Network Communications News (NCN) July 2016 | Page 23

test equipment & tools

S P E C I A L F E AT U R E

Fig 1. Wire map test for physical continuity with no performance information about the link.

Every cabling technician should
carry a tester which acts as a verifier
to test every link after it is terminated.
This is vital as more than 80 per cent
of all network problems can be traced
back to a physical cabling fault –
which a verifier would quickly and
simply detect.
Many verifiers have additional
diagnostic and troubleshooting
functions which can mean that another,
potentially costlier, type of tester isn’t
required. Verifiers can include functions
such as measuring cable length and
distance to fault, cable tracing with
audible tone generation or visual port
blinking, Ethernet service detection and
PoE testing.

Certifier

It is important to take the time to
understand the different types of
testers and the models available.

Verifier
The main purpose of a verifier is to
test electrical continuity of the cabling
between two points, checking for
shorts, opens, crossed and split pairs.
Verifiers are used in the Physical Layer
or Layer 1, to use the Open Systems
Interconnection (OSI) model. The
OSI model separates the process of
transmitting data across a network
into functional blocks. This layer of an
Ethernet/IP system comprises of the
electrical signalling and physical cabling
components that connect devices on
the network.

These cable testers also work on
Layer 1 and have all the functionality
of a verifier, plus much more. Where a
verifier tests only the physical continuity/
termination of a cable, a certifier tests
the performance of the cable. A cable
certifier uses radio frequencies on the
cabling to measure performance to
international ISO and TIA standards,
providing a pass or fail result, ensuring
that the cabling can support a wide
range of applications.

This makes a certifier the right
choice for technicians or installers
who work on jobs where a cable
manufacturer warranty is required, not
where the cabling is simply terminated
and labelled.
Certifiers tend to require a larger
financial investment, but many of the
top end models have additional useful
functionality, such as the ability to work
on both copper and fibre cabling,
troubleshooting, plus options to export
a wider range of data and reports.

Transmission tester
Transmission testers offer a wide and
varied range of functions, but are not
created equal. To make the right choice
of tester it is important to understand
that, unlike verifiers, which work only on
Layer 1, transmission testers can offer
functionality for testing across both
Layer 2 and Layer 3 of an active network.
In selecting the correct network
or data transmission tester, you must
first understand the layers of the active
network and how testers for these layers
work differently.
Layer 2 can be defined as the data
link layer which provides data transfer
between two directly connected nodes
or two nodes on the same network.

Fig 2. Checking advertised link speed of network/device. Reports maximum
possible speed, though no data is transmitted to confirm actual capability.

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04/07/2016 12:55