remotely from a security control center. A third type of camera, called pano-
ramic, is emerging. Panoramic cameras provide a 360-degree view of an area.
The panning and tilting of a PTZ camera are accomplished by the camera
mount, not the camera itself. The one drawback of a PTZ camera is that while
it views a specific area within its range, some event could take place in another
part of its panning area and go unnoticed. To compensate, PTZ cameras can
pan in a predefined pattern or can be interfaced with other systems, such as
access control, so that they automatically pan to a specific area when triggered.
Cameras come in a wide variety of resolutions and some have advanced fea-
tures to control and adjust lighting. Based on the security required, placement
of security cameras must consider the camera, lens, lighting, and power.
Variable lenses are the most commonly used, allowing for adjustment in the
field. Zoom lenses can be adjusted remotely from the security control center.
Color cameras are typically used in most video surveillance systems although
black-and-white cameras are actually better in low light situations. Combina-
tion (“night/day”) cameras are available for exterior use where lighting varies
regularly. Camera mounts and housings for cameras are available for a variety
of placements and aesthetic tastes. Housings are also available for special
environments, such as prisons or laboratories.
The true revolution in cameras has been the digital surveillance camera cou-
pled with an IP network connection. A networked camera digitizes the video
(typically into a MPEG or H.264 or Motion JPEG), compresses the digitized
video, creates a data packet of the video and transmits it over a standard data
network. The cameras may have the capability to store video, buffer it if net-
work traffic is heavy or process the video. In addition to the digital video out-
put, the network connections can transmit PTZ signaling, audio and other
control and management commands. The cameras can also be powered from
a central location utilizing POE.
Video Transmission
Transmission of the video signal captured from a surveillance camera to the
security control center has typically occurred through coaxial cable, the tradi-
tional cable for analog video. With changes in the technology more installa-
tions are using unshielded, twisted-pair copper cable, fiber optic cable and
wireless solutions. Unshielded twisted pair is even being used with analog
cameras, with baluns (an interface betweenbalanced signals andunbalanced
signals) or a manufacturer’s proprietary technology, which may allow signal-
ing over long distances.
Video Surveillance Systems 85