Abstract: An apparatus and method for testing a communication device using a loopback path. A circuit is used to internally generate a test packet and to check the test packet once the test packet is transmitted through a loopback path within the communication device. The loopback path includes a data path from a test transceiver, through a first path within the core logic, at least one selected physical transceiver, a second path within the core logic and back to the test transceiver.

Abstract: A system tests a repeating installation having transmitter-receivers (3, 4) and a line controller (2). The system includes the repeating installation to be tested, a first tester (10), a second tester (11), an input unit (12) for entering a first virtual network into the first tester (10), an input unit (13) for entering a second virtual network into the second tester (11), and a line control table which is provided for the transmitter-receiver (3) and into which the destination transmitter-receiver (4) is written according to address information added to the data input to the transmitter-receiver (4). Test data transmitted from the first tester to the virtual network of the second tester is received by the second tester, and the received test data is examined. This greatly reduces facility costs and installation space and realizes performance evaluation of a repeating installation under a large-scale network environment.

Abstract: A vehicle communications network is provided which includes a ground translation circuit and interfacing transmitter circuits that achieve smooth current sourcing transitions. Included is a communications bus such as a J1850 having multiple-access for interfacing with a plurality of electronics, preferably within a vehicle. Each transceiver has a transmitter and receiver interfaced with the bus. The transceiver is coupled via a resistive element to the communications bus and sources current onto the bus when the transmitter output voltage exceeds the bus voltage. The added resistance advantageously reduces changes in current which may otherwise exist on the communications bus when current sourcing switches on and off.

Abstract: An intelligent data service unit (DSU) which terminates a digital subscriber loop is provided and includes a digital subscriber loop interface which receives incoming data from a DDS line of the service provider, a framing and signal converter for taking the incoming data and formatting the data for output, an output interface, a processor connected to the framing and signal converter and to each of the interfaces, and a data memory buffer coupled to the processor. All data provided to the DSU from the digital subscriber loop is reformatted by the framing and signal converter and propagated to the output interface as it is received. At the same time, a copy of the data is buffered into the memory, and the processor scans the memory to find and synchronize with an networking protocol frame (e.g., an IP frame) Once synchronized, the processor compares the destination address in the IP frame to the network address of the DSU. If the addresses match, the IP frame is stored for processing (e.g.

Abstract: A communication-line-quality measuring system includes transmission and terminal equipment. Transmission equipment has a first frame assembling part transmitting a down-link multiplexed frame signal to a down-link line having a first frequency, and a first frame disassembling part disassembling an up-link multiplexed frame signal transmitted through an up-link line having a second frequency. Terminal equipment has a second frame disassembling part disassembling the down-link multiplexed frame signal, and a second frame assembling part transmitting the up-link multiplexed frame signal obtained by frame-multiplexing an output signal of the subscriber unit with a control signal, to the up-link line. A pattern generation part in the first frame assembling part provides a test signal to an available channel of signal frames in the down-link multiplexed frame signal.

Abstract: A loopback cell control system includes ATM apparatuses and forward and backward paths and serves to perform a loopback test by circulating a loopback cell through a route in an ATM network once. Each ATM apparatus includes a time managing section, a loopback control section, and a route delay measuring section. The timing managing section measures the elapsed time between the transmission of the loopback cell and the reception thereof, and notifies a timeout when the elapsed time exceeds a predetermined reference time. The loopback control section includes a transmission control section, a turning control section, a turning control section, a relay control section, and a reception control section.

Abstract: A computer system which includes data transmission line and a plurality of data transmissions apparatuses connected in parallel to the data transmission line. Each data transmission apparatus generates transmission data and provides the generated transmission data to the data transmission line. In each data transmission apparatus, the generated transmission data provided to the data transmission line is wrapped around back to the respective data transmission apparatus without passing through any other data transmission apparatus. Each data transmission apparatus includes a data abnormality monitoring unit which determines whether the generated transmission data correlates with the transmission data which was wrapped around. It is determined that an abnormality occurred when the data abnormality monitoring unit determines that the generated transmission data does not correlate with the transmission data which was wrapped around.

Abstract: An FTTH (Fiber to the HOME) or FITL (Fiber in the Loop) system comprises a FSN (Fiber Service Node) accommodating various types of subscribers and a RT (Remote Terminal) connected through an optical fiber cable to the FSN and connected through a multiplex transmission line to a central office exchange. A test unit for performing a test of the subscriber is provided within the FSN. A test start message is issued through the central office exchange to the test unit of the FSN and the test results are received through the central office exchange from the test unit of the FSN. Communication between the RT and the FSN is carried out using overhead bits of multi-frames and according to a bit-oriented process. A test command transmitted from the RT to FSN does not include subscriber types and the test unit obtains that information from subscriber circuits. Therefore, the FSN becomes compact and costs are low.

Abstract: A dynamically adjustable communication system and method automatically adjust transmission rates of discontinuous waveforms from one signal level to another for the purpose of optimizing a quality parameter of a transmitted signal. Circuitry coupled to the transmission medium provides feedback to transmitter circuitry for the purpose of adjusting at least one of a rise time and a fall time parameter of a transmitted signal for the purpose of enhancing transmission quality. Transmission rate can also be automatically adjusted to maximize data rate and minimize errors.

Abstract: Multiplex communication equipment 1A used in a multiplex communication system, has a memory portion 12 memorizing the equipment number for the communication test. When there is an incoming call with reference to the same equipment number as one of the multiplex line 1A from the multiplex line 2A, the accommodation line portion 14a under setting a loop receives the incoming call and the communication test is done through a route for the communication test. When there is no accommodation line under setting the loop, the incoming call is rejected.

Abstract: A test signal data structure for supporting the data manipulation functions during testing of a telecommunications apparatus includes a succession of segments of real or synthetic speech which includes different successions of the same sounds; rarely occurring sounds; and sounds at extremes of level, pitch and duration, so as to be similar to natural speech with redundancy removed. In analyzing the performance of the telecommunications apparatus the analyzer takes into account the frequency of occurrence of each sound in natural speech.

Abstract: A peak-reducing waveform is estimated and summed with a composite signal to reduce the peak-to-average power ratio of the composite signal. The estimate of the peak-reducing waveform is modified to have Walsh code components orthogonal to the assigned Walsh codes. An iterative process of estimating subsequent peak-reducing waveform is implemented to produce a peak-reducing waveform which, when summed with the composite signal, results in a composite signal having a peak-to-average ratio at a desired level and thus does not have the effects of remodulating the assigned Walsh codes. Constraints on the magnitude of the unassigned Walsh code components can be included for controlling the power level under the unassigned Walsh codes.

Abstract: A novel high speed telecommunications testing apparatus and method which utilizes field programmable gate arrays to produce dynamic test modules for DS1, DS3, SONET and ATM signals interconnected by a high speed switching fabric. The high speed switch permits the direct exchange of signals from one test module to another thereby permitting simultaneous testing of different communications line protocols and further provides for multiple tests on a single data stream. Individual line interfaces are provided for DS1, DS3, and SONET lines which terminate and frame incoming and outgoing signals. Data exchange between modules in accomplished through the high speed switch fabric.

Abstract: When a first expansion unit in a computer sends data on an auxiliary bus directly to a second expansion unit, the second expansion unit sends the same data directly back to the first expansion unit. If the data sent back are not identical to the data originally sent, the first expansion unit generates an error signal. Alternatively, when a first expansion unit in a computer sends data on an auxiliary bus directly to a second expansion unit, the first expansion unit sends identical data in at least two data streams on the auxiliary bus. If the second expansion unit does not receive identical data from all of these data streams, the second expansion unit generates an error signal.

Abstract: An quality testing apparatus and method for providing an objective and real-time evaluation of voice quality in a wireless communication system. The system under evaluation would include a receiving and transmitting apparatus at both ends of the system. To evaluate voice quality, one apparatus transmits a TDM base band voice test signal to a receiving apparatus. The configuration of the transmitted TDM base band voice test signal permits the receiving end to synchronize a test sentence, contained within the TDM test signal, with a corresponding reference sentence stored at the receiving apparatus. After synchronization, the receiving apparatus uses a model of human hearing to objectively compare the two sentences, and based on the result, outputs an AQS ranking. In addition to voice quality, the apparatus measures SINAD, noise, distortion, and signal level of transmitted test tones and maintains a log of call progress statistics.

Abstract: The invention provides radio communications with an up-down signal link. In accordance with the purpose of the invention, as embodied and broadly described herein, the invention is directed to a method, system and computer readable medium with program instructions (hereafter collectively referred to as "the invention"). The invention includes receiving a downstream signal in a receiver portion of an outdoor unit, producing in the receiver portion of the outdoor unit an intermediate frequency (IF) signal from the downstream signal, and processing the IF signal in the receiver portion of the outdoor unit to produce a clean line code signal.

Abstract: A wrap back test system and method for providing local fault detection within a section of an integrated I/O interface core device on an integrated circuit is disclosed. The system and method of this invention is suitable for use in any I/O interface having both a transmitter and a receiver section. The wrap back of input test data, prior to reformatting for transmission, to the receiver's data alignment stage permits fault detection within the core of an integrated I/O interface. By illustration, in a serializer/deserializer I/O, the wrap back of alignment pattern encoded parallel data, prior to serialization, to the receiver's data alignment stage permits identifying faults in just this portion of the I/O transceiver. The wrap back test system and method of this invention permits fault isolation of within the boundaries of the I/O core and independent of external logic or testers.

Abstract: A circuit and technique whereby loopback testing is performed in a serial communications device by concurrently transmitting from and receiving data into a single FIFO storage unit. The circuit includes a transmitter, a receiver, a single FIFO, operatively connected to both the transmitter and the receiver, for storing both transmitted and received data at the end of a loopback test. The circuit may be part of a transceiver which may in turn be part of an infrared communications controller installed in a personal computer.

Abstract: An arrangement for monitoring for degraded signals in the loop distribution plant of a telecommunications network. Network interface units (NIUs) are used as an interface between a transmission medium, such as a coax cable or a radio channel, and customer premises equipment. One of these NIUs are assigned an additional task, that of generating up stream performance monitor singals, to be monitored by a centralized performance monitor and control unit, and of monitoring downstream signals to determine their performance characteristics, such as error rate, and to report that performance to the centeralized unit.

Abstract: A feedback control apparatus whereby the traditional single control loop for available bit rate (ABR) connections is segmented into a plurality of loops that are handled in a mutually related manner for better responsiveness of ABR connection feedback control. Three control loops are illustratively formed: a closed upward feedback control loop between a source end system and a virtual destination-link unit (VD-L) for an ABR connection, a downward control loop between a destination end system and a virtual source-link unit (VS-L) for the ABR connection, and an intra-switch feedback control loop between an upstream virtual source-internal unit (VS-I) and a downstream virtual destination-internal unit (VD-I) for the ABR connection.

Abstract: A system and method for analyzing network performance by correlating network performance monitoring data reported by monitoring points in the network is described herein. The system analyzes the performance monitoring parameters by: determining whether the performance monitoring parameters contain non-zero values; determining whether the performance monitoring parameters exceed a predetermined threshold value; determining whether prior performance monitoring parameters exceed a predetermined threshold value. The system initiates a problem handling process if the step of analyzing indicates a possible network problem. The system maintains the problem handling process if the performance monitoring parameters continue to indicate a possible network problem.

Abstract: A telecommunications network such as an ATM, Frame Relay or packet based network will be better managed by identifying nodes through which a virtual connection is routed between two end nodes. A new method of tracing the nodes on the route includes sending trace cells downstream of a monitoring node toward one or both end nodes. Each downstream node either loops back a trace cell identifying itself to the monitoring node or forwards the trace cell further. A plurality of trace cells sent along the route identify nodes located thereon. In one embodiment, the trace cell is an extension of the ATM FMOAM cell (ATM Fault Management OAM cell) specified for loopback functions.

Abstract: Provided are methods and systems for message transfer between nodes of a communication network which reduce the occurrence of repeated transfer failures associated with a particular message or messages within a batch. When a batch of messages sent from a sender node cannot be stored at a receiver node, the receiver node identifies which messages within the batch caused the rejection and communicates this information to the sender node. The sender node records the destinations of the identified messages in a "destination black list", and then separates messages having these identified problematic destinations from the other messages. The batch of messages is then retransmitted to the receiver, but with the messages which have the identified problematic destinations excluded from the batch. These excluded messages are then dealt with separately without causing repeated rejection of the batch.

Abstract: A loopback mechanism uses frame relay OAM loopback frames which eliminate the need for location identifiers and reduces overhead and complexity. The frames replace source and destination loopback location identifiers by a loopback indicator field, a send node count field and a return node count field. The originating node of the loopback procedure sets the number of intermediate frame relay nodes to be traversed. The intermediate frame relay nodes simply increment or decrement the node count, depending on the direction of the loopback frame.

Abstract: A digital trunk for in-band line signals, which is capable of performing the local loopback test to verify not only the normality of the digital trunk but also the normality of the operation of upper hierarchy control devices, on-line software controlling the digital trunk and office data, is realized by only adding a small quantity of hardware of signal droppers and signal inserters. The digital trunk has a line signal sender and a line signal receiver of 32 channels and is provided with signal inserters and signal droppers for looping a speech channel at the time of the loopback test of the trunk. Furthermore, signal inserters and a multiplex circuit are provided for looping an in-band line signal. Time slots 0 and 16 which are usually unused as speech channels on the digital circuit are used as an opposed channel and a reserve channel for a loopback test, respectively, and the loopback test of the local trunk is performed.

Abstract: A received ATM layer OAM cell processing apparatus for processing in real time a fault management cell among ATM layer OAM cells of F4/F5 levels applied to a user network interface and a network node interface and performing CRC-10 and CRC-32 operations with respect to the other ATM layer OAM cells such as activation/deactivation cells, a resource management cell, a system management cell and a meta signaling cell, not processed in real time. Further, the received ATM layer OAM cell processing apparatus processes in real time a performance management cell among the ATM layer OAM cells of F4/F5 levels applied to the user network interface and network node interface.

Abstract: A deficiency in a link in a messaging system is detected by sending across the link a request message that includes a coded data string, receiving across the link a reply message that includes the coded data string, and determining whether the travel time involved is excessive. To maximize the likelihood that the coded data string is included in the reply message, the coded data string is preferably included in both the subject and body fields of the request message.

Abstract: An adaptive digital data unit (600) initiates and successfully completes a remote loop back test. The adaptive digital data unit (600) has a controller (610), a local transmitter (620), a local receiver (640) a timer (622) and a detector (634). When a remote adaptive digital data unit (600) transmits a first data sequence and a second data sequence, the local adaptive digital data unit (600) receives the second data sequence from the remote digital data unit and determines if the second data sequence matches one of two predetermined data sequences. If so, a test successful flag is generated.

Abstract: A system and method for monitoring and managing the loading conditions in a CDMA wireless communication system. The system comprises a load monitoring device such as a CDMA mobile station connected to a data logging and processing device such as a diagnostic monitor. The monitoring device is placed within the service area of a base station. The monitoring device periodically initiates a call, is assigned to a traffic channel normally, and logs a power control parameter such as mobile station transmit power or the number of closed-loop power control commands received per unit time. From this information, the load monitoring device can infer the real-time traffic loading conditions of the base station. If the loading of the system exceeds a predetermined threshold, an alarm may be sent to the system management center in order to take some action to limit additional loading on the base station.

Abstract: The apparatus (101) and method provide for data transmission capability on bonded data channels of a communications network (104), such as an integrated services digital network, utilizing a single serial communication controller ("SCC") for the bonded data channels. The apparatus (101) includes an interface transceiver (210), interface circuitry (220), and an integrated multiprotocol processor (200). The integrated multiprotocol processor (200) contains an SCC (420) which may be utilized for data transmission on bonded data channels, with other SCCs (430, 440) available for use on other channels. The apparatus and method provide for proper data alignment of primary (or master) channel data and secondary channel data on the bonded channels, through the same SCC, through utilization of a predetermined information pattern transmitted in a loopback mode (810, 820) of the interface transceiver (210), to the receiver of the SCC (830).

Abstract: A loop back device of a packet communication T1 network includes: a clock generating part which inputs a frame divisional clock and a reference clock, inserts a modulated clock at a predetermined position of the reference clock to generate a main clock and is synchronous to the transformed clock position to generate a system clock for generating and extracting loop back data; a loop back data inserting part which generates the loop back data and is synchronous to the system clock generated from the clock generating part to insert the loop back data into transmission data; a framer and interface part which inputs the transmission data including the loop back data outputted from the loop back data inserting part to transmit the input data to the T1 network and receives is data from the T1 network; a loop back data extracting part which is synchronous to the system clock generated in the clock generating part to extract the loop back data from reception data outputted from the framer and interface part; and a pr

Abstract: A two-wire channel unit or line card for use in a digital loop carrier (DLC) telephone system is disclosed. The channel unit is provided with a loopback test capability by using relays to open-circuit or short-circuit the input terminals of the hybrid circuit that couples the two-wire subscriber line to the separate two-wire transmit and receive paths within the channel unit. When open-circuited or short-circuited in this manner, the hybrid circuit couples voice frequency test signals between the receive and transmit paths of the channel unit, thereby allowing loopback testing to be carried out without providing a dedicated loss/gain circuit in the channel unit. An additional relay may be provided to vary the gain of an amplifier stage in the transmit or receive path of the channel unit during operation in the loopback test mode, in order to control the overall gain of the channel unit during loopback testing.

Abstract: For use in a telecommunications network containing a component to be tested ("UUT"), a system for, and method of, providing in-band and out-of-band signals to test and analyze the UUT. The system includes: (1) a programmable switch coupled to the UUT through the telecommunications network via an in-band and out-of-band signaling path capable of providing in-band and out-of-band signaling to the UUT and (2) a host controller coupled to the switch for communication of data therebetween, the host controller further couplable to the UUT via an out-of-band signaling path capable of providing out-of-band signaling to the UUT, the host controller capable of storing and executing a sequence of instructions to test the UUT via at least one of the in-band and out-of-band signaling paths, the switch being programmable and the sequence of instructions being adaptable to allow the switch and the host controller to adapt to a particular signaling protocol of the UUT.

Abstract: A lightweight, portable, low-power automated bypass device for passing a signal between a first point and a second point on an electrical conductor when an electrical discontinuity exists thereon. The bypass device has two terminals for connection to the electrical conductor, and a continuity detector and a controllable switch. The continuity detector detects a continuous electrical connection between the points along the conductor and supplies a bypass control signal indicating when a discontinuity between the points is detected. The switch is connected to the first and second input terminals and responds to the bypass control signal for providing an electrical connection between the terminals. The bypass device can cycle between an ON time interval and an OFF time interval.

Abstract: To efficiently diagnose local and remote adapters without using dedicated hardware in a communication network to which a plurality of terminals are connected through associated adapters, a local logical address which is different from logical addresses reserved for communication between the terminals, is assigned to communication with a local adapter, and a frame including the local logical address and a diagnostic command is transmitted to the local adapter. When a remote adapter is to be diagnosed, a frame including a logical address assigned to communication with a remote terminal associated with that remote adapter, a diagnostic command, and at least one invalid character, is sent out from the local adapter to the network.

Abstract: Round trip travel time of cells in an asynchronous transfer mode (ATM) communication network is measured by injecting a time stamp into test cells in a first test instrument, transmitting these test cells to a remote node in the network, looping the test cells back from the remote node to an originating node, and detecting their arrival. Preferably the time stamps are injected into test cells configured as OAM-PM (operation, administration, and maintenance performance management) cells. A time-of-departure stamp is injected into the payload of the test cell on transmission, and a time-of-arrival time stamp is appended upon its receipt. The time-of-arrival and time of departure time stamps are compared to determine the actual round trip travel time of the cell within the network. This information can then be used to optimize network traffic flow, especially for available bit rate virtual connections.

Abstract: A novel high speed telecommunications testing apparatus and method which utilizes field programmable gate arrays to produce dynamic test modules for DS1, DS3, SONET and ATM signals interconnected by a high speed switching fabric. The high speed switch permits the direct exchange of signals from one test module to another thereby permitting simultaneous testing of different communications line protocols and further provides for multiple tests on a single data stream. Individual line interfaces are provided for DS1, DS3, and SONET lines which terminate and frame incoming and outgoing signals. Data exchange between modules in accomplished through the high speed switch fabric.

Abstract: A line monitoring apparatus which features a simple configuration is capable of quickly detecting a position where a failure has occurred. A main track signal on an up-stream optical transmission path is set for a different wavelength from that on a down-stream optical transmission path, so that the wavelength of loopback signals fed back from repeaters does not overlap the wavelength of the main track signals transmitted from a transmitting terminal station. This makes it possible to separate the main track signals and the loopback signals by using dividing circuits at receiving terminal stations. In addition, the level of the separated loopback signals can be set higher than that in the past; therefore, a monitoring signal can be quickly detected in the loopback signal.

Abstract: A loop back test system and method for providing local fault detection within the core or macrocell of an integrated I/O interface device on an integrated circuit is disclosed. The system and method of this invention is suitable for use in any I/O interface having both a transmitter and a receiver section. The loop back of input test data from the transmitters output directly to the receiver's input permits fault detection within the core of an integrated I/O interface. By illustration, in a serializer/deserializer I/O, the loop back of serialized, alignment pattern encoded parallel data from the output stage of the I/O transmitter to the receiver's input stage permits identifying faults occurring within the integrated I/O transceiver macrocell. The loop back test system and method of this invention permits fault isolation of within the boundaries of the I/O core and independent of external logic or testers.

Abstract: A method and apparatus for characterizing a communications link. An apparatus is disclosed for performing a series of tests that measure delay time, frequency response, background noise, frame error rate and sample slipping and repetition measurements. A signal generator generates a series of signal optimally selected for the particular test. The generated signal is transmitted through the communication system and then sent back through the system by a loop back element remotely placed. The return signal is then analyzed by a monitor means.

Abstract: An enhanced ISDN-DP transmission device of the present invention allows for testing of ISDN-protocol communication paths using an existing DDS-protocol test infrastructure. The ISDN-DP unit receives a DDS test command and determines whether the command was intended for the immediate receiving unit or a tandem unit. If the command is intended for the immediate ISDN-DP unit, the unit processes the command. If the command is intended for another ISDN device in the transmission path, the ISDN-DP converts the DDS-protocol command to an ISDN-protocol command and transmits the converted ISDN command to an adjacent tandem ISDN device in the communication path in an upstream or downstream direction. After the test path is enabled, loopback testing is available on all available ISDN bandwidth, including the B1, B2 and D+ channels, from a DDS-protocol test set.

Abstract: A method is described for detecting a loopback condition in a trunk. A predetermined bit pattern is inserted in an outgoing channel, and a corresponding incoming channel is continually monitored to detect the presence of the predetermined bit pattern. In this way, premature restoration of faulty circuits can be prevented.

Abstract: A failure detector, connected to receive a signal from an interface at a lower level than the SONET level, detects a failure in that interface, such as a fiber cut or the loss of signals. An AIS generator is responsive to the detection of a failure by the failure detector to generate an AIS at the SONET level (STS and VT levels). A signal processing circuit converts a low-level signal from the interface to an SONET-level signal. When receiving the SONET-level AIS from the AIS generator, the signal processing circuit inserts it onto the SONET-level signal for application to SONET ADMs.

Abstract: A communication control apparatus achieves accurate and efficient detection of errors in transmitted control data. Control data is transmitted from a first node to a second node. If the second node determines that the data is free from errors, the second node returns the data to the first node. The first node compares the returned data to the originally transmitted data. If the data matches the originally transmitted data, the first node sends an acknowledge signal to the second node. If the returned data does not match, the first node transmits an error signal to the second node. In this manner, the first node detects data errors even when error checking at the second node fails.

Abstract: The invention provides advantageous and reliable loop equipment (60) for establishing a test loop for monitoring the condition of a radio station including at least two antennas. The loop equipment (60) comprises input ports (61, 61'), output ports (69, 69') and a controllable selector switch (62) wherewith the signal of one input port (61') is selected to at least one output port (69, 69'). The loop epuipment is so adapted that its input ports (61, 61') are connected to the outputs of tansmitters (TX, TX') and output ports (69, 69') to the input of a receiver (RX, RX'). Various test loops for monitoring the condition of transmitters, receivers and antennas at a radio station can be established by means of the loop equipment.

Abstract: A radio apparatus according to a TDMA/TDD system uses its own transmitter and receiver so as to perform a loopback test for checking normality of the apparatus during a period of an unassigned slot. A loopback test signal is output from its own transmitter during an unassigned transmitting slot and is received by its own receiver. The signal is temporarily stored in a memory and is read during an unassigned receiving slot. The apparatus thus performs a loopback test. Since a loopback test can be performed by use of its own transmitter and receiver during an unassigned slot, a transmitting and receiving device (tester) specifically used for a loopback test is not required. Also, a loopback test can be carried out even while normal communications are being made.

Abstract: A loopback mechanism uses frame relay OAM loopback frames which eliminate the need for location identifiers and reduces overhead and complexity. The frames replace source and destination loopback location identifiers by a loopback indicator field, a send node count field and a return node count field. The originating node of the loopback procedure sets the number of intermediate frame relay nodes to be traversed. The intermediate frame relay nodes simply increment or decrement the node count, depending on the direction of the loopback frame.

Abstract: A method of testing an ATM exchange having a redundant structure that includes an active system and a standby system includes the steps of transmitting a test cell from a testing device to both the active system and standby system, causing the test cell to pass through ATM switches in each of the active and standby systems, returning the test cell that has passed through the ATM switches of both systems to the testing device, and conducting a test of the ACT switches in the active and standby systems by comparing data contained in the transmitted test cell with data contained in a test cell received from the active system or standby system.

Abstract: A communication system testing method for testing a communication unit including a communication line and components of a communication unit such as a terminal unit. In addition, a control apparatus includes pause control means and control means, both of which are incorporated in an integrated communication control circuit. When the integrated communication control circuit is in the pause state, the pause control means outputs a pause permission indicating signal and detecting signal. The control means discontinues the supply of the main-clock signal by outputting the detecting signal, thereby limiting energy consumption.

Abstract: The loopback test consists of a user-application interface that connects the network operator to substantially all of the ATM points in the network. In operation, the network operator selects two ATM points as the loopback and source endpoints for the loopback test. The virtual path identification (VPI), virtual channel identification (VCI) and payload type indicator (PTI) that will be in the address header of the test cell when it arrives at the loopback endpoint location and the identification of the loopback endpoint are transmitted to the loopback endpoint in a setup message via a link from the UAI. The VPI, VCI and PTI that constitute the address header of a test cell injected at the source endpoint and destined for the loopback endpoint, and the location identification of the source endpoint are provided to the source endpoint in a setup message via a separate link from the UAI.