Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2000-07-18
2002-12-17
Le, N. (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S538000, C324S066000
Reexamination Certificate
active
06496014
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods and apparatus for storing data, including error compensation data, locally on probes for use with a cable tester so as to enable accurate identification, maintenance and error correction of data obtained via the probe.
The challenge to manufacturers of cables and connectors has been to improve the performance of their products to provide a better transmission environment for ever-higher data transmission rates. At present, the structured cabling industry is transitioning from category 5 products and standards to category 6 products and standards. This transition will continue for some time as product innovation continues and as standards documents continue to evolve. Cable manufacturers employ a wide variety of materials and construction techniques to improve the performance of cable to meet the new standards. Recent emphasis has been on reducing process variations and optimizing cable construction in an effort to reduce crosstalk between pairs and reflections within pairs.
To ensure that structured cabling systems provide adequate performance to support the utilized application interfaces, cabling standards committees have developed quality control specifications for the installation of new cabling. Cable testers provide a convenient and reliable means of certifying new installations for compliance with structured cabling standards. Standards for structured twisted pair cabling require that both ends of each cabling run be tested in order to find the worst case performance condition. For this reason, all certification testing requires a two-part test set, consisting of a main unit and a remote unit. One unit tests the cabling run from the telecommunications closet end and the other unit tests the cabling run from the telecommunications outlet end at the user location.
Certification testing is highly automated. Typically, an automated function coordinates a series of measurements between the main unit and the remote unit and subsequently analyzes the resulting data to determine if the cabling run passes or fails the required standards. Two key criteria apply in determining the extent of a test for any particular cabling run:
1) Whether the user patch cords are included in the cabling run during the test (i.e., “Link” or “Channel” test configuration)
2) What standard document and which performance level the user wishes to test the cabling to (i.e., for what “category” is the user seeking certification)
FIG. 1
is a diagram of a known testing circuit
100
in a link test configuration. The testing circuit
100
tests a cable
110
which provides a communication path between a telecommunications closet end
112
and a telecommunications outlet end
114
. The configuration of the testing circuit
100
shown in
FIG. 1
is a “link configuration” intended for use in facilities still in the construction stage. The link configuration does not include user patch cords at either end of the cabling run as these cords are often not installed until after the facility is occupied. Because the link configuration does not include the two additional connections which would be added when the patch cords are connected, performance standards are more stringent for cabling tested using the link configuration.
A main unit
116
and a remote unit
118
attach to the link under test, the cable
110
, via special link test probes
120
a
and
120
b
respectively. The link test probes
120
a
and
120
b
are provided with interfaces
122
a
and
122
b
for connection to the main unit
116
and the remote unit
118
respectively. The link test probes
120
a
and
120
b
are typically terminated at their opposite ends with male modular-8 plugs
124
a
and
124
b
, respectively, for connection to the telecommunications closet end
112
and the telecommunications outlet end
114
, respectively.
FIG. 2
is a diagram of a known testing circuit
200
in a channel test configuration. The testing circuit
200
, like the testing circuit
100
, tests a cable
110
which provides a communication path between a telecommunications closet end
112
and a telecommunications outlet end
114
. In addition, the test produced by the testing circuit
200
includes the effect of user patch cords
220
a
and
220
b
, thereby providing a comprehensive end-to-end cabling performance certification. The patch cords are typically created as the network is going live, and, as such, a channel test is typically performed after the facilities have been constructed, either as a final test prior to going live, or to diagnose subsequent problems. The pass/fail limits applied when testing with the channel configuration will typically be less stringent than for the link configuration
A main unit
116
and a remote unit
118
attach to the link under test, the cable
110
and user patch cords
220
a
and
220
b
, via special channel probes
222
a
and
222
b
respectively. The channel probes
220
a
and
220
b
are provided with interfaces for connection to the main unit
116
and the remote unit
118
, respectively. On the opposite ends, the channel probes
222
a
and
222
b
are typically terminated with female modular-8 plugs
122
a
and
122
b
, respectively, for connection to the user leads
220
a
and
220
b
, respectively.
One problem encountered when testing cables, and in particular category 6 cables, is correctly matching the test units (the main unit
116
and the remote unit
118
) to the link under test. This is not as simple as picking between a link and a channel adapter, but rather a broad range of choices faces the user. There exist a multitude of different link probes, along with an equal multitude of channel probes. Not only do users have to select between link and channel probes, but they must also match the probe to the manufacture of the network. This choice is made more difficult by the physical similarities of the probes used, while the difference between a channel probe and a link probe may be self-evident, each of the various probes with the channel probe family or link probe family pretty much look exactly the same. Each probe starts with a tester unit interface and ends in a modular-8 connector. As will be discussed below, the choice of which probe to utilize is critical to obtaining accurate testing results.
The modular-8 connector (also known as the RJ-45), was originally designed for telephone and low rate (under 1 Mbps) data applications. Consequently, the mechanical arrangement of signal contacts is not optimized to address the crosstalk and reflection problems that appear at high data rates (over 100 Mbps). Many ingenious designs have been utilized to compensate for the inherently poor performance that results from the modular-8 contact geometry. In the previous generation of connector designs (category 5), most manufacturers used signal compensation in just the jack (female connector), leaving the plug (male connector) uncompensated. To achieve the higher performance levels required for category 6 and maintain backward compatibility with the modular-8 signal contact geometry, most connector manufacturers place compensation into both the plug and jack. It is important that the compensation techniques used in each plug and jack of the network be compatible. The interaction between incompatible plug and jack compensation designs produces worse performance than previous level 5 connectors. This is one reason why certification is so important
Unfortunately, no standards currently exit for the physical and logical construction of category 6 connectors and associated compensation techniques. In fact, cables and connectors from different manufactures are often incompatible with each other. Accordingly, to construct a category 6 network, users have to make sure that they match the brand and type of category 6 plugs and jacks in order to achieve optimum system performance.
The requirement to match category 6 plugs and jacks also applies to the link probes and channel adapters used for cable certification testing. When testing category 6 or class
Agilent Technologie,s Inc.
Le N.
Sundaram T. R.
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