Abstract: The present invention provides greater capability and flexibility than existing cable headends. Specifically, the invention comprises a modular design for a cable headend and a combiner component for cable headend. The invention is particularly useful in cable television program delivery systems transponding large numbers of digitally compressed program signals. The combiner allows cherry-picking of programs from transponded signals.

Abstract: The present invention is directed to a CATV system in which a broadcasting multiple signal including a plurality of types of broadcasting signals modulated by at least two different modulation techniques is sent to a CATV terminal device from a CATV broadcasting device. In the CATV terminal device, the broadcasting signal corresponding to a requested channel is selected from the sent broadcasting multiple signal. The selected broadcasting signal is sent to a plurality of types of demodulation means respectively corresponding to the modulation techniques. The modulation technique by which the broadcasting signal corresponding to the requested channel is modulated is judged on the basis of data representing the relationship between each of channels sent from the CATV broadcasting device and the modulation technique by which the broadcasting signal corresponding to the channel is modulated.

Abstract: A data management and distribution system for an electronic program guide ("EPG") for television programs comprising an automated data collection subsystem, a manual entry and correction subsystem, a database validation subsystem, an edition generation subsystem, a configuration subsystem, and a status and control subsystem. The system may further comprise a feed generation subsystem if one or more of the EPG providers supported by the EPG distributor requires a live feed of data. The automated data collection subsystem collects EPG data from multiple sources in various formats, filters the data based on the needs of the EPG providers supported, and places the data in a centralized database in a form suitable to support the different environmental contexts of the EPG providers. The manual entry and correction subsystem permits the EPG distributor to make manual corrections, additions, and deletions to the data stored in the database.

Abstract: An apparatus for providing a television guide includes a device for detecting whether a television is off, a device for switching a signal output from a first television signal source to a second television signal source, if television guide data is not contained in the signal output from the first television signal source when the device for detecting detects that the television is off, a device for extracting the television guide data from the signal output when the device for detecting detects that the television is off, and memory for storing the extracted television guide data.

Abstract: A cable system includes a cable head end and a plurality of distribution sites having equipment for supplying subscriber station receivers with digital video cable signals from the cable head end. The digital video signal includes a robust data component that is receivable by distribution site receivers and cable subscriber station receivers under very poor carrier-to-noise conditions, that is, where the video signal itself is not usable. The cable head end has capabilities for interrogating distribution site receivers and subscriber station receivers which respond by transmitting designated information concerning differences between the received robust data component and the transmitted robust data component. At the subscriber station receivers, the robust data component is in the form of a training sequence of known characteristics that is compared with a received training sequence.

Abstract: A universal interactive control system for the downloading and playback of information and entertainment services from one or more network distribution centers, said one or more network distribution centers providing information and entertainment signals selected from video and audio programs, video catalogs, and data files, said universal interactive control system. The interactive control system includes: a controller circuit, a data distribution circuit controlled by the controller circuit, a data processor circuit controlled by the controller circuit, and a first plurality of interface connector circuits, with a first of the interface connector circuits for connecting the distribution circuit to a display device under control of the controller, and a second of the interface connector circuits for connecting the data distribution circuit to a storage device under control of the controller circuit.

Abstract: Apparatus and methods are provided for a television guide. In one embodiment the apparatus includes a device for comparing a current time with at least one stored time period for extracting television guide data to determine if the current time is within the stored time period, a device for switching a signal output from a first television signal source to a second television signal source, if television guide data is not contained in the signal output from the first television signal source when the current time is within the stored time period, a device for extracting the television guide data from the signal output when the current time is within the stored time period, and a memory for storing the extracted television guide data.

Abstract: A television receiver having an input section for splitting a reception signal to a first signal and a second signal, first and second mixers for respectively receiving the split reception signals, a local oscillator for outputting first and second local oscillation signals, a 90.degree. phase shifter for providing the first local oscillation signal to another input of the first mixer after phase-shifting by 90.degree., a first output section for directly extracting outputs from the first and the second mixers, and a second output section for outputting a second output obtained by adding a direct output from the first mixer and the output from the second mixer which has passed through another 90.degree. phase shifter.

Abstract: A system for coding and transmitting traffic alert and collision avoidance data between vehicles (A, B and C) traveling within a given airspace (12). The airspace is divided into a grid of volume elements (14a, 14b . . . 14i), each of which is assigned a unique pseudonoise (PN) code. A vehicle (A) traveling through the airspace determines its position using signals from Global Positioning System (GPS) satellites. The vehicle's position places it within one of the volume elements in the airspace. A Traffic Alert and Collision Avoidance System (TCAS) transmitter (38) on the vehicle creates a navigation message that describes the position of the vehicle. A collision avoidance signal is then generated by modulating a carrier signal with the PN code representing the volume element containing the transmitting vehicle and with the navigation message. The collision avoidance signal is transmitted on a common communications channel using time-multiplexing based on a pseudorandom sequence.

Abstract: An on demand services feature for the provision of video, audio, and data services for a subscription system of the CTV type, or the like. The system comprises a headend coupled to a distribution network having a multiplicity of subscribers. Standard service signals forming scheduled program channels are coupled commonly with on demand service signals forming on demand program channels in a frequency division multiplexed system. The demand services are provided by a demand service processor having an input processor which stores programs for the demand services in a file server or other massive memory and a plurality of output processors which retrieve the programs on demand and convert them to the demand service signals for application to the distribution network. In the illustrated embodiment the input processor scrambles, digitizes and compresses real time or other stored analog programming for storage in the file server.

Abstract: Disclosed is a circuit and system for preventing tampering with services provided in a broadband transmission network. A coaxial relay is coupled between a cable providing signals in the network and the drop cable to the customer's premises. The coil which operates the relay is coupled to the shield conductor of the drop cable and to a source of dc potential. As long as a current flows through the shield portion and the coil, the customer is connected to the network through the relay. If current stops, as when the customer disconnects the drop cable, the customer is disconnected from the network.

Abstract: A broadband communications system for coupling telephony or other digital networks to a CATV network. The system transmits a multiplex of telephony signals in the forward band of the CATV network. Each forward channel is QPR modulated on a carrier and contains multiple subscriber telephony signals. The forward telephony channels are demodulated and demultiplexed by a plurality of subscriber terminals into the individual telephony signals directed to an addressed subscriber. Audio and control signals returning from the subscriber are digitized into standard telephony signals and QPSK modulated on a carrier onto the reverse band of the CATV network. The multiplicity of reverse band telephony channels are demodulated and multiplexed into a standard telephony signal which is directly interfaced to the telephony network.

Abstract: A data transmission system for sending a plurality of signals from a sender to at least one receiving terminal. The sender comprises a memory for storing the plurality of signals, and a controller for causing the stored plurality of signals to be sent in a predetermined order, and for changing the predetermined order when the updating of a signal takes place, so that an updated signal is sent with priority to the receiving terminals.

Abstract: A wireless communication system formed of a plurality of antennae, the antennae being arranged in a grid pattern over a communication region, wireless portable terminals located within the communication region for emitting and/or receiving electromagnetic signals via the antennae, apparatus for determining the position of at least one of the terminals within the communication region relative to the grid pattern.

Abstract: A wireless base station architecture that is particularly well-suited for providing audio, video and data services. An exemplary embodiment preferably transmits to all of an area those "common services" (e.g., broadcast television) that are intended to be received by multiple recipients throughout the area, but, in contrast, transmits only into a sector those recipient-specific services (e.g., point-to-point voice services, interactive video services) that are intended for less than all of the recipients in the area. In an exemplary embodiment, a demultiplexor directs both broadcast video and recipient-specific or "sectorized" video signals to a video processor, which prepares them for transmission. The demultiplexor also directs sectorized audio signals to an audio processor/RF combiner, which prepares them for transmission.

Abstract: A video signal processing system, such as a pay TV system, that includes a smart card access control feature decodes control information from data included in groups of video line intervals that represent data channels. Each channel includes data arranged in packets of data. Each packet includes both descriptor data and application data. The packets of data are extracted from the video lines by a data dispatcher. After receiving a packet from a data channel, the data dispatcher analyses the descriptor data to determine the target for the application data. The data dispatcher transmits the application data contained in the packet, without analyzing the data, to the correct target processor unit, e.g. either a control access processor or a decoder intelligent processor. Information that may be transferred to the decoder processor includes, a specific channel allocation table, data related to the VTR of the customer, and information related to a geographic location.

Abstract: A system and method for adaptive-power control of a spread-spectrum transmitter of a mobile station operating in a cellular-communications network using spread-spectrum modulation. A mobile station transmits a first spread-spectrum signal. A base station has an automatic-gain-control circuit for generating an AGC-output signal, from a received signal. The received signal includes the first spread-spectrum signal and an interfering signal. The base station also has a correlator for despreading the AGC-output signal, a power-measurement circuit responsive to processing the received signal with the despread AGC-output signal for generating a received-power level, a comparator coupled to the power-measurement circuit for generating a comparison signal by comparing the received-power level to a threshold level, a transmitter for transmitting a second spread-spectrum signal, and an antenna.

Abstract: In a presentation system a transmitter station transmits messages that provide information on demand. Such message is divided into parts. An earlier part of the message is presented more often than at least one later part of the messages. In particular, the presentation pattern is such that upon accessing the message's firts parts all other parts can be contiguously accessed according to a standard presentation velocity as from a time instant that is within a prespecified distance in time from the start of accessing said first part. In particular, the distance may be zero.

Abstract: A split-band device for transmitting and amplifying television signals between an input terminal and an output terminal which can each be coupled to a distribution cable having a characteristic impedance R.sub.0. The device comprises first and second parallel-arranged branches comprising, respectively, first and second amplifiers. The first branch has a high-pass first filter arranged between the input terminal and its first amplifier and the second branch has a low-pass second filter arranged between the input terminal and its second amplifier to select a second frequency range different from a first frequency range of the first amplifier.

Abstract: A cable television (CATV) system including a plurality of headends, each headend outputting different video/audio programs to subscribers by way of a plurality of channels. The playlist or scheduling data corresponding to each channel is generated and modified by a separate and distinct scheduling computer, the scheduling computers for each channel being located at different locations. Such a system allows the output of each CATV channel at different headends to be generated, modified, and controlled via separate schedulers. This is advantageous in environments where different companies control the distribution of different channels.

Abstract: A center facility transmits, together with a television signal carrying a broadcast program, a message directed to a particular terminal apparatus, address data indicating an address of the particular terminal apparatus, and information quantity data indicating a quantity of the message. Recognizing that the user's terminal apparatus corresponds to the particular terminal based on the address data, the particular terminal apparatus displays all of the message on a TV receiver based on the information quantity data, and finishes the display of the message when receiving the user's instruction indicating reception of all the message.

Abstract: A method and apparatus providing antenna diversity is disclosed. A set of bits of a digital signal are used to generate a codeword of N symbols. Codewords are provided according to a channel code having a minimum Hamming distance, d.sub.min, where 2.ltoreq.d.sub.m .ltoreq.N. N signals representing N symbols of a codeword are transmitted with N different antennas. The N transmitted signals are received and isolated. A sequence of N received symbols is formed from the isolated symbols and compared with one or more valid codewords to associate the sequence with a codeword. A set of bits based on a codeword associated with the received sequence is generated.

Abstract: A method of operating a cable system having premium channel encoders and dedicated smart pay per view encoders, each associated with an individual channel. The pay per view encoders are provided with the addresses of certain subscriber stations that have been approved to decode pay per view events on the associated channels. These certain subscriber stations are addressed on a priority basis by the pay per view encoder handling the pay per view event to set their authorization memories to decode the pay per view event. The authorization memories are updated by RAM groups of five program tags. All of the PPV encoders are assigned to the same RAM group so that in updating authorization memories, the authorization of a subscriber station memory for another pay per view event is not altered. The authorization process is rapidly accomplished and is repeated for a period of time after commencement of the pay per view event.

Abstract: Based on in-band data transmitted from a center facility that include titles, start times, lengths and channel numbers of respective programs of linked channels, the titles and start times are displayed together with selection numbers on a TV receiver upon depression of a schedule switch by a user. While watching a displayed picture, the user selects one of the selection numbers. Data indicating the start time, length and channel of the selected program is stored in a timer reservation area of a memory. The selected program is automatically displayed based on the stored data.

Abstract: A system for combining AM and FM transmissions. In-band, On-channel, FM Digital Audio Broadcast (IBOC FM-DAB) allows simultaneous transmission of DAB and FM over existing FM allocations without interfering with conventional analog FM signals. The utility of existing FM spectrum allocations is therefore enhanced.

Abstract: A frequency allocation is provided to minimize the effects of amplifier distortion in a mixed analog and digital cable television system. In particular, successive digital channel signals having a bandwidth substantially equal to .omega. are separated by a pair of adjacent analog channel signals, each having a bandwidth substantially equal to .omega.. In an illustrated embodiment, the analog and digital channel signals comprise amplitude modulated carriers having substantially equal power levels.

Abstract: A cost-effective, bandwidth-efficient, and power-efficient system is provided in which data streams received from several different video sources are converted into sequences of symbols selected from a predetermined constellation and are multiplexed on a symbol-by-symbol basis into a single sequence of symbols for transmission on a channel. Using a symbol multiplexer helps to mitigate the effect of bursty noise in the receiver and reduces the processing speed requirement in the receiver.

Abstract: An integrated bi-directional MMDS/MDS converter connected to an antenna for receiving MMDS programming for receiving information/data signals from a set top for retransmission of these signals back to central location. The integrated bi-directional converter has a down converter connected to the diplexer for down converting conventional programming signals into a group of converted programming signals in the 222 to 408 MHz range, an up converter for up converting data/information signals in the 116 to 128 MHz range from the communication line into MDS signals and delivers it into the diplexer. The diplexer applies the outgoing MDS data signals to the feed of the antenna for transmission. The integrated bi-directional MMDS/MDS converter of the present invention uses a common local oscillator for driving both the down converter and the up converter.

Abstract: A broadband cable television system for delivering broadband cable television signals from a headend to a plurality subscribers includes a bridger module. The bridger module allows upgrading of the system to a much higher channel capacity or to a fiber to the service area architecture with a minimum amount of subscriber down-time. The bridger module is advantageous in that it permits CATV systems to be reconfigured without having to relocate the trunk/bridger stations. The bridger module utilizes a signal director which is capable of directing broadband television signal flow from left-to-right or from right-to-left along a trunk cable. The bridger module also incorporates plug-in passive devices, the value of which is selected in accordance with the signal loss levels between independently located distribution amplifiers.

Abstract: A new and improved remote audio monitoring system is disclosed comprising an FM transmitter, and one or more remote cordless FM receiving terminals. The transmitter is coupled to the audio output channel of a cable or satellite television descrambler box so as to rebroadcast the audio signal to the remote FM receiving terminals. As a result, the T.V. sound track may be listened to at selected remote locations without the need for hard wired connections.

Abstract: A CATV center facility transmits, together with the television signals of a plurality of programs, display control data indicating program names and selection numbers of the respective programs and channel data indicating the numbers of channels on which the respective programs are being broadcast or to be broadcast. A terminal apparatus detects the program names, selection numbers and channel numbers from the display control data and the channel data, and makes a TV receiver display the detected program names and selection numbers in an associated manner. While looking at a picture thus displayed, a user selects a desired program by pushing a corresponding numeral button of a remote controller or a keyboard. In response to the program selection by the user, the terminal apparatus is tuned to the channel of the selected program.

Abstract: A CATV system including a CATV network, a multiplicity of subscriber units, apparatus for transmitting over said CATV network encrypted information individually addressed to a subscriber unit and apparatus associated with each of said multiplicity of subscriber units for decoding the encrypted information addressed thereto.

Abstract: Signals, such as television signals, are distributed from a head-end station via a fibre network. The signals are amplitude modulated on carriers at different frequencies, and the different carriers combined to form a composite analogue signal. In the head-end station the composite analogue signal is clipped to reduce the peak-to-mean ratio and the clipped composite signal is digitized. The resulting digital data is transmitted onto the fibre network and is received at an optical receiver. The optical receiver reconstitutes the composite analogue signal for reception by a termination. In one example the composite analogue signal has a bandwidth of one octave or less, and is digitized by sampling at a sampling rate below the Nyquist rate.

Abstract: A combination surge and diplex filter is provided for a CATV distribution amplifier. In a first preferred implementation, an integrated surge and high pass filter section is provided when the CATV amplifier is used only in the forward direction. Provision is made for a plug-in low pass filter section which is matched to the high pass filter section. The plug-in low pass section is used to form a diplex filter if the reverse direction capability of the CATV system is required from the distribution amplifier. In a second preferred implementation, the integrated surge and high pass filter section is segmented into a surge filter segment which is designed as a divisible part of the high pass filter section. A plug-in module is then provided with a high pass filter segment having those components of the high pass filter section which were not necessary for surge protection and a low pass filter section matched to the high pass filter section.

Abstract: Each of a plurality of households includes a channel substitution unit which receives a normal spectrum of television channel signals and at least one substitute channel signal. The substitution unit of each household, upon command from a control arrangement, replaces a channel of the normal television channel spectrum with the substitute channel and distributes the resulting spectrum, comprising the original normal spectrum of television channel signals with one substituted channel, over a distribution medium such as an in-house distribution cable.

Abstract: Method and apparatus are provided for controlling and delivering television programming from a control station to one or more substations, which in turn transmit television programming to remote receiving locations on a pay-per-view basis. Programming is originated and delivered from the control station to record and playback devices at the substation. The record, playback and transmission of the programming at the substation is remotely controlled from the control station in accordance with schedule information generated at the control station. Similarly, scrambling and anti-copy devices at the substation can be remotely controlled in accordance with the schedule information.

Abstract: A bi-directional video signal transmission system is equipped with transmission lines having coupled upsteam and downstream segments. With the entire band of a RF signal being taken as a modulation frequency band, an image signal modulated to a frequency band and RF-multiplexed in the upstream segment is introduced into the downstream segment at the modulated frequency and is then branched to demodulate the same frequency band, thereby obtain one video signal transmission channel. In response to a request by a subscriber, a channel management section assigns and releases the transmission channels and further outputs a control command whereby a transceiver control section performs switching-control of the transmission frequencies to transceiver units.

Abstract: A base unit antenna for a cordless telephone system where the cordless telephone system comprises a base unit coupled via wires contained in a telephone cord to a telephone distribution system and a handset coupled to the base unit by a duplex radio communication link. The base unit includes a base unit antenna for transmitting and receiving the duplex radio communication with the handset. The antenna is preferably integrally contained in the telephone cord, but spaced from the telephone wires therein distribution system.

Abstract: A hybrid transmission system is provided to transmit and receive high-speed digital information in the form of variable length packets using standard television practices and components. The basic building block of this hybrid digital transmission system is the device at the remote location that receives the analog broadcast TV-like signal processed by a standard vestigial sideband video modulator. This device decodes the digital information from the signal and then passes it along as digital information to any form of a data terminal equipment or computer.

Abstract: The disclosed telecommunication overhead cable distribution system 10 includes a plurality of "T"-shaped distribution units 20 that are located at desired distribution locations. A plurality of cable support sections 22 extend, protect, and support the telecommunication cables between the distribution locations. Each section includes a plurality of identical support units 24 that are releasably interconnected to each other. Each unit is pivotable about a horizontal intra-unit axis "A" and about an inter-unit vertical axis "B". Each unit is comprised of a female member 26 and a male member 28 in which the male member is releasably interlocked with an adjacent female member. Such a system provides for a system having a minimum of components with a maximum of versatility. The ends of the section 22 fit into receptive cavities formed in the "T"-shaped distribution units 20.

Abstract: A circuit is supplied at the tap from a feeder which monitors certain signals coming from the single dwelling interdiction unit (SDI unit), and if the signals are interrupted, removes service from the premises. In order for service to be reinstituted to the subscriber DC power from the SDI unit must be received at the tap and the tap address must be communicated from memory in the SDI unit (where it had been previously stored upon installation by an installer) to the tap microprocessor. In accordance with an alternative embodiment in order for the service denial switch to remain closed, supplying signals to the SDI unit then to the home, the following must occur. Direct current power must be supplied from the SDI unit to the tap and data must be supplied from the SDI unit, in the form of pulses going from the normal powering level of, for example 12 volts, to 0 volts momentarily on a continual basis and not just at initialization as in the first embodiment.

Abstract: A wireless communication system comprising a plurality of antennae, the antennae being arranged in a grid pattern over a communication region, wireless portable terminals located within the communication region for emitting and/or receiving electromagnetic signals via the antennae, apparatus for determining the position of at least one of the terminals within the communication region relative to the grid pattern.

Abstract: A subscriber terminal apparatus for a television in an in-band subscription television system is provided. The subscriber terminal includes a receiver for receiving a television signal including video, audio, ana data information. A selector selects a channel of the television signal. A memory stores a plurality of barker screens providing messages regarding one or more channels of the television signal. An on-screen display control circuit controls the display of the barker screens on the television. A processor retrieving a barker screen from the memory supplies the retrieved screen to the on-screen display control circuit if the barker screen provides a message regarding a selected channel. Barker screen information may also be obtained from a dedicated data channel or a six megahertz video barker channel.

Abstract: An interface module may have a customized circuit to enable an operation using modulated signals, which are free of direct current, by way of a serial bus interface. To effect the communication, adapted connecting means are also needed to connect a subscriber to a two-wire line bus. An interface chip achieves a user friendly connection. Starting from its terminal side going toward the two-wire line bus the interface chip features a transformer and, with it, in series a parallel connection consisting of a receiver and a transmitter. Furthermore, in the interface chip, a comparator and a voltage source are provided, which transmit, as a function of the level of the modulated signals, a blocking signal to a circuit used to modulate and demodulate the signals. To release the signals to be transmitted, the customized circuit transmits an enabling signal to the transmitter.

Abstract: A method and apparatus are provided for transmitting, receiving, and reproducing digital audio signals as discrete carriers similar to standard FM broadcast signals. An audio signal is digitized using, for example, adaptive delta modulation techniques. Several channels of audio information, such as left and right stereo channels and a second audio program ("SAP") channel can all be digitized and incorporated onto the digital broadcast signal carrier. The digitized audio signal may be modulated using multiphase modulation of the carrier of an FM broadcast band or cable television band signal. A plurality of audio channels may be digitized and transmitted over the airwaves, or over a cable transmission network. Channels of nondigitized audio channels may be interspersed with the digitized audio channels in the Fm broadcast band.

Abstract: A passenger aircraft video distribution system distributes modulated RF carrier signals from a central signal source (10) to be used at each passenger seat (S1, S2, S3). The carriers are modulated to contain both audio and video data (12,14) and also other digital data, such as graphics, slide shows and the like. Analog video signals (14) from the video source are modulated (100) on individually discrete carriers in the range of 54 to 300 megahertz. Audio information, including audio sound channels and the video audio, are digitized (80,84) and combined with digital data in a combined serial bit stream that is multiplexed (82), and then modulated (96) on an RF carrier having a frequency sufficiently above the frequency band of the video signals so that the resulting spectrum of the modulated audio RF carrier does not interfere with the modulated video carriers. The RF carrier signals are combined (104) and distributed to individual seats.

Abstract: A receiver control circuit for a television, includes a main receiving part, a first receiving circuit, a driving control part, and a comparing part, wherein the main receiving part receives television signals for particular channels and, the first receiving circuit receives the television signals of particular channels and outputs driving adjusting signals. The driving control part outputs driving signals to the comparing circuit which compares the frequency bands of the television signals received by the main receiving part and the first receiving circuit to control the power source of the first receiving in order to prevent minors from watching undesirable broadcasting programs.

Abstract: A method of controlling the allocation of a population of remote units among a plurality of groups of remote units is provided. Each remote unit has a digital identifier respectively associated therewith. A maximum and a minimum average number of remote units per group is fixed. The remote units are assigned to the groups of remote units in accordance with the respective digital identifiers. The average number of remote units per group is then determined as remote units are assigned thereto. Next, the average number of remote units per group is compared to the fixed maximum number of remote units per group. The above steps are repeated while the average number of remote units per group is less than or equal to the fixed maximum number of remote units per group.

Abstract: A method and apparatus for generating and collecting viewing statistics in a cable television system is provided. For example, data relating to television channels being viewed at remote terminals may be generated by each remote terminal and then collected by a system manager. A system manager transmits one or more record times downstream to one or more remote terminals indicating a future point in time at which the terminal is to record the viewing statistics. The remote terminals store the one or more record times in memory and when the record time matches the current real time, the remote terminals store in memory the viewing statistics. Thereafter, in response to a polling signal from the system manager, the set top terminals transmit the previously recorded viewing statistics along with a time code corresponding to the time at which the viewing statistics were recorded upstream to the system manager, and the system manager processes this information accordingly.

Abstract: Disclosed is an improved system for the delivery of entertainment and educational programming from a plurality of electronic libraries to a plurality of users. Users actuate a hand operated control device to: review a listing of available programming; enable the delivery of a program from a library; or control the delivery of forwarding and rewinding through the programming, and authorizing the purchase of advertised consumer goods by entering in personal identification numbers. The network of libraries and the paths for delivering the programming stored therein is arranged for optimum transmission efficiency and maximum access capacity. The key idea in optimizing transmission efficiency and access capacity is to recognize that programming can be grouped into different classes, and that not all classes of programs should be stored in all libraries.