near-end crosstalk (NeXT)

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Near-end crosstalk (NEXT) is an error condition that can occur when connectors are attached to twisted pair cabling. NEXT is usually caused by crossed or crushed wire pairs. The error condition does not require that the wires be crushed so much that the conductors inside become exposed. Two conductors only need to be close enough so that the radiating signal from one of the wires can interfere with the signal traveling on the other. Most medium- to high-end cable testers are capable of testing for NEXT errors.

In order to certify a cable as Category 3 (see Categories of twisted pair cabling systems), the NEXT test must be performed in 1 MHz steps from 1 Mhz to 16 MHz. Since the level of signal loss or interference can change with frequency, a range of frequencies must be used to certify that the cable is acceptable over the entire range. In order to certify a cable for Category 5 use, the test frequency range must be extended up to 100 MHz. A 1 MHz frequency step should still be used. In both cases, you must test both ends of the cable. This is because NEXT occurs on the ends of the cable right where the connector is attached.

Simply using Category 5 cables, connectors, and patch panels does not guarantee that a network will support 100 Mb operation. You must actually certify your network for use at this speed with a CAT 5 cable tester after the network is fully installed.

This was last updated in April 2007

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