Abstract: A method of monitoring moisture in a building is carried out using moisture detectors, which provide an output resistance value ranging from a dry value in the absence of moisture and different wet values in the presence of moisture depending on the quantity of moisture. Rather than emit an alarm based solely on a moisture threshold, a risk assessment of potential damage is calculated for at least a part of the building using the wet values from the moisture detectors for the sensor zones using as input data the wet values and as a first additional factor a value which is indicative of a total area of the moisture as provided by the number of sensor zones that are responding with a wet value and as a second additional value the number of consecutive time periods that the sensor zone has reported wet value.

Abstract: A moisture detection sensor is used in a building structure to detect moisture penetration. The sensor is a flat adhesive tape of a substrate of dielectric, hydrophobic material. Three or four elongate, parallel, conductors are secured to the top surface and a protective layer of non-hygroscopic, water pervious material is secured over two of the conductors so that they are exposed to surface moisture. One or two of the conductors are covered by an insulating layer to prevent moisture access. Pairs of moisture probes along the length of the tape penetrate the insulating layer, the respective conductors and the substrate and to extend into a building component to which the substrate has been adhered. A diode guide arrangement allows a monitoring unit to monitor the exposed conductors for surface moisture and the penetrated conductors for moisture in the component by reversing polarity of the voltage across the conductors.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. A fiber being used for data transmission can be monitored for intrusion by introducing a monitor wavelength different from that of the data signal. Central to this invention is the use of a bulk optic (commonly referred to as a pass/reflect) wavelength division multiplexer, one which maintains the modal distribution within the fiber.

Abstract: Intrusion detection for a multimode fiber optic cable uses a light signal launched into the fiber through the low ratio leg of a tap coupler to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes at the remote end is monitored for transient changes in the mode field power distribution which are characteristic of fiber intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: Intrusion detection of one section only of a multimode fiber uses a light signal launched into the fiber at a location spaced from the source through a single mode fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the fiber. A small portion of the higher order signal modes at the a second location also spaced from the destination is sampled by a tap coupler and monitored for transient changes in the mode field power distribution which are characteristic of intrusion to activate an alarm. The active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion. A translator can be provided in an existing optical fiber system in which the data signals are translated in wavelength and/or launch conditions to optimize the monitoring signals in an otherwise non-optimized system.

Abstract: A telecommunications multimode optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. Pulses are injected using a launch arrangement which generates a narrow spectral width, under-filled, non-uniform mode field power distribution in the multimode optical fiber and Fresnel reflections and Rayleigh backscattering from the pulse are detected at the transmit end to monitor the modal power distribution in the fiber which changes on manipulation of the fiber. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a modal power distribution detection system which includes an optical coupler to tap off a portion of the light which contains the higher order signal modes.

Abstract: An elongated substantially flat four-conductor moisture detection and location sensor is described. The sensor includes four parallel conductors laminated to a dielectric substrate. Two of the conductors are protected by a water pervious dielectric layer and form the water-sensing element. Two other conductors are covered by a water impervious dielectric layer and are used to loop-back one or more of the water-sensing conductors. Precise location of a water leak location is determined by connecting the four conductors to a resistance bridge. The design allows for the connection of a four-conductor cable to extend the monitoring and detection point to a convenient location without loss of location accuracy.

Abstract: A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

Abstract: A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

Abstract: A method and system of intrusion detection system for a multimode fiber optic cable. A light signal is launched into the cable fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes arriving at the remote end of the cable is sampled and monitored for transient changes in the mode field power distribution. The power distribution changes with physical disturbance of the cable. When those changes are detected as being characteristic of fiber intrusion, the system activates an alarm. This method can sense and alarm any attempt to access the optical fibers in a fiber optic communication cable. In preferred embodiments, the active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion.

Abstract: A method and system of intrusion detection system for a multimode fiber optic cable. A light signal is launched into the cable fiber to establish a narrow spectral width, under-filled non-uniform mode field power distribution in the cable. A small portion of the higher order signal modes arriving at the remote end of the cable is sampled by use of a coupler and monitored for transient changes in the mode field power distribution. The power distribution changes with physical disturbance of the cable. When those changes are detected as being characteristic of fiber intrusion, the system activates an alarm. This method can sense and alarm any attempt to access the optical fibers in a fiber optic communication cable. In preferred embodiments, the active signal of a multimode optical fiber is monitored for both signal degradation and transient power disturbance patterns that could indicate fiber damage or physical intrusion.

Abstract: A constant current termination is provided for cable locating tones on communication and control cables that may be buried or placed in underground duct structures. The constant current termination limits the current on each branch of the cable to that required for cable location, thus ensuring that branches furthest from the tone source have adequate current for location purposes. The termination is the same for each branch, regardless of its position along the cable system. This eliminates the need to calibrate and recalibrate termination distances for a cable on installation and when branches are added. It also allows the location of damaged cables where the tone signal strength on a damaged branch is less than that for which the termination was designed.

Abstract: A trace wire is placed alongside an underground utility for long distance transmission of locating tones. The trace wire has a conductive core. There is an electrically insulating sheath on the core. The sheath has an inner layer in the form of a solid foam of dielectric material. An outer layer of the sheath is a solid dielectric material surrounding the inner layer. This combination of a core conductor with insulating materials in a multi-layered design provides significantly improved properties over current commercially available insulated conductors when used as trace wires. In the presently preferred embodiment of the invention, the trace wire construction includes a 1.6 mm (14 AWG) hard drawn copper conductor to provide low resistance along with high break strength. The inner layer of the sheath is gas injected foamed polyethylene (PE) insulation applied to an overall diameter of 7 mm. The outer layer is solid, medium or high density PE applied over the first layer to an over all outer diameter of 8.

Abstract: A trace wire is placed alongside an underground utility for long distance transmission of locating tones. The trace wire has a conductive core. There is an electrically insulating sheath on the core. The sheath has an inner layer in the form of a solid foam of dielectric material. An outer layer of the sheath is a solid dielectric material surrounding the inner layer. This combination of a core conductor with insulating materials in a multi-layered design provides significantly improved properties over current commercially available insulated conductors when used as trace wires. In the presently preferred embodiment of the invention, the trace wire construction includes a. 1.6 mm (14 AWG) hard drawn copper conductor to provide low resistance along with high break strength. The inner layer of the sheath is gas injected foamed polyethylene (PE) insulation applied to an overall diameter of 7 mm. The outer layer is solid, medium or high density PE applied over the first layer to an over all outer diameter of 8.

Abstract: A coaxial drop cable safety device is used for cable television, data and telephony applications. The device is used on buried drop cable where 60 Hz powering voltages applied to the drop cable exceed low voltage safety limits and where the drop cable is buried at depths which is less than the minimum required to meet electrical safety codes. Tap end and premise end units are connected to the drop cable. The tap end unit applies a DC voltage to the center conductor of the drop cable. A monitoring circuit in the tap end unit monitors the DC current in the center conductor. The tap unit will immediately remove the powering voltage in the event of either an open or faulted condition on the center conductor along the entire length of the drop cable. Additionally, while providing fault protection for the low frequency powering circuit due to tampering or damage to the cable, the fault monitoring circuit allows the high frequency television, data and telephony signals to pass with little or no impediment.

Abstract: Open circuit faults in a cable are located by applying a step function DC voltage to one end of a conductor along the cable, for example the metallic shield along a fibre optic cable. The DC current along the conductor is measured over a sampling period and integrated to determine the capacitive charge on the cable. The distance between the end of the conductor and the open circuit fault is computed from the calculated charge and the known capacitance per unit length of the conductor. The DC current in the conductor is measured by sampling the current at a predetermined sampling frequency. The sampling frequency is preferably an integral multiple of the local AC mains power frequency, either 60 Hz or 50 Hz to eliminate the effect of induced AC voltages in the calculations.

Abstract: The invention provides an interactive means to locate and identify underground utilities. The apparatus is used with a marker associated with an elongate electrical conductor, which may be a cable shield or a trace wire. It includes a remote, portable probe that is used to transmit a RF signal to be received by a transponder associated with the marker. The transponder is powered by a DC potential on the conductor. In preferred embodiments it has the capability of communicating with a terminal unit over the conductor to transmit information and instructions between the probe and the terminal unit.

Abstract: A transmission enhancement system is used for strengthening low frequency cable locating signals on the metallic shields of long underground cables. The system includes equalization circuits on the cable armour or shield at regular intervals, for example at splice locations. The equalization circuit includes an inductor that significantly reduces the rate of attenuation of the low frequency tone signal and greatly enhances the strength of the signal at distances where the signal would otherwise be very weak or unusable. The equalization circuit may be a resonant circuit having a capacitor connected in parallel with the inductor. The capacitor compensates for the inductor's attenuation of high frequency tones for local location purposes. The preferred embodiments of the equalization circuit include a surge arrestor coupled in parallel with the inductor and capacitor.

Abstract: A method and apparatus are used for locating cable breaks and resistive faults in cables, including fibre optic cables. The conductive shield or armour of the cable is divided into sections, usually at a splice. A step function voltage is applied to one end of the conductive shield. Remote sensors at the end of each section monitor the voltage and current as a function of time and at steady state. The measured data are encoded as current pulses and transmitted along the armour to the end of the cable. A computer at the cable end calculates from the measured voltages and currents the capacitance of each section of the shield. A broken section is identified by comparing the calculated and original capacitances of the sections and the distance along the broken section to the break is calculated from the calculated and original capacitances of the broken section.

Abstract: A resistive fault location method and apparatus are used on communication and power cables. Two instruments are connected to opposite ends of the faulted conductor. Each takes a series of voltage and current measurements that are then processed to determine the distance from each end of the conductor to the fault. To eliminate voltage and current transients, the data collected is statistically analyzed and data that is analyzed as being affected by transients is discarded. The remaining data is taken as being steady state data. This eliminates any requirement for simultaneous measurements at opposite ends of the conductor and accounts for any situation where local transients at the two ends of the conductor are different at any given instant.