raceway - Any enclosed channel designed for holding wires or cables.

rack - See cable rack.

rack unit (RU) - A unit of measure of vertical space in an equipment rack. One rack unit is equal to 45 mm (1.75 in).

radiating cable/leaky coaxial cable (LCX) - A coaxial cable with an outer conductor into which slots are cut that allow ingress and egress of signals within a limited range of the cable.

radiation pattern envelope (RPE) - A graphical representation of radiation properties of an antenna as a function of space coordinates.

radio frequency (RF) - The group of electromagnetic energy within the electromagnetic spectrum whose wavelengths are between the audio and the light range (usually between 535 kHz and 300 GHz).

radio frequency (RF) dispersion - A term used to describe any process by which radio frequency signal propagating in the air is degraded because the various wave components (i.e., frequencies) of the signal have different propagation velocities.

radio frequency identification (RFID) - A generic term for technologies that use radio waves to automatically identify people or objects.

radio frequency interference (RFI) - The disruption of radio signal reception caused by any source which generates radio waves at the same frequency and along the same path as the desired wave.

radome cover - An antenna cover that safeguards the antenna against environmental concerns and has low loss characteristics.

radome loss - The sum of the ordinary insertion loss of the antenna signal passing through the radome wall plus the scattering loss off the radome panel framework blocking (shadowing) the antenna aperture.

rake receiver - Used in a code division multiple access multipath environment to counter multipath effects. Identifies and combines received multipath signal components using estimated delays and weighting factors.

random spacing - Occurs where telephone cable is buried in the same trench with power conductors and no deliberate attempt is made to maintain a separation between the two systems.

rat - See piston.

Rayleigh scattering - The deflection of light from the path it would follow if the refractive index were uniform or gradually graded. Caused primarily by micro defects, impurities, and molecular structure in the optical fiber.

reader - A device that receives an identification code from a card.

real-time - The recording, processing, storage, transmission, and viewing of a message created by an activity as it occurs. Contrast with store-and-forward.

rearrangement - An action taken to replace, add, adapt, or remove existing premises wiring system components.

rebar - See reinforcing bar.

receiver - An electronic device that detects and demodulates and amplifies transmitted signals.

receiver, optical - An optoelectronic circuit that converts an optical signal to an electrical serial logic signal.

receiver sensitivity - A specification of the minimum input signal power that is required to achieve an output signal power that meets a specified performance criterion (e.g., bit error rate).

reciprocity - A principle by which an antenna behaves in the same manner whether receiving or transmitting.

record - The permanent documentation of installed telecommunications infrastructure obtained from as-builts.

recycle time - The time needed to reset and reinstate the timing function and remain within the specified timing tolerances. Recycle time is generally specified "during timing" or "after timing."

red iron - A structural steel assembly painted with five coats of zinc oxide paint, or prerusted for a specified time in the open environment.

redirector - See shell.

reel dolly - See jackstand.

redundant array of independent disks (RAID) - A technology that makes it possible to group together multiple hard disk drives and allow them to function as a single storage unit. Different configurations (levels) of RAID provide varying amounts of data redundancy arid performance.

reel brake - A device used to control the rate of removal of a cable from a cable reel.

re-fish (conduit) - To repeat the process of installing one or more pull strings or cables into a conduit.

reflection - The abrupt change in direction of light as it travels from one material into a dissimilar material. See also Fresnel reflection.

reflection coefficient - Ratio of the amplitude of the reflected wave and the amplitude of the incident wave.

reflective break - Reflection at an optical fiber cable break caused by the abrupt change in the index of refraction. See also Fresnel reflection.

reflector - In a radio frequency antenna, one or more conducting elements or surfaces that reflect incident radiant energy.

refraction - The angular change in direction of a beam of light at an interface between two dissimilar media or a medium whose refractive index is a continuous function of position (graded-index medium).

refractive index - See index of refraction.

Registered Communications Distribution Designer (RCDDI) - A designation for individuals who demonstrate expertise in the design, integration, and implementation of telecommunications (voice, data, video, audio, and other low-voltage control) transport systems and their related infrastructure components.

registered jack (RJ) - The FCC Part 68 registration program for jacks. Specifies the type of jack, the number of pins to be used, and how the pins are wired.

reinforced concrete - A type of construction in which steel (reinforcement) and concrete are combined, with the steel resisting tension and the concrete resisting compression.

reinforcing bar - A steel bar or rod used in concrete construction to provide additional strength. Also called rebar.

relay rack - A vertical metallic frame or equipment bay that is equipped with threaded holes at a predefined spacing, in accordance with EIA-310-D.It can be floor mounted (free standing) or wall mounted.

reliability - The predictable behavior of a network during operation.

remodulator - A device that receives transmissions and converts them to the baseband level.

remote access - A form of resource access that connects a stand-alone personal computer to a LAN over an extended distance.

remote access interface card - An interface card used to connect a remote access server to one or more telecommunications circuits. Also called a wide area interface card.

remote alarm - A visual or audible signaling device used to signal violations at locations removed from the central control station or monitored openings. For example, a remote alarm may be placed on a roof, in a stair tower, or in a guard station outside of a building.

remote authentication dial-in user service (RADIUS) - An authentication and accounting system used by many Internet service providers (ISPs). A usemame and password must be entered when dialing in to the ISP. This information is passed to a RADIUS server, which checks that the information is correct and then authorizes access to the ISP system.

remote authentication dial-in user service (RADIUS) server - A server for remote user authentication and accounting. Its primary use is for Internet service providers, although it may be used on any network that needs a centralized authentication and/or accounting service for its workstations.

remote client software - Software that makes it possible for a remote station to function in the same manner as a local station. See dialer.

remote control - A form of remote access where the remote station connects to a local station and controls its operation. Contrast with remote node.

remote node - A network connection that utilizes remote access.

remote procedure call (RPC) - A protocol allowing one computer on a network to request services from another computer on the network.

remote station - A station that connects to the network over a telecommunications circuit. See also local station and station.

repeater - A device that regenerates a digital signal. A repeater receives a signal from one source, reads it, generates a completely new signal identical to the original, and transmits it to the next destination. Repeaters can be separate devices to boost long-haul transmissions or can be incorporated into other devices such as switches and routers.

request for information (RFI) - A written request for clarification or information about the contract documents, products, or services offered. It may be issued from a supplier of products or services or it may be issued by the customer.

request for interpretation (RFI) - See request for information.

request for proposal (RFP) - A detailed document of requested services and equipment of a buyer submitted to others for responses.

request for quotation (RFQ) - A detailed document that solicits quotes for projects or equipment and provides vendors with all the information necessary to prepare a quote.

request to exit (RX) signal - A signal that informs the controller that someone has requested an exit from the secure area.

request to exit (RX) switch - Utilized with an access control system, this switch is located on the secured side of a controlled door.

request to send (RTS) - A frame type used to request permission to transmit. The response is a clear-to-send signal if the wireless medium is available for transmission.

resident - The individual responsible and accountable for the telecommunications services provided to the premises who may reside on the premises or, in the case of a rental unit, be the owner or property manager.

residential gateway - A device that enables communication among networks in the residence and between residential networks and service providers' networks.

resilient packet ring (RPR) - A technology implemented using a dual-ring topology with data transfer taking place at all times using both rings. In the event of a fault on one ring, all traffic is transferred to the second ring.

resilient route - See alternate route and diverse route.

resistance - A measure of opposition a material offers to the flow of direct current.

resistance unbalance - The difference in resistance, expressed in ohms, between the conductors of a pair. May also be expressed in terms of percentage by the ratio of unbalance in ohms to the lowest conductor resistance.

resistivity - Resistance per unit of measure. Measure can be of length (e.g., 100 ohms).

resource access - The process of providing a remote user the means to connect to a LAN and obtain the same privileges as when connecting from local stations. See also content access and transactional access.

respondent - A person or company that submits a proposal in response to a request for quote.

response due date - The date by which a response to a request for quote must be received in order to be valid.

retainage - A percentage of a total contract that is withheld from a contractor until the entire scope of work is completed.

retrofit - 1. To furnish a device or system with new parts or equipment not available at the time of manufacture. 2. The installation of a structured cabling system into a preexisting residential structure.

retrofit ring - See low-voltage mounting bracket.

retrofitting - To modify systems that are already in service using parts made available after the time of original installation.

return loss - A ratio, expressed in dB, of the power of the outgoing signal to the power of the reflected signal. When the termination (load) impedance does not match (equal) the value of the characteristic impedance of the transmission line, some of the signal energy is reflected back toward the source and is not delivered to the load; this signal loss contributes to the insertion loss of the transmission path, and is called return loss.

return-to-zero (RZ) - A pulse code modulation line-encoding scheme that uses zero volt as a valid logic (binary) state.

reverberant sound - Sound that is reflected from a surface (e.g., wall, floor) to the listener.

Reverse Address Resolution Protocol (RARP) - A Transmission Control Protocol/ Internet Protocol (IP) providing the IP address when the media access control address is submitted.

reverse firewall - A firewall implemented in a reverse configuration where policies that apply to traffic exiting the organizational network (e.g., Internet access rules for employees) are enforced.

reverse proxy - See Web site acceleration.

reversed pair - A condition in which the conductors in a pair are terminated in the wrong sequence (i.e., tip connects to ring and ring connects to tip).

ribbon cable - 1. An assembly of conduc tors laid side by side in a geometric plane and fastened together. 2. Cable in which many optical fibers are embedded in a plastic material in parallel, forming a flat ribbon-like structure.

rigging - A system of ropes or pulleys used to move material and equipment.

right-of-way (RIW) - A route across public or private lands over (or under) which telecommunications facilities can be legally installed and maintained.

ring - A means for identification of one conductor of a pair. Historically associated with the wire connected to the ring portion of an operator's telephone plug. See also tip.

ring in (RI) - A port on a token ring concentrator that receives signals from the main ring path on the network cable and transmits them to the downstream ring out port or network device. It also provides connectivity to the backup path on the network.

ring laser gyroscope (RLG) - A gyro with no moving parts that uses the interference of laser light within a bulk optic ring to detect and measure changes in orientation and spin.

ring latency - In token ring, the number of bit times it takes for a signal to propagate one time around the ring. This value is the sum of the signal propagation delay through the medium plus the sum of the delays associated with every device attached to the ring.

ring network - See ring topology.

ring out (RO) - A port on a token ring concentrator that transmits signals to the main ring path on the network cable and receives them from the upstream ring in port or network device. It also provides connectivity to the backup path on the network.

ring segment - A section of a token ring communications path that is bounded by repeaters or converters. These boundaries are used to determine the signaling limits that apply to the devices within the segment.

ring topology - A physical or logical network topology in which nodes are connected in a point-to-point serial fashion in an unbroken circular configuration. Each node receives and retransmits the signal to the next node.

ringing tool - A device used to remove cable sheaths.

riser - 1. Vertical sections of cable (e.g., changing from underground or directburied plant to aerial plant). 2. The space used for cable access between floors.

riser cable - See backbone cabling.

riser closet - See telecommunications room.

roadbed - The graded portion of a roadway upon which the base course, surface course, shoulders, and median are constructed.

roaming - 1. In cellular technology (mobile telephony technology), the use of a wireless telephone outside a specified tariffed geographic area defined by the service provider (which is usually called the "home" area); outside of the home area, additional charges usually apply. 2. In wireless LAN technology, this refers to the ability to move seamlessly between the wireless cells from adjacent access points while remaining connected to the network.

rodding - Pushing or pulling a mandrel or duct brush through a conduit, using poles or rods thatjoin together to determine if the pathway is clear and can be used to install a pull string.

roll bar - See mandrel.

rolling cut - A cutover where the crossconnects are relocated one pair after another.

root repeater - In demand priority access method, the Level 1 or topmost repeater in a cascade of repeaters.

rough-in - 1. Cabling installed before walls are enclosed or finished. 2. Cabling installed in anticipation of future use or need. 3. The time in which a residential cabling installer runs the cable between the various termination points, the main task during this period being to complete all the work that is difficult to do once interior ceiling and wall materials are installed.

route loop diversity - A type of loop diversity that assigns circuits along entirely different cable paths to a building.

router - An intemetworking device, operating at the Network layer of the Open Systems Interconnection model, used to direct packets from one network to another.

router table - A database made up of information on the routes a packet can take through an internetwork.

rule of percentage - If a retrofit, the authority having jurisdiction may determine the percentage of existing cable permitted to be removed from the building without requiring a complete replacement of existing cable.

runt - A short, invalid Ethernet frame typically caused by a collision.