Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Testing of subscriber loop or terminal
Patent
1992-05-01
1994-05-03
Chin, Stephen
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Testing of subscriber loop or terminal
H04M 330
Patent
active
053094999
DESCRIPTION:
BRIEF SUMMARY
This invention relates to the testing of the working condition of a spare line pair of a communications cable using a device connected between remote ends of the line pair.
Communications lines, such as telephone cables, are most commonly deployed with an over-capacity in the number of pairs of wires. The cable runs to a distribution point where the various wire pairs are mounted ready for connection to customer telephones and other telecommunication apparatus. The over-capacity is provided to accommodate new customers requiring connection, and is called "spare pairs" or "spare line pairs".
Before a previously redundant (i.e. spare) pair of wires constituting a telephone line can be used to connect a customer, it is necessary to test the wires to ensure they are both in working condition.
To test the pairs before they are put to use, it is presently necesary to send an installation technician to conduct appropriate tests on the nominated wires at the distribution point local to a particular customer. In the event that a pair of wires corresponding to a particular designated telephone number are defective, a technician cannot connect the customer and he must return to the central exchange and have a further pair of wires designated for that customer's use. Once this is done, the technician must again visit the site and conduct the tests. It is clear that nominating a defective wire pair can lead to at least one wasted site visit before the fact is detected.
It is clearly desirable to be able to test a given line pair remotely before the installer conducts the time consuming and expensive site visit.
Line test systems are known which are able to diagnose various line faults, and line characteristics from a remote location. An example of such a proprietary line test system is the 4TEL system made by Teradyne Limited of Western Centre, Western Road, Bracknell, Berkshire, RG12 1RW, England.
These systems use sophisticated software test routines and test signals which exploit the inherent capacitance and resistance in a line pair to determine the nature and location of a fault and/or the parametric data associated with the line, for example, susceptance, resistance, leakance etc. These systems can also be used to determine the length of a line pair. However, they are not accurate enough to be able to determine whether an unterminated pair is in good working condition or whether there is a break in either wire in the vicinity of the distribution point. This latter condition would result in an indication of a pair of unterminated wires apparently in good condition.
It is an object of the present invention to provide a method of testing the working condition of a spare line pair of a communications cable from a remote location, a test device for use in such a method, and a communications system arranged for such testing.
According to the present invention there is provided a method of testing the working condition of a spare line pair of an electrically conductive communications cable which extends from a node to a remote distribution point, from which distribution point the remote end of each working line pair of the cable is connected to a customer's premises or to a further distribution point, as appropriate, and a similar connection is intended for the or each spare line pair of the cable;
the method of including the prior steps of identifying at least one spare line pair of the cable; connecting an individual spare line test device between the ends of the or at least one spare line pair at the remote distribution point, the test device having a first signal conditioning characteristic to a signal of one polarity applied to the line and a second signal conditioning characteristic to a signal of the other polarity applied to the line; and leaving the or each test device connected to its associated line pair while that line pair remains spare;
providing at the node an exchange equipment termination for the or said at least one spare line pair;
and the method including the further steps of applying signals of both
REFERENCES:
patent: 4629835 (1986-12-01), Miller
British Telecommunications Engineering, vol. 2, No. 4, 1984, (London, GB) D. V. Thorpe: "Processor-controlled systems for the testing of customers' lines", pp. 261-266.
British Telecommunications public limited company
Chin Stephen
Loomis Paul
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