Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – For fault location
Patent
1997-04-04
1999-12-28
Regan, Maura
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
For fault location
324522, G01R 3102
Patent
active
060086548
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for testing a telecommunications network.
2. Related Art
When describing a public telecommunications network it is usual to subdivide the network into two parts a first part being a core network and the other part being an access network. The access network is that part of the network which extends from a subscriber's equipment to a local telephony exchange. The access network includes telephone poles, drop wires, cables, junction boxes, primary cross connection points and secondary cross-connection points which are familiar features of the urban and rural landscapes. These are the components which are most exposed to the elements and a large number of faults can occur in this part of the network as a consequence. The core network includes the local and trunk exchanges.
U.S. Pat. No. 4,103,225 describes an apparatus for measuring the capacitance of a telephone cable in order to determine the distance of an open circuit fault from a measurement point.
In the past network operators have relied upon subscribers to report faults. This may take place some time after the fault has occurred because some subscribers only use their equipment infrequently.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a method of testing a method of testing a telecommunications network for the presence of a fault, said method comprising the steps of: time; change in capacitance value; detect the present of a fault; and capacitance value and a known capacitance length ratio a corresponding length of line and hence the distance of the fault from terminating equipment at the end of the line remote from the point of measuring the capacitance values.
The corresponding length of line will be a change in length of that part of the line which is operational. This change in length will be due to a fault occurring between the subscriber's equipment and the exchange. The fault may be caused by an increase in series resistance in the line due, for example, to corrosion, or the fault may be due to a break or disconnection in the line. Such faults have the effect of cutting-off the subscribers equipment. Where the series resistance increases gradually, the quality of transmission over the line will deteriorate gradually until the equipment is effectively cut-off. In the case of a break or disconnection, the cut-off will be immediate. The change in length will be indicative of the location of the fault. The fault will be located by determining a position along the line from the subscriber's equipment equal to the determined change in length of line.
By monitoring the line in this way it is possible to detect and rectify faults before a subscriber discovers a fault exists. This greatly enhances the subscriber's perceived view of the service.
According to another aspect of the invention, there is provided an apparatus for testing at least one line of a telecommunications network for the presence of a fault, said apparatus comprising: first time to obtain a first capacitance value; obtain a second value; second capacitance values; so as to detect a fault; and capacitance length ratio a corresponding length of line and hence the distance of the fault from terminating equipment at the end of the line remote from the point of measuring the capacitance values.
BRIEF DESCRIPTION OF THE DRAWINGS
A specific embodiment of the invention will now be described, by way of example only, with reference to the drawings in which:
FIG. 1 shows in schematic form part of a telecommunications network from a local exchange to a subscriber's premises, the exchange including testing equipment in accordance with the invention;
FIG. 2 shows in schematic block diagram form the testing equipment shown in FIG. 1; and
FIG. 3 is a flowchart illustrating the operation of the testing equipment shown in FIG. 1.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Part of a public telecommunications network is shown in FIG. 1 and it comprises
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Globecom 85--IEEE Global Conference, Dec. 1985.
British Telecommunications public limited company
Regan Maura
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