Published In October 2000
The first release of “TIA-570-Residential Telecommunications Cabling Standard” was published in May 1991. While TIA and a number of manufacturers spent much time and effort promoting this standard to the residential market, the response was so poor that some committee members questioned if it was worth revising. Fortunately, the revisionists prevailed, and in October 1999, ANSI/TIA/EIA-570-A was published. It establishes the new recommendations for telecommunications cabling within single and multi-tenant residents. Most importantly, the standard is gaining industry acceptance for the first time. What happened? Recent market studies reveal the same thing throughout the communications market, from the Internet to the growing number of telecommuters and those maintaining home offices: the home needs to be cabled up for the future-now: Consider the following evidence: - Approximately 18 million people are telecommuting to some degree and over 16 million small office/home office employees are online. - By 2003, there will be 20 million DSL/cable modem subscribers (Forrester Research). - Fifteen percent of all U.S. homes have multiple personal computers (PCs) (Dataquest). - By 2002, there will be 15.3 million home networks (Jupiter). What guidance does the TIA-570-A put forth for the residence? First and foremost, “daisy-chain” cabling is out and “star-wired” cabling is in. The other recommendation is for a distribution device (DD), a facility within the dwelling for interconnection or cross-connection of cabling and electronics (i.e., the home version of the telecommunications room or, better yet, the enclosure). Figure 1 exemplifies the recommended cabling topology for a single residence. The residential cabling shall be installed in a star-wired fashion from the distribution device to each outlet. Additionally, an auxiliary disconnect outlet (ADO) is to be installed between the DD and the demarcation point (typically the network interface device (NID)). The ADO will most commonly be inside the DD enclosure. This guidance must be followed. Otherwise, even the highest performance cabling will not allow successful implementation of a home network. How do I make the grade? Two grades of residential cabling are defined, depending on the level of service required. Both grades are designed to support telephone, television, and data; however, Grade 2 is required to support multimedia. These grades are defined not only by the performance of the cable used, but also by the number of cables installed to each outlet. All unshielded twisted pair (UTP) cables are to be four-pair cables. Table 1 provides the requirements and recommendations for both grades. How many outlets? According to the standard, a minimum of one outlet shall be cabled for each of the following rooms: kitchen, each bedroom, family/great room, and den/study. Additionally, it is recommended that, for each room with unbroken wall spaces of 12 feet or more, additional outlets are installed. Of significant importance, the eight-position modular jack is the only UTP jack allowed for the outlet and it shall be wired in the “A” configuration. The six-position RJ-11 is not allowed. Additionally, splitting of pairs is only allowed with an external adapter and not behind the outlet. What should I do with the distribution device (DD)? Location, space, and electrical power recommendations are provided. The DD should be located in a centralized, accessible location in the tenant space, if practical. This is to minimize the length of outlet cables and to allow for easy maintenance and configuration of the DD. Space allocations for the DD are provided based on grade and number of outlets served, as outlined in Table 2. The recommendations are provided based on the spacing between wall studs. A nonswitchable 15-amp duplex outlet is required at the DD for Grade 2 systems and recommended for Grade 1. The standard also provides recommendations for multi-tenant dwellings and the associated backbone-cabling infrastructure, which are not covered in this article. So, believe it or not, the tide appears to be turning. Soon, one of the first things a potential homebuyer may ask to see is the home’s DD. (Well, maybe after they have looked at the master bath.) It seems as if nobody uses the kitchen anymore. BEAM is director of systems marketing at AMP NETCONNECT Systems. He can be reached at (336) 727-5784 or firstname.lastname@example.org.