release photons with energy equal to the signal photon plus/minus atomic vibration. In other words, a frequency/wavelength shift occurs as the pump wavelength propagates along the fiber in the reverse direction.The energy lost in the pump wavelength excites atoms that shift energy to longer-wavelength signals, typically in the 1550 nm window (C-band), in the forward direction, thereby serving to amplify them. See also amplifier, C-band, E-band, frequency, laser, optical fiber, photon, propagate, Raman amplifier, signal, span, and wavelength. pure mesh In wireless local area networks (WLANs), a mesh network in which any and all devices can interconnect with any and all other devices on a purely wireless basis. Also known as a client mesh, this approach is not highly scalable. A pure mesh is much like a Bluetooth piconet. See also Bluetooth, mesh, piconet, and WLAN. purist One who is preoccupied with and insists on the strict and excessive adherence to a tradition or set of formal, often pedantic, rules, especially with respect to maintaining the purity of language from foreign or altered forms. Photographers who persist in capturing images on film and printing them with a wet chemical process on silver emulsion paper also qualify. See also bit/s, bps, and pedant. push In the World Wide Web, a technology that initiates content transmissions to users who have regis- tered or subscribed to a service,relieving them of the requirement to initiate access to a Web site to retrieve that content, or “pull” it down. See also pull and World Wide Web. push-to-talk (PTT) See PTT. push-to-talk over cellular (PoC) See PoC. PVC 1. Permanent Virtual Circuit. A shared path established between two hosts through a packet net- work on a permanent basis. PVCs are preprogrammed in the routing tables of the transmission nodes throughout the network and are invoked based on various channel, channel group, or address information contained in the header of frames or packets. PVCs are defined on a permanent basis, until such time as they are permanently redefined, perhaps when the service provider rebalances the network to improve overall performance in consideration of changing usage patterns. Because the paths are predetermined and preprogrammed, network switches and routers can identify and exercise them quickly. PVCs are employed in frame relay and X.25 networks, as examples. A switched virtual circuit (SVC) is not preprogrammed, but is set up as the call is placed. See also channel, circuit,frame, frame relay, packet, path, SVC,virtual circuit, and X.25. 2. PolyVinyl Chloride.Actually polychloroethene, a thermoplastic polymer. PVC’s durability, flex- ibility, and dielectric properties, along with its low cost, make it useful as an insulating material in copper cables. See also dielectric. PWE (PseudoWire Emulation) In Multiprotocol Label Switching (MPLS), referring to a Data Link Layer (Layer 2) Virtual Private Network (VPN). Such a network emulates a point-to-point virtual circuit connection, or pseudowire, between two routers or switches.Also commonly referred to as a Draft-Martini VPN. See also connection, Data Link Layer, Draft-Martini VPN, MPLS, point-to-point, pseudowire, virtual circuit, and VPN. PWE3 (PseudoWire Emulation Edge to Edge) A PWE that operates from the ingress edge to the egress edge of a shared Internet Protocol (IP) or MultiProtocol Label Switching (MPLS) network. PWE3 makes use of existing mechanisms specified by the IETF, exerting no control over the network other than using existing quality-of-service (QoS) or path control mechanisms. See also PWE. PWT (Personal Wireless Telecommunications) A U.S. standard for digital cordless telephony, based on the pan-European Digital Enhanced Cordless Telecommunications (DECT) standard. Through fre- quency division multiplexing (FDM), PWT provides 10 carriers in the unlicensed 1910–1920 MHz band, with channel spacing at 1.25 MHz. Each channel will support 1.152 Mbps using ␲/4 differential quater- nary phase shift keying (␲/4 DQPSK) modulation. Each channel supports 12 users through time division multiple access (TDMA) and time division duplex (TDD), for a total system load of 120 users. Voice pump laser 398 74570c16.qxd 9/11/07 12:27 PM Page 398 encoding is adaptive differential pulse code modulation (ADPCM) at 32 kbps. PWT supports call hand- off, so users can roam from cell to cell at pedestrian speeds as long as they remain within range of the system. PWT antennas can be equipped with optional spatial diversity to deal with multipath fading. Secu- rity is provided through authentication and encryption mechanisms. PWT/E is an extension into the licensed bands of 1850–1910 MHz and 1930–1990 MHz.The PWT specification was developed by the Telecommunications Industry Association (TIA). See also ADPCM, antenna, authentication, carrier, channel, cordless telephone, DECT, digital, encode, encryption, ETSI, FDM, handoff, modulation, multipath fading, ␲/4 DQPSK, PWT/E, spatial diversity, TDD, TDMA, and TIA. PWT-E (Personal Wireless Telecommunications-Enhanced) A U.S. standard for digital cordless telephony, based on the pan-European Digital Enhanced Cordless Telecommunications (DECT) standard and essentially an enhancement of PWT. PTW-E extends PWT into the licensed bands of 1850–1910 MHz and 1930–1990 MHz,and tightens the channel separation to 1 MHz.See also channel,cordless telephone, DECT, digital, and PWT. P × 64 (P times 64) An ITU-T videoconferencing specification more correctly known as H.320 and sometimes referred to as H.261, which actually specifies the video encoding technique. Designed for videoconferencing applications, P × 64 supports p channels of 64 kbps, up to a maximum of 30 chan- nels, which is equivalent to E-1. P × 64 video formats include Common Intermediate Format (CIF), which is optional, and Quarter-CIF (QCIF), which is mandatory in compliant codecs. H.261 CIF sup- ports 352 × 288 = 101,376 pixels per frame and 30 frames per second (fps), although lower frame rates also are supported. QCIF supports 176 × 144 = 25,344 pixels per frame, exactly 1 ⁄4 the resolution of CIF. See also CIF, codec, encode, frame, frame rate, fps, H.261, H.320, ITU-T, pixel, video, videoconference, and QCIF. PXC (photonic cross-connect) Also known as transparent optical cross-connect (transparent OXC). See transparent OXC. 399 PXC (photonic cross-connect) 74570c16.qxd 9/11/07 12:27 PM Page 399 74570c16.qxd 9/11/07 12:27 PM Page 400 Q1.One of the two letters, along with Z, that traditionally did not appear on a telephone dial or key- pad.The thought was that Q could be confused with O, and that Z could be confused with 2. Q now appears with P, R, and S on number 7. Alphanumeric dialing was, and remains, a North American prac- tice. Telephones in most other countries do not sport letters. 2. Q interface or Reference Point Q in ISDN. See Reference Point Q. Q.931 The ITU-T Recommendation for the user network interface (UNI) for integrated services dig- ital network (ISDN) basic call control, such as call setup and teardown.The specifications include user-to- user and network-to-network call control messages for both circuit-switched and packet-switched networking. ISDN signaling and control takes place over the D channel. Q.931 also is included in the ITU-T H.323 protocol suite for multimedia communications over packet networks. See also D channel, H.323, ISDN, and ITU-T. QAM (Quadrature Amplitude Modulation) A signal modulation technique that splits the carrier into two waveforms that are 90° out of phase, and specifies two possible amplitude values for each of four phase shifts separated by 90° (0°, 90°, 180°, and 270°).This yields eight distinct signal states, as illustrated in the signal constellation graph in Figure Q-1.Thereby,each signal impulse,or symbol, carries one of eight possible signal combinations and represents three bits (2 3 = 8). As a result, the transmission rate is thrice the signaling rate, or baud rate.At a signaling rate of 2400 baud, for example,this tribit modulation scheme yields a transmission rate of 7200 bps.The ITU-T V.29 recommendation is for 16-QAM. More complex schemes include 64-QAM, 128-QAM, 256-QAM, and 512-QAM.Trellis-coded modulation (TCM) uses the same modulation scheme as QAM, but adds forward error correction (FEC) to overcome the increased susceptibility to signal impairments which make it harder for the receiver to judge correctly which state is signaled with each baud. QAM applications include asymmetric digital subscriber line (ADSL). See also 16-QAM, 64-QAM, 128-QAM, 256-QAM, 512-QAM, carrier, FEC, modulation, phase, signal, signaling rate, symbol, TCM, transmission rate, and tribit. Figure Q-1 Q band The portion of the radio spectrum in the range of 36–46 GHz, as specified by the ITU-R. Applications are military in nature. See also electromagnetic spectrum and ITU-R. 180° 0° 270° 90° Binary Values 000 001 010 011 100 101 110 111 74570c17.qxd 9/11/07 12:27 PM Page 401 QCIF (Quarter Common Intermediate Format) In the ITU-T H.320 umbrella standard for video- conferencing and multimedia communications over narrowband ISDN (N-ISDN), a mandatory video for- mat that supports resolution of 176 × 144 pixels, which is exactly 1 ⁄4 the resolution of CIF at 352 × 288 pixels. See also CIF, H.320, ITU-T, multimedia, N-ISDN, pixel, resolution, video,and videoconferencing. QoS (Quality of Service) A measure of parameters that affect the level of performance a network offers a specific type of traffic. QoS parameters include access priority, bandwidth availability, latency, jit- ter, and packet loss.Toll quality, real-time compressed and uncompressed voice and video require fairly immediate network access, guaranteed availability of bandwidth throughout the call, low latency, zero jit- ter, and zero loss. E-mail is at the opposite end of the QoS spectrum, as it is highly tolerant of a low level of priority; high levels of latency, jitter, and loss; and does not require any bandwidth availability guaran- tees during the course of a mail transfer. QoS also must ensure that granting a QoS level to one traffic type or call does not violate the data flow requirements of another traffic type or call.The circuit-switched pub- lic switched telephone network (PSTN) offers all applications the highest level of QoS. Asynchronous transfer mode (ATM) offers multiple QoS levels appropriate for different traffic types. Frame relay, Inter- net Protocol (IP), and Ethernet networks can employ various priority mechanisms to offer differential grade of service (GoS) levels, but cannot guarantee QoS. See also ATM, compression, Ethernet, frame relay, GoS, IP, jitter, latency, loss, and PSTN. QPSK (Quadrature, Quadriphase, or Quaternary Phase-Shift Keying) A modulation technique that achieves dibit transmission by defining four phase shifts separated by 90 degrees (0°, 90°, 180°, and 270°). IEEE 802.11a (Wi-Fi5) wireless LAN (WLAN) standards call for binary phase-shift keying (BPSK) at 6 Mbps and QPSK at 12 Mbps. IEEE 802.11b (Wi-Fi) calls for BPSK at 1 Mbps and QPSK at 2 Mbps. Bluetooth specifies BPSK for use in the 868 and 915 MHz bands, and QPSK for use in the 2.4 GHz band. µ/4 differential quaternary phase shift keying (µ/4 DQPSK) can be viewed as the superposition of two QPSK constellations offset by 45 degrees relative to each other. See also 802.11a, 802.11b, Bluetooth, BPSK, modulation, phase, PSK, µ/4 DQPSK, and WLAN. QPSX (Queued Packet Synchronous eXchange) A technology that formed the basis for the Dis- tributed Queue Dual Bus (DQDB) defined in the IEEE 802.6 standard for metropolitan area networks (MANs). QPSX was developed at the University of Western Australia. See also 802.6, DQDB, IEEE, and MAN. quadbit 1. A set of four bits. Some line coding techniques encode blocks of 4 bits of data at a time, rather than 1 or 2 bits.The 4B/5B technique, for example,encodes a 4-bit block of data into a 5-bit block of signal in order to provide sufficient clocking pulses and signal transitions to synchronize the network and to provide some level of error detection. 4B/5B is used in 100Base-TX, 100Base-FX, and Fiber Dis- tributed Data Interface (FDDI) LANs. Compare to nibble. See also 4B/5B, line coding, and synchronization. 2. Referring to a modulation technique that impresses 4 bits on a baud, so that the bit rate is quadruple the baud rate. Such a technique employs 16 signal states. 16-QAM is a quadbit technique achieved by defining two amplitude values for each of eight phase shifts. See also 16-QAM, amplitude, amplitude modu- lation, baud, baud rate, bit, bit rate, dibit, modulation, phase, QAM, quartet, signal, tribit, and unibit. quadraplex A circuit or device that supports simultaneous transmission or reception of four independ- ent signals. Quadraplex communications technology is a simple form of multiplexing that improved on diplex (two independent signals) and was considered quite revolutionary in the early days of telegraphy, when the four signals could be transmitted in one direction, only.The term is generally considered obso- lete. See also diplex and multiplex. Quadrature Amplitude Modulation (QAM) See QAM. quadrature phase-shift keying (QPSK) See QPSK. quadriphase phase-shift keying (QPSK) See QPSK. QCIF (Quarter Common Intermediate Format) 402 74570c17.qxd 9/11/07 12:27 PM Page 402 quadruple play A marketing term used by broadband service providers to describe the triple play com- bination of voice, high speed data, and television services over a single local loop, plus wireless services. While there is no standard approach, quadruple play wireless services generally are designed to operate as cordless telephony when within range of a base station on the subscriber premises and as cellular teleph- ony when out of range. As contemporary high-end cellular terminal devices are capable of supporting voice, data,image,and video, and as broadband cellular and other wireless networks are capable of support- ing transmission rates in the range of hundreds of kbps and even Mbps, wireless capability is a significant addition to an integrated suite of service.The term triple play is a baseball analogy, referring to the very rare act in which the defense makes three outs on the same play. See also broadband, cellular radio, cordless telephone, local loop, and triple play. quality of service (QoS) See QoS. quantization and compaction encoding Referring to a step in the video compression process that reduces the number of bits required to represent a color pixel. Compaction techniques include run-length encoding, Huffman coding, and arithmetic coding. quantize To express in multiples of a quantum number, in other words an integer or basic unit. In telecommunications, the term refers to the conversion of the amplitude of an analog sine wave into a digital signal, which necessarily requires expressing the amplitude value in binary terms. See also quantiz- ing noise. quantizing noise A type of distortion that occurs when an analog waveform is encoded into a digital signal and then decoded back into an analog signal. The digital-to-analog conversion process occurs at sampling intervals and always involves some amount of approximation as the amplitude of the waveform is quantized, which involves converting each sample amplitude value to the nearest of 256 (2 8 ) standard approximate binary values.When the approximate digital values are reconverted and the analog waveform is reconstructed, the effect of the approximation manifests as quantizing noise. If the sampling rate is too low (i.e., infrequent) and/or the approximation is too extreme, the result is a phenomenon known as alias- ing in which the reconstructed signal is inaccurate, or even unintelligible, and the resulting voice quality unacceptable. See also aliasing, amplitude, analog, binary, digital, distortion, noise, quantize, and waveform. quantum The elementary quantity of radiant energy, a photon. See also photon. quantum leap 1. In physics, an abrupt, or step, change in the energy state of an elemental unit, such as a molecule, atom, or subatomic particle. Such particles do not smoothly transition from one energy state to another; rather, they jump or leap from a state of rest to an excited state, for example, accompanied by the absorption or emission of a particle carrying the equivalent energy. Such changes are dramatic and instantaneous, but small in magnitude. 2. In the vernacular, a change that is abrupt and large in magnitude. Quarter Common Intermediate Format (QCIF) See QCIF. quaternary phase-shift keying (QPSK) See QPSK. quatraplex A synonym for quadraplex. See quadraplex. queue A list, string, or stack of things constructed so that items are added to one end and relieved from one end or the other. Generally speaking, items are added to one end, known as the tail,and relieved from the other end, known as the head. In the absence of some priority mechanism for purposes of establish- ing and maintaining quality-of-service (QoS) differentiation, items are relieved from the head of the queue in the order they entered the tail.This approach is known as first-in-first-out (FIFO). Incoming call centers employ automatic call distributors (ACDs) that queue incoming calls, serving them to agents as they become available. Fax servers can queue documents for transmission during non-prime time hours, when international calling costs are lowest. PBX systems commonly have the capability to queue outgoing calls for expensive long distance circuits. Switches and routers queue packets in buffers until internal resources 403 queue 74570c17.qxd 9/11/07 12:27 PM Page 403 are available to process them or until bandwidth is available to forward them. Systems may support multi- ple queues for different types of calls or packets. Priority mechanisms can cause a call or packet to move up in the queue or even advance to the head of the queue in order that it can be served more quickly. See also ACD, call, facsimile, packet, PBX, QoS, router, and switch. Queued Packet Synchronous Exchange (QPSX) See QPSX. Q series The series of ITU-T Recommendations specifying protocols relating to switching and signal- ing. See Table Q-1 of selected Q-series Recommendations. For a full listing of ITU-T Recommendations, see the contact information in Appendix A. Table Q-1: Selected ITU-T Q-Series Recommendations Recommendation Description Q.20 Comparative advantages of in-band and out-of-band signaling systems Q.21 Systems recommended for out-band signaling Q.22 Frequencies to be used for in-band signaling Q.23 Technical features of push-button telephone sets Q.71 ISDN circuit mode switched bearer services Q.700 Introduction to CCITT Signaling System No. 7 (SS7) Q.716 SS7 - Signaling connection control part (SCCP) performance Q.721 Functional description of SS7Telephone User Part (TUP) Q.824.1 ISDN basic and primary rate access Q.824.2 ISDN supplementary services Q.824.3 ISDN optional user facilities Q.824.4 ISDN teleservices Q.921 ISDN user-network interface - Data link layer specification Q.931 ISDN user-network interface layer 3 specification for basic call control Q.2763 SS7 B-ISDN User Part (B-ISUP) - Formats and codes Q.2764 SS7 B-ISDN User Part (B-ISUP) - Basic call procedures QSIG (Q Signaling) A standard that defines services and signaling protocols for interconnecting TDM-based PBXs based on the ITU-T ISDN standard Q.931. QSIG is a Common Channel Signaling (CCS) protocol that runs over the ISDN D-channel for signaling between nodes in a Private Integrated Services Network (PISN). QSIG supports call setup, call teardown, and transparency of features such as message waiting, camp-on, and callback. The ISO (International Organization for Standardization) has adopted QSIG as Private Signaling System No. 1 (PSS1). See also CCS, ISDN, ISO, Q.931, and Q series. Q Signaling (QSIG) See QSIG. quality of service (QoS) See QoS. quartet A four-bit byte.Also known as a nibble. Compare with quadbit. See also bit, byte, and nibble. QuickConnect A feature of V.92 modems that reduces the time required for handshaking by approxi- mately 50 percent, to about 10–15 seconds.QuickConnect trains the modem on the first call and remem- queue 404 74570c17.qxd 9/11/07 12:27 PM Page 404 bers the characteristics of the circuit.Assuming that the circuit is the same on the next call, the circuit char- acteristics do not have to be relearned, which results in faster connect times, yielding obvious advantages to the end user and Internet service provider (ISP), alike. See also handshaking, ISP, modem, and V Series. quintet A five-bit byte. See also bit and byte. QWERTY The standard layout for English-language computer keyboards, so named for the top left six alphabetical characters.The QWERTY layout was patented by Christopher Sholes in 1868 for use with the first mechanical typewriter, which he also invented. Sholes sold the patent rights to Remington in 1873.The original layout was in alphabetical order, which caused the typebars to become entangled fre- quently once the typist gained proficiency and speed.Although the original justification is lost in time and there have developed a number of theories about it, the QWERTY layout certainly split up commonly used pairs of letters (e.g., s and t) and mitigated the issue of typebar entanglement. 405 QWERTY 74570c17.qxd 9/11/07 12:27 PM Page 405 74570c17.qxd 9/11/07 12:27 PM Page 406 R1.The symbol for Resistance. See resistance. 2. R interface or Reference Point R in ISDN.See Ref- erence Point R. R1022 ATM Technology Testbed (RATT) The result of the 1987 RACE sponsored project 1022. See also RACE. RA (Registration Authority) In a public key infrastructure (PKI), an entity that verifies the certifi- cate authority (CA) prior to the issuance of a digital certificate to the requesting party. See also CA, digi- tal certificate, and PKI. RACE (Research for Advanced Communications in Europe) A consortium of European carriers, end users, and universities. In 1987, RACE sponsored project 1022 to demonstrate the feasibility of asyn- chronous transfer mode (ATM).The result of the RACE initiative was the R1022 ATM Technology Testbed (RATT). RACE project 2061, also known as EXPLOIT, is a more recent RACE project intended to prove the viability of integrated broadband communications (IBC) in the European Union (EU). The National Research and Education Network (NREN) was the first (1990) test-bed ATM network in the United States.Advanced Communications Technologies and Services (ACTS) was developed as the successor pro- gram to RACE, and continues that work on ATM networking and some 200 other projects.See also ATM. radar (radio detecting and ranging) A microwave radio technology that uses reflected energy to detect and determine the direction of and distance to remote objects. Multiple return signals can be cor- related over time to determine the velocity and direction of moving objects.Applications include naviga- tion, targeting, and tracking for civilian and military purposes. See also microwave, radio, and sonar. radian From the Latin radius. A unit of plane angular measurement equivalent to the angle between two radii that enclose a section of a circle’s circumference (arc) equal in length to the length of a radius.There are 2π radians in a circle. See also frequency and radius. radiant flux The time rate of energy flow of radiant energy as measured in watts or joules per second. See also flux, joule, radiation, and watt. radiation 1. The act or process of the spreading out of energy in rays. 2.The emission, or outward flow, of energy in the form of electromagnetic waves, including radio waves and photons. See also electromag- netic, photon, and waveform. radio Electromagnetic energy with a waveform having a frequency above the upper limit of the audio range of 3 kHz and equal or less than the lower limit of the infrared light range of 300 GHz.At the low end of the range is extremely low frequency (ELF) radio, which operates at 30–300 Hz, and at the upper end of the range is extremely high frequency (EHF) radio, which operates at 30–300 GHz. See also electromagnetic spectrum, frequency, and Hz. Radio Act of 1927 In the United States,the act that established the Federal Radio Commission to reg- ulate all radio spectrum, except bands owned by federal government.The Communications Act of 1934 replaced the Federal Radio Commission with the Federal Communications Commission (FCC). See also band, Communications Act of 1934, FCC, and spectrum. radio access network (RAN) See RAN. radio area network (RAN) Synonymous with wireless radio area network (WRAN). See WRAN. radio common carrier (RCC) See RCC. 74570c18.qxd 9/12/07 12:39 AM Page 407 [...]... as ISO/IEC 1 381 8 Packet transport involves a serial data stream of packets of 188 octets, 1 octet of which is a synchronization byte and 187 octets of which are payload.This packet approach is suitable for ATM switching, as each 188 -octet MPEG-2 packet maps into the payload of 4 ATM cells, with only 4 octets of padding required SDTV employs ReedSolomon forward error correction (FEC) and 8- level vestigial... Cable Types RG Number Center Wire Gauge RG-6/U 18 AWG RG -8/ U Impedance (Ω) Outside Diameter (OD) Core Type Example Applications 75 ohms 332 in Solid CATV, cable modems, DBS TV 10 AWG 50 ohms 405 in Solid 10Base5 Ethernet, Ham radio RG- 58/ U 20 AWG 53.5 ohms 116 in Solid 10Base2 Ethernet, Ham radio RG-58C/U 20 AWG 50 ohms 116 in Solid RG-58A/U Military Spec RG-58A/U 20 AWG 50 ohms 116 in Stranded 10Base2... States of Operation), Pre-divestiture Regional Bell Operating Companies (Headquarters), Post-divestiture New England Telephone (Massachusetts, Maine, New Hampshire, Rhode Island, and Vermont) NYNEX (New York) Acquired by Bell Atlantic (August 1997); now Verizon Communications New York Telephone (New York) Pacific Bell (California) Nevada Bell (Nevada) Pacific Telesis (California) Acquired by SBC (April... 1 28 kbps to 2.32 Mbps.Typical signaling rates are 400 kbps for local loops of up to 18, 000 feet in length, and 784 kbps 74570c19.qxd 9/12/07 12:41 AM Page 430 SDSL (Symmetric Digital Subscriber Line) 430 for loops up to 12,000 feet At those signaling rates, SDSL yields a payload transmission rates of 384 kbps and 7 68 kbps, respectively See also 2B1Q, HDSL, HDSL2, HDSL4, payload, signaling rate, transmission... (Synchronous Code Division Multiple Access) A modulation technique that transmits 1 28 orthogonal codes simultaneously S-CDMA is used in combination with 1 28- point quadrature amplitude modulation trellis-coded modulation (1 28- QAM TCM) in cable modems specified in the Data Over Cable Service Interface Specification (DOCSIS) See also 1 28- QAM, cable modem, DOCSIS, modulation, orthogonal, QAM, and TCM Schools and... different tones for different callers, and to vary the tone by time of day, perhaps to have one tone for business hours and another for all other times See also ring tone 74570c 18. qxd 9/12/07 12:39 AM Page 4 18 ringlet 4 18 ringlet In Resilient Packet Ring (RPR) networks, a small local ring where the larger ring drops traffic off to nodes See also node, ring topology, and RPR ringing signal See ring... Code of Federal Regulations, Title 47, part 68, providing a standardized physical and electrical interface to the public switched telephone network (PSTN) See also jack, Part 68, and PSTN RJ11 A six-pin, two-conductor physical interface for connecting single-line telephone sets to the public switched telephone network (PSTN) See also PSTN and RJ 74570c 18. qxd RJ45 9/12/07 12:39 AM Page 420 420 RJ45... extensively on business, conducting business warfare on the road The term originates in the Mel Gibson movie Mad Max 2:The Road Warrior (1 981 ) Robustness Principle Also known as Postel’s Law A principle stated by Jon Postel in RFC 793 (1 981 ) and again in RFC 1122 (1 989 ), Requirements for Internet Hosts – Communications Layers.The Robustness Principle states,“Be liberal in what you accept, and conservative... by various organizations, including the Electronic Industries Alliance (EIA) RS-3 28, for example is a set of standards for facsimile machines published by the EIA See also EIA 2 Reed-Solomon A block coding algorithm for forward error correction (FEC) See Reed-Solomon RS-232 See EIA-232 RS-3 28 (Recommended Standard 3 28) A set of standards for facsimile (fax) machines published by the Electronic Industries... for providing endto-end network transport functions suitable for applications transmitting real-time data, such as audio, 74570c 18. qxd 423 9/12/07 12:39 AM Page 423 rule of thumb video, or simulation data, over multicast or unicast network services Defined in IETF RFC 188 9 (1996), RTP provides end-to-end delivery services including payload type identification, sequence numbering, and timestamping In . description of SS7Telephone User Part (TUP) Q .82 4.1 ISDN basic and primary rate access Q .82 4.2 ISDN supplementary services Q .82 4.3 ISDN optional user facilities Q .82 4.4 ISDN teleservices Q.921 ISDN user-network. Texas) Pacific Bell (California) Nevada Bell (Nevada) New England Telephone (Massachusetts, Maine, New Hampshire, Rhode Island, and Vermont) New York Telephone (New York) Bell Operating Companies (Primary States. patented by Christopher Sholes in 186 8 for use with the first mechanical typewriter, which he also invented. Sholes sold the patent rights to Remington in 187 3.The original layout was in alphabetical