Abstract: An in-service composite triple beats (CTB) measurement system for a cable television (CATV) system isolates and measures weak composite triple beat components in the presence of a visual carrier modulated with program material for selected channels of the CATV system. Each channel is demodulated and digitized in a frequency bandwidth about the visual carrier for the channel (the CTB frequency range). The digitized video is sampled during the vertical interval, and corresponding samples from consecutive frames are differenced, squared and accumulated to produce a CTB value, which may be scaled and corrected for noise. Noise correction is achieved by performing the same measurement, but digitizing in a frequency bandwidth offset from the CTB frequency range. The difference between the two measurements provides a corrected CTB value.

Abstract: An alignment apparatus for determining angular coordinates for offset and intersecting optical fibers in a mechanical optical switch has an analytical apparatus for imaging the end faces of the ferrules containing the opposing optical fibers of the switch for determining the respective axes of rotation of the mounting members, the locations of the optical fibers in the respective mounting members and coordinates of the optical fibers relative to the axis of rotation of the respective mounting members, the location of at least one reference point within one of the mounting members, and the relative angular coordinates of intersecting points between each of the closed curves of the plurality of optical fibers within the second mounting member and the closed curve of the first optical fiber as a function of the offset of the first and second mounting members and the reference point.

Abstract: System for automatic signal recognition and selection in a Synchronous Optical Network (Sonet) and Synchronous Digital Hierarchy (SDH) signal. The system automatically looks for signal location, signal rate, signal structure, signal payload mapping, and signal test patterns and displays the results in a matrix form. A user is allowed to select a specific channel within a specific structure, thereby setting the instrument's receiver.

Abstract: An improved M.times.N mechanical optical switch has opposing input and output optical fiber bundles disposed within offset ferrules forming an optical interface with the ferrules having sleeve members secured to one of the end faces thereof. The sleeve members have a hardness greater than the ferules and the optical fibers for forming respective recessed polished end face regions on the ferrules at the optical interface. Each ferrule is mounted in three-point kinematically correct V-groove holder allowing the optical fibers in each optical fiber bundle to traverse on a closed curve path during the rotation of the respective ferrules. Each V-groove holder has a spring clamp with first and second clamp members and wear resistant inserts secured to the clamp members and the sidewalls of the V-groove holder. The closed curve paths of each optical fiber in one of the optical fiber bundles intersect at least one of the closed curve paths of the optical fiber in the opposing optical fiber bundles.

Abstract: An adapter for a measurement test instrument electrical probe has a flexible dielectric substrate with electrically conductive runs thereon. One end of the conductive runs has first electrical contacts with a pitch geometry corresponding to the pitch geometry of electrical contacts of an electronic device that is electrically connected to a substrate via the electrical contacts of the device. The other end of the conductive runs has second electrical contacts that have a pitch geometry compatible with the electrical probe of the measurement test instrument.

Abstract: An optical time domain reflectometer acquires and displays waveform data as a waveform trace on a display device having a viewport defined by a start distance and an end distance using waveform data segments having data points where each waveform segment is acquired using different pulsewidth and sample spacing and different starting distance. A processor sets a horizontal pixel skip value and a horizontal distance skip value for each waveform segment and calculates a horizontal distance per pixel value for the display area as a function of dividing the distance between the viewport start distance and the viewport end distance by the number of horizontal pixels in the display area.

Abstract: A signal source provides an output signal which can sweep over a broad frequency range in a well-controlled manner. The signal source includes a voltage controlled oscillator (VCO) producing the output signal and a waveform synthesizer producing a reference signal. The VCO output signal is phase locked to the reference signal. To make the VCO signal continuously sweep over a broad frequency range, the reference signal sweeps repeatedly over a narrow frequency range. During each sweep of the reference signal, the VCO frequency tracks an integer harmonic of the reference signal frequency. The frequency and phase of the reference signal for each successive sweep are abruptly reset at the beginning of each sweep selected such that the VCO signal frequency locks to another integer harmonic of the reference signal frequency and does not change.

Abstract: A split-path isolation amplifier (10) employs a transformer (30) in a high path (26) and a single-input, dual-output closed-loop optocoupler (66) in a low path (24) to achieve a flat, wide frequency response without need for frequency compensation adjustments. In a low path frequency region (106), the optocoupler provides all or most of the signal to the output. The isolation amplifier employs a substantially overlapped crossover frequency region (104) in which the high path signal is applied to a primary winding (28) of the transformer, and the low path signal is applied differentially to secondary windings (40, 42) of the transformer. At frequencies below the crossover frequency range, the signal from the optocoupler dominates as the signal coupled from the primary winding rolls off. At frequencies above the crossover frequency range, the signal coupled from the primary winding dominates as the signal from the optocoupler rolls off.

Abstract: A spectrum analyzer (50) has a tunable trigger acquisition system (52) that includes a selectable trigger acquisition bandwidth. Sufficiently wide signal acquisition bandwidth is obtained by tapping into a high-frequency IF amplifier (54) signal and down-converting it to a moderate IF frequency for trigger extraction. A down-conversion local oscillator (62) is phase-lock-loop (64) tunable over a range of the high IF frequencies to allow extracting a time and frequency selectable trigger from the desired carrier signal frequency even if the spectrum analyzer is substantially offset in frequency from the desired carrier. The moderate frequency IF amplifier (66) includes a switchable bandpass filter (68) that provides adequate selectivity to detect triggers from a variety of signal types while rejecting unwanted signals such as adjacent channel CATV carriers that are often detectable when the measurement frequency is offset toward the channel edges.

Abstract: A current probe comprising a Hall device and a secondary winding in a flux linking relationship with a magnetic circuit is self-calibrated by disconnecting the Hall device from the winding, passing a current through the winding so as to induce a magnetic flux in the magnetic circuit, measuring voltage developed by the Hall device in response to linking by the magnetic flux, calculating the Hall gain of the Hall device, and then adjusting the gain of a scaling output amplifier on the basis of the calculated Hall gain to compensate for variation in Hall gain due to changes in operating conditions.

Abstract: A wide dynamic range optical receiver has low and high sensitivity signal channels for converting first and second portions of an optical input signal into voltage values representative of the various portions of the optical input signal. The voltage signals are converted into digital values by a converting means and a reconstruction is performed in a combining means to produce a digital output representative of the optical input signal. The wide dynamic range optical receiver may be used in an optical signal measurement instrument, such as an optical time domain reflectometer, where the optical return signal from a fiber under test is coupled to the wide dynamic range optical receiver in first and second portions with the first portion having an optical power level substantially less than the second portion.

Abstract: A current probe comprising a Hall device and a secondary winding in a flux linking relationship with a magnetic circuit is self-calibrated by disconnecting the Hall device from the winding, passing a current through the winding so as to induce a magnetic flux in the magnetic circuit, measuring voltage developed by the Hall device in response to linking by the magnetic flux, calculating the Hall gain of the Hall device, and then adjusting the gain of a scaling output amplifier on the basis of the calculated Hall gain to compensate for variation in Hall gain due to changes in operating conditions.

Abstract: An M.times.N mechanical optical switch has opposing input and output optical fiber bundles disposed within offset ferrules. Each ferrule is mounted in three-point kinematically correct V-groove holder allowing the optical fibers in each optical fiber bundle to traverse on a closed curve path during the rotation of the respective ferrules. The closed curve paths of each optical fiber in one of the optical fiber bundles intersect at least one of the closed curve paths of the optical fiber in the opposing optical fiber bundles. The intersection points of two opposing closed curve paths establish the optimum positioning locations for two opposing fibers. Offsetting the axes of rotation of the opposing optical fiber bundles and mounting the bundles in a three-point kinematically correct holder produces a mechanical optical switch having superior cycle-to-cycle repeatability, long term repeatability, and absolute alignment using loosely toleranced components.

Abstract: An error corrected wide dynamic range amplifier has a transimpedance amplifier where the input signal node is used as a monitoring point for providing an error correction voltage to a combining circuit that also receives the voltage on the output node of the transimpedance amplifier. The combining circuit subtracts the input signal node voltage from the output signal voltage to produce a resultant voltage substantially free of errors produced by non-ideal characteristics of the transimpedance amplifier. The combining circuit may be implemented using analog or digital circuity. The digital combining circuit may also add digital correction values representative of circuit component errors of the wide dynamic range amplifier. Such a wide dynamic range amplifier is usable in high sensitivity, wide dynamic range optical receivers, such as found in optical time domain reflectometers or other optical measurement instruments.

Abstract: An apparatus for directly positioning a hand-held electrical test probe onto leads of a surface mounted integrated circuit, IC, device has a housing with a central bore therethrough for receiving the probing tip of the test probe, which is coupled to compensation circuitry in the probing head. One end of the housing which is normal to the central bore has at least four teeth extending therefrom defining slots for engaging the leads of the IC. The central bore is exposed in the central slot of the housing for exposing the probing tip therein for providing an electrical connection between one of the leads on the IC and the electrical circuitry of the probing head.