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Near-end crosstalk is a phenomenon that can take place when there is some form or electromagnetic interference taking place with relatively close to the point of measurement. The effect of near-end crosstalk is that the signals being carried by two different cables or wires may begin to interfere with one another in a manner that degrades the signal of at least one of the two transmissions. The problem can take place due to something as simple as a temporary twisted pair cabling or worn spots in the insulation of the cabling proper that allow the wiring of the two cables to come into close proximity.
Along with near-end crosstalk or NEXT, there is also the occurrence of what is known as far-end crosstalk or FEXT. FEXT is essentially the same set of circumstances that occur with near-end crosstalk. The only difference is that far end crosstalk is the detection of a signal crossing or disruption that is located at a distance from the point of measurement.
As can be imagined, the occurrence of any type of crosstalk can lead to communication issues. In general, modern communication equipment must be designed to meet with standards set by the Telecommunications Industry Association and the Electronic Industries Association in order to receive the endorsement of these two organizations. The standards set by the TIA and EIA also form the basis for standards established by many countries with nationalized phone and communication networks. These standards require that the type of cabling used in the equipment be designed to minimize the chances for both far end and near-end crosstalk to take place on a recurring basis.
Many persons who have participated in an audio conference call have experienced the end result of far end or near-end crosstalk during the meeting. When the conference call is being conducted through the bridging equipment operated by an audio conference call service, it is usually possible for a conference operator to track the crosstalk to a particular line or trunk in the meeting. The operator can then instruct the attendee to disconnect and either redial the party or have the party use a toll free number to dial back into the conference.
The chances of the second connection using the same combination of cables, trunks, and wire connections a second time is astronomical, so generally this eliminates the problem for the end user. The conference call provider normally will note the trunk number that the original connected used for bridge connectivity and run diagnostics to ensure the origin of the crosstalk was not located in the conference bridge.