Piecing together the residential-wiring puzzle
Standards from several organizations govern the way residential voice, video, and data wiring is installed.
Standards from several organizations govern the way residential voice, video, and data wiring is installed.
Genesis Cable Systems LLC
The term "futureproofing" has been used and abused in the structured cabling industry. Ideally, a commercial voice and data installation will be equipped to handle future protocols, such as Asynchronous Transfer Mode or Gigabit Ethernet. That is why the industry has seen a strong preference by end-users to install Enhanced Category 5 cable and associated connectivity hardware as well as a strong interest in the development of Category 6 products. But, no matter how much a commercial building is futureproofed, historically it must be rewired every five to 10 years. The need to rewire is only partially driven by changing technology; business reasons, especially office relocation and network reconfiguration, are the strongest drivers of network recabling.
The idea of futureproofing traditionally has not applied to residential wiring for voice, video, and, more recently, data. However, now more than ever before, a persuasive case can be made for upgrading a home`s wiring. Some senior citizens may still have the same rotary telephones that the telephone company installed in 1967 (when there was only one telephone company and they installed telephones) and the same cable-TV converters that cable operators installed in the mid- to late 1980s. Typically, home wiring has a life of 25 to 50 years. With 1.6 million residential units being built this year, it is clearly time to specify upgraded wiring in new installations. Many current homeowners have recently discovered, while outfitting home offices or installing satellite dishes, that their wiring is inadequate.
When consultants, builders, or developers try to install upgraded wiring in a single- or multi-family residence, they run into a plethora of published information, some pieces of which appear to contradict each other. These apparent contradictions can be demystified, and when they are, cabling consultants and other construction-industry professionals can chart a viable path to implementing a residential wiring system that will support current and future needs for years to come.
A modern home likely contains a home office that requires high-speed access to the Internet and may also use a small local area network (LAN) inside the house. The family room may have a home theater that requires connections to the cable-TV system or a satellite dish; the home may have a surveillance camera for the front door and the backyard; it will likely have a central alarm and security system with dial-up service to a monitoring station; and the house may also contain several home-automation features.
A number of published and soon-to-be-published standards provide design and installation guidelines for wiring residential units. The TIA/EIA-570A Residential Cabling Standard is in its final stages of approval and may be published later this year by the Telecommunications Industry Association (TIA--Arlington, VA). It recommends two grades of information outlets for residential applications.
Grade 1 is intended to provide basic telephone and video service. The standard recommends one 4-pair Category 3 or better (typically Category 5) unshielded twisted-pair (UTP) cable and one RG-6 coaxial cable to each information outlet. Grade 2 is intended to provide enhanced voice, video, and data service to the residence. The standard recommends two 4-pair Category 5 UTP cables and two RG-6 coaxial cables. One of the Category 5 cables is for voice and the other is for data; one of the RG-6 cables is for satellite service and the other is for local programming via a rooftop antenna or cable-TV connection.
The EIA-6000 cebus Standard for Consumer Electronic Bus, developed by the Electronic Industries Alliance (EIA--Arlington, VA), provides a communications and control network for the residence. This standard allows for a variety of media types to be used to accomplish this purpose: twisted-pair cable, power-line carrier, coaxial cable, fiber-optic cable, infrared devices, and radio-frequency (RF) transmission. Protocols are included for communicating with home automation and security devices at low data rates.
The IEEE-1394 FireWire Standard is intended to facilitate the convergence of computers and consumer electronics in the home. The Institute of Electrical and Electronics Engineers (New York City) has developed a standard protocol for sending and receiving sound, images, and data and a specialized cable to route the information. This standard will allow for plug-and-play interconnection among a user`s camcorder, TV receiver, stereo amplifier, and computer. A user will be able to download music and videos from a satellite dish and edit content with a computer, edit home movies and add titles, or insert data in graphical or tabular format.
Complementary, not contradictory
Believe it or not, all these standards work together to provide a futureproof wiring system for the home. Think of TIA/EIA-570A as the physical-layer platform for accommodating all of the low-voltage applications in a residence, including voice (telephone, computer modem, and facsimile); video (baseband for surveillance and broadband for cable-TV or satellite service); data (a LAN to interconnect computers and printers); alarm and security devices (dial-out capability for fire and burglar alarms); and home automation control of heating, air conditioning, and lighting.
The cebus standard provides the protocols necessary to allow your computer to talk to your thermostats to change temperature profiles. It allows your infrared remote to change music programming from any room in the house and allows your handheld RF security device to summon help when the panic button is pressed.
The IEEE standard provides for short-distance interconnection, using prefabricated patch cords, so consumer electronics can simplify home-theater wiring and thus speed the convergence of computers and electronic audio and video devices.
This system is configured as a serial bus, using a cable with two shielded pairs to provide the signal and one unshielded pair for power. As many as 63 devices can be interconnected and multimedia rates of 100, 200, and 400 megabits per second are available. However, cable distance is limited to 41/2 meters, or 15 feet. Consequently, this protocol is only suited for the interconnection of audio and sound equipment located close to each other, as is the case in a home-theater application. The high-speed multimedia signaling opens the door to powerful entertainment applications.
Designing a home system
To design a structured-wiring system for the home, first follow the TIA/EIA-570A standard by picking a central location in the home, close to the telephone company demarcation point and point of entry of the cable-TV coaxial cable, where the residential cabinet should be mounted. Typical locations include a basement, garage, or utility-room wall. Installers typically anchor the cabinet to the wall and sometimes install incoming telephone and cable-TV services in a conduit or duct to facilitate pulling a new cable if an upgraded drop is provided. Then they can pull twisted-pair and coaxial cables to each information outlet and terminate them. Finally, they can install telephony connecting blocks and coaxial splitters in the cabinet and properly terminate all cables.
The TIA allows maximum cable runs of 90 meters (295 ft) and a total of 10 meters (33 ft) of patch cords on both ends. The EIA CEBus standard allows twisted-pair cable runs as long as 500 ft for cases in which 22 AWG twisted-pair cable is used. However, the standard allows its control and data channels to coexist on 24 AWG twisted-pair cables, along with telephony services for distances not exceeding 300 ft. As a result, it is prudent to employ 4-pair, 24 AWG Category 5 twisted-pair cable to accommodate both tia and eia requirements. Doing so will provide for two telephone lines, a control channel, and a data channel. Incidentally, both standards call for an 8-pin modular jack for cable termination.
Strategically deploy information outlets, also called telecommunications outlets, throughout the house. For example, a four-bedroom home may need 12 outlets. Each bedroom requires an outlet behind the bed for the telephone, a laptop computer, and security signaling and an outlet on the opposite wall for the TV set and pay-per-view programming. The kitchen needs an outlet for the telephone, TV, and home-management computer. The family room needs an outlet for home-theater apparatus. The den or study requires two sets of outlets to accommodate the telephone, facsimile, computer modem, printer, and a LAN connection.
The twisted-pair cable in both tia and eia standards has the same blue, orange, green, and brown color code, and the 8-pin modular plugs have the same T568A punchdown configuration. The blue and orange pairs on pins 4-5 and 3-6, respectively, provide two telephone lines; the green pair--pins 1 and 2--provides the CEBus data; and the brown pair--pins 7 and 8--provide CEBus power. It is best to install a second 4-pair Category 5 cable to each information outlet to accommodate high-speed data such as Ethernet or Token Ring, which uses pins 1-2 and 3-6 and pins 3-6 and 4-5, respectively. These LAN protocols will be required for home-office applications.
The CEBus provides 32 channels--each of which is 32 kilohertz wide--on each pair of cables. A bipolar three-level encoding scheme used for the data allows all home-automation devices to communicate with each other using a common protocol. Functions covered include remote control, status indication, remote instrumentation, energy management, security systems, and entertainment-device coordination. Although there may be applications for RF or infrared signaling, such as garage opening or channel changing, a hard-wired system will be more reliable. The power-line carrier option is difficult to implement, because on larger systems a lot of filtering is necessary to prevent signal interference. However, wireless transmission may be a viable option for controlling energy use at a remote building on the same property without having to bury a new cable.
For video applications, both the TIA and EIA recommend 75-ohm coaxial cable. The EIA states a requirement for dual-shielded cable with 100% foil coverage and a minimum 59% braid coverage. Both RG-59 and RG-6 types are acceptable and should be tested to 1 gigahertz. Although many installations employ dual- and tri-shielded coaxial cable, many cable-TV service providers will refuse to provide service to a residence unless quad-shielded coaxial cable is used. Satellite service requires an RG-6 coaxial cable tested to 1.8 GHz, which is the bandwidth of the satellite signal. This bandwidth provides for two to three times the number of channels than are available from a conventional cable system.
When installing the 4-pair twisted-pair cables, do not exceed a pulling tension of 25 pounds or violate the minimum bend radius of four times the cable diameter. Since the tia only recommends a maximum 0.25-inch cable diameter, the minimum bend radius is typically 1 inch. RG-6 coaxial cable has a maximum pulling tension of 35 pounds and an installed minimum bend radius of 10 times the cable diameter, which typically equates to 3 inches. Normally while pulling cable, you should observe twice the installed minimum bend radius to avoid degrading cable performance. Leave a minimum of 8 inches of slack cable at both ends to allow for retermination.
The 4-pair utp cable is terminated to an 8-pin modular jack, commonly known as an RJ-45. A punchdown tool is required for this termination. The quad-shield RG-6 cable is terminated in an F-style connector, in which the center conductor of the cable functions as the pin. Several types of crimp-on and screw-on connectors are available, and you will need cable strippers and crimping tools to complete the job. You should also use a handheld tester to verify pinout, continuity, and electrical-performance parameters of Category 5 cables.
Both the TIA and EIA standards include provisions for fiber. Many high-end homes today include two fibers to each information outlet for future applications. But because Gigabit Ethernet can be run over Category 5 cabling and cabling runs in homes are considerably shorter than those found in commercial applications, it may be a number of years before a fiber application is used in the home. It may even make sense to install singlemode rather than multimode fiber to accommodate future multimedia applications.
The best approach to wiring a home is to follow TIA/EIA-570a and run two Category 5 and two RG-6 cables in a homerun fashion from a cabinet in the basement or utility room to information outlets in each room. It is important that the RG-6 be quad-shielded considering many cable-TV operators will not provide service to a residence wired with a cable providing lesser amounts of shielding. With this infrastructure in place, it is easy to populate the cabinet with a dial-up interface for the alarm and security system, a splitting network for the local and satellite-TV signals, baluns for remoting a surveillance video signal over the utp wiring, and an Ethernet hub for the home`s LAN.
You can then connect EIA-600-compliant home-automation devices into the structured cabling system, as they are required, to support home automation and security needs. Equipment for the home theater can be interconnected using ieee-1394-compliant patch cords with plug-and-play use, resulting in a residence that is truly state-of-the-art for alarm and security, home automation, and voice, video, and data services.
The EIA-600, IEEE-1394, and tia/eia-570a standards specify different applications but incorporate the same or similar media types. The transmission distances specified in each also differ.
The cable specified in the IEEE-1394 standard includes an unshielded twisted-pair and two shielded twisted-pairs, surrounded by aluminum-mylar tape, an overall braid, and a jacket.
The residential cabinet, typically mounted in a basement or garage near the telephone company demarcation point, is the central point at which all residential wiring converges.
This layout of a residential cabling run shows that a home will require two outlets per bedroom and several other outlets for other living areas. It also suggests areas in which to place a distribution device, waterproof outlet box, and an auxiliary disconnect outlet.
It`s best to install both T568A and EIA cebus modular connectors, which have the same pin assignments, because the cebus connector handles cebus data and power while the T568A connector handles high-speed data like Ethernet.
John Pryma is vice president and general manager of the structured cable division for Genesis Cable Systems llc (Pleasant Prairie, WI). He is a registered PE in Illinois and a bicsi-certified rcdd and lan specialist.