomercials and advertising. The promotionals, infomercials and advertising may be targeted to the individual set top terminal  220  described previously in section B, Network Controller Description. The other videos may be displayed on the entire display, or a portion of the display, as previously described. 
     C.3. Promotion 
     As noted above, the menu system generated by the operations center  202  may be used for promotions. For example,  FIGS. 33   a  and  33   b  relate to promotion of HDTV.  FIG. 33   a  is an example of a menu  1032  advertising a new feature of the system. Promotional menus, such as  FIG. 33   a , may be dispersed throughout the menu driven program selection system. This particular menu describes the HDTV feature and explains its unavailability until a future date.  FIG. 33   b  shows the integration of HDTV services into the menu driven program delivery system. The user who selects the major menu for HDTV receives a description of the service with a suggestion to order the system, or a text note that the user is a current user and a listing of the currently available program selections in HDTV as shown in a second screen  1232 . A user who has not paid to join the particular service, HDTV, may be allowed to join one of the programs in progress for a limited time as a demo to entice the user to order. The user who has paid the HDTV fees proceeds as the user would in any other major menu screen. 
     This particular major menu shows an example of how a follow-on or second screen may exist for the same menu. In this case, a second screen exists for the major menu HDTV  1032 . The user may access the second screen  1232  by selecting the last menu display block in the lower part of the screen “Other HDTV Selections”. Following this selection, the user is given the second screen  1232  of program selections. In this manner, any menu can have multiple screens with many program choices. This type of screen pagination on one menu allows the packager to avoid categorizing program selections within that same menu. In an alternative embodiment, the options available to the user may be scrolled on one menu screen with the text within the menu display blocks changing as the user scrolls up or scrolls down. 
       FIGS. 34   a ,  34   b , and  34   c  demonstrate the use of promotional menus to sell subscriptions to services in the system. In particular,  FIG. 34   a  is a promotional menu  1304  for Level A interactive services. Level A interactive services offers users additional information about programs such as quizzes, geographical facts, etc. This information may be received by the set top terminal  220  in several data formats including the vertical blanking interval and in the program control information signal.  FIG. 34   b  is a promotional menu  1306  for Level B interactive services which include a variety of on-line type services such as America-On-Line, Yellow Pages, Airline Reservations, etc. 
       FIG. 34   c  is a promotion menu  1308  for the Level C interactive services. The Level C interactive services utilize local storage such as CD technology to offer an enormous range of multi-media experiences. The Level C interactive services require a hardware upgrade as described earlier. Specially adopted CD-I and CD-ROM units are needed for this service. 
     C.4. Interactive Services 
       FIGS. 35   a  through  35   e  show menus that are available using the interactive Level A services. When interactive Levels A services are available in a television program, the system may display the interactive logo consisting of the letter “I” and two arrows with semicircular tails, for example. In an embodiment, the set top terminal  220  will place the interactive logo on the television screen as an overlay menu  1310 . In the embodiment, the set top terminal  220  will detect that there is data or information available about a television program that can be displayed to a user using the interactive service. When the set top terminal  220  senses that interactive information is available, it will generate the interactive logo overlay menu and place it on the television screen. For example, the set top terminal  220  may detect that information on a television program is being sent in the vertical blanking interval and will generate an interactive logo overlay menu. The interactive logo overlay menu may appear on the user&#39;s television screen for approximately fifteen seconds during each ten minute interval of programming, for example. 
     The user who sees the interactive logo on his television screen is made aware of the fact that interactive services are available in conjunction with the program. If the user presses an interactive remote control button, an additional overlay menu will be generated by the set top terminal  220  and placed on the screen. This menu  1310  is shown in  FIG. 35   a  being overlayed on an interactive television program. From this menu the user may select interactive features or return to the television program without interactive features. 
     The user who selects interactive features is presented with the interactive Level A submenu  1312  in  FIG. 35   b . From this submenu the user may choose a variety of different types of textual interactivity with the current program or a related video. Some examples are quizzes, fast facts, more info, where in the world, products, and advertisements for products. At any time during the interactive submenus the user may return to the current program without interactive features. 
     This interactive submenu has an example of taking a complete television program video, scaling it down to a smaller size and directing the video into a video window of a submenu. 
       FIG. 35   c  shows an interactive fast facts submenu  1314 . In this submenu textual information is given to the user in the lower half of his screen. This textual information will change as additional data is received by the set top terminal  220  relating to this television program. The textual information may relate to a promotion or may advertise a product or service. 
       FIG. 35   d  shows the use of the subcategory “more information” in the interactive service. This submenu  1316  gives additional information related to the television program to the viewer in textual form in the lower half of the screen.  FIG. 35   e  is an interactive submenu  1318  for the subcategory “quiz.” In this interactive subcategory, the user is presented with questions and a series of possible answers. If desired, the user selects one of the answers to the quiz question. After the selection, the set top terminal  220  sequences to the interactive quiz answers submenu which informs the user whether the correct answer was chosen. 
     C.5. On-Line Connections 
       FIG. 36   a  is an example of a submenu for Level B interactive services. From this menu screen  1330 , any of a number of on-line data services could be accessed, including access to Internet service providers such as America-On-Line. In  FIG. 36   a , the airline reservations selection has been selected by the user. 
       FIGS. 36   b  through  36   e  provide an example of a sequence of menus that a user may encounter with an on-line data service. The example relates to airline information and reservations and the user in this sequence is reserving and purchasing airline tickets.  FIG. 36   b  is an example of the first submenu  1332  for a data service offering various options. In this case, the user has the option of checking current reservations or making new reservations. In each of these submenus related to a data service, the user is able to return to the Home menu  1010  or regular cable television and exit the data service. 
       FIG. 36   c , an airline information and reservation submenu  1346 , allows the user to choose a one-way or round-trip ticket and to confirm his reservations. The user who desires to proceed may charge the airline ticket to a credit card by choosing the appropriate strip menu on the lower part of the screen. 
       FIG. 36   d , an airline information and reservation submenu  1348 , is an example of how credit card purchases may be made using the on-line data services. In this menu  1348 , the user charges a round-trip plane ticket on a credit card. The user simply needs to enter the credit card number, expiration date, and credit card type to charge the airline ticket. 
       FIG. 36   e , an airline information and reservation submenu  1350 , is an example of a menu that may be shown whenever an on-line data service is processing a request sent by the user. In this menu  1350 , the on-line data service is processing the user&#39;s credit card charge for his airline ticket. 
     C.6. Digital/Audio Program Choices 
       FIG. 37   a  is a major menu  1038  displaying the digital/audio program choices that are available for users who have paid the monthly fee. In a chart format, the major menu shows the top five, top ten, and top forty songs available in six different categories of music. Below the chart, the system is able to provide a text message describing the particulars of the audio program selected. 
     The digital/audio feature of the invention allows a user to listen to CD quality audio selections through his stereo. This can be accomplished by running cables directly from the set top terminal  220  to the user&#39;s amplifier/stereo system. Alternatively, the user may listen to audio selections through the television. 
       FIGS. 37   b  and  37   c  are promotional menus  1400 ,  1404  for the digital/audio feature. Using the same logos and menu format, the system can provide a text description enticing the user to pay the monthly fee and join the service. In  FIG. 37   b , the menu allows the user to test the system with a free demonstration. The menu in  FIG. 37   c  allows the user to request additional promotional information about the system. Both  FIGS. 37   b  and  37   c  are representative of promotional menus that may be used throughout the menu system. 
     The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. Those skilled in the art will recognize that numerous variations are possible within the spirit and scope of the invention as defined in the following claims.