Unshielded twisted pair (UTP) cabling is solidifying its position as the most common medium for bringing data and telephone connections to the desktop. Having taken the voice and data worlds by storm, the popularity of UTP is expanding into the world of low-quality video.
“Experts agree there is a place for UTP. “But it’ll never replace good old coax for broadband applications,” maintains Peter Lockhart, vice president/technology for product design, at Anixter Brothers, Skokie, Ill. “Coax is the cheapest, easiest way to go.” But all is not lost for UTP.
In any application where full motion video is not required, but a link to the digital world is a bonus, UTP will come to the forefront. The world of Internet Protocol (IP) is expanding rapidly into the security camera and low-quality video world.
Lockhart points out that coax usually is 18 gauge while UTP typically is 24 gauge and the only way to get UTP to look like coax is to add baluns and gain. Of course, that costs distance.
Where UTP has an advantage is in really long-distance applications––for example remote security monitoring and other low-bandwidth uses where the signal might have to be transmitted a very long distance or viewed from a remote site. In the wake of the Columbine High School shootings, school security has become a major market for such UTP video links. These applications typically involve as many as 100 security cameras.
“One guy with a computer can do it all,” Lockhart said. “If you don’t need full motion—you only need to see the people once a second—then UTP is the way to go,” he added. However, he’d stick with coax if the job required bringing 40 channels of broadband to each classroom.
Besides, coax is going to be cheaper, Lockhart maintained. Typically, a non-plenum Category 5 cable will run a contractor about $100 per thousand feet. RG-59 will be about $40 per thousand, with RG-6 running a bit more. Either RG-59 or RG-6 will give much greater bandwidth. Again, for broadband the coax wins out.
Not everywhere does coax rule financially. “The advantage of twisted pairs is the cost/performance ratio. Dollar-for-dollar, you can buy and install twisted pairs significantly cheaper than coax or fiber,” said Steve Lampen of Belden Electronics Division, (www.belden-wire.com), Richmond, Ind. “While the other two systems offer some advantage in bandwidth, this advantage is rapidly dropping. It should be pointed out that standard premise/data cable contains four pairs in a single cable, so the actual cost per pair is one-quarter of the per-foot price,” he said.
In fairness to both sides, the application will be a sizable determinant as to cable type used. Any installed base also will tip the scales. Many industries, CATV being a prime example, have a huge installed base in coax, which they are not about to abandon, Lampen said. Instead, they are pushing to expand the use of coaxial networks (often with fiber optic backbones feeding the coaxial drops to houses) to handle nontraditional signals, such as data or telephone.
In the case of fiber, a key reason copper is cheaper is the cost of conversion from electrical-to-optical that occurs at each end. Bridging, amplifying and routing—simple in the copper world—are difficult in the optical world. Such devices would require even more conversions from optical-to-electrical, further increasing the cost.
An advantage of UTP is that is not shielded. At data rates over 16 Mbps, cables can emanate radiation, which could interfere with the signal being carried, unless it is allowed to escape.
Lampen noted that many people think that shielding is necessary and unshielded cable is asking for trouble. “There is no doubt that, if a cable will radiate signals, especially at high frequencies, a shield will help reduce the problem. Generic (low-quality) UTP will not help reduce noise.” However, he said that cables that use bonded pairs can pass the noise immunity of shielded cables, even though they are UTP. “Not all UTP can claim this. The one big advantage to UTP is no ground loops, since there is no shield, and no ground wire. Thus, unshielded cable has a real advantage in such applications.”
Hooking up systems
Another key advantage to using video on UTP is the associated uses of that cable. Data cables such as Category 5 can carry data, such as 10BASE-T or 100BASE-T, token ring or Ethernet networks. Applications can include not only networked data for computers, but also telephone, fax, modem, or even integrated services digital network (ISDN), T-1, or other data lines furnished by the telephone company. “With some restrictions placed by the video uses, one could wire up a building, school, hospital, or other facility with nothing but Category 5 UTP and do almost anything one might want,” Lampen notes.
Security cameras are a key UTP video market and indeed, several companies provide cameras that work with UTP systems.
Leviton (www.leviton.com), Little Neck, N.Y., has two Decora-styled video cameras that use complementary metal oxide semiconductor (CMOS) image sensor technology for efficient, stable operation under a range of conditions.
The color Decora-Cam comes in a custom-molded Decora plate. It has a precision 3.5mm wide-angle, fixed-focus, high-resolution lens that eliminates the need for constant readjustment—a bonus in difficult-access locations.
It comes with an innovative RJ-45 output jack that provides quality long-distance point-to-point or networked video transmission over UTP cabling by using the company’s media system.
A second version of the camera uses conventional RCA output jacks for connections to legacy systems.
Another new camera is an outdoor swivel camera, housed in a weather-resistant enclosure. It also uses an RCA jack and provides black and white National Television Standards Committee (NTSC) baseband video output for direct connection to any CCTV monitor, line-level video, or designated channel using a video modulator.
Others are taking a media-independent approach to security. That usually means going over the Internet. Advantages, in addition to being able to use any cable type include sound capability, being able to access the security camera from anywhere one can plug in a computer and a broad range of products available to use.
Intetcam (www.ivista.com), San Diego, Calif., produces the iVista Web camera software package which allows streaming live video and audio over the Internet.
It works with any Internet connection, including ISDN, DSL, cable modem, or other broadband connection. Or, a standard telephone line can be used. The audio streaming can accompany video or stream by itself, and is adjustable based on the available bandwidth.
The iVista Java applet downloads automatically, so there is no plug-in, chip or player required to view locations.
Array Microsystems (www.array.com), Los Gatos, Calif., produces the VideoOne Communicator which is basically a Microsoft NetMeeting hardware accelerator. The surveillance supports 16 cameras on a UTP base. “We really are agnostic as to the underlying network type,” said Kirby Kish, vice president of marketing.
With the unit, one can do surveillance and monitoring of one, four, nine, or 16 cameras. In addition, Kish said the system will do motion detection via MPEG-1. It is H.261 compliant for video acceleration, and conforms to the G.711 and G.723 audio standards. It supports NetMeeting 2.1 and 3.01. The system requires a 233 MHz Pentium II with Windows 95, 98, 2000, or NT 4.0. The company recommends 64 MB RAM availability.
Bristol, United Kingdom-based Motion Media (www.motion-media.com), produces an ISDN video surveillance system called the eyesite 300. It first is connected to an existing security camera. Then one simply phones the 300 from a videophone and watches and listens to what is happening on site. If an on-site alarm is triggered, the 300 out-calls and lets security see and hear whether or not a true emergency exists. The unit can be set to accept only calls from authorized numbers.
The unit has four video and audio inputs with automatic cycling or remote switching. It gives 352x288 resolution at 15 frames per second in full color. It is H.320, H.261, and H.263 standards compliant.
Array Microsystems (www.array.com), Los Gatos, Calif., produces the VideoOne CCTV Surveillance System. It uses a PC and MPEG-1 compression to provide live multiplexed NTSC or PAL video and MPEG audio, which can be recorded and typically stored on an inexpensive 3 to 6 GB disk.
According to Kirby Kish, vice president of marketing, an available software development kit supports programmable multi-way split screen display of incoming multiple camera video and audio signals. The unit will handle up to 16 NTSC cameras at once.
“VideoOne Sentry will prove to users of analog surveillance systems that computer-based digital surveillance systems are dependable and reliable,” he said. The kit includes a Sentry PCI card, video mux daughter-card and four BNC cable connector panels.
While these companies specifically target the security and premises monitoring markets, truth be told, almost any good videoconferencing system can be adopted to do static monitoring. The systems can be tweaked to allow anyone with Internet access to monitor any site remotely with a PC.
Lampen said there are three key problems with using UTP for analog video. First, the majority of video equipment uses coaxial connectors, usually BNCs. Second, the output impedance of the coaxial systems is 75 (ohms), while UTP has an impedance of 100. The third difference is that UTP, being twisted pairs, is a “balanced line” system, while coax, which is one conductor shielded, is “unbalanced.”
“You can solve all three problems to a greater or lesser degree with a balun,” Lampen said. Balun means BALanced to UNbalanced. A balun is a small box, which contains a transformer and other matching components. These allow the signal to be converted from 75 impedance to 100 impedance. They also change the system from unbalanced to balanced; and can be easily built with a BNC on one side of the box and an RJ-45, the most common UTP connector, on the other.
Another solution to balancing problems is to choose a very well-balanced cable. Category 5 is better balanced than Category 3, Lampen said. But if the device is unbalanced, such as an RCA or BNC output of a camera, it doesn’t matter how well balanced the cable is, you will still need a balun to convert from one system to the other, he added.
HARLER, a contributing editor to Electrical Contractor, is based in Strongsville, Ohio. He can be reached at (440) 238-4556 or firstname.lastname@example.org.