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 test instrument and method for testing switched LANs using a set of available MIBs in a switch is provided. The test instrument is designed for the characterization, diagnosis, and testing of a LAN having at least one switch which divides the network traffic into segments. A network device such as a switch will have a set of available MIBs, usually determined by the vendor, which may be accessed via an SNMP agent in the switch. Using the information selectively gathered from this set of available MIBs, various reports may be generated and displayed as reports which allow for a detailed analysis of switch parameters and traffic patterns. For any given report, optimal data items are chosen according to a predetermined hierarchy which provide the most pertinent, detailed information for each given report.

Abstract: A digital baseband modulator having a flexible architecture that is readily adaptible to a variety of digital modulation types is provided. A symbol builder maps the input data to a series of modulation states corresponding to data symbols that are represented as state indexes. A pair of digital filters accepts the state indexes being generated by the symbol builder to provide both up-sampling and filtering functions. The digital filters are implemented using random access memory (RAM) to implement blocks of interpolating look-up multipliers which may be readily configured between fast, normal, and long modes. The filtered output data from the digital filters is provided to a resampler that converts the filtered output data to an output sample rate that corresponds to the sample rate of output DACs and corresponding analog low pass filters.

Abstract: A method of maintaining an electronic device, the method including the steps of monitoring ambient an environmental condition such as temperature or humidity; monitoring a self-test initialization criterion; performing an automatic device self-test if the self-test criterion is met and if the environmental condition is within a predetermined range; and not performing the automatic device self-test if the self-test criterion is met but the environmental condition is outside the predetermined range. In a preferred embodiment, the device is an external defibrillator.

Abstract: An efficient method for calculating Power Sum cross-talk loss is provided. Cross-talk loss measurements may include near-end cross-talk (NEXT) loss, far-end cross-talk (FEXT) loss, multiple disturber NEXT (MD NEXT) loss, and multiple disturber FEXT (MD FEXT) loss. Pair-to-Pair cross-talk loss responses are collected between a given wire pair and all the other wire pairs of concern, with each pair-to-pair cross-talk loss measurement having a number of frequency data points corresponding to the frequencies of interest. The pair-to-pair cross-talk loss response having the lowest positive value for a particular frequency data point is first selected as the baseline cross-talk loss response. The effects of each of the remaining pair-to-pair cross-talk loss responses on the baseline cross-talk loss response are then accounted for by applying power sum contribution values obtained from a look-up table.

Abstract: In a local area network (LAN) test instrument, a method for detecting duplicate internet protocol (IP) addresses without disrupting the LAN is provided. The LAN test instrument provides a method of choosing an IP address for itself without disrupting the ARP caches of devices connected to the LAN. Duplicate IP addresses between devices on the LAN may then be tested using a series of network broadcasts chosen to elicit responses from as many nodes on the network as possible because some nodes respond to some types of broadcasts and not others. A data base of the various nodes is collected and the newly arriving responses are dynamically compared with the responses already in the data base to detect duplicate IP addresses. Separate entries in the data base for devices having duplicate IP addresses are maintained and then displayed to the user of the LAN test instrument to selectably and reliably communicate with the devices having duplicate IP addresses for further diagnosis and correction.

Abstract: A method in a LAN test instrument for detecting proxy ARP agents and misconfigured routers in a TCP/IP LAN is provided. The method first allows for detection of routers running proxy ARP for the default route by issuing a single ARP command for a unique remote host. Because the target IP address chosen as a unique, non-existent device, the router will respond to the ARP request with a proxy ARP reply for its default route if this function is enabled. The method further allows for distinguishing between responses from actual devices having duplicate IP addresses and responses from misconfigured routers replying in proxy ARP for local hosts. The false duplicate IP addresses due to proxy ARP replies may be identified as phantom entries in a data base that can then be appropriately tagged or eliminated to display only the entries that correspond to actual physical devices to the user of the LAN test instrument.

Abstract: A detector circuit operating in parallel with a bandwidth limited measurement channel in a measurement instrument generates a warning signal when an input signal exceeds a predetermined repetition rate or has a pulse width less than a predetermined value. To provide a warning signal to the measurement instrument that the input signal contains high frequency components that are likely to be missed by the measurement channel, the detector circuit operates in parallel with the measurement channel. A pulse width in the input signal that is sufficiently narrow or a repetition rate that is too high causes the detector to generate the warning signal that is provided to the measurement instrument.

Abstract: A potable electronic test instrument is adapted for the automatic testing of semiconductor diodes regardless of the orientation of the diode relative to the test probes. The test instrument supplies an a.c. sine wave test voltage coupled to the test probes. The maximum negative voltage and the maximum positive voltage are measured and compared against a set of predetermined open and short circuit values to obtain a decision of open, short, or ok for each value. The combination of the two comparisons is used to determine the device status according to a decision criteria. The diode status is accordingly displayed on the graphical display of the test instrument, indicating the device is open, shorted, a diode with a forward orientation or a reverse orientation with respect to the test probes, or of an unknown type. The diode forward bias junction voltage is displayed regardless of its orientation.

Abstract: A pulse-based LAN cable test instrument that processes time-domain cross-talk measurement information in order to troubleshoot and quickly locate sources of cross-talk as a function of distance along the LAN cable system is provided. A pulse-response time record between a pair of transmission lines of the LAN cable system is first acquired. A series of steps to process the time-domain pulse response data in the time record are then performed to enhance the ability of the user to locate and troubleshoot the primary contributors to NEXT along any point of the LAN cable system. The pulse response data are first normalized as a function of distance from the LAN cable test instrument in order to compensate for losses along the LAN cable. Next, the pulse response data are integrated over the time record and the absolute value of the pulse response data is calculated to more clearly show the individual sources of cross-talk within the overall LAN cable pulse response.

Abstract: An adaptive digital filter is provided to obtain improved measurement accuracy in an electronic instrument which has a front-end circuit for coupling to an input signal to be measured. An analog to digital converter converts the input signal received through the front-end circuit into a stream of measurement values during the measurement phase. The stream of measurement values are then provided to the adaptive digital filter which mathematically operates on them to remove the frequency response effects of the front-end circuit in a process of convolution in the time domain using a set of digital filter values obtained during the calibration phase. Because the frequency response requirements of the front-end circuit have been eased with the addition of the adaptive digital filter, a simpler front-end circuit with fewer components and with no need for manual adjustment may be employed in electronic instruments.

Abstract: A method of displaying continuously acquired measurement values as a plurality of traces in a display with a fixed number of pixels is provided. An input signal is captured as a series of acquired input signals. Measurement values are calculated from the acquired input signals according to a set of measurement parameters. The measurement values are plotted to a display as a plurality of traces according to the measurement parameters. Each of the traces may be scaled vertically independently of one another. At the end of the fixed number of pixels of the display, the pixel values are compressed to half the fixed number of pixels and the pixel rate is halved, thereby doubling the time scale. As a minimum pixel rate is eventually reached, the traces are then scrolled in a roll mode in which the newest measurement value is added to one end of the display and the old value at the other end is discarded.

Abstract: A method of displaying continuously acquired measurement data in a display with a fixed number of pixels is provided. Measurement data is provided at a predetermined fixed sample rate independent of a pixel rate which is equal to or less than the sample rate. The measurement data is convened to pixel data which includes the minimum, maximum, and the average of the measurement data gathered and the pixel data is plotted to the pixels at a pixel rate. At the end of the fixed number of pixels of the display, the pixel values are compressed to half the fixed number of pixels and the pixel rate is halved, thereby doubling the time scale. This process can continue indefinitely, requiring no operator intervention or prior knowledge to set a total measurement time. Furthermore, the sample rate is independent of the pixel rate so that a tradeoff of sample rate and total measurement time need not be made.

Abstract: In accordance with the present invention, a measurement instrument employing an improved method for measuring relative compression is provided. The compression signal is first acquired by digitizing the battery voltage over multiple engine cycles using an analog to digital converter (ADC) to obtain a series of digital samples. The compression signal is filtered using a low pass digital filtering technique such as a finite impulse response (FIR) filter along with spike removal that removes high frequency noise and impulse-type ignition noise from the compression signal. The filtered compression signal is then "zero-lined", meaning that each of the peaks corresponding to a compression curve of a cylinder, which are bounded on either side, are re-scaled such that the local minima reside along a zero base line. Next, the zero-lined compression signal is averaged over the multiple cycles of the engine.

Abstract: In accordance with the present invention, a pulse-based impedance measurement instrument is provided. A pulse generator repetitively generates a stimulus pulse to a device under test (DUT). A digitizer circuit, consisting of a sample-and-hold circuit, an analog to digital converter, and acquisition memory, repetitively samples the response voltage across the DUT to create a time record of the voltage as a function of time during a pulse response measurement. Each time record is operated on by a Fast Fourier Transform (FFT) which converts the voltage versus time information into voltage versus frequency information in a manner well known in the art. By measuring a set of calibration resistors with known resistance values to generate a set of complex calibration constants, the impedance measurement instrument provides measurements of complex impedance and return loss versus frequency of a DUT.

Abstract: An instrument and method for the troubleshooting and verification of copper-wire local area network (LAN) cable systems provides a series of resistance and capacitance measurements between all possible wire pairs using a pair of switch matrices and a software method for evaluating the measurements which are stored in a two-dimensional matrix. The stored measurements are evaluated against predetermined figures of merit and the decision pattern in matrix form is compared to that of a known good LAN cable system. Error messages responsive to mismatches are generated and presented to the operator via a user interface. Near-end cross talk (NEXT) isolation is evaluated using a mathematically calculated differential capacitance technique. Error messages are generated responsive to difference capacitance values larger than a figure of merit correlated to an acceptable level of NEXT isolation.

Abstract: An inductive pickup sensor employing an isolation transformer to achieve substantially improved immunity to capacitively-induced cross-talk signals is provided. A magnetic pickup coil is coupled to a spark plug wire to receive a spark signal. The spark signal developed across the magnetic pickup coil is then coupled to via a sensor cable to the primary winding of an isolation transformer which is configured to provide a relatively low interwinding capacitance level to substantially reduce the cross-talk signal amplitude relative to the spark signal at a detector circuit. The detector turns the spark signal into a trigger signal at a pair of output terminals.