Published In October 2001
Recently, a new term has evolved to describe an integration of all low-voltage systems, such as TV, radio, telephone, and Internet/computer interlinks from one main distribution hub to serve all rooms within a building with multifunction communications capability. This new term is called “structured wiring systems.” The concept is to provide a single-point connection of all video, satellite TV, cable TV (CATV), computers, telephone lines, security, cameras, and sound systems. If this concept sounds vaguely familiar, a similar system was inserted into the 1987 National Electrical Code (NEC) as a new Article 780, Closed-Loop and Programmed Power Distribution. This new article provided requirements for electrical wiring systems controlled by a computer system and linked to solid-state chips in electrical appliances. The computer system monitored the electrical appliance in the circuit, turned it on or off, and determined if the current draw was correct for that particular appliance. If the appliance drew too much current, the computer monitor sent a signal to the appliance, shutting it down and taking it off line. This system provided safety by constantly monitoring all appliances. Dwellings that used this technology were called “Smart Houses” and special cabling was used to inter-link the computer to the appliance. The special cable was a single loop of hybrid cable used to supply 120-volt power to appliances and devices, 24-volt uninterruptable power supply for backup power, multiwire telephone cable for voice communication, television coaxial cable for TV, and other remote control and signaling cables for other functions. This special cable was called “NMS cable” and covered in Article 336. The entire system was controlled at a central location and supplied receptacles at remote locations called “convenience centers.” Structured wiring systems appear to be the next generation of this idea with a few major differences. A single closed loop is not used in most structured wiring systems and normal power is not supplied to appliances through the structured wiring system, as was done in the “Smart House” concept. In a structured wiring system, a single central distribution panel or media center is installed. Cabling, such as Category 5 or 6 communications cable, coaxial cable, and fiber optic cable are installed as home runs from media outlets in a room. Once the wiring is installed and the walls are finished within the building, connections for the various systems are available at the control or media center. Connections to the basic systems can be easily accomplished as well as changes in the systems. As technology changes, expensive rewiring within the building can be minimized. Structured wiring systems permit lighting and thermostat control from the computer at the panel. Individual appliances can be controlled via computer and, if using a modem, connected through the telephone lines to the computer, ultimately from a long distance. Computers can be networked within the building to share data, printers, and high-speed Internet links. Telephone lines can be multiplexed or operated at multiple locations. Security cameras can be inter-linked with the TV system to permit monitoring of individuals, such as infants and the elderly. Door monitors can provide security while still providing communications with a person ringing the doorbell. Systems can provide sound to as many as six different rooms simultaneously, with surface or in-wall speakers and individual volume control at each location. An existing amplifier, stereo system, or surround-sound system can supply the audio for the system. Since each room has a home run back to the media panel, multiple amplifiers can be connected: this permits different stations or different types of music. A module can be added to the media panel that permits remote infrared control of a video system, a DVD player, or a cable TV box. One satellite or cable TV control box can be used to connect the signal at the media panel and then can be accessed by dedicated entertainment channels at each remote TV location. Since each remote location is supplied with an infrared cable connection, channel changing of the control box is easily accomplished without requiring an individual TV control box at each location. This provides both an inexpensive installation and an easy method of connecting all of TVs of the building to one TV source. Since Category 5 or 6 cable is installed to each remote location, data networking between computers, printers, and other peripheral equipment is easily and inexpensively accomplished by installing a data-networking hub in the media panel. Now one fax machine or printer can serve multiple computers. Data files can be shared between computers. Even computer games can be interconnected so that multiple players can access and play at one time. Any of these systems can readily be changed or interchanged by a simple switching of cables within the media panel. All of these systems and their installation are already covered in the NEC. Article 640 covers audio systems. Article 725 covers remote control, signaling, and power-limited circuits. Article 770 covers optical fiber cables and their raceways. Chapter 8 covers telecommunications systems, such as telephone, CATV and their antennas, and broadband systems. Becoming familiar with these articles will provide guidance in the installation requirements for all of the systems connected to your structured wiring systems. ODE is staff engineering associate at Underwriters Laboratories, Inc., in Research Triangle Park, N.C. He can be reached at (919) 549-1726 or via e-mail at firstname.lastname@example.org.