The symbol designation for Resistance.
When you see CD-R, it means that the name of the disc ending in "R" can be used only once. Discs ending in "RW" can be erased and rewritten.
An ISDN term . The 2-wire physical interface which is used for termination between a TA (Terminal Adapter) and TE2 (Terminal Equipment type 2), which is non- ISDN compatible terminal equipment. The physical connection generally follows either the RS-232 or the V.35 specification in terms of its electrical, functional and physical characteristics. TE2 can be in the form of a telephone set, a PC or a fax machine; none of these devices are ISDN-compatible unless specially equipped to be so. TE1 is ISDN-compatible terminal equipment, generally at significant additional cost. See also ISDN, S Interface, T Interface, TE1, TE2, and U Interface.
An ISDN reference point between non-ISDN terminal equipment (TE2) and a terminal adapter (TA). Non-ISDN (TE2) terminal equipment connects to ISDN at the R-reference point through a terminal adapter.
Fremont, California, December 13, 1999. The Enterprise Computer Telephony Forum (ECTF) today announced the availability of R.100, a new interoperability agreement that addresses the need for easily gathering, consolidating and reporting call center data. According to the ECTF, today's call centers contain a proliferation of systems that enhance the effectiveness of the center, but each one collects separate information on individual calls. All of the data collected by these different systems is needed to intelligently modify and fine-tune call center activities, but this very proliferation of systems presents a barrier to the correlation of data for an individual call. R.100 presents standardized techniques for gathering this data in a consistent manner from all the devices in a call center. R.100 defines common terminology for elements within the call center environment, minimum data sets to be available from call center functions, a common tracking method from call initiation to conclusion regardless of number of segments, to eliminate multiple counting, a method for clock synchronization, and data structures. According to ECTF, the model presented by R.100 is applicable in environments with intelligent networks, virtual call centers, networked call centers, circuit switched networks, IP telephony networks, computer telephony integration (including ECTF C.001, TAPI, TSAPI, JTAPI, and ECMA CSTA); and/or multimedia systems and calls. www.ectf.org.
Research & Development.
Research & Education.
A designator used to name one of the color signals (red minus luminance) of a color difference video signal. The formula for deriving R-Y from the red, green, and blue component video signals is .70R - .59G - .11B.
Internet-speak for Real Time. R/T means the time it takes to download stuff. Writing in the New York Times, Charles McGrath said it was "customary in Net-speak to make a distinction between r/t, or real time ” the time in which all these delays and jam-ups occur and v/t, or virtual time, which is time on the Net: a kind of external present in which it is neither day nor night and the clock never ticks . V/t is time without urgency, without priority."
The ITU-T's name for a particular North American digital trunk protocol that happens to use multi-frequency (MF) pulsing. Some Europeans refer to any North American MF signaling protocol as R1 when distinguishing it from their own R2. See R2, Multi-Frequency Pulsing .
R1.5 is Russian inter-switch address signaling over digital trunks (E1). It is based on MF R1 signals and "pulse shuttle" rules of their exchanging.
A whole series of ITU-T specs which refers to European analog and digital trunk signaling. It refers to a type of trunk found in Europe which uses compelled handshaking on every MF (multi-frequency) signaling digit.
Digital version of supervisory signals in R2, based on bits A and B in E-1 (in contrast to 3825 Hz signaling over analog lines).
Registration Authority. An authority in a network that verifies user requests for a digital certificate and tells the certificate authority (CA) to issue it. RAs are part of a public key infrastructure (PKI), a networked system that enables companies and users to exchange information and money securely. The digital certificate contains a public key that is used to encrypt and decrypt messages and digital signatures.
Same as Return Material Authorization Number, or RMA. A code number provided by the seller as a prerequisite to returning product for either repair or refund. An indispensable tracking procedure, it operates like a purchase order system. If you return computer or telephone equipment without an RMA, chances are your equipment will be lost.
Remote Access Concentrator. A RAS is a larger Remote Access Server. According to Mark Galvin, president of RAScom, many people are now distinguishing between RAS (Remote Access Server) and RAC (Remote Access Concentrator). There seems to be two different cut-offs for the transition from RAS to RAC. The first, I believe originally defined by Dataquest, is when the port count exceeds 12. The industry seems to be adopting a different cut-off at anything T-1 or bigger as a RAC. A remote access server or remote access concentrator is a piece of computer hardware which sits on a corporate LAN and into which employees dial on the public switched telephone network to get access to their email and to software and data on the corporate LAN (e.g. status on customer orders). Remote access servers are also used by commercial service providers, such as Internet Access Providers (ISPs) to allow their customers access into their networks. Remote Access Servers are typically measured by how many simultaneous dial-in users (on analog or digital lines) they can handle and whether they can work with cheaper digital circuits, such as T-1 and E-1 connections. See also Remote Access Concentrator and Universal Edge Server.
Real Application Clustering. See Database Clustering for an explanation.
An association in the European Economic Community. RACE stands for Research and development for Advanced Communications in Europe.
A network security term. A condition caused by the timing of events within a piece of software. Race conditions typically are associated with synchronization errors that provide a window of opportunity during which one process can interfere with another, possibly introducing a security vulnerability.
Metal or plastic channel used for loosely holding electrical and telephone wires in buildings . A raceway is usually located in the floor and is encased on three or four sides by concrete. A raceway is used for interior wiring and performs the same job as a conduit but is typically larger.
A ceiling distribution method in which open or closed metal trays are suspended in false ceilings from the structural floor above. The raceway method is generally used in large buildings or for complex distribution systems that demand extra support. When closed metal trays are embedded in the floor, this distribution method is often called underfloor raceways. See also Ceiling Distribution Systems and Underfloor Duct Method.
The rachet factor is part of CABS ” Carrier Access Billing System. It used to describe the apportionment of channels on a trunk between switched and facility usage. It's a percentage. Both switched usage and leased (facility) lines can be co-resi- dent on the same trunk. The rachet percentage refers to the percentage of the trunk dedicated to facility. Obviously, you would want to know this because switched usage is tariffed and facility usage is charged at flat contract rates.
An equipment rack. In our industry, the standard equipment rack is 19 inches (48.26 cm) wide at the front. Much equipment is designed to fit into a standard rack. A rack is typically made of aluminum or steel , onto which equipment is mounted. A rack is typically attached to a building ceiling or wall. Cables are laid in and fastened to the rack. Sometimes a rack is called a tray. What a rack is to equipment, so a frame is to wiring. See also Distribution Frame.
Rack (the digits). a term which implies the storing or registering of numerical data. See Register.
RU. Unit of measure of vertical space in an equipment rack. One rack unit is equal to 1.75 inches (4.45 cm).
Designed to be installed in a cabinet, usually 19" wide.
RAdar transponder beaCON . Short-range navigation devices that provide target images on a ship's maritime navigation radar system. The transponder beacons transmit, either automatically or in response to a predetermined received signal, a pulsed radio signal with specific characteristics. RACONs generally operate in the 9300-9500 MHz band , and are used to identify specific locations such as hazards to navigation; think of them as replacements for lighthouses and you won't be far off. Most RACONs are operated by the U.S. Coast Guard. See also Radar.
A fancy name for someone who strings tennis racquets. Also spelled Racket Technician in America.
The unit used to measure the absorption of ionizing radiation.
A British Term. Recorded Announcement Device, a device which automatically answers a line and delivers a pre-recorded message. Often used to tell a caller to a tele- business unit that the call is in a queue and will be dealt with soon. More sophisticated RADs gather information, take messages or work in conjunction with interactive fax machines.
An abbreviation for Rapid Application Development. Most relate it to a quick programming environment.
RAdio Detection And Ranging. See Radar Detector.
Picture a trooper sitting in his car aiming his radar gun down the highway. The gun emits a beam of electrons at microwave frequency. Those beams bounce off approaching vehicles and reflect back to the trooper's radar at an altered frequency (the Doppler Effect). By measuring the change in frequency, the trooper calculates the speed of the oncoming vehicle. The trouble is the radar beam fans out like a searchlight. At a distance of 1,000 feet, the beam is about as wide as the highway itself. That makes it difficult for the trooper to know which vehicle he's tracking.
Also, his reading can be thrown off by any number of operating errors or by interference from power lines, neon lights or even the fan motor in the trooper's car. According to some estimates, Esquire Magazine reported , as many as 30% of all radar-generated speeding tickets were given in error. In 1979 a Miami TV station showed a police radar clocking a house going 28 miles per hour and a banyan tree doing 86! Radar detectors are very much like FM receivers. They can pick up radar signals more than a mile from the source. At that distance the beam is too weak to bounce all the way back to the trooper's car but strong enough to make the detector beep.
A typically circular cathode ray tube (CRT) showing movement of the sweep of a swirling radar beam and the objects it hits.
A slang expression typically deriding something. "I'm studying the market for computers laptops, but Winbook is not on my radar screen." This typically means that Winbook, as a manufacturer, is so small they're not worth studying . To be on my radar screen means they're large enough and significant enough for me to study them.
The rate at which a track on an optical disc accelerates toward and away from the center, because it is not perfectly aligned or perfectly round.
See Ground Radials.
Energy as measured in joules which is transferred via electromagnetic waves. There is no associated transfer of matter. And typically the giver or energy and the receiver of energy are not touching.
Energy emitted in the form of waves (light) or particles ( photons ). See Radiation Pattern.
The propagation characteristics of an antenna.
A forum established to promote common public key infrastructure standards for ecommerce using wireless phones.
RF. System of communication employing electromagnetic waves propagated through space. Because of their varying characteristics, radio waves of different lengths are employed for different purposes and are usually identified by their frequency. The shortest waves are the highest frequency, or numbers of cycles per second; the longest waves have the lowest frequency, or fewest cycles per second. In honor of the German radio pioneer Heinrich Hertz, his name has been given to the cycle per second (hertz, Hz); 1 kilohertz (Khz) is 1000 cycles per second, 1 megahertz (Mhz) is 1 million cycles per second, and 1 gigahertz (Ghz) is 1 billion cycles per second. Radio waves range from a few kilohertz to several gigahertz. Waves of visible light are much shorter. In a vacuum , all electromagnetic waves (but not audio waves) travel at a uniform speed of about 300,000 km (about 186,000 miles) per second.
Radio waves are used not only in radio broadcasting but in wireless devices, telephone transmission, television, radar, navigational systems, and communication. In the atmosphere the physical characteristics of the air cause slight variations in velocity, which are sources of error in such radio-communications systems as radar. Also, storms or electrical disturbances produce anomalous phenomena in the propagation of radio waves.
Because electromagnetic waves in a uniform atmosphere travel in straight lines and because the earth's surface is spherical, long distance radio communication is made possible by the reflection of radio waves from the ionosphere. Radio waves shorter than about 10 m (about 33 ft.) in wavelength ” designated as very high, ultrahigh, and super high frequencies (VHF, UHF, and SHF) - are usually not reflected by the ionosphere; thus, in normal practice, such very short waves are received only within line-of-sight distances. Wavelengths shorter than a few centimeters are absorbed by water droplets or clouds; those shorter than 1.5 cm (0.6 in) may be absorbed selectively by the water vapor present in a clear atmosphere.
A typical radio-communication system has two main components , a transmitter and a receiver. The transmitter generates electrical oscillations at a radio frequency called the carrier frequency. Either the amplitude or the frequency itself may be modulated to vary the carrier wave. An amplitude - modulated signal consists of the carrier frequency plus two sidebands resulting from modulation. Frequency modulation produces more than one pair of sidebands for each modulation frequency. These produce the complex variations that emerge as speech or other sound in radio broadcasting, and in the alterations of light and darkness in television broadcasting.
RBDS. A new system designed to let radio stations broadcasters send text messages, such as emergency warnings and traffic alerts to radios equipped with special LCD screens. The system is designed ultimately to replace the Emergency Broadcast System.
A call center term. A button used for selecting from a group of options that are mutually exclusive. As with a car radio, selecting a particular button de- selects the previously selected button.
An World Wide Web term. Radio buttons are used in forms on Web sites to indicate a list of items. Only one button can be selected at one time.
RCC. A common carrier engaged in Public Mobile Service, which also is not the business of providing land line local exchange telephone service. These carriers were once known as Miscellaneous Common Carriers .
Any telecommunication by means of radio waves.
That group of electromagnetic energy whose wavelengths are between the audio and the light range. Electromagnetic waves transmitted usually are between 500 KHz and 300 GHz.
Radio frequency flooding turns a telephone into a room listening device by transmitting a high power radio signal down a telephone line. The high power radio frequency is able to bypass the open hookswitch in the mouthpiece circuit. Room sounds cause the carbon microphone to modulate the RF signal. Radio frequency flooding is hard to implement but can only be detected by security professionals with the right equipment.
RFID. A method of identifying unique items using radio waves. Typically, a reader communicates with a tag, which holds digital information in a microchip. But there are chipless forms of RFID tags that use material to reflect back a portion of the radio waves beamed at them. For a fuller explanation, see RFID.
RFI. A metal shield enclosing the printed circuit boards of the printer or computer to prevent interference with radio and TV reception .
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.
RFI Shield. A metal shield enclosing the printed circuit boards of the printer or computer to prevent radio and TV interference.
Provides attendant and phone user dial access to customer-owned radio paging equipment to selectively tone-alert, or voice-page individuals carrying pocket radio receivers. The paged party can answer by dialing an answering code from a phone within the PBX.
Allows access to customer- provided paging systems and provides the capability in the PBX to connect the paged party when the former answers the radio page by dialing a special code from any PBX.
A management entity or subentity concerned with the operation of the radio resources management protocol. A cellular radio term.
A management entity or subentity concerned with the operation of the radio resource management protocol. A cellular radio term.
Electromagnetic waves of frequencies between 10 KHz and 3MHz, propagated without guide in free space (air).
A telegram sent by radio. Totally obsolete term, but cute.
An instrument, distinct from a photometer, to measure power, in Watts, of electromagnetic radiation.
Apparatus for transmitting and/or receiving speech or music by radio. Totally obsolete term, but cute.
An automatic radio transmitter in the meteorological aids service usually carried on an aircraft, free balloon, kite, or parachute , and which transmits meteorological data.
The use of a radio (instead of wire) to communicate telegraphy messages over a distance. An old term, not used much any more. See also Radiotelephony.
The science, art, and act of transmitting speech by means of radio. Now called telecommunications.
Remote Authentication Dial-In User Service is an authentication and accounting system used by many Internet Service Providers (ISPs) and end user organizations to provide secure Internet access, especially in a VPN (Virtual Private Networks) application. When you dial in to the ISP, for example, you must enter your username and password. This information is passed to a RADIUS server, which checks that the information is correct, and then authorizes access to the ISP systems and network. Though not an official standard, the RADIUS specification is maintained by a working group of the IETF. RADIUS is a client/server-based authentication software system that centralizes the administration of user profiles maintained in authentication databases, thereby simplifying the process of supporting multiple VPN switches. The remote access servers act as RADIUS clients which connect to the centralized authentication server. RADIUS is an open specification that can be adapted to work with legacy systems and protocols. RADIUS was developed by Steve Willins of Livingston Enterprises, Inc., which was acquired by Lucent Technologies. See also Authentication, Client/Server, and VPN.
A plastic cover for a microwave antenna. It protects the antenna from awful weather, but has little effect on the radiation pattern of the antenna. Here's a more technical explanation: A radome is a dielectric cover placed over an antenna to protect it from the environment. For example, the nose of an aircraft which contains the airplane's weather radar antenna. There are hundreds of other radome applications encompassing telecommunications, wireless, radars, satcom, terrestrial communications, ECM equipment and other commercial and military sensors.
Rate Adaptive Digital Subscriber Line. Transmission technology that supports both asymmetric and symmetric applications on a single twisted pair telephone line and allows adaptive data rates. RADSL employs intelligent ADSL modems which can sense the performance of the copper loop and adjust transmission speed accordingly . These devices adjust dynamically as the performance of the loop varies during a session, much as does a V.34 modem. Depending on various characteristics of the subject cable plant, ADSL accommodates downstream transmission speeds of as much as seven megabits per second, plus bidirectional transmission speeds of as high as 640 Kbps over a single UTP (Unshielded Twisted Pair). Some RADSL equipment can be manually configured See ADSL.
Redundant Array of Inexpensive Disks. The idea is simple: Put several disk drives into a single housing. Then write your data over the disk drives in such a way that if you lose one or more of the drives, you won't have lost any of your data. Thus the term "redundant." At its simplest, RAID mirrors data to an equal number of disk drives, e.g. two sets of two. At its most complex, RAID writes data across a bunch of drives, so that if one goes the data can be retrieved from the remaining drives . The opposite of RAID is SLED (Single Large Expensive Disk). See also Redundant Array of Inexpensive Disks for a much more detailed explanation.
The railway revolution took place from about 1825 to 1875 in Britain. It saw a great connecting of commerce and the coming of steam power. See also the Steel and Electicity Revolution.
When radio signals encounter a heavily moisture-laden atmosphere, the signals will lose their strength. Generally, the higher the radio frequency, the more attenuation (i.e., the greater the signal loss). Since satellite and terrestrial microwave signals for satellite are essentially line-of-sight, these types of signals are very susceptible to signal attenuation caused by rain, and especially heavy rain and snow. Modern microwave paths are engineered with weather patterns in mind. In areas where heavy rainfalls occur, microwave links may be placed closer together or more attention is paid to diverse and duplicated routing. You can't have more than one path with satellite TV signals directly to the home, e.g. DirecTV or Sky Satellite. These signals tend to fade or drop out completely during rain and snow storms. And they usually drop out at the movie's climax. Moisture also affects FSO (Free Space Optics) systems, with fog impacting the signal much more than rain. Optical fiber systems are affected by residual moisture deposited during the manufacturing process. Moisture, in general, is a bad thing in transmission systems. See also Free Space Optics and Water Peak.
Signal distortion of a voice telephone line caused by the under- attenuated echoes on the return path.
See Rain Attenuation.
Loss of signal at Ku or Ka Band frequencies due to absorption and increased sky-noise temperature caused by heavy rainfall.
According to the National Security Agency (NSA), the Rainbow Series is a six- foot tall stack of books dealing with the evaluation of "Trusted Computer Systems." The term comes from the fact that each book is a different color. Colors include orange, aqua, burgundy, lavender, venice blue, pink, peach, turquoise, and violet .
When a sports event is rained out, they give you a "raincheck," voucher for a seat when the event will be played . It's used also in personal relations. "Thanks for your invitation . I can't come to dinner tonight. Can I take a raincheck?" Which means, "Can I come at another time?"
A floor distribution method in which square, steel and wood-laminated plates resting on aluminum locking pedestals are attached to the building floor. The plates are usually covered with cork, carpet, or vinyl tiles, and each plate can be removed for easy access to the cables below. Also referred to as access floor.
A wireless receiver which can support a number of tines, or fingers, which can be combined to form a stronger received signal. Each tine is an individual radio channel.
Random Access Memory. The primary memory in a computer, RAM keeps the CPU (Centralized Processing Unit) efficiently fed with data or programs from the hard drive, or other storage medium. RAM can be overwritten with new information. The "random access" part of its name comes from the fact that the next "bit" of information in RAM can be located ” no matter where it is ” in an equal amount of time. This means that access to and from RAM memory is extraordinarily fast. By contrast, other storage media (e.g., hard drive, magnetic tape, and CD-ROM) store information serially , one bit after another. Therefore, the computer has to search for them, with the search time depending on the distance between the current bit and the target bit. Floppy disks are faster than magnetic tape because their information is readily at hand, though the read/write head will have to search for it. Hard disks are even faster because there are multiple heads and because the disks spin faster and everything moves faster. The speed of a CD-ROM search depends on the speed of the CD-ROM drive, but it can be pretty slow. RAM memory is the fastest of all. The problem with RAM memory is that it's volatile. This means when power is turned off (or power glitches occur) RAM memory is erased. RAM memory can be protected with rechargeable batteries ” just remember to charge the batteries.
All of that having been said, RAM comes in two types, at least along one dimension: buffered and unbuffered. Buffered RAM contains buffer chips that serve intermediaries between the control chips and the memory chips. The buffers help deal with the relatively large electrical load involved when a computer has a lot of memory. For example, a large server may have 16 DIMM (Dual Inline Memory Module) modules, each with as many as 36 RAM chips, yielding a total of 576 RAM chips. Since the controller cannot directly power so many chips, a buffer associated with each DIMM module assumes that responsibility. Unbuffered RAM typically is used on desktops, laptops, and smaller servers. Now for registered and unregistered RAM. Registered RAM includes a small register, or memory element, that imposes a slight delay, typically one clock cycle on the information transfer, from input to output. Large servers serving large volumes of information to large numbers of users employ registered RAM in order to ensure the integrity of the data being transferred. Now let's tie these two concepts together: buffered RAM may be registered, and unbuffered RAM is always unregistered. See also DDR-SDRAM, DRAM, EDO RAM, Flash RAM, FRAM, RDRAM, SDRAM, SRAM, and VRAM.
Remote Access Multiplexer. The various DSL (Digital Subscriber Line) services all involve some form of splitter or modem at the customer premises, and a matching device at the edge of the carrier network. Across the UTP (Unshielded Twisted Pair) local loop, the matching DSL units variously perform such functions as analog-to-digital conversion, data compression and packetization, ATM Adaptation, and Frequency Division Multiplexing (FDM). Generally speaking, the centralized unit at the edge of the carrier network is in the form of a DSLAM (DSL Access Multiplexer) contained within a Central Office (CO) owned by the ILEC (Incumbent Local Exchange Carrier). This approach works well for most subscribers, as they are served by "home run" UTP local loops from the CO to the premises. However, customers served through DLC (Digital Loop Carrier) systems are denied DSL service, as the DLC grooms and shapes all local signals into voice-grade channels of 64 Kbps. A ngDLC (next generation DLC) may contain one or more RAMs, which effectively are remote DSLAMs. Unfortunately, the RAMs are about the size of a pizza box, and currently serve no more than eight DSL lines. See also DLC, DSL, DSLAM, and ngDLC.
BIOS transferred to RAM so things go faster.
A logical device made from semiconductor (i.e. chip) memory which emulates the functioning of a disk drive as closely as possible. Since most semiconductor memory (RAM) is volatile, most RAM disks are also volatile, i.e. they lose their memory when you turn off power.
Hardware attachment that holds ASW (Aerial Service Wire) drop clamps in aerial span applications.
A symmetric cryptographic algorithm developed by Marconi.
RAndoM ACcess. Built in 1956 by IBM, RAMAC was the first hard drive computer memory device ever built. Consisting of 50 fixed disk platters, each approximately two feet in diameter, RAMAC could store five million characters at a rate of about 2,000 bits per square inch and at a cost of approximately $10,000 per MB (MegaByte). Contemporary (1999) hard drives store information less than a dime ($.10) per megabyte.
A means of amplification used in optical fiber transmission systems. Raman amplifiers are of two basic types: Distributed and Discrete. That was easy. The rest of this definition is hard, very hard, but some things in life are just hard. I worked hard to make this easy, but it's still hard. So, read it several times, at least.
Distributed Raman amplification uses the fiber itself as the gain medium, whereas the more traditional approaches use separate network devices such as EDFAs (Erbium Doped Fiber Amplifiers) to amplify the light signal. EDFAs accept a weakened light signal and boost it to a high power level before launching it, i.e., presenting it to the next fiber link. Over a distance, of course, the light signal weakens, and must be boosted again. Distributed Raman amplifiers front-end the EDFAs, serving as "pre-amplifiers." Diode- pumped Raman amplifiers pump an optical signal in the direction opposite the data flow (i.e., in the direction of the incoming optical signal carrying the transmitted data). Raman amplification occurs when higher energy (i.e., higher frequency, and shorter wavelength) pump photons scatter off the vibrational modes (i.e., vibrating atoms in the optical fiber), resulting in coherent (relating to electromagnetic waves that have a definite relationship to each other) stimulation (i.e., adding energy to) of the lower energy (i.e., lower frequency, and longer wavelength) photons associated with the incoming optical carrier signal (i.e., the one carrying the transmitted data). The pump photons actually can simultaneously amplify multiple carrier wavelengths in a DWDM system. At the same time, the Raman amplification process serves improve the SNR (Signal-to-Noise Ratio, expressed as Signal/Noise), which improves the quality of the incoming carrier signal and, thereby, improves error performance. As Raman amplifiers use the entire fiber as the gain medium, the signal weakens much less over a distance and the overall "launch power" level of the transmission signal need not be as high. That translates into lower power costs. Also as a result of Raman amplification, the spacing of both the EDFAs and the optical regenerators can be increased considerably. That results in lower overall network cost.
For example, a counter-propagating light signal at a wavelength of 1450 nm (nanometers, or billionths of a meter) can be pumped in the direction opposite the transmission wavelength of 1550 nm. At the point that the SNR (Signal-to-Noise Ratio) begins to drop, and the BER (Bit Error Rate) therefore becomes an issue, the Raman effect contributes gain (i.e., amplification) to the transmission signal. Raman amplification reduces the number of amplifiers required by lengthening the distance between them, say from approximately 80 km (8,000 meters ) between EDFAs to approximately 100 km between Raman amplifiers. Raman amplification also allows the increasing of the bit rate at a given frequency of light, say from 10 Gbps to 40 Gbps. Raman amplification also works effectively with DWDM (Dense Wavelength Division Multiplexing), as multiple wavelengths can be amplified simultaneously.
Discrete Raman amplification occurs in a box, rather than in the optical transmission fiber. The incoming optical carrier signal enters the standalone Raman amplifier and is channeled into a length of specialty fiber, where the amplification process takes place. The likely application for this approach (it is not used commercially at the time of this writing in April 2001) will be to overcome localized loss such as that which might occur internal to a switch or multiplexer. See also DWDM, EDFA, and Raman Scattering.
Also known as the Raman Effect. Chandrasekhara Venkata Raman, an Indian physicist , discovered (1928) this phenomenon of the inelastic scattering of light as it encounters physical matter. Raman was awarded the Nobel Prize in Physics in 1930 for this discovery, which confirmed the quantum theory of light, which theory is that light is made up of particles. As incident light (i.e., light falling on or striking something) is scattered as it strikes an atom of solid physical matter, most of the photons retain their incident energy, or frequency, which we would see as a color of light. This "elastic" (i.e., snaps back into its original "form") scattering effect is known as Rayleigh scattering. Raman scattering describes the fact that the incident light also causes the electrical bonds between atoms to vibrate which, in turn, causes a small fraction of the photons to experience a shift in energy, or frequency (which is the inverse of wavelength). In this "inelastic" (i.e., doesn't snap back into its original "form") scattering phenomenon, the difference in the energy of the incident photon and the Raman scattered photon is equal to the energy of the vibration of the scattering molecule .
Raman scattering clearly impacts optical fiber transmission systems. The impact is especially significant in the case of DWDM (Dense Wavelength Division Multiplexing), which involves very precise frequency division multiplexing at the optical level. As the diode lasers introduce high-energy light signals into the clear core of the optical fiber, the phenomenon of Stimulated Raman Scattering (SRS) occurs. SRS occurs when light waves interact with vibrations of atoms in a crystalline lattice (i.e., optical fiber in this context). The atoms absorb the light and re-emit a photon with energy equal to the original photon plus/minus the atomic vibration. This scattering effect travels both forwards and backwards , and can cause frequency shifts in the individual light streams, which negatively affects the integrity of the bit stream. However, a Raman Gain amplifier, also known as a Raman laser, can overcome this effect by shifting the wavelength (frequency) of the incident light to a vastly different value at the output. If the incident light signal is monochromatic and sufficiently intense to reach a certain threshold value, the signal is amplified to the point that it exhibits the characteristics of a stimulated emission. The ultimate impact of this effect is both to clean up the signal, and to amplify it. See also DWDM, Raman Amplifier, and Rayleigh Scattering.
Random Access Memory Digital-to-Analog Converter. The chip on a VGA board that translates the digital representation of a pixel into the analog information needed for display on the monitor. A RAMDAC actually consists of four different components ” SRAM to store the color map and three digital-to-analog converters (DACs), one for each of the monitor's red, green, and blue electron guns.
The process of reducing transmission power from the nominal power level to a level below a defined threshold.
Return Authorization Number, also called RMA, Returned Merchandise Authorization. A number you need for returning busted equipment to the factory. You call the factory, tell them what you want to return and its serial number, and the factory rep gives you an RMA, which you write on the outside of the box containing the thing you're sending back. The idea is that the factory sees the number on the box and immediately logs your busted thing into its computer system. This way, when you call, it can tell you where your thing is and when you might get it back and what it might cost you. At least that's the theory. The moral of this story: Don't send stuff back to the factory without a RAN or RMA (whatever the factory calls it.)
Recorded trunk ANnouncements. RAN devices are devices connected on 4-wires to older central offices (public exchanges). They are used to give recorded messages to callers , e.g. "The number you have called has been changed. Please make note of the new number..."
Regional area network. A data network that interconnects businesses, residences and governments in a specific geographic region. RANs are larger than local area networks (LANs) and metropolitan area networks (MANs), but smaller than wide area networks (WANs). RANs are usually characterized by very high-speed connections using fiber optic cable or other digital media.
I don't know the full derivation of this term. But a nice reader sent me this email about ranch radio, "I ran across this many years ago when I worked in the sales office for a oil rig drill bit manufacturer. The sales guys in the field would call in on the "ranch radio" or we would call an operator to connect us to them. It sounded horrible, like she was laying the receiver next to a CB."
Scattered, unfocused, a non sequitur. A favorite expression of Bill Gates, chairman and founder of Microsoft, to dismiss ideas or strategies that lack logic (or he thinks lack logic). According to Stewart Alsop writing in the February 2, 1998 issue of Fortune Magazine, "Bill Gates is the ultimate programming machine. He believes everything can be defined, examined and reduced to essentials, and rearranged into a logical sequence that will achieve a particular goal. Anything that doesn't work this way, anything illogical is 'random.' In the world of Bill Gates, being illogical is the most serious sin." See Randomize for another Microsoft extension. See Randomness for its statistical meaning.
Usually refers to computer memory or storage. Random Access is the ability to reach any piece of data in the memory directly without having to pass by other pieces of data. In telephony, this means the ability to reach any other subscriber through the telco switching network. See Sequential Access.
Interference to telephone communications occurring at irregular intervals.
A device which generates random numbers without following any known algorithm. See Pseudo Random Number Generator.
RED. A congestion avoidance mechanism for TCP/IP networks. Implemented in a router at the edge of the network, RED takes advantage of TCP's inherent congestion control mechanism. In advance of periods of high network congestion, RED will drop TCP/IP packets from queues on a random basis in order to avoid buffer overflow. RED is accomplished by dropping packets on a random basis, which is determined statistically, when the mean queue depth exceeds a threshold over a period of time. This technique effectively advises the packet source router to decrease its packet rate. Once the source router has been advised by the destination device that all packets in a TCP packet stream have been received, the source can assume that the congestion condition is relieved, and can again increase the packet rate. While the queue is still relieved on the basis of FIFO (First In First Out) logic, RED is an improvement over pure FIFO, which simply drops data packets from the tail of the queue, all at once. This pure FIFO approach causes all source routers to resynchronize, and reduce their transmission rates. When the congestion condition clears, the TCP sources again increase their transmission rates, which results in wave peaks of congestion followed by troughs of network underutilization. See also FIFO and Weighted Random Early Detection.
Traffic that, over time (from moment to moment), has chance fluctuations around an average value of some measure of the traffic, such as the number of attempts arriving in a specified time interval.
A Microsoft made-up word. To become distracted, as in "I got heavily randomized by other stuff going on." See also Random.
The state of being random. See random. As a telephone industry assumption used in the development of blocking and delay formulas, randomness states that: All subscribers originate calls randomly , that is, without common cause such as a declaration of war, and each subscriber originates calls independently of all other subscribers.
The difference between the greatest and least of the items being considered . A measure of dispersion.
RDP. The Minimum Point of Entry (MPOE) of the property or premises where the customer's service is located as determined by Verizon. This point is where network access recurring charges and Verizon responsibility stop and beyond which customer responsibility begins. Also known as the End User Point Of Termination (EUPOT).
There are two definitions. I don't know which one is correct. I thought the first one was correct. That is that a range extender is a device that increases the length of a local loop by boosting battery voltage being sent out from the telephone company central office. Bellcore, however, says a range extender is a device that permits a central office to serve a line that has resistance that exceeds the normal limit for signaling. A range extender does not extend transmission range, according to Bellcore. See Range Extender with Gain.
REG. A unit that provides range extension in a loop for both signaling and transmission.
Reserved Alternate Path with Immediate Diversion. This is a frame relay option which does pretty much what it says on the tin. See Frame Relay.
IT term, used mainly on laptop computers. When a laptop freezes or has a touch pad issue, as in the pointer movin on its own, if you make two fists, and bang on the plastic on either side of the touch pad, it will usually remedy the situation. A reader gave me this definition. I think I'd only try it when all else has failed and after I'd removed the laptop's hard disk. This definition provided by Jonathon Scott.
Revenue Accounting Office. Identifies each LEC processing billing data through CMDS. Governed by BRADS.
Reseaux Associes pour la Recherche Europeenne. European association of research networks.
Here is an article on rare earth doping from The Economist Magazine of July 6, 1991: Optical fiber is the darling of the telecommunications world. Because light waves can be superimposed on one another, fiber can carry thousands of laser generated messages at the same time, over longer and longer distances. The longest fibers were once those which doctors use to explore their patients innards. Now they can stretch 70 km (40 miles). But even that does not get you across a sea much bigger than the English Channel without the messages fading. So today's transatlantic and transpacific optical cables are interrupted about every 70 km so that the messages can be sorted out, passed through an electronic amplifier, and then, turned into light again. These amplifiers are costly. Soon, though, they may be replaced .
The key technique is called rare earth doping, which was developed not by crooked bookmakers but by scientists at Southampton University in England, and AT&T Bell laboratories in New Jersey. The rare earths are a group of chemical elements with particularly restless electrons in their atoms. If these electrons are stirred up by a laser, they rise to higher energy levels inside their atoms. When they fall back again, they emit light. The frequency of the light emitted depends on the element. The trick is to pick one which emits at frequency used for telecommunications. By adding the right rare earth to a stretch of fiber, you can make it amplify signals. You can also make a laser out of the fiber itself.
In the optical amplifier developed at Southampton University, a laser is used to lift electrons in the rare earth atoms in a stretch of fiber up to higher energy levels. When a light signal comes along, it may knock one of these electrons off its perch. The falling electron gives off light, which boosts the signal. The enhanced signal then knocks down more electrons, gathering strength as it goes. Rare earths in the cable can be used for other things, as the team at Bell Labs has found. Normal light waves, even those in laser beams, spread out and dissipate as they travel.
Solitons, a special kind of wave, do not. Tidal bores, the best known form of soliton, can move up rivers for miles without losing their shapes. Light that traveled in solitons could travel much farther along an optical fiber between boosts. Solitons are created either by pumping the initial signal through an optical amplifier, or by using a laser made from doped fiber. The soliton holds its shape because the passage of light through the fiber temporarily increases the speed of light in that part of the fiber, so the back of the wave is always trying to travel faster than the front. The stronger the light, the stronger the effect.
Rare earth doping, with metals called erbium and praseodymium, has resulted in fibers which can handle billions of bits of data per second, and carry them thousands of kilometers. AT&T hopes to use erbium amplifiers in its new transoceanic cables in the 1990s. Other companies ” such as British Telecom and NTT ” also like praseodymium, which is harder to handle, but emits light at a more commonly used frequency.
An element of sound. When you speak in native mode, or acoustically, you create disturbances in the molecules in the air. Those disturbances vary in terms of frequency (i.e., pitch or tone) and amplitude (i.e., volume or power), and travel in a waveform. The wave comprises the compression phase and the rarefaction phase. The compression phase is the phase of high pressure in which the molecules are packed together more tightly than normal. The rarefaction phase, or decompression phase, is the phase in which the high pressure is relaxed and the molecules snap back into position.
Reverse Address Resolution Protocol. A low-level TCP/IP protocol used by a workstation (typically diskless) to query a node for purposes of obtaining its logical IP address. See Reverse Address Resolution Protocol.
Remote Access Server or Remote Access Services. See Remote Access Server.
Registration, Admissions, and Status signaling function. See H.323.
Sun Raster Image File image format.
A pattern of horizontal scanning lines on a TV screen. Input data causes the beam of the TV tube to illuminate the correct dots to produce the required characters. See Raster Graphics, Raster Scanning and Rastering.
There are two ways you can digitize a picture ” use raster graphics and vector graphics. Raster graphics are line drawings, such as cartoons, logos, and line art, that computers render using mathematical logarithms. Raster graphics are created using pixels. A raster is a grid of x and y coordinates on a display space. (And for three-dimensional images, a z coordinate.) A raster image file identifies which of these coordinates to illuminate in monochrome or color values. The raster file is sometimes referred to as a bitmap because it contains information that is directly mapped to the display grid. A raster file is usually larger than a vector graphics image file. A raster file is usually difficult to modify without loss of information, although there are software tools that can convert a raster file into a vector file for refinement and changes. Examples of raster image file types are: BMP, TIFF, GIF, and JPEG files. The most popular vector graphic software program is Adobe Illustrator. The most popular raster graphic program is Adobe Photoshop. Vector graphics are saved as GIF files for the Web, using websafe colors when practical.
The method of scanning in which the scanning spot moves along a network of parallel lines, either from side to side or top to bottom.
The process by which a document image is converted to a stream of bits representing either black or white, or one of sixteen levels of gray, for each element of the image. For Group 3 faxes, there are either 98 or 196 raster lines per vertical inch, with a horizontal resolution of 203 lines per inch (yielding 1.86 or 3.72 million elements per 8 1/2 by 11 inch page). Sixteen levels of grey ("halftone " setting ” requiring four bits per element, rather than the one bit required for black and white) can be specified, but are not typically used for documents containing only text and/or line drawings. The bit stream is compressed for transmission, and decompressed when received.
When Michael Marcus was a kid, he asked his father what a ratchet was. His father answered : "it's a little bigger than a mouse shit."
A process where the monthly charges for the USOCs on a HI-CAP account are reduced in proportion to the use of the available channels by switched services. See Ratchet.
The price of a particular service or piece of equipment from a telephone company. Telephone companies don't use the word "price." They use the word "rate." No one knows why, except that if they didn't cultivate their own jargon, there'd be no job for telecommunications dictionary writers. God forbid !
The process of converting a digital stream of data into a different format and rate. For example, rate adaption allows a 64-Kbps data channel to inter- operate with a 56-Kbps channel. In this context, rate adaption also is known as flow control. As is true for much in life, the lowest common denominator rules.
An ISDN term for bandwidth-on-demand. Sensitive to the application and to its underlying bandwidth requirements, the Terminal Adapter (TA) in a BRI implementation, or the PBX or router in a PRI implementation, will establish some number of 64-Kbps channels. These channels are established either automatically or by conscious selection of the user. For example, a voice session requires only one channel; a videoconferencing session requires two or more channels, depending on the quality desired. On demand and as available, the proper number of channels are selected in order to support the connection; as is the case with all connection-oriented protocols, those channels remain active during the entire session, regardless of whether they are required.
A telephone company term. A geographic area within which rate treatments are the same.
Telephone customer prices charged by tariffs for specified telephone services.
Telephone companies' method for establishing uniform pricing by distance rather than on the relative cost (to them) of the particular route. The theory is that some routes are more heavily trafficked, have huge transmission equipment and achieve great economies of scale. Some routes, on the other hand, have little traffic, small transmission equipment and achieve no economies of scale. Therefore, it costs more to provide calls on these less-trafficked routes. But the phone industry doesn't charge more to call small towns than big cities. The phone industry simply charges by distance, averaging its costs. This is called rate averaging.
A regulated telephone company's plant and equipment which forms the dollar base upon which a specified rate of return can be earned. The total invested capital on which a regulated company is entitled to earn a reasonable rate of return.
A means of flow control in which devices (e.g., switched or routers) in a network control the rate of data flow from a transmitter. In an ATM network, for instance, the edge switches negotiate the rate of flow from the transmitting device in consideration of both its desired rate and the ability of the destination switch (and all intermediate switches) to handle that flow without overflowing buffers. Overflowed buffers would result in lost data and overall degradation of QoS (Quality of Service). See also Flow Control and ER. Contrast with QFC.
Telephone company-designated geographic locations assigned vertical and horizontal coordinates between which airline mileages are determined for the charging of private lines. Or as defined by the telephone industry, rate center is that point within an Exchange Area defined by rate map coordinates used as the primary basis for the determination of toll rates. Rate Center may also be used for the determination of selected local rates. See Airlines Mileage and V & H.
A standard, nonvolatile memory device used to retain data base information on call pricing by Area Code and Central Office. Typically used in call accounting equipment.
Utilities have a specific rate for every service provided. The rates must be approved by the PUC. In a major rate case, rates for many services will be changed in tandem. In a rate design hearing, different proposals as to rate levels are considered. The level of one rate can have an impact on what the level of another rate should be. The interrelationship between rates and the impact of demand must all be considered in "designing" a rate structure.
The pricing structure of various telecommunications service offerings usually described in tariffs.
The percentage of net profit which a telephone company is authorized (by a regulatory commission) to earn on its rate base. See Price Cap and RATE BASE.
Rate of return regulation provides carriers with a guaranteed rate of return on their eligible telecommunications asset base. Current FCC guidelines set in 1990 provide for an 11.25% return on interstate assets. State rates of return on intrastate assets vary. Rate of return regulation allows carriers to charge consumers a price that, when combined with government subsidies, yields a regulated return above the cost of providing service. Companies that do not achieve the mandated rate of return due to higher costs, be they operational or capital related , may petition regulators for a price increase. 'this provides relative certainty of returnS but does not allow operators to benefit from cost efficiencies. Such regulation typically exists in rural jurisdictions where it would not be economical to serve most customers without such guaranteed subsidies.
Dividing a day into various slices of time for the purpose of charging differently for long distance and local calls. There are three rate periods in force today in North America for intra-North America calls. One rate period is from 11:00 P.M. to 8:00 A.M.; one is from 8:00 A.M. to 5:00 P.M. and one is from 5:00 P.M. to 11:00 P.M. If you call outside the United States, there are different rate periods.