Abstract: A method, system and apparatus for frequency sweeping and frequency sweep testing a CATV system wherein the CATV system has a plurality of channels and is transmitting television signals over at least some of the channels. The system includes a head end test unit coupled to the CATV system at its head end and a remote test unit coupled to the CATV system at a location remote from the head end. The head end test unit sweeps the CATV system by either generating and transmitting test signals at the channel frequencies over the CATV system or, if a television signal is being transmitted on a channel, using the television signal as the test signal. The head end test also measures the signal levels of the test signal and at the end of the sweep, transmits telemetry signals, which include the frequencies to be swept and the measured signal levels, over the CATV system to the remote test unit using the same transmitter that it use to generate and transmit the test signals.

Abstract: To facilitate the measurement of the quality of a video transmission, a bar code is embedded in the top part of the frames of the transmitted video signal to enable identification of each frame. The audio signal may be synchronised with the different bar codes. The bar code may be formed of several blocks in the top of the image, and may be formed of superimposed binary bar codes, each binary bar code being in one color of a color system. This permits measurement of transmission quality, and notably of dropped frames, audio holes, transmission delay, audio and video synchronisation.

Abstract: An apparatus for receiving a television signal containing a ghost cancellation reference signal, and for using the reference signal to process the television signal so as to substantially eliminate path induced distortion.

Abstract: A tap (125) for use in a cable television system (100) includes an incoming port (202) for receiving an incoming signal from a head end section (105) and at least first and second outgoing subscriber ports (225, 230) for transmitting outgoing signals to system subscribers. The first and second subscriber ports (225, 230) can be enabled or disabled, depending upon whether cable service is to be provided from a particular port. The tap (125) also includes light sources (250, 260) located on the body of the tap (125) to indicate statuses, i.e., enabled or disabled, of the subscriber ports (225, 230).

Abstract: An exemplary leakage tagging signal generator according to the present invention is intended for use in connection with a leakage tagging signal detector that detects signal leakage in a communication system. In particular, the leakage tagging signal generator is intended for use with a leakage tagging signal detector that identifies leakage tagging signals based on the detection of a characteristic leakage tagging frequency component. The leakage tagging signal generator includes an RF signal source, an output, a switch, and a pulse signal source. The RF signal source is operable to generate an RF carrier signal having a first frequency. The output connects to the communication system. The pulse signal source is a device operable to generate a pulse signal having a first state and a second state, said pulse signal having a pulse period.

Abstract: In FIG. 5, a plurality of signal sources 21.sub.1 to 21.sub.N each generate a carrier with different frequencies. A pulse signal generating portion 23 generates a pulse signal with the same period and time width as those of a horizontal synchronizing signal in NTSC system color television broadcasting. Delay devices 32.sub.1 to 32.sub.N delay timing of the pulse signal for a randomly predetermined delay amount. Level adjuster 52.sub.1 to 52.sub.N generate a modulating signal by adjusting each pulse base of the delayed pulse signal for a level within a range between 12.5% and 74.375% with respect to a pulse top. Modulators 42.sub.1 to 42.sub.N output a signal obtained by modulating the carrier with the modulating signal. A multiplex portion 24 multiplexes the modulated signals to output a resultant signal as a test signal. The error rate of a QAM signal is evaluated with the test signal.

Abstract: A portable HDTV testing device inserts a deterministic test signal having a frequency close to the symbol rate of the received HDTV signal. As the received HDTV signal is randomized prior to broadcast for synchronization purposes, the addition of the deterministic test signal to the randomized data signal is essentially equivalent to the addition of a random (or white) noise signal to an information bearing signal. The use of a deterministic test signal avoids the expense associated with a random signal generator, thus making possible an inexpensive and portable HDTV test device. To test the noise margin of a received signal, which is used to determine if the installation of the antenna and HDTV receiver is optimized, the test unit inserts known levels of the noise signal incrementally and measures the bit error rate until the bit error rate exceeds a known threshold above which proper decoding is not possible.

Abstract: A distribution amplifier (210) for a cable television system (100) includes an output gain stage section (215) for receiving an input signal from a cable head end section (105). The output gain stage section (215) includes multiple active amplifier circuits (225, 230) for amplifying the input signal to generate main and auxiliary outputs that are processed by a radio frequency (RF) detector (255) having at least a first detector circuit (300) for processing the main output to generate a first voltage and a second detector circuit (305) for processing the auxiliary output to generate a second voltage. Further included in the distribution amplifier (210) is a status monitor (260) coupled to the RF detector (255) for converting the first and second outputs to first and second digital values and transmitting the first and second digital values. In this manner, an indication of a system or amplifier malfunction can be provided.

Abstract: In a system for measuring the quality of a received video sequence with respect to an original video sequence a low duty-cycle transport of video reference images from the original video sequence is used to transmit full quality images. Such a reference frame from the original video sequence is selected and transmitted as a full quality video image, either separately or as part of the transmission of the original video sequence after processing. The processed original video sequence becomes a received video sequence at a receiver, and the frame corresponding to the reference frame is extracted and compared with the full quality received reference frame to obtain a measure of the quality of the received video sequence.

Abstract: In order to provide a monitoring system of a multimedia communication terminal which can detect abnormal reproduction of multimedia data, reliably with a simple configuration together with a sufficient consideration of the user's interface, surely discriminating the scheduled interruption of the multimedia data delivery, the monitoring system of the invention comprises a decode counter (49), a count value of said decode counter being incremented each time when video data of a picture frame is decoded from multimedia data delivered through the transmission line (23) by a video decoder (48), and control means (41) for discriminating whether the multimedia data are supplied or not by detecting beginning and ending of reproduction of the multimedia data, and detecting occurrence of an abnormal state in the multimedia communication terminal (22) by checking alteration of said count value.

Abstract: An automatic testing method and device is described that can test a video sequence coder/decoder system and either assess the quality of decoded sequences or rate the fidelity of the coding chain. The device produces synthetic test patterns that induce the appearance of known artifacts, then tracks and evaluates such artifacts. Based on this evaluation, it can rate the system's performance in a way that correlates well with human assessments. In our testing device, the quality estimation module performs this function.

Abstract: A picture quality monitoring system for a television chain provides incremental metrics for each layer of the chain--video, compression and modulation. The output of each layer is stored as a reference signal for the next or subsequent layers. The output from each layer is compared with the output from a prior layer to determine an incremental degradation metric. All of the incremental degradation metrics may be combined to produce an overall degradation metric for the entire television chain.

Abstract: A communication circuit comprises sources of program material, carrier frequency signal sources and first modulators for modulating the carrier frequency signal sources with the program material sources. Each of the first modulators has a first input terminal, a second input terminal and a first output terminal. Terminal apparatus for demodulating program material-modulated carrier frequency signals include automatic gain control (AGC) circuits having AGC bandwidths. One of the program material sources is coupled to the first input terminal of a respective first modulator through a second modulator having a third input terminal, a fourth input terminal and a second output terminal. A source of signals having a frequency in the AGC bandwidth is coupled to the third input terminal. The source of program material is coupled to the fourth input terminal. The second output terminal to the first input terminal.

Abstract: A method of testing ADSL (asymmetric digital subscriber line) circuits is provided. A test instrument is connected to the customer premises end of the ADSL circuit, consisting of an ATU-C modem on the central office end and an ATU-R modem on the customer premises end, with a twisted-pair telephone line connecting the ATU-R and ATU-C modems. A remote test instrument is coupled to the ATU-C modem, typically on a semi-permanent basis in the central office, dedicated for testing multiple ADSL circuits by communicating with multiple ATU-C modems via a switch or router. The test instrument and remote test instrument communicate with each other in full duplex via the ADSL circuit using Internet Protocol (IP) data packets. The test instrument generates the upstream data traffic, controls the test sequence, and controls and coordinates the throughput test with the remote test instrument.

Abstract: A system and method for detecting unauthorized access to a CATV system at a site, including inserting a cable fraud detection unit into the site drop, periodically obtaining a first sample of a content signal from the site with the detection unit so as to determine if the site is accessing the content signal, storing the first sample in the detection unit, periodically obtaining a second sample of the content signal from the CATV system with the detection unit to serve as a reference for the first sample, and storing the second sample in the detection unit. The stored samples may be transmitted to the CATV system in response to a control signal or may be transmitted to a portable unit.

Abstract: A cable television monitoring system to monitor the return signals of a CATV system is disclosed. The system monitors the CATV system in a frequency range of 5-225 MHz and measures voltage and frequency parameters. The system provides an analysis in NTSC compatible base-band video which, when modulated to TV channel frequency and sent downstream in a cable TV system can be received at any point in a cable TV system.

Abstract: An apparatus for detecting the properly terminated connection between video components transmitting a video signal from one video component to the other. The video and/or data signal is input to a resistance element. A first comparison input device is connected to the input side of the resistance element and a second comparison input device is connected to the output side of the resistance element. A comparison unit is provided for comparing the voltages from the first comparison input device and the second comparison input device to determine whether there is a voltage drop across the resistance element thereby determining whether the video component is properly terminated. A data processing element connected to the output of the comparison unit receives data from the comparison unit which is detected across the resistance element.

Abstract: A test system for performing pair gain tests within a co-axial cable termination unit of a combined telephony/video system is described. The combined telephony/video system provides a set of telephony channels and video channels to the co-axial cable termination unit over a single combined telephony/video transmission line. The co-axial cable termination unit includes interface circuitry in the form of modems, CODEC's, and the like, for interfacing the set of telephony channels provided on the combined telephony/video transmission line with a set of respective telephone lines connected into a subscriber location The interface circuitry also routes the video channel of the combined telephony/video transmission line onto a video-only co-axial cable also connected into the subscriber location.

Abstract: Attentional maps that reflect the subjective view of an observer to the effects of degradation in a video image are used in the objective measurement of video quality degradation. The observer assists in generating an attentional map for each image of a test image sequence, which provides different thresholds or weighting factors for different areas of each image. A video image sequence from a system under test is compared with the test image sequence, and the error results are displayed as a function of the corresponding attentional maps.

Abstract: A method for ascertaining the temporal relationship between two signals that traverse a network via two different channels concurrently sends a test signal through the two channels and evaluates the temporal relationship of the signal received at the outputs of the channels. The test signal is divided into presentation units and the temporal relationships are evaluated for foursomes of presentation units. A foursome of presentation units consists of an output presentation unit of one channel (channel 1), a matching input presentation unit of the same channel (channel 1), an input presentation unit of the other channel (channel 2) which has a time stamp that is identical, or essentially identical, to the time stamp of the input presentation unit of the one channel, and an output presentation unit of channel 2 which matches the input presentation unit of channel 2.

Abstract: An apparatus for removing unnecessary data in communication networks and used in a television transmitting and receiving devices of a cable television system and the like is disclosed. In a television receiving device capable of carrying out data communications, if an unnecessary data such as an address change command is contained in the data stream transmitted from the transmitting device to the receiving device, the unnecessary data is removed in advance. That is, in the present invention, if an unnecessary data is contained in a command, then a CRC error is forcibly generated, so that the receiving device can ignore a data stream containing the unnecessary data, thereby removing unnecessary data. In this manner, the damages to the software or hardware of the receiving device can be prevented.

Abstract: A method and apparatus are disclosed for bypassing a first RF broadband amplifier in a CATV network so as to permit substitution of a second broadband amplifier for the first amplifier to permit repair, replacement and/or analysis of the bypassed first RF amplifier. A switching circuit is employed to rapidly substitute the second amplifier for the first amplifier and to reinsert the repaired of replaced first amplifier in the CATV network following maintenance thereof. Bypassing of the first amplifier and utilization of the second amplifier in its stead allows maintenance to be performed on the first amplifier without disruption of service to the portion of the network downstream of the first amplifier.

Abstract: Alignment of two video sequences, one being a reference video sequence and the other being a processed video sequence corresponding to the reference video sequence, is performed using selected partial pictures from the reference video sequence. The reference video sequence is evaluated for portions that have maximum information content spatially and/or temporally to select the partial pictures, and the location and size of the partial pictures are stored together with the reference video sequence. The processed video sequence is then initially aligned to the reference video sequence by first finding the locations of features from the partial pictures in the processed video sequence to provide a coarse misalignment error between the two video sequence, and then using a correlation algorithm with a scanning window based on the size of the partial pictures to refine the misalignment error.

Abstract: Emulating human faculties of sight, image, and hand control by a testing system to interact with a multimedia switching system. The testing system can control a multimedia video unit by the transmission of infrared command signals emulating a user actuating buttons on a hand-held infrared transmitter unit to verify that the system responds correctly to such actuations. Also, the testing system can analyze quality of images to be transmitted, transmit those images through the switching system via user multimedia video units, receive those signals at other user multimedia video units, and analyze the quality of the resulting video images. Further, the testing system can place varying levels of multimedia traffic through the multimedia switching system. Further, the testing system can test call control performed by the multimedia switching system by utilizing an infrared transmitter unit to place and receive calls.

Abstract: An apparatus for testing a CATV transmission line according to the present invention, wherein a down-signal to subscribers from a CATV broadcasting station is split into a plurality of signals and an upstream transmission line for leading said down-signal and a plurality of downstream transmission lines for transmitting split signals are separated from each other, whereby said upstream transmission line and said downstream transmission lines are tested separatedly, comprises one main input terminal adapted to be connected to said upstream transmission line, a plurality of main output terminals adapted to be connected to a plurality of downstream transmission lines respectively, a splitter for splitting a signal from said main input terminal to a plurality of first split output terminals, said splitter being connected to said main input terminal and provided with said plurality of first split output terminals, and a plurality of second split output terminals, connected to said plurality of main output terminal

Abstract: A system for determining the quality of data received by settop terminals including at least one settop terminal which analyses each data packet received by the settop terminal and determines whether the received data packet includes errors. The bit error rate is continually calculated, monitored and stored. When the bit error rate exceeds a predetermined threshold, the settop terminal generates a warning signal for transmission to the headend, which diagnoses the problem. The cable system headend utilizes the results from a group of households that have the same problem in order to isolate the source of failure.

Abstract: A method, system and apparatus for frequency sweeping and frequency sweep testing a CATV system wherein the CATV system has a plurality of channels and is transmitting television signals over at least some of the channels. The system includes a head end test unit coupled to the CATV system at its head end and a remote test unit coupled to the CATV system at a location remote from the head end. The head end test unit sweeps the CATV system by either generating and transmitting test signals at the channel frequencies over the CATV system or, if a television signal is being transmitted on a channel, using the television signal as the test signal. The head end test also measures the signal levels of the test signals and at the end of the sweep, transmits telemetry signals, which include the frequencies to be swept and the measured signal levels, over the CATV system to the remote test unit using the same transmitter that it used to generate and transmit the test signals.

Abstract: A method and apparatus in a communication system (100) for allocating and controlling data transmissions to and from communications unit (134) in communications system (100). The communication systems (100) includes a cable distribution network (106) with a base communications unit (102) and a number of downstream communications units (134) all connected to the cable distribution network (106). A plurality of channels are used to transmit data transmissions between the base communications unit (100) and the downstream communications unit (134). Uplink and downlink channels are monitored to determine channel quality for each of the channels in communications system (100). The determined channel quality is used to both initiate transfers of communications links to other frequencies and for assigning channels to various communications units (134).

Abstract: A line driving system according to the characteristic of a transmission medium is disclosed, including: a setup signal generator for generating a setup signal; an amplifier, connected to the setup signal generator, for amplifying an entire frequency band to a constant level, and changing the setup signal and a subscriber transmission signal; a frequency compensator, connected to the amplifier, for adjusting an amplification gain of a corresponding frequency; a line connector, connected to the frequency compensator and a cable, for connecting a driving signal to a transmission line medium; a setup signal receiver for receiving the transmitted setup signal; a clamp/signal detector, connected to the setup signal receiver, for detecting a (-) directional pulse signal of the setup signal, generating a signal clamped to a reference point, calculating a value based on a clamp level, and converting the value to a voltage value; a combination/discrimination/control generator connected to the amplifier and the frequenc

Abstract: A method of automatic measurement of compressed video quality superimposes special markings in the active video region of a subset of contiguous frames within a test video sequence. The special markings provide a temporal reference, a spatial reference, a gain/level reference, a measurement code, a test sequence identifier and/or a prior measurement value. The temporal reference is used by a programmable instrument to extract a processed frame from the test video sequence after compression encoding-decoding which is temporally aligned with a reference frame from the test video sequence. The spatial reference is used by the programmable instrument to spatially align the processed frame to the reference frame. The measurement code is used by the programmable instrument to select the appropriate measurement protocol from among a plurality of measurement protocols.

Abstract: Apparatus for and a method of monitoring the transmission of an analog video signal through a video signal transmission channel, e.g. a fiber optic cable from a headend capturing the analog video signal at a location remote from the headend and select a signal channel from the captured video signal. The selected signal channel is digitized and serialized as a digital signal and the digital signal is transmitted as an optical signal through an optical fiber cable to a monitoring location, where the digital signal is converted to an analog video signal which is displayed on a video monitor.

Abstract: An apparatus for testing video ordered type terminals by using a computer, and a testing method therefor, employ a personal computer and a bit stream board of the computer to form a virtual server of an ordered type video terminal testing system, thereby making it easier to test a video terminal. In the conventional apparatus for testing an ordered type video terminal, a server is required in order to test such a terminal. This server includes a memory system of a large capacity and computer capable of carrying out a high speed arithmetic operation. Therefore, its installation and movement are not easy, while its price is very high. Accordingly, it is uneconomical to procure it only for testing purposes.

Abstract: An improved telephone test device and a method of the same for an optical cable television which are capable of easily testing a telephone function of an optical cable television system by connecting to the subscriber's line of the optical cable television system without using an additional switch system, which includes the steps of a first step for initializing a database, selecting a predetermined bus, Cept interface boards-10, and a hardware, executing a menu, and judging the inputted menu; a second step for performing an extended common control board assembly loop-back test routine when the extended common control board assembly is selected in the first step for testing the extended common control board assembly loop-back; a third step for performing Cept interface boards-10 loop-back test routine when the loop-back is selected in the first step for performing the Cept interface boards-10 loop-back; a fourth step for performing a common test routine when the common test is selected in the first step; a fi

Abstract: A system and method for measuring and evaluating video fidelity. A test video signal is transmitted over a baseline system under test (SUT). A reference video signal is delayed by an amount equal to a latency of the baseline SUT. The test video signal and the reference video signal were previously generated from a common source. The transmitted test video signal is synchronized with the delayed reference video signal, and the synchronized test video signal and the synchronized reference video signal are digitized. The digitized test video signal is inverted, and the digitized reference video signal and the inverted test video signal are summed to thereby generate a video fidelity value of the baseline SUT. A subjective determination is then made as to whether the transmitted test video signal is adequate. If the transmitted test video signal is adequate, then the video fidelity value of the baseline SUT as established as the baseline video fidelity value.

Abstract: A test signal generator presents a test signal of pseudorandom data in a format which simulates the Grand Alliance Transmission Layer Signal for the 8- or 16- vestigial sideband (8/16-VSB) signal for Advanced Television (ATV) systems. An actual (non-test) Transmission Layer 8/16-VSB signal for ATV is in a particular format with properly formatted sync information and includes data which have been randomized, Reed-Solomon coded, interleaved, and trellis coded. The test signal generator provides data in the particular 8/16-VSB format which simulates the Grand Alliance transmission signal.

Abstract: Method and apparatus for non-invasively testing performance of a digital communication system. The test system finds particular application in digital broadcast systems where interruption of regular service for test purposes is impracticable. In one embodiment oriented to digital television cable broadcast systems, unwanted reflections due to loose connectors and other causes may be localized within a subscriber's home. The test system takes advantage of information typically generated by digital receivers to correct for communication channel imperfections. Examples of such information include current filter parameters computed for use in an internal adaptive equalizer, internal loop parameters, and the difference between the signal received and a reconstruction of that signal from the symbols estimated by the receiver.

Abstract: An error is identified in a video image by calculating frequency-related coefficients for blocks of the image and considering the statistical distribution of said coefficients. The variance of the coefficients is calculated and a block of original image data is concealed if the variance calculated is significantly higher than a stored threshold and/or if said variance calculated is significantly different from variance values derived for similarly positioned blocks within a previous frame. Concealment is effected by selecting image data from a previous frame, displaced in response to transmitted motion vectors.

Abstract: A simulator for simulating the attenuation characteristics of a length of coaxial cable in a cable television (CATV) network employs a diplex filter to separate the CATV signal and AC power into at least two separate signal paths. The AC power path has a resistance selected to simulate the DC loop resistance of the desire length of cable. The CATV signal path is in parallel with the AC power path, and has an attenuation selected to simulate the characteristics of the cable at CATV frequencies. In the preferred embodiment, the simulator is equipped with separate signal paths for the upstream and downstream CATV signals that have attenuations selected to simulate the characteristics of the cable within the frequency bands used for upstream and downstream CATV signals, respectively. The resistor in the AC power path has a sufficiently high power rating to handle realistic AC power levels.

Abstract: A serial digital video data analyzer combines a co-processor capable of handling the serial digital video data stream bit rate with a microprocessor operating at a slower bit rate. The co-processor includes a video feature detection/decision module that identifies specified errors or features from the serial digital video data stream and freezes the portion of the serial digital video data stream around such feature/error in a video data store. The co-processor may also insert a cursor into the serial digital video data stream prior to display on a monitor to indicate the position of indicated errors. The acquired serial digital video data is transferred to the microprocessor for an initial determination as to whether further processing is required.

Abstract: An IC for generating various signals for television includes a switch circuit for selecting a signal to be monitored from the various signals and outputting the selected signal through an external terminal. A selection signal for selecting and outputting the signal to be monitored is supplied from a microcomputer to the IC. The microcomputer compares data contained in the signal selected and output from the IC with data which has been prepared in advance. Based on the comparison result, adjustment data used in generating a corresponding signal in the IC is renewed.

Abstract: A testing jig is comprised of a circuit board which replaces and emulates the data transfer between a network interface module and a decoder engine of a settop box in a digital network. The testing jig receives the encoded video output of an encoder used in the network and converts the protocol of the encoded video directly into the protocol used for data transfer between the network interface module and the decoder engine, thus bypassing all of the elements in the network between the encoder and the settop box and facilitating the testing of the video output by an encoder or the decoding performed by a decoder engine of a settop box.

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: An in-service composite triple beats (CTB) measurement system for a cable television (CATV) system isolates and measures weak composite triple beat components in the presence of a visual carrier modulated with program material for selected channels of the CATV system. Each channel is demodulated and digitized in a frequency bandwidth about the visual carrier for the channel (the CTB frequency range). The digitized video is sampled during the vertical interval, and corresponding samples from consecutive frames are differenced, squared and accumulated to produce a CTB value, which may be scaled and corrected for noise. Noise correction is achieved by performing the same measurement, but digitizing in a frequency bandwidth offset from the CTB frequency range. The difference between the two measurements provides a corrected CTB value.

Abstract: A communication circuit comprises a plurality of sources of program material, and a plurality of modulators for supplying a plurality of carrier frequency signals. Each modulator is modulated by a respective one of the sources of program material. Each of the program material sources is coupled to a respective modulator. The program material-modulated carrier frequencies are coupled in the circuit. Terminal apparatus is provided for demodulating at least one of the program material-modulated carrier frequency signals. The terminal apparatus includes automatic gain control (AGC) circuitry having an AGC bandwidth. The terminal apparatus is coupled to the circuit. One of the program material-modulated carrier frequencies is coupled in the circuit through a variable attenuator having an attenuator control signal input, a program material-modulated carrier frequency input, and a variably attenuated program material-modulated carrier frequency output.

Abstract: A method for objectively and non-intrusively measuring the audio-visual quality of a destination audio-video signal that generates measurement parameters that are indicative of human image quality perceptions. Subjective human test panel results are generated for a variety of audio-video test samples and objective test results are also generated by the apparatus of the invention for the variety of audio-video test samples. Accordingly, when the apparatus extracts test frames from the actual source and destination audio-video signals and compares them, audio-visual quality parameters are output by the apparatus that are indicative of the audio-visual quality of the destination audio-visual signal based upon the source audio-visual signal.

Abstract: A method, system and apparatus for frequency sweeping and frequency swap testing a CATV system wherein the CATV system has a plurality of channels and is transmitting television signals over at least some of the channels. The system includes a head end test unit coupled to the CATV system at its head end and a remote test unit coupled to the CATV system at a location remote from the head end. The head end test unit sweeps the CATV system by either generating and transmitting test signals at the channel frequencies over the CATV system or, if a television signal is being transmitted on a channel, using the television signal as the test signal. The head end test unit also measures the signal levels of the test signals and at the end of the sweep, transmits telemetry signals, which include the frequencies to be swept and the measured signal levels, over the CATV system to the remote test unit using the same transmitter that it used to generate and transmit the test signals.

Abstract: An electrical network emulates the transmission characteristics of a video signal cable, allowing tests to be made as to the length to which the cable may be extended before video signal degradation occurs. The preferred embodiment emulates a Beldon.RTM. 8281 coaxial cable, used for the transmission of serial digital video signals, and comprises four sections. The sections are arranged to emulate cable lengths of 25 meters, 50 meters and 200 meters.

Abstract: A system for determining the quality of data received by settop terminals including at least one settop terminal which analyses each data packet received by the settop terminal and determines whether the received data packet includes errors. The bit error rate is continually calculated, monitored and stored. When the bit error rate exceeds a predetermined threshold, the settop terminal generates a warning signal for transmission to the headend, which diagnoses the problem. The cable system headend utilizes the results from a group of households that have the same problem in order to isolate the source of failure.

Abstract: A system for improved echo cancellation for use in particular in television receivers. The system features a superior ghost cancellation reference signal which exhibits improved performance in noisy environments and which exhibits the flat and wide bandwidth necessary for effective channel characterization while exhibiting a higher and more evenly distributed amplitude versus time characteristic than that provided by known, non-cyclic ghost cancellation signals.

Abstract: The apparatus and method described herein shows a system of determining the delay of a delayed version of a sequence of images with respect to a relatively undelayed version. The system operates to take multiple samples of the delayed and undelayed versions at approximately the same sample position on the image and to correlate these samples over multiple image frames to determine which of a plurality of delayed images most closely match a given undelayed image. By knowing which delayed image frame most closely matches a given undelayed image frame it is shown to arrive at a coarse number of frames of delay. A fine delay measurement is achieved by adding a measure of the instantaneous frame to frame delay with respect to a known corresponding feature of the respective video type signals. The invention is also useful for comparing a given image to other images to determine the closest match.