24.11.2023 /Testing

Wire map (continued)

Half of the eight wires in a cable have a white insulation. Happens from time to time that wires are swapped. This issue and the following ones will focus on the different type of “swaps” and what to do against it.

Wire map checks whether all wires of a cable are terminated properly on both ends of the cable an whether there are shorts or opens in the link. The last issue focused on short, open, open shield and shield integrity. This issue focuses on reversed Pair, crossed pairs and split pairs.

Reversed pair

The wires of one pair have been swapped on one end of the cable.

Typical cause of the problem	This might help (without engagement)
Wires in patch panel, outlet or plug connected to the wrong contacts.	Re-terminate wires
Wires in patch cord connected to the wrong contacts	Replace patch cord

Crossed pairs

Two pairs got swapped on one end of the cable. This might happen, for example, when the cable is terminated according to T568A on one end and according to T568B on the other end or when a cross-over patch cord is used. Another term for crossed pairs is transposed pairs.

Typical cause of the problem	This might help (without engagement)
Wires in patch panel, outlet or plug terminated in the wrong contactst	Re-terminate wires
Wires in patch panel, outlet or plug terminated according to T568A on one end and according to T568B on the other end	Terminate wires on both ends following the same pattern
Cross-over patch cord used	Replace patch cord
Wires in patch cord terminated in the wrong contacts	Replace patch cord

Split pairs

Split pairs means that one wire of a pair is terminated on both ends in the contacts that belong to another pair. For example if the contacts are marked with both colour codes T568A and T568B, the orange wire might be terminated in the contact that belongs to the green one, but as the connecting blocks have both colour codes printed on them, there are both, the orange and the green mark on the same contact. The same applies when the white wires of two pairs are swapped on both cable ends.

Split pairs also occur when the pairs are not terminated in the assignment 1-2, 3-6, 4-5, 7-8 as common in IT networks but in the assignment 1-2, 3-4, 5-6, 7-8 as common in telephony cabling.