Abstract: An equivalent time sampling system employs two clock frequency sources, phase locked, wherein an analog to digital converter sampling clock is derived from one source and a pulse generator clock is derived from the other. Choice of the clock frequencies determines minimum time step and the set of available time steps, and pulse repetition period determines the time step size, for equivalent time sampling. The system is suitably implemented in a time domain reflectometer, optical time domain reflectometry system, or other systems for obtaining time domain responses to a periodic stimulus of a system under test, with stimulus rate and the sampling intervals varying over a wide range.

Abstract: An ICMP ping is sent from a test instrument to all known bridges and switches on a network, which respond by populating the forwarding data base (FDB) tables with the MAC addresses of adjacent bridges. Then an SNMP query is sent to the FDB table of a selected bridge, retrieving not only MAC addresses, but interface indices associated with ports of downstream bridges. These ports are identified as uplink ports.

Abstract: A multimeter with a filtered measurement mode. By pressing a single button or key, a low-pass filter is switched into the signal path to filter voltage spikes, noise, and switching transients from pulse-width modulated pulses, or lower frequency sinusoidal signals with higher frequency components, and at the same time an on-screen icon indicates to a user that the filtered mode has been selected. The user can switch back and forth between filtered and unfiltered modes. The filtered measurement mode is useful in measuring the outputs of modern adjustable-speed motor drives, uninterruptible power sources, and switch power supplies.

Abstract: A test instrument employs main and remote test units at respective ends of a cable under test. The units operate in an active or passive measurement mode, wherein one of the units begins as the active unit, applying test signals to the cable under test to make a set of measurements related thereto, while the other unit takes measurements based on the signals applied by the first end. Then, after a set of measurements has been completed, the units swap roles, and the original passive end becomes the active end, applying test signal stimuli, while the original active end now becomes passive, and takes a series of corresponding measurements based from the test stimuli from the active end. The measurements are thereby overlapped and accomplished from both ends of the cable, saving time.

Abstract: A network test instrument provides maximum compensation of FEXT by use of mutual inductance between one or more signals. The inductance is suitably formed as a PCB trace component, or as discrete components.

Abstract: A method of correcting distortions resulting from loss and dispersion in cable fault measurements. A cable is measured in the frequency domain to obtain a reflected response. Fractional sinusoidal components of the reflected response having attenuated amplitude and delayed phase values at points defining the junctures of adjacent equal predetermined lengths are collected and normalized. Then the fractional sinusoidal components of the reflected response are extracted from normalized sum by mathematically calculating the real value at each point, thereby removing all loss and dispersion distortion components.

Abstract: A digital toner/locator employs tone packets using a 455 Khz. carrier. Plural packet quanta provide multiple test modes which are advantageously selected from a probe without requiring returning to the tone generator to change mode. A locate and isolate mode are provided, as well as multiple song selection, for choice of alternative songs played by the detector when the tone packets are detected.

Abstract: A voltage detector is combined with a test instrument probe to provide an indication of the presence of a.c. voltage when the test instrument probe approaches or comes in contact with a source of a.c. voltage.

Abstract: A multimeter with a filtered measurement mode. By pressing a single button or key, a low-pass filter is switched into the signal path to filter voltage spikes, noise, and switching transients from pulse-width modulated pulses, or lower frequency sinusoidal signals with higher frequency components, and at the same time an on-screen icon indicates to a user that the filtered mode has been selected. The user can switch back and forth between filtered and unfiltered modes. The filtered measurement mode is useful in measuring the outputs of modern adjustable-speed motor drives, uninterruptible power sources, and switch power supplies.

Abstract: A time domain reflectometer having a first impedance when in a first test mode and a second impedance when in a second test mode. The first impedance is substantially the same as the nominal characteristic impedance of a network link cable not connected to a network and the second impedance is substantially different from the impedance of a network link cable that is terminated into a network. A method for measuring the length of a terminated network cable includes the steps of determining that the network cable is terminated at a network, selecting a test mode suitable for testing the terminated network cable, and performing time domain reflectometry testing on the terminated network cable.