Norscan Instruments Ltd.

Other

Automated Light Technologies, Inc.

Kenneth N Sontag

David E Vokey

Gilles Aminot

Heinrich Kraft

John Charles Chamberlain

Myron Loewen

Ronald L Lavallee

Oleh J Sniezko

John C Chamberlain

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.

Locating system for a cable system having a backbone and branch cables defining multiple terminations

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.

Method and apparatus for locating resistive faults in communication and

Cable grounding device

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 center conductor DC voltage to a fault from the center conductor to ground along the drop cable. 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.

Coaxial cable protection device

A novel method and apparatus are used for monitoring cables for wear and damage. The system is particularly applicable to a cable system with multiple branch terminations. The cables have detection conductors, for example the metal cable jackets or other detection conductors extending the length of the conductors. These are connected electrically at the splice points in the system. At the end of each branch and at the end of the main cable, the detection conductors are each connected to a novel termination circuit. In the normal monitoring mode, the termination circuit appears as an open circuit. A DC voltage is normally applied to the detection conductors. Any current is a result of current leakage at a resistive fault along the detection conductors. The termination circuits are activated by altering the DC voltage, e.g. by reversing the polarity and increasing the magnitude of the voltage. This causes the termination circuit to perform a series of functional tests. These include a loop test which places a short across the end of the detection conductor for a timed period. The resulting high level loop current is used to calculate the total detection conductor resistance. A second test transmits a coded signal simulating a triggered splice sensor unit. The signal is detected and decoded to verify proper operation of end to end coded signaling after completing a test cycle, the termination circuit turns off and the next termination to be tested is addressed.

Cable monitoring system with multiple branch terminations

The invention provides a monitor for monitoring the condition of fibre optic communication cables. The system employs one or more of the optical fibres of a cable to monitor the cable structure for damage or kinks. By using two separate laser sources and simultaneously monitoring the optical losses at two distinct and separate wavelengths, the loss signature of the monitored fibre is determined, analyzed and related to the mechanical condition of the cable structure. To monitor splice points for moisture, a special optical splice sensor unit detects any penetration of water into the splice and transmits a coded alarm signal over the monitored fibre to the optical receiver. Every splice location is assigned a unique sensor code. The optical splice sensor is driven by moisture detection cell, which forms a single cell water activated battery. Water entering the monitored splice closure wets the tape, which activates the cell. The cell generates sufficient voltage and current to power timing, code generation and modulator circuits in the sensor unit for an extended period of time. The activated circuit drives a modulator which modulates the light travelling down the fibre. The modulated light is monitored at the equipment office and the address of the alarming sensor decoded.

Fiber optic cable moisture monitoring system

Fiber optic cable monitoring method and apparatus including moisture

A system is provided for monitoring a communications cable for moisture penetration. A line signal generator is connected to a metal armour layer of the cable to apply a line signal to the armour. Changes in the line signal current are monitored to detect the condition of the cable. Moisture penetration can be monitored throughout the length of the cable. The armour layer is maintained at a negative potential with respective ground. This provides an additional cathodic protection to the cable.

Cable failure detection system

A resistive fault in an electrical cable is located by applying a DC voltage to one end of the faulted cable conductor. The steady state DC voltage and current are measured at the end of the conductor where the voltage is applied. Simultaneously, the DC voltage is measured at the other end of the cable. The voltage is then reversed in polarity and the measurements repeated. Several repetitions of this procedure at each end of the conductor yields sufficient information to compute the location of the fault with reasonable accuracy. The procedure is carried out using two computer-based units, one at each end of the cable, with the two units communicating over the conductor under test.

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Springfield, Canada

Kenneth N Sontag