Selecting the Right Pair
Making the most of copper twisted-pair recommendations
When it comes to choosing cabling infrastructure for
security, it is essential to work with a distribution
partner that can provide the right education, training
and products for your project needs.
In a modern physical security network, each camera or access
door controller should be viewed as a data point and not just a security
node on the network. Using high performance structured cabling
allows a range of devices from IP-based systems to serial devices
to be interconnected.
For example, a camera connected to an equipment outlet can be
easily replaced with a wireless access point or intelligent lighting as
the application requirements of an organization change over time. By
reconfiguring the physical security network for data points instead of
specific applications, users can create a network infrastructure with a
longer life cycle, more flexibility and greater scalability to meet shifting
demands and to accommodate new technologies.
Likewise, designers for wireless data networks, DAS systems, voice
systems and other IP-based systems look to create infrastructure networks
that could support IP security devices. To have a fully supportable
Internet Protocol (IP) network solution, it is becoming increasingly
important to make the right choices up front when considering
the structured cabling and components.
Users can protect network investments by matching the cabling
infrastructure to its components based on the organization’s technical
and life-cycle requirements to support current and future applications.
The two primary choices for cabling infrastructure to support
an IP-based system are balanced copper twisted-pair and fiber optic
cabling. Some recommendations for designing a robust copper twisted-
pair infrastructure follow.
CABLING REQUIREMENTS
Over time, the cost of replacing electronic hardware increases with
technology advancements whereas high-quality, existing cabling infrastructures
can be expected to support these future changes. The
right cabling installation can be expected to last up to 20 years; however,
many security products only last up to five years due to either
obsolescence or feature revision preferences from the end user as
needs change. Therefore, it is recommended to install at least a Category
6 cabling infrastructure to meet any future requirements.
UNSHIELDED TWISTED-PAIR AND SHIELDED
TWISTED-PAIR OPTIONS
Due to its affordability and ease of installation, twisted-pair cabling is
often the choice for security cabling infrastructure today. Unshielded
twisted-pair (UTP) cabling is by definition manufactured without a
shield on either the outer jacket or wire insulation. UTP uses a balanced
pair design to reject noise that affects data transmission. In
contrast to UTP, shielded twisted-pair cabling (F/UTP or S/FTP) has
a different set of installation and maintenance rules due to the foil
and/or braid shield used in its design.
In a shielded solution, all cables, patch cords and connecting hardware
are manufactured with an added metallic shield element to further
reduce potential electromagnetic interference (EMI) that could
get coupled onto the transmission line. The metallic shield must be
grounded to the telecommunications grounding system to ensure its
performance, which requires additional installation materials, tools
and procedures. However, in areas that have high levels of EMI, such
as a manufacturing floor, this is the recommended solution because
of the high prevalence and risk of EMI.
BACKWARD COMPATIBILITY
All cabling compliant to the standards of the Telecommunications Industry
Association (TIA) or International Organization for Standardization
(ISO) is backward compatible with the lowest component
dictating the performance. An end-to-end channel is only as good
as its weakest link. For example, mixing the performance ratings, or
Categories, of cables, connectors and patch cords can negatively affect
network performance by increasing the potential of IP equipment
transmission errors, resulting in video quality degradation.
This is largely due to the fact that IP-based video depends on best
effort delivery protocol (UDP) for delivery of the video data throughout
the network and is very sensitive to transmission errors that
manifest themselves on the network. Because information is dropped
if data packets are received in error, this could cause significant degradation
in the video that is viewed on the network.
POWER OVER ETHERNET SUPPORT
The delivery of DC power over twisted-pair cabling using the Ethernet
protocol, also known as Power over Ethernet or PoE, is supported
over the same copper cable infrastructure that supports the production
network device applications.
When looking to use PoE, there are important factors to consider:
- Today, up to 25 watts of power can be delivered to PoE-compliant
devices on Category 5e and above cables using IEEE 802.3at compliant
equipment.
- A new version of PoE over twisted-pair cabling is being developed
by the IEEE 802.3bt Task Force and is expected to deliver up to
70 watts to compatible equipment. With the increase in available
power, it becomes even more important to specify cable constructions
with larger conductor sizes such as Category 6 and Category
6A to mitigate potential heat effects on bundled cables.
- Higher power over a bundle of cables has the potential to generate
greater heat dissipation on each cable within the bundle. Heat will
attenuate (i.e. insertion loss) a data signal, and in some cases, it
can degrade the signal enough to cause network errors and therefore
degrade video quality.
This article originally appeared in the September 2017 issue of Security Today.