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Security cameras come in many styles, but the most important aspect associated with camera selection is whether the technology matches the application. This requires knowledge of the many attributes associated with analog and Internet protocol (IP) technology.
Twenty-six million video surveillance cameras later, we have seen that private-sector business widely approves of video surveillance as a cost-effective method of fighting crime. From the early 1940s into the 1990s, analog enjoyed a position of prominence in the video security marketplace; it still does. For more than 30 years, retail, for example, used analog cameras to reduce internal shrinkage and bolster slip-and-fall defense in the face of a rising sea of legal claims.
However, this position of preference will eventually change because of the convergence of video and network technologies, commonly called IP video. In fact, respected security experts believe IP video will one day be the standard in the security market. Others believe IP video still has far to go.
“My experience indicates, while popularity of IP cameras is accelerating rapidly, the majority of the market continues to use analog cameras. Most of the coaxial and fiber are used to carry analog camera images to multichannel IP encoders that then convert the analog video into digital. From here, it’s put on the IP network,” said Bob Banerjee, product marketing manager, Bosch Security Systems Inc., Lancaster, Pa.
The IP video advantage
The power of IP video technology turns on a unique data-oriented addressing method that enables installers to readily identify each camera in a data-driven network. Binary by nature, each camera is given a unique IP address, thereby allowing operators to manually perform a multitude of camera-specific tasks directed at specific cameras. This same IP addressability enables the automatic control over a variety of other subsystems as it relates to specific cameras.
Examples of this include rapid searches of video footage using a number of data types, made possible through integrating IP video systems with other electronic systems within a facility, such as data from a cash register and batch and run number information in manufacturing. Other data types also can be saved to the same network video recorder (NVR), linking them with associated video images.
The connection of specific activities and camera-related criteria to one or more preprogrammed outcomes is another use for addressing cameras. A good example of this is the detection of motion in a specific group of pixels within a video image. Through programming, movement can cause lights to turn on or off, audio messages to play and gates to open. Remote central station operators also can be notified of situations that require immediate attention. This can be done from the head-end or through a relay output on a camera. Another option is an addressable output module placed somewhere on the network itself.
Analyzing the analog/IP difference
IP technology also offers a more efficient means of transporting video images across short and long distances. This is true whether it involves a small local area network (LAN) or a wide or global area network (WAN/GAN). Where analog cameras typically require two cables per camera—a two-conductor cable for low-voltage power and a coaxial to carry the video signal—IP cameras use a single unshielded twisted pair (UTP) cable such as a Category 5e, 6 or 7 to transport images and power. This is where Power over Ethernet (PoE) comes into play.
In some IP camera systems, the manufacturer offers a PoE power supply that must be used to power their brand of cameras. In many cases, this power supply is made to fit into the same rack that holds other IP-video equipment, such as network video recorders and data switches and routers.
Because IP cameras are network-based, adding one or more to an existing system requires less time than its analog counterpart because the installer can easily add a hub or data switch to the existing network where required.
Traditional cameras use the National Television Standard Commission (NTSC) signal standard, which is also referred to as composite video. NTSC, which is analog by nature, uses what is commonly called baseband frequencies (20 Hz to 6 MHz) to carry video. By comparison, IP technology involves the conversion of analog images into a binary equivalent. Binary coding involves the use of 1s and 0s, which are actually represented by two different voltage states.
An analog camera converts analog video from the output of an imager into a digital signal, so it can be processed. Once the signal has been conditioned to suit the application and end-user preference, it is then converted back into its near-original analog state. In some situations, these analog signals are susceptible to radio-based and other sources of electromagnetic interference (EMI).
By comparison, in an IP camera, the analog signal is converted into digital, and it remains in that format until it arrives at the other end of a wire where the technician can elect to do any number of things with it. In addition, digital is not as susceptible to outside interference as analog is.
One of the most serious shortcomings associated with analog camera technology involves the introduction of EMI found in the environment. Although analog cameras use a shielded coaxial cable for signal transport, EMI can still adversely affect the 1-volt, peak-to-peak video signal contained within it.
IP camera technology is not as prone to outside EMI for two reasons: First, digital video equipment can more readily dial out noise than analog counterparts. Digital data contains only two voltage states as opposed to analog, which has nearly a limitless range of amplitudes to consider. Second, IP-based video relies on a balanced line methodology using a UTP cable. A balanced line helps cancel out interference problems by virtue of its physical construction. Because of the twists in each pair, any interference that may find its way into the cable will likely be cancelled out by virtue of the opposing magnetic fields that surround each conductor.
Although digital IP is not as susceptible to problems due to outside sources of EMI, there are other things that can adversely affect the performance of an IP-based system. This is because of the nature of the Category 5, 6 or 7 cable used when transporting IP signals.
The first problem that can affect system performance is crosstalk. Crosstalk is caused by the inductive and capacitive characteristics of the twisted wire. Although digital signals are commonly less prone to noise, it can cause a reduction in throughput.
“What this means is interference can come from poor cable installation techniques and from nearby cables,” said Steve Surfaro, group manager strategic technical liaison, Panasonic System Solutions Company, Secaucus, N.J.
Unlike coaxial cable, UTP cable does not have the benefit of a shield to protect the signal it carries from outside EMI.
Instead, it contains numerous pairs of twisted conductors that act to protect the signal.
“As you know, twisted-pair cable uses multiple pairs of twisted conductors that actually cancel out the crosstalk,” Surfaro said. “But when the connections are not done correctly and you have a straightening of loose cable at the connectors, you could introduce interference and crosstalk. The effect of that interference is a reduction of the throughput of the digital signal.”
Colombo is a 32-year veteran in the security and life safety markets. He is currently director with FireNetOnline.com and a nationally recognized trade journalist in East Canton, Ohio.