Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Of trunk or long line
Reexamination Certificate
1998-05-28
2003-06-10
Tieu, Binh (Department: 2643)
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Of trunk or long line
C379S001010, C379S009000, C379S009030, C379S012000, C379S022000, C379S029090, C379S032020
Reexamination Certificate
active
06577711
ABSTRACT:
The present invention relates to methods and apparatus for efficiently detecting defective communications lines within a wired communications network.
BACKGROUND OF THE INVENTION
Most people are familiar with the wired, public telephone network; they have either used telephones connected to that network or seen some of the physical elements making up the network itself, such as aerial cables, buried or underground cables or terminal boxes coupling such cables to houses or other facilities. Virtually everyone is also familiar with the general fragility of the telephone network since most people have experienced a telephone outage caused by trees falling on lines or underground cables damaged by ground shifts or inattentive diggers.
A variety of less obvious and less easily identifiable problems effect the cables that carry telecommunications, internet traffic and data communications through the public telephone network, however. For instance, corrosion at the contact between the telephone cable and a terminal, wear of the insulation surrounding the wires carrying communications, or a wet telephone cable may cause the cables to malfunction. Likewise, lightning can damage the sheath surrounding the cable and wind or water entering the splice between cables can then cause malfunctions. Problems with water entry may be particularly pronounced with older cables, which sometimes were formed using paper insulation surrounded by a lead sheath that was not impervious to water. Moreover, problems may occur even in the more benign environment inside of a building or home. Lint or other material may build within line jacks or interfaces and become sufficiently damp to inject moisture into the lines to cause shorts. Or, insulation on wires running underneath carpet or the like may become worn from constant travel. Stepping near to or on top of worn wires then causes a malfunction.
Often, malfunctions take the form of a low resistance between conductors or a conductor and ground. This is caused by water conducting within the line or a wire carrying power touching a wire that is grounded because of insulation wear or the like.
These problems occur despite extensive measures to protect the many lines that make up a telephone cable. For instance, the typical telephone cable comprises numerous lines. Each line uses a pair of copper (or other) wires. Often the wires are given a slight twist (thus, the name “twisted pair”) in order to minimize interference among the communications signals the wires carry. A cable is made by stranding together several groups of wires to form the cable core. A sheath, comprising layers of aluminum, steel, lead or polyethylene, surrounds the core. The sheath provides electric shielding, water resistance and some armor against blows to the cable. These protections, however, do not always prevent entry of water, insulation wear, corrosion, cuts or other problems from causing shorts.
If the damage to the line causes a permanent short, the defective line is easily identified because it will not work at all. If, however, the short is intermittent, detecting it will be substantially more difficult, if not impossible. Customers may notice some disruption in service and report that to the telephone company. Typically, the company may dispatch a technician to try and identify the problem. Many times the technician will be unable to identify the defective cable pair or the reason for the intermittent failures. Often, it may take several customer complaints and several (expensive) trips before the technician will be able to identify and correct the problem.
Efforts have been made to more proactively identify defective lines. For instance, periodically, switches installed within the network may run an “ALIT” test. The ALIT or “Automatic Line Insulation Test,” may identify some of the lines with permanent breaks or shorts. Telephone companies' service departments periodically may retroactively analyze trouble reports that record customer complaints or ALIT results to determine whether the cables or “plant” in a particular area need to be rehabilitated completely because they have aged and performance has degraded.
Some telephone companies have used a system called the Loop Cable Administration and Maintenance Operations System (called “LCAMOS” or “Predictor system”) that is a corputer system that monitors and utilizes information obtained from customer reports, switch messages, and ALIT results to identify trouble areas within the telephone network. The aim of many of the switch messages received by the Predictor system is to provide information that helps protect the telecommunications switches from overload or other negative conditions. Thus, thresholds may be set such that intermittent pulses are not viewed as a triggering event that would cause the system to identify a particular cable pair or, more likely, a group of cables, as having a problem. The Predictor system reportedly correlates this data with other information so that lines with trouble messages will be tested automatically when they fall within limits of preset thresholds. Also, the Predictor system can issue reports indicating problems developing in the telephone network depending on thresholds set by the user in order to control the flow of information appearing on the report.
However, neither ALIT nor the Predictor system properly identifies particular lines or cables that are generating intermittent shorts or pulses. Dealing with these intermittent pulses by dispatching technicians every time a customer calls is very expensive. The intermittent problems or pulses may additionally prevent telephone companies from offering valuable “N11” services. “N11” services are those in which telephone users can dial a “N11” number, where N is a number from 2 to 9, and be automatically routed to one point within the telephone network. The most familiar such service in North America is the emergency 911 service, through which telephone users can immediately contact emergency services such as police, fire or ambulance units.
Many telephone companies, however, would also like to offer other N11 numbers to their clients. For instance, BellSouth Telecommunications, Inc. has offered 211 service to United Way. Anyone dialing 211 throughout a particular area, such as metropolitan Atlanta, Ga., would be immediately routed to United Way's customer calling center. Other N11 services have been contemplated or offered, including 411 service to provide telephone information; 511 service for commercial information; or 611 service for repairs.
Pulse dialing, also known as rotary dialing, interrupts the telephone line current with a series of breaks or “clicks” that are essentially shorts and opens on the line. By changing the number of breaks (or pulses) in the string over a preset period, the number being dialed can be changed. The telephone switch is designed to recognize dial pulses at the standard rate of 10 pulses per second and may recognize pulses well outside that range. If there is a single pulse, the number being dialed is “1”; if ten pulses occur, the number being dialed is “0.” Offering 211 and other N11 services where “N” is a smaller number results in generation of many spurious calls by defective telephone lines that effectively dial the N11 number by means of the intermittent shorts and opens in the line caused by the defects mentioned above. These shorts and opens, which temporarily interrupt line current, may be viewed by network switches as pulse dialing signals, which the network switches interpret as actual calls by customers if the pulses are grouped and timed to resemble an actual number. Switches filter out many of these pulses, e.g., a pulse that generates a single digit, like 1, 2 or 3, or several series of pulses that generate a set of numbers less than three, like 21, 32 or 11, simply because switches are not designed to recognize those numbers as legitimate calls. But because switches are biased to complete telephone calls once they receive the correct number or set of digits, a defective communicati
Greer William Halliburton
Jones Robert Franklin
Williamson, III William A.
BellSouth Intellectual Property Corporation
Tocups Nora M.
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