Q: I am currently bidding on some new homes. The builder wants to know what type of cable should be used for Internet service, digital cable, and for anything else that will likely be coming in the future. I am pretty convinced a good RG-6 67% braided coaxial cable should support whatever the future may bring. Even if optical fiber ends up at the house, RG-6 should handle it, right? He has also inquired about running Category 5 cable to the main location, but I don`t see the advantage of that when all we have to connect it to is a "plain old telephone service" line.
T. Ray
T. Ray`s Wiring Inc.
Fenton, MI
A: It sounds like the builder may have heard about the soon-to-be-released Residential Telecommunications Cabling Standard from the Telecommunications Industry Association and the Electronic Industries Alliance (tia/eia--Arlington, VA).
More than 30 organizations, including manufacturers, consultants, end-users, and associations within the telecommunications industry, have contributed their expertise during the development of the ansi/tia/eia-570a Residential Tele-communications Cabling Standard in hopes of standardizing telecommunications-cabling requirements for residential applications. These applications include voice, data, video, multimedia, home automation systems, environmental control, security, audio, television, sensors, alarms, intercom, and other emerging telecommunications services. All types of residential construction--new work, additions, and remodeling of single and multitenant residential buildings--will be addressed in tia/eia-570a.
tia/eia-570a establishes a grading system based on services that you would expect to support within residences:
Grade 1 is intended to provide a generic cabling system for basic services such as telephone, satellite, community antenna television, and data services. Grade 1 cabling requires a minimum of one 4-pair Category 5 unshielded twisted-pair (utp) cable and one 75-ohm coaxial cable and recommends Category 5 over Category 3 utp. Grade 1 specifies that all cabling be placed in a star topology.
Grade 2 is intended to provide a generic cabling system for basic, advanced, and multimedia services. Grade 2 cabling requires a minimum of two 4-pair Category 5 utp cables and two 75-ohm coaxial cables, provides an option for two strands of optical fiber, and recommends Category 5E over Category 5 utp. Grade 2 also specifies that all cabling be placed in a star topology.
tia/eia-570a will require that all 75-ohm coaxial cables other than backbone be either Series 6 or Series 11, as described in the ips-sp-001 standard of the Society of Cable Telecommunications Engineers Inc. (scte--Exton, PA).
Adequate shielding is especially important when selecting coaxial cables. The scte standard specifies a minimum shield construction consisting of a laminated metal tape and a 60% coverage braid. This is a dual-shield construction. But, for broadband services extending up to 1 gigahertz, consider using coaxial cables with tri-shield or quad-shield construction.
Donna Ballast is a communications analyst at the University of Texas at Austin and a bicsi reg-istered 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].