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Products | Understanding Analog
and IP TV CCTV Cameras.
One of the most significant
technological changes in CCTV market is
the advent of so called “IP cameras.” Despite
the fact this technology has been available
for quite a few years, there is scant little
objective information on what sets them
apart from the analog cameras that had powered
the industry for decades before. The complexity
of what goes into design of IP cameras is
partly responsible for this, requiring users
to be fluent in everything from advanced
video compression to computers and networking.
Complicating matters is the confusing specifications
and often misleading terminology used to
describe the basic performance of CCTV systems.
Simple terms like “lines are resolution”
are used where the intuitive meaning (how
many lines there are in the picture) actually
is not what the metric measures! Add to
this the typical marketing hype and the
picture becomes even muddier.
The purpose of this series of articles is
to simplify these concepts and distill them
down to a level where you can make purchasing
decisions intelligently. While the coverage
will be comprehensive, significant simplification
is applied as to make the concepts easy
to grasp, assuring that the proverbial “forest
is seen from the trees.”
With that introduction, now let’s take a
“deep dive” into each technology and what
sets them apart.
Analog Camera Overview
As with any imaging device,
the analog CCTV camera has a sensor which
captures the video image. The resolution
of the sensor varies but for reasons which
will be described later, it is limited to
720×575. This is 720 pixels across the screen
(horizontal resolution) and 575 up and down
(vertical resolution).
The video is captured at 60 intervals called
“fields” and transmitted to the receiver.
Two fields together are called a “frame.”
This is called interlaced transmission.
More on this later.
To get the video out of the CCTV camera
into a recording and display device, a single
coax cable is used. To maintain compatibility
with analog televisions (and hence make
it easier to use off the shelf products
for display and recording), the signal that
comes out of the camera complies with broadcast
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