Abstract: An instantaneous value of alternating current signal from an instrument potential transformer 10 or an instrument current transformer 9 is processed with an analog filter 21, 22, the frequency to be used for correction being detected with a frequency detector 103, frequency correction of the gain of the detected signal being performed with a frequency corrector 104, 114 after detecting the root-mean-square value of the frequency, the corrected signal being supplied to a digital automatic voltage regulator 120. Thereby, it is possible to remove a direct current component and absorb a surge in a signal, and to correct the signal in coping with the fluctuation of the input signal to detect a stable signal.

Abstract: 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.

Abstract: A pulse-based cable attenuation measurement system provides a measurement of attenuation characteristics of a cable over a wide frequency spectrum. A main test and troubleshooting unit of a cable test instrument applies stimulus signals via a selected one twisted pair in a LAN cable to a pulse receiver in a remote unit that in turn causes a pulse generator to produce a specified pulse of known amplitude and duration that is applied as a measurement pulse to a separate but adjacent twisted pair within the same bundle or cable. A measurement system analyzes the measurement pulse after it reaches the main unit, and provides attenuation versus frequency information to determine whether the amount of signal loss due to attenuation in the cable is acceptable or not.

Abstract: An arc detector or detecting potentially hazardous arcing in electrical connections comprises detection and signal processing circuitry for monitoring high-frequency noise on the power line characteristic of arcing and distinguishable from other sources of high-frequency noise. If high-frequency noise is present and a gap is detected at intervals synchronous to the power frequency, arcing is determined to be present, and an alarm is given.

Abstract: A test system for measuring the characteristics of an active circuit employs a pulsed bias technique for periodically biasing the input control port of the active circuit into the active region of operation. Biasing is achieved with a bias voltage that is periodically pulsed ON and OFF. An RF source is pulse modulated ON and OFF synchronously with the pulsed bias voltage and applied to the input control port of the active circuit. The pulsed RF occupies a portion of the time interval encompassed by the pulsed bias voltage. These voltages are combined and applied to the input port of the active circuit which operates only during the presence of the pulsed bias voltage and which is OFF during the absence of the pulsed bias voltage. A DC supply is utilized to bias the output port. The amplified RF power is then measured at the output port of the circuit, after the RF power has been separated from the DC bias by a non-reciprocal device.

Abstract: A method and apparatus (3, 60, 202, 300) for measuring the dynamic, or alternating current, and static, or direct current, characteristics of a cable pair (2, 10, 24, 133) from one end, the local end, by utilizing an element (1, 19, 20) possessing known non-linear electrical characteristics connected across the other end, the remote end, together with methods and apparatus (30, 111) for connecting the non-linear element (1) across the remote end of the cable pair (2, 10, 24, 133) and disconnecting the non-linear element 11) by means of electrical voltages impressed across the cable pair (2, 10, 24, 133) at the local end. In the method and system of the present invention, the near end test set (3, 60, 202, 300) is electrically transposed to the far end of the cable pair (2, 10, 24, 133) making it appear, to be at the far end during the test while, physically remaining at the near end.

Abstract: A portable hearing protection device evaluation apparatus which can be taken into the field to measure noise attenuation of a muff type hearing protection device under actual working conditions is provided. The apparatus includes two miniature microphones, one positioned inside a muff near the ear, the other positioned outside the muff to detect the noise in the environment. These two microphones simultaneously receive input signals which are provided to circuitry which determines and displays a single number output representing the noise attenuation.

Abstract: An equalized eye pattern instrument inserts an equalizer between the input of the instrument and a display device for the instrument. The equalizer compensates for losses and other distortions in a transmission path so that a digital signal at the input of the instrument may be presented to the display device in a form suitable for eye pattern display. A switch may be used to bypass the equalizer when not needed so that the input digital signal may be directly displayed. Further the equalizer is preferably adaptive so that the input digital signal may be restored to its undistorted form from the source.

Abstract: A signal detector includes a signal input section, a detector, and a converter. The signal input section inputs a high frequency signal to be measured. The detector detects the high frequency signal to be measured input by the signal input section. The converter amplifies the output from the detector and includes a variable gain preamplifier which has a first gain higher than a linear gain when the detecting output is smaller than a predetermined value and a second gain lower than the linear gain when the detecting output is larger than the predetermined value. A cable line transmits an output from the variable gain preamplifier of the converter of the signal detector. A measuring equipment body includes a decoder and an analyzer.

Abstract: An emitter assembly of low-power electromagnetic signals with random or pseudo-random frequency variation is located inside an electromagnetic shield to be monitored. These signals are detected by at least one synchronous detection receiver located outside the shield, a second transmission channel, preferably constituted by an optic fiber, connecting the emitter and receiver assemblies to enable synchronous detection of signals transmitted via an electromagnetic channel through the shield. The amplitude of the electromagnetic signals received by the detector is significant of the quality of the shielding.

Abstract: A vector network analyzer comprising a circuit for measuring the real and imaginary components of the central spectral line in an RF pulse from a device-under-test is provided. The circuit comprises a modulator in response to a profiling pulse for modulating the amplitude of the RF pulse, mixers for down-converting the frequency of the amplitude modulated RF pulse, a narrow band filter for filtering the RF pulse having a bandwidth of 500 Hz and a synchronous detector responsive to the output of the crystal filter for providing a pair of dc outputs, which correspond to the real and imaginary components of the output of the device under test as the profiling pulse is shifted in time relative to the RF pulse.

Abstract: The present invention provides a precision variable gain current-to-voltage amplifier which has a test mode of operation wherein the gain is independent of the gain of the amplifier when operated in the normal amplification mode. The invention enables a test signal, preferably a test voltage, to be injected into the amplifier circuit to test the functioning of the op amp and thus the amplifier. Because the gain of the amplifier in the test mode is independent of the gain of the amplifier when in the normal mode, a simple and easy method of checking the functioning of the op amp is provided which does not require knowing the gain of the amplifier and then selecting the proper test input to use.