Abstract: A system and method for disabling the output of a data transmission system when a relatively high error rate is detected in the transmitted signal. The error muting technique of the invention functions as the digital equivalent of a leaky integrator with hysteresis. In particular, the signal quality of the received data transmission is monitored, and a predetermined value is added to an accumulator or error counter when an error is detected. This value varies depending upon the nature of the detected error such that more serious errors are given greater error values. The error counter is also decremented by one or some other amount at a programmable time interval in accordance with the maximum acceptable error rate. The error count (accumulator sum) is continuously compared to a programmable error threshold, and if the threshold is exceeded, the output of the data transmission system is disabled, or in the case of a digital audio transmission system, is muted.

Abstract: A digital audio communication system includes a digital modulation and demodulation scheme which efficiently uses the bandwidth and channel spacing of a cable television system. A 30 channel digital bit stream is demultiplexed into six groups of five channels. Each group of channels thereafter modulates a carrier by a quadrature partial response (QPR) process. The QPR signal, an amplitude modulated, double sideband, carrier suppressed (AM DSBSC) signal, is then transmitted over the cable system to a multiplicity of subscribers, each of which has a QPR demodulator. The demodulators are of the decision feedback type having a modified Costas loop carrier recovery circuit. The grouping of an odd number (five) of digital audio channels per QPR modulator minimizes error propagation due to the correlative QPR demodulation process. The decision feedback decoding is implemented in simple current nodes where a bilevel output from the decoded data is subtracted from a tertiary level output of a mixer.

Abstract: A system for signal level control in AM fiber systems is provided. The system provides level controls at both transmitter and receiver ends of the fiber transmission system, utilizing compensation and control techniques at each end to maintain and optimize the performance of the system. The transmitter includes two stage level control based on a composite power level of a detected RF signal. The receiver includes two stage level control based on a pilot channel filtered from the channels transmitted to the receiver.

Abstract: An off-premises method and apparatus for the interdiction of unauthorized channels of a broadband cable television signal includes common circuitry for adjusting the amplitude and equalization levels of the broadband CATV signals and one or more subscriber modules for generating jamming signals of different frequencies which are used to interdict one or more unauthorized channels. Each subscriber module is associated with a subscriber and is programmable and addressable to adjust the jamming parameters of that subscriber independently of other subscribers. Each subscriber module circuit comprises a plurality of latches, each of which is associated with one of a plurality of digital to analog converters. Each of the digital to analog converters drives one or more frequency agile oscillators with its analog output to generate the jamming signals.

Abstract: A communications network uses optical fibers to carry amplitude modulated broadband CATV signals over a considerable distance (6-30 km) to a fiber node. Electrical to optical transmitters at the headend launch, and optical to electrical receivers at the fiber node receive, optical signals corresponding to the broadband CATV signals. Distribution from the fiber node to the subscribers is obtained by transmitting electrical signals through a limited cascade of amplifiers over an electrical transmission line (coaxial cable). The limited cascade is much shorter than the fiber span and may include trunk amplifiers which are insufficient in number to add significant losses or distortion. Line extender amplifiers may be connected to output couplers located off the subscribers premises and the CATV signals then carried via electrical cables to the subscribers.

Abstract: A multiplication circuit for use in an FM television transmitter and receiver is provided. The multiplication circuit includes a limiting circuit for limiting a subcarrier supplied thereto and a dividing circuit coupled to the limiting circuit and dividing the output of the limiting circuit by a predetermined factor. A mixer is coupled to the dividing circuit and mixes the output of the dividing circuit with the subcarrier.

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: An Off-premises CATV system having an interdiction apparatus includes a remote microprocessor which receives commands and data from the headend over the cable distribution plant. The data is in a modified Manchester format (biphase-M) at 19.2 K baud which is then frequency modulated on a carrier of 108.2 MHz. A receiver detects the base band signal and outputs a serial digital signal to one input port pin of the microprocessor. The microprocessor rejects incorrect messages by measuring the duration between the negative transitions in the data signal. For those negative transitions which do not fall within predetermined windows where data transitions or a start of message character should be, an error is detected and the message is discarded.

Abstract: A subscriber terminal apparatus for a television in an in-band subscription television system is provided. The subscriber terminal is adapted to receive a television signal including video, audio, and data information. A tuner of the subscriber terminal tunes channels of the television signal and an on-screen display control circuit selectively provides a display of characters on the television. A tuner control tunes the tuner to a channel having in-band data when the display of characters is provided on the television.

Abstract: An off premises CATV system is disclosed. A headend transmits programming including pay-per-view programming and a cable distribution system distributes the programming. An off premises unit is coupled to the cable distribution system for supplying the programming to at least one subscriber. A subscriber terminal is coupled to the off premises unit over a communication link. The subscriber terminal including an input device for inputting subscriber-supplied signals indicative of a pay-per-view event to generate a message. A transmitter responsive to the subscriber-supplied signals transmits the message to the off premises unit over the communication link. The message is transmitted at a plurality of random times within a predetermined period of time.

Abstract: Apparatus for broadband signal distribution is equipped with a detector for detecting when the apparatus is open and is further adapted to receive an entry code generator. If the entry code generator is not installed or, if installed, fails to generate an entry code which matches an authorized entry code stored in the apparatus, the apparatus enters a particular mode of operation whereby service provided by the apparatus is interfered with. The entry code generator comprises a circuit board for coupling with an electrical connector of the apparatus having at least one ear which precludes closure of a cover to the apparatus. A method of screening access to the apparatus from others than authorized service personnel includes waiting a predetermined period of time for coupling the access code generator before service is interfered with. Furthermore, the stored access code may be changed or the predetermined time varied by addressable command from a headend of a broadband signal distribution system.

Abstract: A fiber optics communications system and method are provided. The system includes a transmitter apparatus located at a first location and having a plurality of laser transmitters and a plurality of optical switches coupling optical signals from the laser transmitters to optical fibers. A receiver apparatus is located at a second location remote from the first location and includes a plurality of receivers and a plurality of optical switches coupling optical signals from the optical fibers to the optical receivers. A first control circuit controls the switches of the transmitter apparatus in accordance with conditions at the first and the second locations. A second control circuit controls the switches of the receiver apparatus in accordance with conditions at the first and second locations. The backing up of a plurality of transmitting lasers by a single back up laser and the backing up of a plurality of receivers by a single back up receiver are also described.

Abstract: An apparatus and method is described for transmitting, receiving and communicating program data signals which are combined with digital data signals. Preferably, the present invention compresses 30 digital audio signals, multiplexes them with title, track, artist, record label, year, etc., program information, and transmits the combined signals via satellite to a receiving station. The receiving station demultiplexes the signals and sends them via a cable distribution system to a subscriber's digital music tuner. This tuner further demultiplexes and decodes the signals so that the digital audio signals may be converted to analog and output for listening, while the corresponding data signals are communicated to the subscriber. In an alternative preferred embodiment, the program data signals are transmitted to a remote control receiver where they are displayed. The system described in the present invention may be used for transmitting video, software or games with program data to subscribers.

Abstract: A receiver is described for optical signals which are amplitude modulated with broadband radio frequency signals. The receiver includes an optical detector which receives the incoming optical signal and generates a radio frequency electrical signal which varies with the power level of the incoming optical signal. This electrical signal is applied to a pair of amplifiers which are connected in a push-pull relationship. In a preferred embodiment, a tuning network is connected between the two amplifiers for optimizing the amplification of a selected band of radio frequencies.

Abstract: A off-premises CATV system includes a compensation control including a picture carrier controlled automatic gain control and an automatic slope control. A broadband television signal output from a variable gain device is distributed by a radio frequency signal splitter to a number of subscribers for interdiction by the generation of a number of jamming signals. The variable gain device and a variable impedance device which is frequency dependent are connected in series for automatic gain control and automatic slope control, respectively. A first feedback control is used to compare a first portion of the broadband television signal to a reference power level and to control the variable gain device to null the error. A second feedback control is used to compare a second portion of the broadband signal to a second reference power level and to control the variable impedance device to null the error.

Abstract: A method for automatically selecting optimum frequencies for transmitting data from remote terminals upstream to a system manager is provided. The system manager initially selects a set of frequencies from a larger set of available frequencies and transmits a command downstream to each remote terminal indicating which frequencies to use. Each remote terminal transmits data messsages on each selected frequency in response to addressed commands generated by the system manager. The system manager receives and counts the data messages on each of the frequencies, and after a statistically significant number of messages are received, removes from use the frequency with the lowest number of data messages received. This frequency is replaced with either (1) a previously untried frequency, or if all frequencies have been tried, (2) a previously tried frequency with the highest number of data messages received.

Abstract: A fiber optic cable connector secures a fiber optic cable to an equipment housing (e.g., a CATV equipment housing) and allow individual fibers of the cable to pass into the housing in a strain relieved condition for connection to electro-optical componentry. A strength component of the fiber optic cable is clamped within the connector body, exterior of the equipment housing, to strain-relieve the optical fibers from forces imparted to the cable, without taking up housing space. Also, the connector clamps a strength component of a protective "fan-out" tube covering the individual fibers of the cable passing from the connector into the housing, to strain-relieve the fibers from forces imparted to the fan-out tube. The clamping action is effected by progressive threaded engagement of two connector bodies.

Abstract: A digital audio communication system includes a digital modulation and demodulation scheme which efficiently uses the bandwidth and channel spacing of a cable television system. A 30 channel digital bit stream is demultiplexed into six groups of five channels. Each group of channels thereafter modulates a carrier by a quadrature partial response (QPR) process. The QPR signal, an amplitude modulated, double sideband, carrier suppressed (AM DSBSC) signal, is then transmitted over the cable system to a multiplicity of subscribers, each of which has a QPR demodulator. The demodulators are of the decision feedback type having a modified Costas loop carrier recovery circuit. The grouping of an odd number (five) of digital audio channels per QPR modulator minimizes error propagation due to the correlative QPR demodulation process. The decision feedback decoding is implemented in simple current nodes where a bilevel output from the decoded data is subtracted from a tertiary level output of a mixer.

Abstract: In order to facilitate the installation of off-premises equipment which distributes CATV signals from a distribution cable to subscribers and to allow different subscribers to receive different classes of service (basic service alone or with one or more premium or pay-per-view channels), a pair of housings are used, one containing circuits for tapping the signals from the cable and the other for electronics hardware which processes the signals and distributes them to subscribers in accordance with the class of service which is ordered by the subscribers. The housing containing the tapping circuits is permanently connected to the cable and need not be removed or replaced when connecting additional subscribers or changing the class of service. The housing containing the electronics hardware for processing the signals may be attached to or along side of the first housing. The first housing may be suspended from the strand which supports the cable in an aerial mount configuration.