Fluke Corporation

Hewlett-packard Company

Forte Networks, Inc.

John Fluke Mfg. Co., Inc.

Gordon A Jensen

Stephen M Ernst

Mark Copley

Charles H Whiteside

David G Fish

William R Marbaker

Scott S Neal

Thomas S Wisdom, Jr

Chris L Odell

Mark D Keisling

Stephen P Reames

Jerry David Morris

Steve Ernst

Christopher A Clabaugh

A network analysis instrument employs a CPU, display and field programmable gate array circuitry to receive network data and detect various error conditions. Percent utilization is determined and information pertaining thereto is displayed to provide a user with information regarding network operating conditions. Ghosts are detected as well as collisions, jabber conditions and runt conditions.

Method and apparatus for network analysis

A time-domain reflectometry device and method are provided wherein TDR may be performed on active Ethernet systems. A crossover network provides proper impedance termination both for pulse information generated by the TDR and for DC path signals. If a potential collision is detected when generating TDR pulses, a collision is forced by asserting a DC bias on the network thereby simulating a collision and generating a timeout at a much lower protocol level for reducing noticeable delay to network users and increasing network throughput.

time-domain reflectometer for testing coaxial cables

A termination control circuit is coupled to a far end of a cable. A modulated test signal is reflected back to a near end of the cable at a different frequency but at substantially the same level of attenuation as the test signal. Signal attenuation in the reflected signal is then measured to determine the amount of attenuation in the test signal. A second embodiment of the termination control circuit measures crosstalk by enabling and disabling termination resistors at the far end of the cable. A DC bias voltage located at the near end of the cable selectively turns on switching diodes to enable the termination resistor. Alternatively, both the attenuation and crosstalk circuits are combined together allowing both signal attenuation and crosstalk measurements with the same termination control circuit.

Method and apparatus for measuring attenuation and crosstalk in data and

A testing apparatus for token ring local area networks (LANs) which can insert into the token ring network without requiring a separate port on a media access unit (MAU). The testing apparatus of the present invention is connected between a regular network station and the MAU. The testing apparatus is insertable into the network through the MAU, and the regular network station is able to insert into the network through the testing apparatus. Once inserted, the regular network station and the testing apparatus act as separate stations in series on the LAN. Due to its central position in this configuration, the testing apparatus is able to test for possible faults that might be present in the network and/or in the station to which it is connected. In addition, since the testing apparatus does not require a separate port on the MAU, no active user on the network needs to be disconnected for any extended period of time.

Token ring local area network testing apparatus inserted in an active 'T' c

A token ring local area network (LAN) testing apparatus is provided. The apparatus utilizes time delay reflectory (TDR) in testing cable conductors that link or interconnect stations on the token ring with the token ring media access unit (MAU). In making the TDR related measurements, a directional coupler device is used in transmitting and receiving signals relative to the cable conductor. Information related to the magnitude and location of any cable conductor fault that is obtained. A TDR measurement can be used to determine the existence of a fault at the end of a cable conductor. A single matching impedance element is selected to match the impedance of the cable conductor before conducting any TDR measurement.

Token ring local area network testing apparatus using time delay

A token ring local area network (LAN) testing apparatus is provided. The apparatus is able to conduct a phase jitter measurement without disruption of normal token ring operation. The apparatus transmits a frame that includes phase jitter test data. This frame is transmitted into the token ring, together with a clock signal. After return of the frame with the phase jitter test data, a comparison is made between the recovered clock signal accompanying this frame and a reference clock signal. The result of this comparison provides a sample used in determining phase jitter. In making the measurement, an interpolation circuit is utilized to increase the resolution of the time difference between the recovered clock signal and the reference clock signal. A clamp circuit is used to ensure that each interpolation begins at the same reference voltage, as well as ensuring that the interpolation process is properly discontinued.

Token ring local area network testing apparatus for phase jitter testing

An apparatus for digital filtering of sequences of data units, such as sequences of bytes. The apparatus uses parallel application of more than one filter and stores the results of applying all filters to a whole sequence of data units. The apparatus involves the interaction of random access memories. Hence, filters are programmable. In addition, individual data units in a sequence may be trapped for comparison solely as a function of their ordinal position in the sequence.

Digital data filter for local area network

Provided is a circuit for preventing local area network packets shorter than a predetermined bit length from being received by a local area network coprocessor. Serial data which would otherwise be received by the coprocessor is delayed by a data-shift register of predetermined bit length. Simultaneously, a carrier-sense-signal, which alerts the coprocessor that serial data is ready to be received, is modified by a carrier-sense-signal regeneration circuit. If the carrier-sense-signal is detected true by the regeneration circuit for a number of clock cycles equal to the number of bits in the data-shift register, then the carrier-sense-signal is delivered to the coprocessor and the data in the data-shift register is received by the coprocessor. Once the carrier-sense signal goes false, the regeneration circuit continues to deliver the carrier-sense-signal until the data-shift register empties.

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Colorado Springs, CO, United States of America

Gordon A Jensen