Too Many Choices?
CCTV installers face seemingly endless transmission options
- By Dan Nitzen
- Aug 07, 2009
Remember the 1984 movie "Moscow on the Hudson," where a Russian immigrant, played by Robin Williams, is befuddled by an entire supermarket aisle filled with an endless array of coffee product choices?
CCTV choices are a bit like that—with literally thousands of cameras, DVRs and IP solutions to choose from. Most installers select their products based on recommendations from sales representatives or from those stocked by their favorite distributor. Other times, the choice is made simply based on what has worked in the past. Although the results of these choices are usually predictable, this comfortable approach does not foster improvement in performance, cost or serviceability. In this competitive economy, it's those choices that allow the innovative installer to come out ahead.
Perhaps the single most expensive part of the installation is transmission. Transmission encompasses the transport of video signals, camera power and, sometimes, telemetry data between the camera and the storage and monitoring location. It is often overlooked when designing a CCTV system.
Selecting a transmission solution depends on the application. Installers need to consider whether the camera installation will be fixed or PTZ. Will heaters, blowers or IR illuminators be required? Will the cameras and peripheral equipment receive local power, like 12 volts DC or 24 volts AC? Other questions include, how long are the cables between the cameras and control equipment? Does the installation require an underground or other wet cable-pull? Is conduit access available? And finally, how important is the perception and/or need for IP cameras?
Once these questions are answered, end users may select an optimal transmission method. Compare your needs against the available solutions:
- Which method provides the most appropriate picture quality?
- Which method has the lowest materials cost?
- Which method has the lowest installation (labor) cost?
- Which method is most easily expandable and standards compatible?
- What later additions, changes or IP migration are contemplated?
- Which solutions are most easily serviced?
- What level of reliability and support is needed?
- What is the total cost of ownership, and who bears that cost?
It's easy to dismiss one solution as being more expensive based solely on equipment cost. However, when thorough analysis includes the labor of pulling power and/or telemetry cables, serviceability or the calculation of the total cost of ownership, specifiers are often surprised by changes in the expense gap between solutions.
Coax. Most CCTV installations still use coax cable. This wire is acceptable for short distances but quickly becomes expensive at longer distances due to its large copper composition. It also is an unbalanced transmission line, which means it can be susceptible to interference. Coax cables must be kept away from power cables and other interfering sources. They do not have immunity to ground differences, which can result in ground-loops or hum-bars.
PTZ telemetry can be supported up to about 1,000 feet using up-the-coax protocols. However, camera power and longer distance telemetry require additional cable pulls, or expensive and bulky Siamese cable.
The CCTV industry is one of the last to abandon coax cable in favor of structured building wiring.
Conventional wireless. Expensive radio devices are used when the transmission path is inaccessible. This method works best in line-of-sight applications. Bandwidth is limited, and the video is often susceptible to interference.
Fiber. The non-conductive nature of fiber works well in long-distance, lightning- prone or high-noise environments.
Cost, radius of curvature, installer tools and skills, and the inability to send power make this an outlier technology.
Ethernet. This solution, used by IP cameras, is easy to install, supports structured building wiring practices (EIA/TIA 568B standards) and can support distances up to 300 feet. PoE allows the camera to be powered through the same four-pair Cat-5 cable.
Materials costs are significantly higher when one includes IP cameras and enterprise- level routers. Higher priced labor and reliability is the Achilles' heel of this technology. Configuration, warranty service and ongoing maintenance costs often present a rude TCO surprise.
Wi-Fi. Also used by IP cameras, this solution has interference, bandwidth and potentially serious security issues, in addition to those of Ethernet.
Hybrid video. Growing in popularity, this reliable solution allows camera power, analog video and RS-422/RS-485 telemetry to reside within one low-cost fourpair Cat-5 cable. It supports structured building wiring practices (EIA/TIA 568B standards) and can support distances up to 2,000 feet, depending on camera power.
RJ-45 connections can be easily tested and verified with a handheld LAN tester. Cameras may be powered from power supplies located mid-span in IDF closets, or from the MDF room (head-end), facilitating UPS backup.
As a balanced transmission line, it is inherently interference immune and has built-in transient protection. Video signals can be sent several thousands of feet when active (amplified) devices are used. Further, the customer can migrate to an IP solution if desired. Often, when deploying a hybrid solution, IP is just a video server away.
Selection of a good transmission method may not be as daunting as a camera or DVR selection, but its impact on system performance, reliability, future IP migrations and cost can often make the difference between a winner and a money pit. Choose wisely and consider costs/performance, flexibility and overall ROI/TCO.