IR Illumination Eliminates AGC

To beat noise, another option is the use of IR illumination to improve video quality and eliminate the need for AGC. Infrared light is a designed light source used with black-andwhite or color cameras designed to switch over to black-and-white during low-light level applications. Since the human eye cannot see infrared light, the camera system can still provide proper video surveillance without excessive amounts of visible light sources. This type of application is becoming more and more common for several reasons.

When incorporating activity detection for outdoor applications, the installer needs to provide higher video output signals, usually measured in IRE units. For most cameras, low-light signal levels are between 20 and 50 IRE units. Digital video devices usually require more than 50 IRE units to operate properly during activity detection.

IRE units are a measure determined by the Institute of Radio Engineer. It lists full or recommended video at 100 IRE units. One hundred IRE units will produce a high-quality video image, and, as one can see, the lower the number, the lower the quality of an image produced.

IR illumination is also popular because this additional light source is relatively low in cost and designed for each camera application. With this addition of a low-cost IR illumination, proper video levels can be achieved. However the camera must be designed to operate in the spectrum of light.

The one drawback to incorporating IR is the auto-iris lens. Most lenses focus in the visible-light range but not the IR range. This can cause focusing problems with switchover camera assemblies. Special lenses are now available with the ability to focus in the visible- and infrared-light spectrums, thus eliminating this problem.

These suggestions are used to improve performance of cameras incorporated with digital video systems during low-light applications when most systems need that extra help. This help is extremely important if activity or motion detection is part of your application.

Cabling Can Compromise Digital

What other areas affect the performance of digital video? The first on the list are the camera and lens assemblies. Howe
ver, what about the transmission of that video signal to the monitoring location?

The monitoring location is usually where the digital recording and processing equipment is located. Even if the camera and lens produce a quality image, this quality image must get inputs of the digital processing and storage units without excessive losses.

Coaxial cable still has the highest percentage of use. However, users should beware of updating to digital by using parts of an existing system, especially if the parts are existing coaxial cable. Moisture may enter the cable structure over time. When this occurs, the copper cable as well as the connections can be become corroded, thus increasing the signal loss.

If these losses become excessive, the levels may be too low to provide a useable video image. Since most digital equipment relies heavily on image signal strength for their processing (analog- to-digital converters and activitydetection circuitry), all of the aforementioned losses can create problems.

Digital video discussions would not be complete without mentioning fiber optics. Fiber optics has done for coaxial cable what digital recording has done for CCTV.

Many system designers are now considering fiber optics but limit their decisions to more sophisticated CCTV systems. Most still refuse to incorporate fiber optics because of a preconceived notion that fiber is expensive and complicated to install. However, the growth and advantages of fiber, plus manufacturers’ greater adaptability to fiber have caused an increased number of installations, both large and small, to use fiber optics as a method of transmitting video and data in security applications.

Fiber optics offers capabilities well beyond those of coaxial cables without the high cost and restrictions of other mediums. High bandwidth, low noise and electromagnetic immunity are probably the three most outstanding features of fiber optics.

Because optical fiber is a nonmetallic conductor, it is not affected by electro-magnetic (EMI) or radio frequency (RF) interference. This property enhances the performance of the fiber system as more and more system installations demand higher electrical energy standards. These properties make fiber optics well suited for modern installations.

Another main electrical advantage is fiber optics’ elimination of ground loops that cause problems in more than 60 percent of all security systems using standard coaxial cable. Ground loops cause major distortion problems for video, audio, as well as controlling signals.

The reason for ground loops is simple: Coaxial cable uses current — rather than light — to transmit information and this current can cause differences of electrical potentials especially in larger systems or systems incorporating long cable runs. This elimination of ground-loop correctors can greatly reduce the overall cost of any installation.

All of these features add up to one thing: reduced noise. The reduction of noise allows digital video equipment to provide higher-quality recorded images as well as properly function under the many features offered such as activity detection, postimage enhancements and remote monitoring.

Digital Recording Unit Applications

Applications for selection of digital recorders can be divided into four groups:

• DVR-in-a-box

• DVR plug-in-play

• DVR multiplexed

• DVR multichannel

The DVR-in-a-box is appearing everywhere. Just add boards to a standard home computer and you instantly have a digital recorder. At first, it sounds rather simple, but in many cases, just inserting a separate board into any old computer may cause a negative reaction.

For the most part, the computer used for the digital recorder must be dedicated to that system alone. Mixing and matching other software programs can cause a total system crash. All standard computers do not supply alarm inputs or outputs, thus creating a very limited application machine.

The DVR plug-in-play differs from the DVR-in-a-box because the unit is designed and built only for digital video recording. These systems can be found in either single or four channels and offer little or no setup parameters. This reduces the user’s ability to customize picture quality and size or alarming features to meet system needs.

The cost of the unit usually determines the playback quality, storage capacity and reviewing characteristics. Many dealers and integrators are incorporating this type of DVR for direct replacements of standard analog recording systems.

The multiplexed DVR is the largest of the four groups and also can cause some confusion in both selection and setup. Multiplexed digital recorders combine an eight- or 16-channel multiplexing unit with a digital recording device. The sharing of video inputs operates in the same manner as the standalone video multiplexers found in the market. The advantage being installers no longer worry about interface wiring and compatibility of setup programs.

Multiplexed digital recorders offer many additional features, and, in some cases, all of these added features cause additional confusion when selecting the perfect unit for any given application. Many manufacturers keep adding features to their machines to meet all applications, when in fact only about 40 percent of all listed features are ever incorporated into a system and much fewer are understood by end users.

(For additional information on DVR features, see Part 3 of this series, “Essentials of Digital Video Recording,” in the September 2004 issue.)

A Digital Unit for Every Application

With more than 275 different digital units available, you should find one that meets your application. The change to digital is slow but very steady. More surveillance systems will incorporate digital recording methods as dealers and integrators become familiar with the operation of computers, digital in large applications improves and grows in acceptance, and these units reduce in cost. With the demand for increased recording performance and remote video retrieval, the digital video security system growth curve has started its upward journey.

One thing that causes many problems after the purchase and installation of a digital recording system is discovering the it’s not upgradeable, a lack of factory support, no capability with existing equipment or the manufacturer is no longer is business.

To thwart these potential snafus, be sure to ask questions of your manufacturer before making a purchase. What’s the company’s history? What support will it offer? Can the system be upgraded? How easily programmed and operated is this system?

The digital world is here and those who wait too long will be left behind. However, there are many suppliers of digital video equipment that understand the making of a DVR because they know computers, but do not understand basic CCTV. The need for proper support, special key features and simple programming methods is a must.

With wise product selection and the knowledge provided in this and the previous “Digital Video for D.U.M.I.E.S.” articles, security dealers and integrators should be ready to take on the brave new digital world

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