Although UTP cable was designed for use with phone and data networks, its popularity in the CCTV world is growing rapidly. UTP is often chosen over coax and fiber because of its ease of installation, cabling options, noise immunity, ground-loop isolation and surge protection.
UTP employs a robust, balanced mode of transmission, making it highly resistant to interference. Video signals can reside in the same wire bundle with signals for ringing telephones, Ethernet, 24 VAC, RS-422, RS-485 and other video signals. They can also reside in high-noise environments such as elevator traveling cables, or near fluorescent lights, radio transmitters or motors.
UTP wire is about one-tenth the diameter of RG-59, which makes it easier to pull and terminate. Both UTP and coax are available with plenum-rated jackets, but if you compare plenum coax and plenum UTP, the differences become quite apparent. As the number of cables needed increases, each added coax adds bulk in addition to its own plenum jacket. But since up to 100 UTP pairs can reside under a single plenum jacket, the UTP bulk is much less. One four-pair plenum Cat 5 UTP costs about one-fourth per channel what plenum coax does. However, for non-plenum wire runs under 250 feet, UTP transceivers may cost more than standard coax.
UTP transmission is also significantly less costly than fiber, from cable and installation to tooling and transceivers. A UTP passive-to-active system offers the same features as fiber. That's why many installers have switched from fiber to UTP cable for longer runs. Nonetheless, fiber is still the answer for extremely long runs (more than 8,000 feet, for instance). For safety, fiber is a good choice when video must run in the same conduit as high voltage.
What Is UTP Cable?
Sometimes called category cable, UTP cable is generally 22 or 24AWG copper wire that is twisted into pairs, with each pair color coded for easy tracing. Bundles can range from two to 2,400 pairs and are available in plenum, PVC, direct-burial, gopher-resistant, and aerial formats, among others. UTP is categorized into grades depending on cable characteristics. Category (Cat) 2 cable is what most buildings 20 years old and older have installed for their phone systems. Cat 3 cable has a tighter twist and better performance. Cat 2 or 3 cable is perfectly adequate for CCTV applications.
Cat 5 has been designed for optimum performance in data networks and phone systems, with a tight, controlled twist. Cat 5, 5e and new Cat 6 cables are also capable of sending CCTV signals but aren't necessary for distances under one mile.
Though Cat 5 data networks need to follow a specific set of rules to be certified, breaking some of these rules will not affect your video signal unless you are planning on sharing your cable with a high-speed data network. The most important UTP CCTV rules are simple:
1) Don't use shielded wire with individually shielded pairs (capacitance above 19pF/foot). A multi-pair cable with an overall shield surrounding six or more pairs is fine.
2) Don't use untwisted wireÃ¢â‚¬â€it will compromise noise rejection.
Types of UTP Systems
There are three types of UTP systems, defined by the transceivers used: passive transmitting to passive (un-amplified), passive transmitting to active (amplified), and active transmitting to active.
Totally passive systems are for short distances. They are low in cost and support up-the-coax pan/tilt/zoom (PTZ) control. The signal loss through the wire is similar to that of RG-59, so UTP can be used for normal-resolution cameras and analog recording and multiplexing up to 1,000 feet. For high-resolution and DVR applications, the maximum recommended distance is 750 feet. Passive-to-passive solutions have signal attenuation similar to that of RG-59 and do not provide ground-loop immunity.
Passive-to-active UTP systems accommodate cable runs of up to 3,000 feet. Good-quality gain equalization compensates for cable loss, supporting high-resolution systems or digital head ends. Many amplified receivers also provide ground-loop isolation and surge protection. Although most amplified models don't support up-the-coax PTZ signals, most systems use RS-422 or RS-485, which can easily run on spare pairs within the same wire bundle as the video signals.
The active-to-active solution offers all the same features as the passive-to-active system, but at extended distances to 8,000 feet. Generally, there is no need for an amplified transmitter unless the cable runs are longer than 3,000 feet.
Most of the leading camera manufacturers are now offering cameras with UTP transmitters built in. This major trend provides a real benefit to the installer, both in price and ease of installation.
Getting Creative with UTP
To improve rack-space efficiency, many UTP manufacturers offer high-density, multi-channel solutions in which as many as 32 channels inhabit one rack space. Reduced installation labor and cable costs are achieved by using a shared cable. Multiple pairs in a single cable allow the sharing of video, PTZ control and 24VAC power. Video signals can even reside in the customer's existing telecom or datacom infrastructure without interference. This can be especially useful in multi-building environments.
Cable usage can often be maximized by employing a new, low-cost cable that contains two pairs of 24-gauge Cat 5 plus one pair of 16-2 or 18-2. Designed specifically for CCTV, this new cable enables the installer to run video, power and PTZ control within a single bundle, either zipped or composite. The cable is run from each camera to the local intermediate distribution frame wiring closet, which contains a multi-port power supply and cross-connect punch blocks. The pairs for power are terminated at the power supply, while the pairs for video and PTZ control get punched down and continue their path home in larger, multi-pair bundles. Vendors include Coleman, Genesis, West-Penn and Belden.
Transmission in Working Applications
The Aladdin Resort and Casino in Las Vegas has a state-of-the-art system that provided a testing ground for UTP video transmission. After the casino had operated for one full year on a UTP backbone, Mike Hollaway, lead surveillance technician at the Aladdin, commented, "There's no bad video here. All of our video is excellent. All cameras look the same whether they are at 10 or 3,000 feet. If I run across bad video, I know something happened recently to that camera due to camera failure, low voltage, input card or some other similar problem."
The system at the Aladdin is standardized for every camera. At the camera end, an NV-213A or equivalent adaptor that fits right into an Ultrak dome is used as a transmitter. All video and data runs back through the Cat 5 cable to the head-end termination wall, where the data is split out from the video. This termination wall is very important because it allows moves and changes to occur away from the head-end gear, requiring only that cross-connection wires be changed or added. The end result is a cleaner head end without the coax "rat's nest" so many large systems end up with after years of additions.
The video then goes to 16-channel amplified receivers handling more than 700 cameras via NV-1662R video receiver hubs. The only coax in the Aladdin's entire system runs between the hubs and the Ultrak multiplexers, then from the output of the multiplexers to the Max Pro video matrix.
In this passive-to-active configuration, video signals travel up to 3,000 feet without experiencing any loss and are protected from all types of noise, surges, lightning and ground loops. The resulting quality is more like fiber than coax, without the expense or hassle of either.
The Aladdin installed nearly three times the UTP cable necessary to begin with. Planning for expansion by pulling more cable than is initially needed can be a real time saver. Now, when the Alladin needs to add a camera, they rarely have to run new cable. This tactic can be a money saver as well, because a 25-pair bundle is about the same size and cost as three coax cables. In a given conduit space, you can pull 10 times more UTP cable than coax. This is especially important in cities like Las Vegas, where all low-voltage cable is required to be in conduit.
"The system took only five months to install, including field terminations. It would have taken much longer had we used coax or fiber," Hollaway noted. Because the terminations are faster and easier, technicians can easily manage the system after the installation company has finished its job.
After experiencing the high performance of their UTP CCTV system and comparing it to their past coax and fiber experiences, neither surveillance director Gary Vicchairelli nor Hollaway would trade their UTP transmission system in if they had to do it over again.
Said Hollaway, "We are running at 100 percent all the time, and UTP helps me maintain this percentage. How many strip properties can say that their system is 100 percent all the time?"
Future-Proof Video Systems
While many believe that video transmission between cameras and DVRs will eventually be done digitally, analog is an effective solution now. This is borne out by the introduction of UTP cameras by most leading camera manufacturers cognizant of the advanced features and benefits of a UTP solution. The installer is no longer constrained by the size of bulky coax or the high cost of fiber and its installation time. Further, UTP technology is forward compatible with future all-digital solutions.
Guy Apple is vice president of Network Video Technologies.