Plenum
The air-handling space between the walls, under structural floors, and above drop ceilings when used to circulate and otherwise handle air in a building. Plenum-grade cable can be run through these spaces if local building codes permit it.

Decibel (dB)
A standard unit used to express a relative measurement of signal strength or to express gain or loss in optical or electrical power. A unit of measure of signal strength, usually the relation between a received signal and a standard signal source. The decibel scale is a logarithmic scale, expressed as the logarithmic ratio of the strength of a received signal to the strength of the originally transmitted signal. For example, every 3dB equals 50 percent of signal strength, so therefore a 6dB loss equals a loss of 75 percent of total signal strength.

Signal Attenuation
A reduction of signal strength during transmission, such as when sending data collected through automated monitoring. Attenuation is represented in decibels (dB), which is ten times the logarithm of the signal power at a particular input divided by the signal power at an output of a specified medium.

Crosstalk
The coupling or transfer of unwanted signals from one pair within a cable to another pair. Crosstalk can be measured at the same (near) end or far end with respect to the signal source. Crosstalk is considered noise or interference and is expressed in decibels.

Federal Communications Commission - FCC
An independent U.S. government regulatory agency responsible for overseeing all interstate and international communications.

National Fire Protection Association (NFPA)
United States trade association, albeit with some international members, that creates and maintains private, copyrighted, standards and codes for usage and adoption by local governments.

Telecommunications room
An enclosed space for housing telecommunications equipment, cable terminations, and cross-connect cabling used to serve work areas located on the same floor. The telecommunications room is the typical location of the horizontal cross-connect and is distinct from an equipment room because it is considered to be a floor-serving (as opposed to building- or campus-serving) facility.

Backbone
A cable connection between telecommunications or wiring closets, floor distribution terminals, entrance facilities, and equipment rooms either within or between buildings. This cable can service voice communications or data communications. In star-topology data networks, the backbone cable interconnects hubs and similar devices, as opposed to cables running between hub and station. In a bus topology data network, it is the bus cable. Backbone is also called riser cable, vertical cable, or trunk cable.

10Base-T
The Ethernet wiring standard for 10 Mbps (megabits per second) for a maximum distance of approximately 100 meters per segment over unshielded twisted pair cables terminated with RJ-45 connectors.
Grounding methods
Bond and ground the primary protector and the metallic member of cable sheaths per 800.100 (A) through (D). What does this entail? The two simplest requirements are:
(C) Comply with 250.70 when connecting to grounding electrodes.
(D) If you install a separate grounding electrode (for example, a ground rod) for a communications system, then bond it to the building’s power grounding electrode system with a minimum 6AWG conductor.
Section 800.100(A) provides requirements for the bonding or the grounding electrode conductor:
(1) Insulation. Must be listed.
(2) Material. Copper or other corrosion-resistant conductive material.
(3) Size. At least 14 AWG with a current-carrying capacity of not less than the grounded metallic sheath member or protected conductor of the communications cable. Not required to be larger than 6 AWG.
(4) Length. As short as practicable. For one- and two-family dwellings, the bonding conductor or grounding electrode conductor can’t be longer than 20 ft.
(5) Run straight. Run in as straight a line as practicable.
(6) Physical protection. The bonding conductor and grounding electrode conductor must not be subject to physical damage. If installed in a metal raceway, bond each end of the raceway to the contained conductor or connect the ends to the same terminal or electrode to which the bonding conductor or grounding electrode conductor is connected.
There is an exception for 800.100(A)(4). If the bonding conductor or grounding electrode conductor is more than
20 ft long for one- and two-family dwellings, then install a separate ground rod at least 5 ft long [800.100(B)(3)(2)] with fittings suitable for the application [800.100(C)]. Bond this to the power grounding electrode system with a minimum 6AWG conductor [800.100(D)].
Section 800.100(B) provides requirements for the grounding electrode for three types of applications:
Structure with intersystem bonding termination (IBT). The bonding conductor for the primary protector and the metallic sheath of communications cable must terminate to the IBT as required by 250.94 (1) Building/structure grounding electrode system [250.50].
(2) Interior metal water piping system, within 5 ft from its point of entrance [250.52(A)(1)].
(3) Accessible means external to the building, as covered in 250.94 Ex.
(4) Nonflexible metallic service raceway.
(5) Service equipment enclosure.
(6) Grounding electrode conductor or the grounding electrode conductor metal enclosure of the power service.
(7) Grounding electrode conductor or the grounding electrode of a remote building/structure disconnecting means [250.32].
Structure without IBT or grounding means. The grounding electrode conductor must connect to:
(1) Any individual grounding electrode described in 250.52(A)(1), (A)(2), (A)(3), or (A)(4).
(2) Any individual grounding electrode described in 250.52(A)(6) and (A)(7), or to a ground rod not less than 5 ft long and ½ in. in diameter located at least 6 ft from electrodes of other systems.

Electrical Codes – Why?
An electrical code is a set of regulations for electrical wiring. The intention of an electrical code is to provide standards to ensure electrical wiring systems that are safe and unlikely to produce either electric shock or fires. Ways in which electrical codes ensure safety include ways to prevent (or mitigate) short circuits, ground faults, and overheating from inadequate current-carrying capacity (ampacity). Appropriately rated fuses or circuit breakers are used to interrupt a circuit loop whose ampacity is exceeded to avoid overheating of wires or other fixtures. Electrical codes are usually devised by national or international technical organizations, and adopted as law to make them enforceable. Electrical codes differ based on geographic area.

Horizontal Cabling
The cabling between and including the telecommunications outlet and the horizontal cross-connect. Horizontal cabling is considered the permanent portion of a link; may also be called horizontal wiring.
Backbone Cables
The inter-building and intra-building cable connections in structured cabling between entrance facilities, equipment rooms and telecommunications closets. Backbone cabling consists of the transmission media, main and intermediate cross-connects and terminations at these locations.

Punch Down Blocks
The predecessors to patch panels and were commonly used to support low-bandwidth Ethernet and token-ring networks. Punchdown blocks typically are not capable of supporting Cat-5 cabling, which is the common cable used in modern Ethernet designs.

Twisted Pair Cables
Two insulated copper wires twisted around each other to reduce induction (thus interference) from one wire to the other. The twists, or lays, are varied in length from pair to pair to reduce the potential for signal interference between pairs. Several sets of twisted-pair wires may be enclosed in a single cable. In cables greater than 25 pairs, the twisted pairs are grouped and bound together in groups of 25 pairs.

Fish Tape
Also called fish cord. A tool used by electricians to route new wiring through walls and electrical conduit.
Fiberglass Pushrods
Rods used to push cable.