- Wiremap For UTP Cabling
is a simple test that confirms that each wire is hooked up
correctly, with no opens or shorts. UTP intended only for POTS (plain
old telephone service) voice applications actually only needs to be
tested for wiremap. Wiremapping is very straightforward. Structured
cabling standards do not consider simple voice grade cable, only cable
of Category 3 or above, so most cable testing will require more than
just wiremapping, either certification or verification, so wiremap
testing is done in the tester before other tests. Each pair must be
connected to the correct pins at
the plugs and jacks, with good contacts in the terminations. A
"wiremapper" is basically a continuity checker that determines if pins
are correctly connected.
- Most of the failures are simple
enough to understand, like reversed wires in a pair, crossed
pairs, opens or shorts. One possible failure, crossed pairs,
is caused when both wires of a pair are crossed at one termination.
The usual cause of a crossed pair is a 568A termination on one
end and a 568B on the other.
- The most difficult wiremap problem
is a split pair, when one wire on each pair is reversed on both
ends. It causes the signal to be sent on one wire each of two
pairs. The usual DC wiremap will pass but crosstalk will fail.
It takes a more sophisticated wiremapper or Cat 5e/6/6a tester to
find a split pair, as some wiremappers which use only DC tests
do not check crosstalk. In our experience, a split pair is usually
caused by someone using punchdown color codes on jacks which
splits the pairs.
Here are examples of wiremap faults. Compare the diagrams to the correct one above to see the wiring errors.
Shown here, pair 2 (orange) is open because tip is not connected.
- Shorts and Opens
Pair 3 (greeen) is shorted on pin 6.
Pair 3 (green) has tip and ring reversed.
- Reversed Pairs
2 (orange) and pair 3 (green) are crossed, connected to each
others pins. The usual cause of crossed pairs is one end is
terminated at T568B and the other end T568A, where pairs 2 and 3 are
- Transposed or Crossed Pairs
pairs are when one wire of each pair is improperly connected. Here
pairs 1 (blue) and 3 (green) are connected such that a DC wiremap
tester will test OK, but the signals are being carried on one wire of
two pairs, so the cables are unbalanced. Split pairs are often caused
by the wires being punched down on a jack using the color codes for
- Split Pairs
- Test your comprehension with the section quiz.