Showing papers on "Loopback published in 1993"

Configuration data loopback in a bus bridge circuit

Abstract: A method and apparatus for reducing cost and complexity of devices in a bus bridge circuit by dividing address and data paths between separate devices to reduce pin count, and by looping back "bridged" configuration data to access configuration registers. The host bridge circuit "bridges" all I/O accesses received over a host bus directly to a peripheral component bus without any decoding. The CDC is both initiator and target on the peripheral component bus for I/O access cycles generated by the host bridge circuit that are targeted for a host bridge configuration register.

Asynchronous transfer mode link recovery mechanism

Abstract: An inter-node communications link failure recovery system for ATM nodes in which connections are quickly switched from a faulty link to one or more existing links. Within a node, alternate connection routes are predetermined for every connection originating at or terminating to a circuit connected to a link of interest (i.e., a link where recovery from a link fault is desired). The routing information for alternate connections is stored in the ATM node CPU memory. In response to an alarm indicating a break or other failure of link, the Network Management System sends a command to the node to establish hardware "loopback" path in the node interface circuit connected to the faulty link. The ATM node 10 then down-loads the alternate routing information for the failed link to the node routing tables used to route a cell onto a link in accordance with the cell header data. This causes all cells originally set up for transmission over the faulty link to be re-routed to a predetermined alternate link.

Out-of-band loopback control scheme

Abstract: A communications method and a network for carrying out the method are provided. The network includes a loopback command system and a first link station connected to a communications link. The link traverses several loopback-capable devices as it extends from the first link station to a second link station remote from the first link station. The loopback command system controls the loopback-capable devices to cause them to loopback. In order to command a loopback of a particular loopback-capable device, the first link station generates an initial loopback value and forwards the same over the link to a downstream loopback-capable device located along the link. Each loopback-capable device receives a loopback value from an upstream device, and compares if the received value is equal to a predetermined value. If the loopback value is equal to the predetermined value, the device is placed into a loopback state. Otherwise, the loopback value is modified by the device, and the modified loopback value is forwarded to the next downstream device located along the link. The loopback value may be represented by a digital bit word, or by the position of a particular bit within a bit stream of the link.

Local loopback of isochronous data in a switching mechanism

Abstract: A data communication system such as a local area network or a wide area network capable of transmitting isochronous data. The system conveys both isochronous data and non-isochronous data by time multiplexing data into a recurring frame structure on a 4-bit nibble basis. The arriving data is de-multiplexed at a hub into separate channels which are forwarded to separate hardware appropriate for handling the particular data stream. The data is passed hierarchically from a source, through a node, and to a hub. The hub places the data into an internal connection memory for switching onto a high bandwidth bus for distribution to other destination hubs, nodes, or sinks, except, where the source node and destination node are attached to the same hub, the hub provides a local loopback to the destination node, thus avoiding the need to place the transmitted data onto the bus. This system conserves room on the bus for other isochronous and non-isochronous data.

Apparatus for detection and location of faults in two-way communication through single optical path

Abstract: In a first apparatus, transmission signals are inverted in a sending side and are restored in a receiving side in one direction of two-way communication, and transmission signals are not inverted in another direction, to thereby distinguish a signal reflected at a fault point of an optical fiber from normal receiving signals from the station of the other party. In a loopback test, an inverter provided in the receiving side of the former direction is bypassed and an inverter is inserted in the receiving side of the latter direction. In a second apparatus, overhead information for identifying stations is added in a sending side. In a receiving side, the overhead is extracted. The extracted overhead is compared with an identifier of the station of the other party in a normal operation and is compared with an identifier of the station itself in a loopback test.

Loopback test circuit

Abstract: A digital multiplex communication system for carrying out digital multiplex communication between a plurality of terminal stations, at least two including one initiating party and the other party to communicate with, via a branching unit. In this system, groups of bits in a communication frame are allocated in advance for use in communication between one party and the other. In order to diagnose the state of the transmission line to the other party including the branching unit, loopback setting signals for setting the other party in the loopback test mode and loopback test signals are inserted into specific bit positions of the preallocated groups of bits in performing communication.

Digital data loopback device

Abstract: The need to equip a digital data service termination with the ability to decode digital loopback commands is obviated by a relatively simple hardware modification of a four wire telephone circuit connecting an office channel unit and customer premises equipment. In addition, the signal processing and test control firmware of the office channel unit equipment (OCU DP) is modified so as to realize a simplified circuit configuration for performing loopback testing of the four wire circuit. The hardware modification of the four wire circuit connecting the office channel unit and the customer premises involves the use of a sealing current-dependent relay circuit that responds to respectively different sealing current flow states: normally; interrupted; and reversed, as converted by the OCU DP. The present invention is particularly useful in subscriber loop circuits that are less than 10,000 feet in length, whereby the need for additional amplifier and noise reduction components is obviated.

Enhanced port activity monitor for an integrated multiport repeater

Abstract: A system is provided on an Integrated Multiport Repeater (IMR) to monitor the activity of the IMR when the repeater is in minimum mode. Through this system the serial output pin outputs status based upon inputs at two input pin the signal in and the clock signal. In a preferred embodiment there are four different status outputs, partition, loopback/link, Bitrate and SQE/Polarity. This system finds use in low end applications where complex control circuitry is not desired.

Optical transmission system

Abstract: An optical transmission system comprises amplified forward and return paths between a local station and a remote station. Each amplifier of the forward path has an attenuated loopback coupling its output to the return path. Frequency modulated supervisory signals generated at the local station are returned via the loopbacks. These signals are analysed e.g. by Fourier analysis to obtain a measure of the performance of each amplifier. The system may also be employed for the location of fiber breaks.

Token ring test simulation method and device

Abstract: A loopback connector system for testing token ring components such as routers or interface assemblies with requiring that the component to be tested be connected into the local area network (LAN). The connector permits the component to be tested to be isolated from the LAN, permitting the integrity of the component to be tested without regard to the integrity of lobe cables or other devices on the ring, and without degrading network performance. The connector system includes two different multi-pin connector types, a DB9 and an RJ45 connector, used to connect into the network, separated by a short two-pair cable. Resistors used to simulate the network loading on the component are connected between appropriate pins, with the resistors being shared between the two types of connectors.

Hybrid loopback for FDDI-II slave stations

Abstract: Embodiments of the present invention provide methods and circuits for testing the hybrid capabilities of a station before the station is connected into an FDDI-II hybrid ring. One embodiment tests hybrid mode operation of an FDDI-II non-monitor station by creating a loopback ring, generating cycles for isochronous transmission on the loopback ring, and measuring the progress of the cycles around the loopback ring. The loopback ring created may be internal to a single integrated circuit, internal to a single slave station, or limited to a pair of stations, such as a concentrator and a single attachment station. Another embodiment provides a circuit for use in station on an FDDI-II ring. The circuit includes a loopback circuit which may be configured to create a hybrid ring and a cycle generator for generating cycles on the hybrid ring. The cycle generator includes a small latency adjustment buffer (LAB) and a limited isochronous media access control unit (IMAC) which are incapable of cycle master operation but are sufficient to provide test cycles.

Accelerated token ring network

Abstract: Methods and apparatus, including a concentrator for operating a station (92) coupled to a ring in a token ring network (80). The ring carries signal at an active monitor clock rate. The method includes the steps of generating a local clock (86) at an accelerated clock rate (84) that is equal to or greater than the active monitor clock rate, operating the station (92) at the accelerated clock rate (84) when the station (92) is a standby monitor, operating the station (92) at the active monitor clock rate when the station is the active monitor, operating the station at its own clock rate when the station is in loopback mode, and receiving signal from the ring and transmitting signal to the ring at the active monitor clock rate. The station (92) operates at the accelerated clock rate (84) of the local clock (86) except when the station (92) is active monitor or is in loopback mode.

Linear power amplifier circuit

Abstract: PURPOSE:To reduce phase modulation distortion caused in a saturation type power amplifier due to negative feedback in the linear power amplifier circuit amplifying transmission power of multi-phase PSK modulation system linearly. CONSTITUTION:A feedback voltage amplitude adjustment circuit (loopback band variable circuit) 28 used to allow a negative feedback circuit implementing negative feedback to change its loop back band for adjusting a loopback voltage is provided to a gain variable terminal 14 of a saturation type gain variable terminal 14. The loopback band circuit 28 under the control of a control circuit 22 sets the loopback band to be a frequency band lower than an amplitude change frequency at a linear region of the power amplifier 12, that is, at a small output power area so as to reduce or interrupt its high frequency component thereby passing only a DC component required for power control. Thus, a loopback voltage amplitude at the small output power region not requiring distortion compensation is reduced to reduce the phase modulation distortion of the power amplifier.

Full duplex ethernet

Abstract: A method and apparatus for providing full duplex operation of a link-based, point-to-point network that transmits signals in accordance with a carrier sense multiple access with collision detection protocol. The network may be a wide or local area network. The system includes a first data terminal equipment unit coupled to a first medium attachment unit, the first medium attachment unit including a collision detection disabling circuit (54) and a loopback disabling circuit (52) so that the first medium attachment unit provides full duplex transmission and reception of signals. The system additionally includes a second data terminal equipment unit coupled to a second medium attachment unit, the second medium attachment unit including a collision detection disabling circuit (54) and a loopback disabling circuit (52) so that the second medium attachment unit provides full duplex transmission and reception of signals.

Bi-directional transmission line changeover ring network

Abstract: PURPOSE: To simplify the configuration of the hardware relating to loopback circuit and its control. CONSTITUTION: When a fault takes place in a ring transmission line 11 and a node 12 adjacent the failed node forms a loopback to loop back a transmission line between a 1st optical fiber 21 and a 2nd optical fiber 22 to relieve the line, a time slot number of a slot group 21W for forming a real line allocated in the 1st optical fiber 21, a time slot number of a time slot group 21P for line relieve, a time slot number of a time slot group 22P for line relief allocated by the 2nd optical fiber 22 and a time slot number of a time slot group 22W for real line are set identical to each other respectively. COPYRIGHT: (C)1994,JPO

Alarm transfer system and atm communication equipment using the system

Abstract: PURPOSE:To prevent congestion of data in the communication equipment by transferring an alarm signal at a speed below an average transmission information speed. CONSTITUTION:The system consists of an existing terminal interface section 1, a VCI termination section 2 provided with an ATM cell composition decomposition section, a loopback control section, an alarm detection section and an alarm transmission section, a VPI termination section 3, a line interface 4 and an internal bus 5 used for interfacing each section. Then alarm information is transferred at a speed below a minimum VC speed when the alarm and loopback execution information detected by the VCI termination section 2 are noticed to the VCI termination section in an ATM communication equipment of an opposite station.

Experimentation on the concentrator tree with loopback

Abstract: The fiber distributed data interface (FDDI) concentrator tree topology with loopback is proposed for use in networks which need to continue operation after multiple faults. Initial experiments to use the concentrator tree with loop-back result in configurational dependencies which are not initially understood. A few caveats are found which can be handled through careful cabling. Both a theoretical and an experimental analysis of various cases of the concentrator tree with loopback are provided. A discussion on the use of bypass relays in the concentrator tree with loopback is given.

Cable length measuring system for loop network

Abstract: PURPOSE:To measure a length of a cable without stopping a network system by measuring a time of a packet from being looped back from a node equipment till being returned to a montor equipment so as to measure the length of the cable connected between equipments. CONSTITUTION:A monitor equipment 1 allows a node equipment 3 to cause loopback operation to send a signal packet to the operating system. The signal packet is sent to a node equipment 2 through cables 11, 12 and inputted to the node equipment 3. Then a loopback is caused and the packet is looped back to a standby system, the packet is sent to the standby system of the node equipment 2 through cables 21, 22 and returns to the standby system of the monitor 1. Then the monitor 1 measures the delay time after the signal packet is sent to the operating system till it returns to the standby system. The time resulting from subtracting a delay time of the operating system, the standby system of the node equipment 3 and the loopback from the measured delay time is divided by a delay time of the cable per unit length to obtain the length of the cable. Then the length of the cable is measured without stopping the network system.

Automatic loopback test system for data transmission system

Abstract: PURPOSE:To provide an automatic loopback function to a system even when the signal of the V25bis interface is transmitted. CONSTITUTION:The measuring section 13 of a station A outputs a loopback code composed of consecutive 4 envelopes respectively including the bit pattern data of a data 100100 and in which the status bit of each is the pattern of alternate 1/0 in the unit of each envelope. The data code detection circuit 110 of a station B detects a data whose bit pattern is 100100 and outputs the signal of logic '1' when the data are consecutive for 4 envelops. An S bit code detection circuit 111 outputs the signal of logic '1' when the status bits are changed as 1010 in the consecutive 4 envelopes. In this case, an AND circuit 112 outputs the signal of logic '1', a loopback latch circuit 114 is set and a loopback circuit 115 sets a loopback path.

Loopback system in optical relay system

Abstract: PURPOSE:To prevent a loop island in an optical relay system having a loopback function. CONSTITUTION:A signal from an oscillator 9 whose frequency is fo is used to modulate a transmission signal at loopback, a monitor control circuit (5) detects the fo component at an input of an optical repeater 8 or other optical repeater 4 through a reception circuit 6 and a band pass filter 7, an optical shutter 3 is controlled to reject a loopback command or to release the loopback.

1:n path loopback method for ring transmission line network

Abstract: PURPOSE:To restore a loopback for a 1:n path on a double ring transmission line with a simple operation by setting a return standby path and a distribution standby path to a transmission line in an opposite direction to that of an active path transmission line so as not to be closed as a ring. CONSTITUTION:A reception node 4 at a down-most point of an active path 51 is set to be an outgoing node and an outgoing node 1 of the active path 51 is set as an incoming node in a return standby path 62 and the nodes are connected to a path connection section 63 by a distribution standby path 64. Then a path identification number is set to the same number as the active path 51. The distribution standby path 64 is branched at the nodes 3, 4 of the 1:n path from a transmission node 1 of the active path 51 till the uppermost node 2. The distribution standby path 64 is connected to the active path 51 by path connection sections 92-94 in the nodes 2-4. Then a different path identification number from that of a relevant return standby path 62 is allocated. Thus, the loopback is restored by having only to set reflection connection of a transmission line or a path against a fault of the transmission line.

Digital signal processing circuit

Abstract: PURPOSE:To improve the loopback distortion caused by the presence of a digital nonlinear limiter circuit in a digital nonlinear emphasis circuit without increasing a sampling frequency. CONSTITUTION:The digital nonlinear emphasis circuit consists of a digital high pass filter(HPF) 1 passing the high frequency component of an input digital signal S1, a Hilbert transformation circuit 2 shifting the phase of a signal S2 from the HPF 1 by 90 deg., a digital nonlinear limiter circuit 3 composed of a ROM or the like limiting the amplitude of an analysis signal in complex expression composed of a real component S2 from the HPF 1 and an imaginary component S3 from the Hilbert transformation circuit 2 while keeping the phase, a digital band pass filter(BPF) 4 having a complex band pass characteristic and a digital signal adder circuit 5. By such circuit constitution, since no negative frequency component is present on harmonics, the loopback distortion is eliminated without increasing the sampling frequency.

Optical communication system

Abstract: PURPOSE:To release loopback with an optical signal by arranging 1st and 2nd control means toward the input side of an optical signal more than 1st and 2nd optical switches. CONSTITUTION:A 2nd optical switch 24b is arranged to a post-stage of a 1st main function section 25a controlling a 1st optical switch 24a and a 1st optical switch 24a is arranged to a post-stage of a 2nd main function section 25b controlling a 2nd optical switch 24b. In this case, an optical signal sent to a 1st transmission line 22 is fed to the 2nd optical switch 24b via the 1st main function section 25a and the optical signal sent from the 2nd transmission line 23 is fed to the 1st optical switch 24a via the 2nd main function section 25b. Thus, even when the 1st loopback and the 2nd loopback are formed, the signal is fed to the 1st and 2nd main function sections 25a,25b by using the 1st and 2nd transmission lines 22,23.

Osi/transport layer loopback system

Abstract: PURPOSE:To reduce the operation of collision of transfer data and the operation of an excess protocol stack on a line in the OSI/application. CONSTITUTION:The system is provided with an address comparator section 4-1 comparing a publication source address of an application with a publication destination address (both are below the network layer), a conventional processing protocol section 4-2 of an OSI/- transport layer, and a loopback processing section 4-3 looping back the high-order layer of the transport layer when the address is the same.

Remote loopback system for radiocommunications transceiver

Abstract: Respective transmission (CT1) and reception (CT2) facilities of the remote loop-back system respectively transmit and receive sequences of data at the input of a transmission chain and at the output of a reception chain of a transceiver system. The remote loop-back system thus makes it possible locally to test the transceiver system. A processing member (CT3) activates an oscillator (OS) which produces a signal (SOS) having a frequency equal to the difference in the transmission and reception frequencies of the system. This oscillator signal (SOS) is applied to an input of a microstrip circuit comprising a low-pass filter (FI), a mixer (ME) and a coupler (C0). This circuit is fixed in the vicinity of a waveguide receiving a microwave signal originating from the transmission chain. This microwave signal is transposed in the waveguide to the reception frequency by means of the mixer (ME) and coupler (CO) before being retransmitted to the input of the reception chain.

Communications terminal equipment and automatic adjustment circuit

Abstract: PURPOSE: To unnecessitate the adjustment of an analog signal processing system especially in the communications terminal equipment of the time division multiple access time division communications system. CONSTITUTION: The terminal equipment is provided with a transmission reception antenna 16, a transmission amplifier 14 amplifying a transmission signal of a concerned station subject to orthogonal transformation, a reception amplifier 17 amplifying a reception signal from another station received by the antenna 16, a switch circuit 15 receiving a transmission signal from the transmission amplifier 14 to apply it to the antenna 16, applying a reception signal received by the antenna 16 to the reception amplifier 17 and applying part of the transmission signal to the reception amplifier 17 via a fixed attenuator 15a as a loopback signal, an orthogonal detection circuit 18 applying orthogonal detection to the reception signal amplified by the reception amplifier 17 or a loopback signal at the concerned station, and an error detection circuit 21 detecting a DC offset error and a gain error of the two amplifiers 14, 17 by the detection output of the orthogonal detection circuit 18 and feeding back the detected error signal to the amplifiers 14, 17. COPYRIGHT: (C)1994,JPO&Japio

Port activity monitor for an integrated multiport repeater

Abstract: A system is provided on an Integrated Multiport Repeater (IMR) to monitor the activity of the IMR when the repeater is in minimum mode. Through this system the serial output pin outputs status based upon inputs at two input pin the signal in and the clock signal. In a preferred embodiment there are four different status outputs, partition, loopback/link, Bitrate and SQE/Polarity. This system finds use in low end applications where complex control circuitry is not desired.

Remote loopback test method

Abstract: PURPOSE:To check a line without interrupting line service. CONSTITUTION:A synchronization digital multiplexer converting an asynchronous hierarchy signal into a signal format of the North America SONET hierarchy and multiplexing the signal at a local side is provided with a pattern generating circuit 8 and an error detection circuit 10, and the local side inserts test data from the pattern generating circuit 8 to excess bits and the result is sent to the remote side, and the remote side receiving the transmission signal replaces again the test data with excess bits and sends the result back to the local side and the error detection circuit 10 monitors the sent-back test data.

Fault detection system

Abstract: PURPOSE:To easily detect a fault location by providing a generating circuit for a test signal, a loopback switch for each system and a fault detection control circuit so as to loop back a standby side automatically depending on the function when an active side is in use. CONSTITUTION:The system is provided with a fault detection control circuit 1, a signal changeover switch 2, a signal generating circuit 3, loopback switches 6, 8, 10, a signal reception circuit 11 and a fault location detection circuit 16. The fault detection control circuit 1, for example, outputs a loopback switching control signal (h) for discriminating a fault location. The signal reception circuit 11 receives a test signal (b) without an error for a prescribed time to discriminate it that the transmission interface circuit 4 and the reception interface circuit 12 are normal. Then the fault detection control circuit 1 stops the loopback switching signal (h) and when a signal (i) is outputted, since the signal (b) cannot be received without error, a fault detection signal (k) is outputted to the fault location detection circuit 16. A transmission code processing circuit 5 or a reception code processing circuit 13 is discriminated to be a circuit fault.

Optical transmission device

Abstract: PURPOSE:To switch an optical transmission line almost without momentary interruption and to detect a fault location immediately by providing an optical loopback means to the device so as to loop back an optical signal to an incoming optical transmission line toward an outgoing optical transmission line CONSTITUTION:In the case of loopback, an optical loopback means 3 uses an ultrasonic wave modulator or the like to loop back an optical signal from an optical transmitter major section 2 to an incoming optical transmission line 4 toward an outgoing transmission line 5 Thus, the optical signal is switched almost without hit to attain loopback without implementing jumpering Thus, when an active line is broken due to any cause, which of a cable in a ring or each optical transmitter has a fault is immediately discriminated