Steve Lampen
Technology Specialist
Multimedia Products
Belden Wire & Cable Co.
Donna, I read your column every month and consider yours one of the voices of sanity amidst the chaos. But, I would suggest an addendum to the last question in your April 1999 column (see "Home telecom wiring," page 12). You appropriately noted that the reader should be concerned not only with Category 5 and the tia/eia-568a standard but also with coaxial-cable specifications of the Society of Cable Telecommunications Engineers (SCTE--Exton, PA). But home wiring extends far beyond these choices. While alarm and control wiring comes into play, many installers use broadband coaxial cable (essentially where you were heading with the SCTE specification) for a number of applications for which it is inappropriate.
Key among these are analog and digital baseband video, such as between video cameras and recorders or from recorder to recorder, and security cameras. The appropriate cable for these applications is all-copper center with high-coverage copper braid or foil-plus-braid shields. This construction, intended for the 4.2-megahertz bandwidth of video, is very different from the copper-clad steel center of broadband/cable-TV coaxial cable, which has a foil shield and minimal aluminum braid. The latter is intended for operation at Channel 2 (54 MHz) or higher. When such a cable is used for baseband, losses are doubled or even lower.
Just a few years ago, I would have said that Category 5 was inappropriate for audio and video cabling. However, a number of companies now make adapters (baluns) for using Category 5 and similar cables to run unbalanced audio and video. One such manufacturer is ETS (www.etslan.com). We have done a number of demonstrations using their baluns running two video signals and two audio signals (using consumer VCRs and televisions) using 4-pair Belden 1872A MediaTwist Enhanced Category 5 (5E) and running the signals over 1000 feet.
Speaker cable--must be large-gauge for low resistance--is another kind of home wiring that is a far cry from Category 5. If a home-wiring system is installed as a 70-volt "distributed" system, then Category 5 can be used--incredible overkill, but it will work.
In other words, there are many applications that, with modifications, can be run on Category 5 or 5E products. And many such applications are required or desired in homes today. Thanks for allowing me to elaborate on them, and keep up your excellent column.
Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, the University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: [email protected].