Abstract: In order to identify a fiber optic cable (10) a beam (14) of polarised light is caused to pass down the cable to a first site (A) at which an electromagnetic field (24) is applied to the cable (10). The electromagnetic field (24) traverses the cable (10) in an essentially transverse direction and has a time-varying component orientated along the length of the cable (10) at the first site (A), with the component varying so that the line integral thereof along the cable (10) is non-zero. This results in a variation in the polarisation of the light, which can then be detected by a polarisation discriminator (20) at a second site (B), thereby to identify the cable (10).

Abstract: A method of and apparatus for identifying fibers of fiber optic cables is disclosed. Waveforms may be generated by integer subdivision of a clock, the waveforms for modulation of a laser beam into a set of unique signals. Preferably, however, each waveform has two states and a different integer X associated therewith. The repeat period of the waveforms is preferably set at 2Y cycles of the clock, Y being an integer greater than the highest value of X, and the waveforms can be generated by counting X mod Y and changing the state of each waveform whenever this counting reaches or exceeds Y. The signals may be applied either successively or simultaneously to individual fibers at one end of a fiber optic cable. At another end of the cable, each signal can be detected as having a frequency by taking a Fourier Transform; the frequencies detected preferably being in arithmetic progression, whereby each fiber can be identified individually.

Abstract: A digital phase-quadrature oscillator generates a series of sine values representative of a sine wave, and a series of cosine values representative of a cosine wave. In each iteration of the oscillator, a sum of the squares of past sine and cosine values is used as a negative feedback term in synthesizing next sine and cosine values, in order to stabilize the amplitudes of the sine and cosine values.

Abstract: An excavator vehicle has sensors thereon at different heights. Each sensor may have a coil which is generally horizontal and which detects the magnetic field generated by a current in a buried conductor. By detecting the relative magnitudes of the component of the field parallel to the ground, as detected by the sensors, it is possible to determine whether or not the excavator vehicle is proximate the buried conductor. A warning may be generated, or the excavating tool of the excavator vehicle controlled, to prevent the excavating tool damaging the buried conductor.

Abstract: Cathodic protection voltages are used to resist the damage to pipes or cables from electrolytic effects. However, localised fields can lead to stray currents and may result in corrosion and it is therefore desirable to detect and analyse those stray currents. Frequently there are several pipes in the area of interest and so it is necessary to distinguish between those pipes. Therefore the cathodic voltage on the pipes is modulated, with different pipes having different modulations. This modulation may be applied using an interrupter. Orthogonal modulations with non-unitary aspect ratios improve the discrimination between the pipes whilst maximising the energy content of the modulation pattern. The analysis is improved when the interrupters are synchronised with each other and so repeating on the same time-base. This synchronisation may be achieved using an external time signal such as GPS. An interrupter which can be used in this regard is also proposed, and may be powered from the cathodic voltage itself.

Abstract: A system and method to locate electronic marker balls includes receiving a signal representative of a detected marker ball. The signal includes the resolved in-phase and quadrature-phase (I and Q) components, each centered about a first frequency. The I and Q components are filtered in order to shift the first frequency to a second frequency and match the second frequency I and Q components to exponential decay characteristics associated with the marker balls. The second frequency I and Q components phase integrated in order to distinguish the components from noise. The integrating is based upon predetermined gain coefficients and produces integrated I and Q components in accordance with the predetermined gain coefficients. Next, a magnitude of the integrated I and Q components is determined to produce an I and Q magnitude vector and a noise variance associated with the magnitude vector is determined. Finally, the recursive coefficients are adjusted in accordance with the determined noise variance.

Abstract: A system and method to locate electronic marker balls includes receiving a signal representative of a detected marker ball. The signal includes the resolved in-phase and quadrature-phase (I and Q) components, each centered about a first frequency. The I and Q components are filtered in order to shift the first frequency to a second frequency and match the second frequency I and Q components to exponential decay characteristics associated with the marker balls. The second frequency I and Q components phase integrated in order to distinguish the components from noise. The integrating is based upon predetermined gain coefficients and produces integrated I and Q components in accordance with the predetermined gain coefficients. Next, a magnitude of the integrated I and Q components is determined to produce an I and Q magnitude vector and a noise variance associated with the magnitude vector is determined. Finally, the recursive coefficients are adjusted in accordance with the determined noise variance.

Abstract: A remotely configurable locator system includes a detection device to locate concealed underground conductors. The detection device is configured to connect to a communications network via a graphical user interface. Also included is a database management tool configured to connect to the communications network and communicate with the detection device via the communications network. A database is included and is adapted to store data related to the detection device wherein the data is configured to be accessed by the database management tool. Finally, the graphical user interface is configured to permit a user to remotely perform one of updating, analyzing, and diagnosing the detection device based upon the accessed stored data.

Abstract: A digital phase-quadrature oscillator generates a series of sine values representative of a sine wave, and a series of cosine values representative of a cosine wave. In each iteration of the oscillator, a sum of the squares of past sine and cosine values is used as a negative feedback term in synthesizing next sine and cosine values, in order to stabilize the amplitudes of the sine and cosine values.

Abstract: Methods and systems for digitally generating sound from phase and amplitude information of a narrow bandwidth signal, such as a narrow bandwidth locator signal. Phase-derivative information is determined from the phase information. The bandwidth of the phase-derivative information is spread out, or stretched, over a wider bandwidth, so that the frequency variations will be more perceptible to users. The result is combined with an audio band carrier frequency, the result of which controls an oscillator. The oscillator output is combined with the amplitude information to generate an analog audio signal that is modulated with the amplitude information and the phase-derivative information. The amplitude information wider bandwidth phase-derivative information are used to modulate an audio carrier in both frequency and amplitude.

Abstract: In order to control the sonde of an underground object, such as an underground boring tool, a predetermined sequence of rotation steps is applied to the object and that sequence is detected. The detection of the appropriate sequence causes the sonde to change its function, for example by changing the carrier frequency of the signal transmitted by the sonde on to change the data output sequence or transfer rate, or to change output power. While it is possible to use a single rotation step, the use of more than one step, with each step to be carried out within a predetermined time, reduces the risk of error.

Abstract: A monitoring device defines a boundary for movement of an underground object such as a booring tool. The underground object generates a magnetic field which is detected by the monitoring device. The monitoring device then determines the position of the underground object relative to itself, and hence to the boundary. The movement of the underground object can then be controlled so that it does not cross the boundary. The monitoring device may therefore define a protection zone so that a buried object within that protection zone will not be contacted by the moveable underground object.

Abstract: A system for tracing routes of conductors has a transmitter (10) for applying an alternating signal (11) to the conductor to be traced (12), and the field produced by this signal is detected remotely from the conductor. In order to distinguish between the field produced by the conductor being traced and the fields produced by nearby conductors (14) due to capacitive coupling (17), the alternating signal has phase-locked first and second components with frequencies F1 and F2 respectively, related by N×F1=M×F2, where N and M are non-adjacent integers greater than 1, one of which is odd and one of which is even, having no common factors. The field is detected at a plurality of positions. The phase relationship of the detected signals is investigated to determine unambiguously the position of the object concerned.

Abstract: A data recovery subsystem for use in a receive system configured to receive a magnetic field signal, the magnetic field signal including a carrier component usable for locating an underground object and at least one modulation sideband. The data recovery subsystem includes a first mixer to mix a Radio Frequency (RF) signal with a first Local Oscillator (LO) signal to produce an Intermediate Frequency (IF) signal representative of the magnetic field signal. A Phase Locked Loop (PLL) phase-locks a second LO signal to an IF carrier component of the IF signal. A second mixer synchronously mixes the IF signal with the second LO signal to produce a baseband signal including a demodulated sideband.

Abstract: Method and systems for reducing effects of magnetic field interference that may interfere with a magnetic field signal generated at or near an underground object, where the magnetic field signal is used to monitor the location of the underground object. At least two different moving averages of a plurality of samples that are representative of a detected magnetic field signal strength are produce. Each of the different moving averages is a moving average of a different number of the plurality of samples. A respective quality metric (e.g., variance) is then determined for each of the different moving average. One of the moving averages is selected based on the determined quality metrics. Further signal processing is then performed using the selected moving average. For example, the selected moving average is used to monitor the location of the object.

Abstract: Transmitted magnetic field signals useable for locating an underground object, and methods and systems for generating the same. The magnetic field signal has desired spectral characteristics. More specifically, the transmitted magnetic field signal includes a carrier component useable for locating an underground object. The carrier component has a carrier component frequency substantially equal to an integer multiple of 300 Hz. This guarantees that the carrier component frequency is substantially equal to an integer multiple of both 50 Hz and 60 Hz. Such a carrier component allows use of maximum information sidebands in environments that often include harmonically derived interference signals at regular 50 Hz (±0.1 Hz) or 60 Hz (±0.1 Hz) intervals caused by power lines. The transmitted magnetic field signal may also include at least one information sideband including sideband energy.

Abstract: In order to identify a fiber optic cable (10) a beam (14) of polarised light is caused to pass down the cable to a first site (A) at which an electromagnetic field (24) is applied to the cable (10). The electromagnetic field (24) traverses the cable (10) in an essentially transverse direction and has a time-varying component orientated along the length of the cable (10) at the first site (A), with the component varying so that the line integral thereof along the cable (10) is non-zero. This results in a variation in the polarisation of the light, which can the be detected by a polarisation discriminator (20) at a second site (B), thereby to identify the cable (10).

Abstract: In order to locate an inaccessible object such as an underground boring tool, the inaccessible object having means, for example a solenoid, to generate a magnetic field, a locator is provided with a detector for detecting the generated magnetic field. The detector may be an aerial array of three mutually perpendicular coils. When the locator is moved from a first position to a second position errors may arise in the measurements due to misalignment of the locator. In order to minimise such errors, a magnetic compass is provided on the locator to ensure that the locator can be maintained in the same position relative to the Earth's magnetic field. The magnetic compass is not affected by the magnetic field generated by the solenoid as this magnetic field is an A.C. magnetic field.

Abstract: Apparatus for detecting a leak in a pipe, and determining the location of that leak, comprises a cover plate for an opening into the pipe to be tested, such as an end cap for threading onto the end of a pipe, the cover plate having an aperture through which extends a flexible hose having an inflatable bladder at its free end. The hose is calibrated from its free end and is pushed into the pipe through the aperture for a known distance, whereafter the bladder is inflated by air supplied under pressure to the hose, so as to seal the pipe between the bladder and the cover plate. Air under pressure is then supplied to the sealed portion of the pipe and the pressure drop within that sealed portion is monitored over a period of time. By repeatedly performing the method but each time moving the hose further into the pipe, the location of the leak may accurately be determined.

Abstract: A method of locating a concealed conductor is performed by generating a magnetic field with a direction in which the field is a maximum. The magnetic field is rotated until that direction is directed towards the conductor. In this way, a signal is induced in the conductor which has a maximum value when that direction is directed towards the conductor. The induced signal is detected in the conductor, using a detector arranged to determine the direction of the conductor relative to the detector. The detector detects when the induced signal has the maximum value.