Abstract: A method for detecting failures in electrical cable assemblies is provided. A cable test instrument obtains frequency domain data representing electrical characteristics of a cable link under test. A number of connectors in the cable link under test is determined based on the obtained frequency domain data. An estimated location of each of the connectors along the length of the cable link under test is determined by the cable test instrument. The connectors are ranked in accordance with their respective contribution to detected failures in the cable link under test.

Abstract: A method of controlling a power generation system following a transient grid event, and a system and controller to control the power generation system are described. The method includes sensing a rate of change of electrical frequency at terminals of a generator, determining a rate of change of shaft line acceleration, and identifying the transient grid event based on the rate of change of shaft line acceleration. The method also includes triggering an action to recover from the transient grid event when the rate of change of electrical frequency exceeds a first specified value and the rate of change of shaft line acceleration exceeds a second specified value for a specified duration.

Abstract: A minimum level for a stimulation signal used in room correction processing is determined by measuring background noise. The stimulation signal is repeated a number of times and resulting responses are recorded. The recording responses are averaged, and the average is subtracted from each recorded response to obtain the background noise present in each recorded response. A stimulation signal to background noise ratio is computed from the stimulation signal and background noise and compared to an SNR threshold to determine if the stimulation signal level is sufficient to support the room correction processing. The background noise may be AC hum introduced electronically into the response signal, acoustic noise introduced by AC ventilation systems or noise emitting devices (refrigerators, etc), and it may be structure-born noise introduced by shaking the microphone, e.g. a bus drives by, shaking the floor the microphone is standing on.

Abstract: In a method for detection of an arc in a current path of a converter arrangement (2) for converting a DC input power to an output power, an arc is detected by sensing the current (4) in the current path by means of a current transformer (11), filtering the current signal (4?) with an analog band pass filter (14), converting the analog filtered current signal (4?) into a digital current signal (4??), determining the harmonic content (19) of the digital current signal (4??) and then deciding whether an arc exists if the harmonic content (19) exceeds a threshold, where the threshold is determined at the beginning as a multiple of the average harmonic content during a certain period of time of the current signal.

Abstract: In monitoring an isolation of an ungrounded power grid an AC voltage source is connected to the power grid via at least one test resistor. A test signal with a periodic continuous voltage course with regard to ground and with a frequency is applied to the power grid by means of the AC voltage source. A leakage current flowing due to the test signal is measured; and an ohmic isolation resistance is determined from the leakage current. The frequency of the test signal is varied such that an active current part of the leakage current keeps a predetermined recommended value at varying leakage capacitances of the power grid. This provides for a desired level of accuracy at maximum speed of isolation or ground fault detection.

Abstract: A circuit interrupter that includes a passive integration channel structured to receive an output signal from a di/dt current sensor and generate a first signal output based on the output signal, and an active integration channel structured to receive the output signal from the di/dt current sensor and generate a second signal output based on the output signal that is proportional to the primary current received by the di/dt current sensor. Circuit protection functionality is provided based on the first signal output responsive to the primary current being determined to be greater than a threshold level, current metering and circuit protection functionality is provided based on the second signal output responsive to the primary current being determined to be less than or equal to the threshold level, and a seed current value is provided to the active integrator based on the first signal output.

Abstract: A device includes a biosensor, a sensing circuit electrically connected to the biosensor, a quantizer electrically connected to the sensing circuit, a digital filter electrically connected to the quantizer, a selective window electrically connected to the digital filter, and a decision unit electrically connected to the selective window.

Abstract: A method for identifying arcing faults within a circuit having a system frequency, an electrical current and an electrical voltage, in which method an interference signal occurring, which has a frequency below an LF1 frequency and a current intensity above an LF1 limit threshold, defines an LF1 signal, in which a number of interference signals occurring, which have a frequency below an HF2 frequency, are combined to form an HF2 signal if the number of interference signals occurring is greater than or equal to an HF2 number and the time interval between two successive interference signals is less than an HF2 time, in which the number of time periods with a respective length which amounts to an accumulation length and which follow one another directly in time and in which in each case at least one HF2 signal is present define an accumulation when the number of time periods is greater than or equal to an accumulation number.

Abstract: An arc fault circuit interrupter test circuit is disclosed. The test circuit incorporates a controller along with at least one power transistor, a current sense circuit and a voltage sense circuit. When the power transistor is operated, the current flowing through the transistor is sensed, and if the current is not at least equal to a threshold value, the voltage at which the power transistor is operated is increased.

Abstract: Systems and methods of detecting arcing in a DC power system that can provide improved noise propagation immunity. The system includes at least two current sensors for monitoring at least two current outputs, respectively. The current sensors have reverse polarities, and are configured and arranged in parallel to provide a combined current output signal. The current sensors monitor the respective current outputs, which are provided for monitoring by the current sensors over at least two adjacent conductors. If arcing occurs at a location on a first conductor, then arcing (adjacent conductor crosstalk), having an arc current signature like that of the arcing on the first conductor, can occur at a location on the other adjacent conductor. The system can effectively cancel out such adjacent conductor crosstalk within a photovoltaic (PV) system, thereby improving the capability of an arc fault detection device for detecting arcing at the PV string level.

Abstract: The invention relates to a sports- and general pole element. The pole element includes components for an arrangement for operating a handheld geophysical locating device with at least one sensor, a power supply, an operating unit, and an interface for wireless data transmissions, wherein the components are arranged concealed in a body of the sports- or general pole element and wireless transmission of locating data is provided through the interface to a mobile evaluation- and display unit.

Abstract: An early fault detection system for a low voltage distribution network including: at least two detectors, each located on one of two power poles at either end of a section of a power distribution line; each detector includes a GPS unit, an uninterruptable power supply, a communication means to send data to a base station, antenna sensors having a bandwidth range of 1 MHz to 3 GHz for each wire in the power line, and a processor receiving signals from each sensor and collecting data relating to a maximum value, a time of maximum value, a minimum value, and a time of minimum value for partial discharge signals within the bandwidth range; and the processor or base station being programmed to analyze the collected data to identify a location of pulses above a predetermined value and record the number of such pulses at each location over a predetermined time interval.

Abstract: An aircraft having an avionics system comprising a plurality of avionics equipment and a system of connections, the avionics equipment incorporating protection means for providing protection against indirect effects of lightning, the system of connections including wired connections and connectors between the wired connections. The avionics system has at least one avionics equipment with protection means that are insufficient for providing total protection against the indirect effects of lightning when the equipment is incorporated in the structure, which equipment is connected to at least one connector including a resistor connected in series relative to at least one wired connection secured to the resistive connector.

Abstract: A method for characterizing an integrated circuit that includes ramping the supply voltage to an integrated circuit as a function of time for each of the transistors in the integrated circuit, and measuring a power supply current for the integrated circuit during the ramping of the power supply voltage. The measured peaks in the power supply current are a current pulse that identifies an operation state in which each of the transistors are in an on state. The peaks in the power supply current are compared to the reference peaks for the power supply current for a reference circuit having a same functionality as the integrated circuit to determine the integrated circuit's fitness.

Abstract: An electrical test device may include a power supply, a conductive probe element, and a spectral analysis block. The power supply may be connected to an external power source. The conductive probe element may be connected to the power supply and may be configured to be energized by the power supply. The probe element may be configured to be placed in contact with an electrical system under test and apply an input signal containing current for measuring at least one parameter of the electrical system. The spectral analysis block may be connected to the probe element and may be configured to receive an output signal from the electrical system in response to the application of the current to the electrical system. The spectral analysis block may be configured to analyze frequency spectra of the output signal and detect a broadband increase in energy of the frequency spectra above a predetermined energy threshold.

Abstract: A method for determining the place of origin of a passive intermodulation product excites a distributed device under test with two first excitation signals (x1(t), x2(t), each with a single spectral line, of which the frequencies (f1, f2) provide a frequency spacing relative to one another. Following this, the phase (?IM3Meas) of a first passive intermodulation product generated at the place of origin in the distributed device under test from the first excitation signals ((x1(t), x2(t)) by nonlinear distortion is measured, and the delay time of the first passive intermodulation product from the place of origin to the measuring device is calculated from the measured phase (x1(t), x2(t)) and the frequency (2·f1?f2) of the first passive intermodulation product. Finally, the place of origin of the passive intermodulation product is determined from the delay time and the topology of the distributed device under test.

Abstract: A method for controlling an induction heating cooking apparatus, comprises the steps of a) transforming a supply current (Iin) having a base frequency, for example 50 Hz or 60 Hz, into an induction current (Iw) having a higher frequency than the base frequency of the supply current, b) feeding the induction current into at least one inductor of the induction heating cooking apparatus to generate a magnetic induction field, c) detecting a deviation or distortion of the actual shape or frequency spectrum of the supply current or a rectified supply current from a predetermined admissible shape or frequency spectrum lying outside of a pre-given tolerance range, d) adapting the induction current or the electrical power associated with the induction current until the detected deviation or distortion of the actual shape or frequency spectrum of the supply current or a rectified supply current from the predetermined shape or frequency spectrum lies within the pre-given tolerance range again.

Abstract: Probes of a conductor length measurement device are connected to piping, and an output voltage is applied to the piping through the probes. A frequency spectrum curve is subsequently calculated by subjecting a voltage signal to FFT. Resonant frequencies of the piping are then determined from this frequency spectrum curve, and the total length of the piping is calculated on the basis of the resonant frequencies. The total length of the piping can therefore be easily measured without the need to install, for example, any measurement instruments at branch terminals.

Abstract: A power equipment protection system is provided. The power equipment protection system includes a first trip unit configured to monitor a first circuit, a second trip unit configured to monitor a second circuit that is downstream from the first circuit, an arc-flash (AF) sensor configured to detect an arc flash, an AF mitigation device, at least one current sensor, and a controller. The power equipment protection system is operable in a first mode and a second mode, wherein in the first mode, the controller is configured to activate the AF mitigation device based on signals generated by both the AF sensor and the at least one current sensor, and wherein in the second mode, the controller is configured to activate the AF mitigation device based on signals generated by at least one of the at least one current sensor and the AF sensor.

Abstract: An impulse voltage generator uses a predetermined rectangular waveform signal and a high voltage to generate an impulse voltage. The high voltage is obtained by boosting an instruction voltage of the rectangular waveform signal on a per-cycle basis. A partial discharge frequency calculation section receives detection signals based on partial discharges occurring in an object to be measured by the application of the impulse voltage and counts the detection signal on a per-cycle basis as a partial discharge frequency. An application voltage signal observation circuit observes an application voltage signal indicating the impulse voltage applied to the object to be measured. In a first cycle in which the partial discharge frequency reaches a specified frequency or more, a voltage value acquiring section sets, as a partial discharge starting voltage, the peak value of the voltage indicated by the application voltage signal output from the application voltage signal observation circuit.

Abstract: A system and method for testing lines to determine service-affecting conditions on a line, such as telephone wiring. Conditions may be identified from low frequency variations in a frequency spectrum measured on the line. The line may be stimulated with a broad spectrum signal, such as may be generated by a DSL modem operating in the L0 state or may be the result of noise on the line. Analysis of the low frequency variations may yield information about the nature of service-affecting conditions allowing conditions, such as un-terminated or poorly-terminated extensions to be identified. The method may be performed by a test device attached to premises wiring in a telephone network and used to determine whether the premises wiring will support VDSL2 or other high speed data services without modification or may indicate changes at the premises to enable the wiring to support high speed data services.

Abstract: A controller and infrastructure for an impedance analyzer measures responses to perturbations to respective phases of a multi-phase system at an interface between stages thereof (which may be considered as a source and load in regard to each other), such as a multi-phase electrical power system, to determine a transfer function for each phase of the multi-phase system from which the impedance of each of the source and load can be calculated, particularly for assessing the stability of the multi-phase system.

Abstract: Method and arrangement in a telecommunication system for estimating frequency dependent resistance of a transmission line. Insertion loss per length unit of the transmission line at a first frequency is determined. Thereupon a first resistance per length unit based on the determined insertion loss per length unit of the transmission line is calculated. Effective resistance per length unit at a second frequency based on the calculated first resistance is calculated. The calculated effective resistance could be used when estimating the insertion loss for the second frequency and all frequencies of interest.

Abstract: An arc detection and intervention system for a solar energy system. One or more arc detectors are strategically located among strings of solar panels. In conjunction with local management units (LMUs), arcs can be isolated and affected panels disconnected from the solar energy system.

Abstract: A system and method for detecting excess voltage drop (EVD) in a three-phase electrical distribution circuit includes a diagnostic system comprising a processor that is programmed to receive three-phase voltages and currents provided to terminals of the electrical machine, determine fundamental components of the three-phase voltages and currents provided to the terminals, and compute positive, negative, and zero sequence currents from the fundamental components.

Abstract: A system for the early detection of faults in a low voltage distribution network in which at least two detectors are each located on one of two power poles at either end of a section of a power distribution line, each detector includes a GPS unit, an uninterruptable power supply, a communication means to send data to a base station, antenna sensors having a bandwidth of 1 MHz to 3 GHz for each wire in the power line, a processor to receive signals from each sensor and collect data relating to the maximum value, time of maximum value, minimum value and time of minimum value for partial discharge signals within the range and the processor or base station being programmed to analyse the collected data to identify location of pulses above a predetermined value and record the number of such pulses at each location over a predetermined time interval to enable identification of likely sites of faults in the distribution line.

Abstract: A method of testing an electronic device includes measuring radio frequency emissions at a plurality of positions relative to a trusted unit of a particular electronicdevice during operation of the trusted unit, and measuring radio frequency emissions at the same plurality of positions relative to a second unit of the particular electronic device. For each of the plurality of positions, the radio frequency emissions measured from the second unit are compared to the radio frequency emissions measured from the trusted unit. The method then determines whether there is any frequency at which the measured amplitude of the radio frequency emissions from the second unit and the measured amplitude of the radio frequency emissions from the trusted unit exhibit a statistically significant difference.

Abstract: A monitor for monitoring isolation resistance, impedance, or other isolation reflective conditions between vehicle systems as contemplated. The monitor may be useful in assessing insulation resistance between a high-voltage power net and a low-voltage power net. The monitor may be configured to assess a sufficiency of the insulation resistance based on a frequency response of the high-voltage power net.

Abstract: A system for measuring passive intermodulation (PIM) comprises a port connectable with a load and a PIM source, a test signal source providing a test signal having components of two or more frequencies, and a receiver including a phase-coherent detector to receive a reflected signal obtained at the port in response to the provided test signal. The phase-coherent detector has an output that provides a signal indicative of PIM. A reference signal source connected with the phase-coherent detector provides a reference signal derived from the test signal. A signal combiner having a first input connected with the output of the phase-coherent detector, a second input connectable with storing a measurement of residual PIM generated by the apparatus, and removes the residual PIM from the signal indicative of PIM and provides measured PIM of the PIM source at the output.

Abstract: An apparatus for inspecting a passive component having a signal transmission line on a printed circuit board (PCB), includes a reflectometry unit for inputting an incident signal to an input port connected to the signal transmission line, receiving a reflected signal in response to the incident signal, and computing a plurality of frequency-based reflection coefficient values in a preset frequency range and a plurality of time-based reflection coefficient values in a preset time range based on the incident signal and the reflected signal; and a defect detection unit for determining whether the signal transmission line has a defect based on the plurality of frequency-based reflection coefficient values, and determining a location of the defect on the signal transmission line based on the plurality of time-based reflection coefficient values.

Abstract: A method, system and computer program product are disclosed for identifying false positive indications of high impedance faults in an AC electric power transmission and distribution network. In one embodiment, the method comprises using a procedure to monitor a phase conductor of the network for faults, said procedure generating a fault signal indicating a specified fault in the conductor. In this embodiment, the voltage and current waveform of the electric power conducted through the conductor are monitored. When a phase shift in said waveform is detected over a defined period of time, and said detected phase shift meets one or more given criteria, a correction signal is generated indicating that said fault signal is a false indication of the specified fault. The given criteria may include, for example, that the phase shift is more than a threshold value for a specified period of time.

Abstract: A method and apparatus are described for generally passive intermodulation measurement to specify a location and strength of an intermodulation source of a passive component in a transmission line. Beneficially, the apparatus and method are comparatively simple and inexpensive.

Abstract: A system includes a plurality of sensors configured to measure one or more characteristics of an impeller. The system also includes an impeller condition indicator device, which includes a plurality of sensor interfaces configured to receive input signals associated with at least one stage of the impeller from the sensors. The impeller condition indicator device also includes a processor configured to identify a fault in the impeller using the input signals and an output interface configured to provide an indicator identifying the fault. The processor is configured to identify the fault by determining a family of frequencies related to at least one failure mode of the impeller, decomposing the input signals using the family of frequencies, reconstructing a impeller signal using the decomposed input signals, and comparing the reconstructed impeller signal to a baseline signal. The family of frequencies includes a vane pass frequency and its harmonics.

Abstract: The present invention is implemented by deploying an enhanced ground fault detection and location apparatus and by using the apparatus in conjunction with specific circuit analysis methods, using the information generated by the ground fault detection and location apparatus. The ground fault detection and location apparatus comprises the functionality of a voltmeter, an ammeter, a phase angle meter, a frequency generator, and a variable power supply, thereby providing for a variety of signals and analyses to be performed on a unintentionally grounded circuit in an ungrounded AC or DC power distribution system. The ground fault detection and location apparatus is capable of operating in six different modes, with each mode providing a different capability or opportunity for detecting, analyzing, and locating one or more unintentionally grounded circuits in an normally ungrounded AC or DC power distribution system.

Abstract: An integrated circuit die comprises an electronic circuit and one or more output ports for outputting signals from the die via an external impedance, to a load, external from the die. The output port is connected to the electronic circuit. The die is further provided with an on-die sampling oscilloscope circuit connected to the output port, for measuring a waveform of the outputted signals.

Abstract: In order to locate a cable fault in a cable, a testing apparatus applies a test signal to the cable so as to induce an electrical oscillation. The testing apparatus includes a voltage source that generates the test signal, which e.g. ignites an electrical arc at the cable fault or applies a voltage surge to the cable, to cause the electrical oscillation. The apparatus further includes a measured signal evaluation device to measure the resulting oscillations in the time domain or the frequency domain, and carry out a spectral analysis in the frequency domain, so as to automatically determine the location of the fault preferably from the total phase rotation of the signal, the phase rotation of the reflection at the first cable end, the phase rotation of the reflection at the cable fault, and the imaginary part of the propagation constant of the signal in the cable.

Abstract: The present invention relates to a non-contact arc detection, recognition, and warning apparatus for the detection of arcing in an electrical system. The apparatus includes an electric field detector having first and second electric field sensors adapted to sense electric fields; a magnetic field detector having a multi-axis magnetic field sensor adapted to detect a magnetic field; and a digital signal processor. The digital signal processor compares and enhances signals obtained from the electric field detector and the magnetic field detector and creates a response to alert a user of the presence of arcing.

Abstract: Systems for intelligent automated response to line frequency and voltage disturbances by a central control point communication with a plurality of load control devices. The systems may include a load control device adapted to communicate with one or more energy consuming devices. The load control device may have a load control device firmware adapted to receive and process control directives to change the load of at least one energy consuming device. A central control point may be associated with the building and may be connected to the line power. The central control point may include a circuit adapted to monitor the line power and a central control point firmware adapted to detect the line disturbance. The central control point firmware may be in communication with the load control device firmware and may be adapted to transmit the control directives to the load control device firmware.

Abstract: Systems and methods are shown for detecting a blown fuse in a three-phase line by comparing neutral points in the line before and after the fuses. Diode rectifier circuits may be used to compare the neutral points and generate a DC output voltage when neutral points are off from one another, and photocoupler circuits may provide electrical isolation when signaling a neutral point shift. The neutral points compared need not be on immediate sides of the fuses, so intermediate components may exist, and in some embodiments one of the compared points may be within a load connected to the three-phase line.

Abstract: A touch sensor interface includes one or more touch detection electrodes whose capacitance increases when touched. A processor converts the increase in capacitance into a change in a counter value. A detector compares the change in the counter value with one or more count thresholds to detect faults in the touch sensor interface.

Abstract: A distance to PIM measurement circuit is made using a device such as an AWS transceiver that has separate transmit and receive bands. With a typical AWS transceiver placed in close proximity to a PCS transceiver, the AWS device will include a band reject filter to eliminate interference from the PCS signals. The PIM measurement circuit includes two frequency sources F1 and F2 that are provided through a combiner for characterization of the PIM circuit. To enable distance determination, an FM measurement is created by using a offset sweep generator attached to one of the two frequency sources. To avoid frequencies blocked by the band reject filter, a desired harmonic of a test PIM harmonic signal is selected outside the band of the band reject filter.

Abstract: A method and system for remotely monitoring the status of a standby generator. The system includes a PLC transmitter in communication with the control unit for the generator. The PLC transmitter receives error codes from the control unit of the generator and transmits encoded error codes over the power distribution network in a home using a PLC frequency. A remote status display device can be connected to the power distribution network in the home at any convenient location. The remote status display device includes a PLC receiver that decodes the error codes. The decoded error codes are displayed on a display of the remote status display device for viewing by the home occupant at a location remote from the standby generator.

Abstract: A method for determining a load capability of a direct current (“DC”) voltage source connectable to an alternating current (“AC”) power grid having a predetermined frequency via an inverter and a grid disconnect switch includes controlling, while the grid disconnect switch is in an open position, the inverter so as to convert a DC input voltage to a test frequency different than the predetermined frequency of the AC power grid so as to increase a test load acting on the DC voltage source above an internal consumption of the inverter at the predetermined frequency. The DC input voltage is measured while the grid disconnect switch is in the open position.

Abstract: The invention relates to a switching device for the alternate connection of at least one first test port or of a second test port to a measuring-device connection, where the measuring-device connection provides at least one test-signal input. The test-signal input is connected to a first signal path and to a second signal path, where the first signal path is connected alternately to the first or to the second test port, and the second signal path is connected at least to the respectively other test port.

Abstract: An arrangement for protecting equipment of an AC electrical power system comprises first means configured to measure the frequency of the current and voltage at at least one location in the electrical power system along an interconnection between two theoretical electric machines of an equivalent two machine system. Fourth means are configured to use the values of the frequency of the current and voltage measured to determine whether a power swing has occurred and if an occurrence of a power swing has been determined determine whether the measuring location is located on a motor side or a generator side of a potential pole slip electrical centre along said interconnection, the electrical centre being defined as the location where the voltage becomes zero during a pole slip, and send this information further to third means for use in a control for protecting equipment of the electrical power system.

Abstract: A semiconductor circuit apparatus having a clock oscillating circuit includes a first inverter circuit having a power supply terminal connected to a power supply potential via a first power supply potential connection transistor and a ground terminal connected to a ground potential via a first ground potential connection transistor, an inverter circuit block having a second inverter circuit connected to the power supply potential via a second power supply potential connection transistor and to the ground potential via a second ground potential connection transistor and connected to the first inverter circuit in parallel and a selection circuit block that outputs a power supply potential connection signal to any one of gate terminals of the first and second power supply potential connection transistors and a ground potential connection signal to any one of gate terminals of the first and second ground potential connection transistors.

Abstract: A distance to PIM measurement circuit is made using a device such as an AWS transceiver that has separate transmit and receive bands. With a typical AWS transceiver placed in close proximity to a PCS transceiver, the AWS device will include a band reject filter to eliminate interference from the PCS signals. The PIM measurement circuit includes two frequency sources F1 and F2 that are provided through a combiner for characterization of the PIM circuit. To enable distance determination, an FM measurement is created by using an offset sweep generator attached to one of the two frequency sources. To avoid frequencies blocked by the band reject filter, a desired harmonic of a test PIM harmonic signal is selected outside the band of the band reject filter.

Abstract: A wind energy system is provided including a geographical position sensing module and a cable for transmitting energy from the wind energy system. The cable includes a first sensing device at a first location of the cable. The first sensing device is adapted for sensing a relative position of the first sensing device. Further, the cable includes a second sensing device at a second location of the cable. The second sensing device is adapted for sensing a relative position of the second sensing device. The first and the second sensing devices are adapted to communicate with each other; and one of the first and second sensing devices is adapted to communicate with a geographical position sensing module of the wind energy system.

Abstract: Embodiments of the present invention relate to methods and systems of transmitting data signals from at least one transmitting terminal with a spatial diversity capability to at least two receiving user terminals, each provided with spatial diversity receiving device. The methods and systems are useful, for example, in communication between terminals, e.g., wireless communication. In certain embodiments, transmission can be between a base station and two or more user terminals, wherein the base station and user terminals are each equipped with more than one antenna.

Abstract: A sensor system includes a first sensor, a second sensor, and an analyzer circuit, the first sensor including a first seismic mass having a first resonance frequency and the second sensor including a second seismic mass having a second resonance frequency, and the analyzer circuit being provided for analyzing a first output signal of the first sensor as well as a second output signal of the second sensor and, moreover, the first resonance frequency being unequal to the second resonance frequency.