Connecting the Dots
Specifiers scrambling for solutions to link analog, digital equipment
- By George Wojtan
- Sep 01, 2008
The evolution of video surveillance
systems to IP-based systems
will be application-, budget-
and choice-based. It’s not only a
choice of product, but also a choice of
transmission media.
To maximize the customer’s technology
options at the camera, transmission
system and head end, CCTV system
specifiers are scrambling to provide solutions
that fill the gaps between installed
analog and digital equipment. They want
to be sure their system choices provide an
upgrade path that is forward compatible
to include a fully digital architecture in
the future, without throwing out perfectly
good analog equipment.
Most people don’t know it’s possible
to use the same transmission media for
both analog and IP systems. The transmission
media becomes the bridging
point to implement a cost-effective surveillance
system that gives customers the
product choices they need. This bridging
system is commonly known as a hybrid
IP system or just a hybrid system.
The typical hybrid medium is
unshielded twisted pair, though a hybrid
system can include fiber as well. The
UTP hybrid system choice can support
today’s cost-effective analog camera and
recording systems while providing an IPready,
standards-based cabling infrastructure
when a switchover occurs. The following
are key points of a hybrid surveillance
system:
Structured cabling should be used
in all surveillance systems. In a hybrid
system, the media being deployed can
drive down system cost and increase
product choice whether the end user is
using analog or Ethernet as the video
transmission method. Structured
cabling has been used in the LAN data
and telecom world for decades. It is
quick to install and easy to change, and
it can be performance-certified to an
industry standard. This performance
standard rating is dependent on whether
Cat-5e, Cat-6 or augmented C6 components
are used and EIA/TIA installation
rules are followed.
Future proof by avoiding coax. By
using a structured cabling system, a customer
can deploy an analog system on
UTP and reuse the cabling plant when the
end user migrates to an IP-based surveillance
system. If coax is used as the
method for wiring analog cameras, when
the customer decides to migrate to IPbased
surveillance, all of the coaxial
cable will have to be removed.
In 2002, the National Electric Code
was modified to require the removal of
communications cables that cannot be
tagged for future use. The mandate was
meant to reduce fire loads in commercial
structures. Coaxial cable has no future
use, so it will have to be removed.
Four-pair UTP cable is the basis of
all structured cabling plants. Since only
one pair of UTP is needed to transmit
analog video, it allows the other pairs
under the jacket to be used for other
things—typically, one pair for video, two
pairs for power (mid-span power injection)
and one pair for telemetry. So, with
a single four-pair UTP cable pulled to a
camera site, it is possible to power the
camera, bring the video signal back and
control the PTZ camera.
Normally, the end user would have to
pull three separate wire types to get the
same functionality. The same advantages
of four-pair UTP cable apply to IP-based
systems; a single four-pair can transport
the video signal back, power the camera
(with PoE) and control the PTZ camera.
Structured cabling can be an economic
choice. Installation labor is a big
part of the cost of any wiring job. The
cost of the individual components represents
a small percentage of the overall
system cost. When deploying an analog
camera system, large cost reductions can
be achieved by using a multi-pair UTP
cable (25, 50, 100 or 300 pair) between
the IDF and MDF. Since analog video
only requires one pair for transmission, a
50-pair UTP cable carries 50 channels of
video. The integrator can pull a 50-pair
cable in one pull, but it’s not possible to
pull 50 coaxial cables at one time. So the
savings come from the reduced labor of
pulling a single multi-pair cable versus
multiple pulls of coax.
Consider fiber. Alternately, fiber can
be used to connect the IDF and MDF. To
truly future proof an installation, the end
user would also have to pull a “dark”
fiber between the IDF and MDF. The
conversion to IP lights up the dark fiber.
That might mean removal of the multipair
UTP cable if it is not tagged for
future use. Since it is a UTP multi-pair
cable, there is likely a future use—such
as phone systems, access points or any
other device that uses UTP.
Be aware that there are choices regarding
the media used for cabling infrastructure,
allowing the end user more flexibility
in future systems’ needs and choices.
The most common media for IP transmission
is UTP. Whether deploying an analog,
a hybrid or a purely IP-based system, UTP
is worthy of consideration.