0-99

0 - The “in fact” standard number to dial for reaching a local phone company operator or answering service.

0080 - A dial prefix for toll free services in some countries. See also 800 Service, area code, and toll free service.

020 - A dial prefix for toll free services in some countries. See also 800 Service, area code, and toll free service.

0500 - A dial prefix for toll free services in some countries. See also 800 Service, area code, and toll free service.

0800 - A dial prefix for toll free services in some countries. See also 800 Service, area code, and toll free service.

0B+D - Referring to a variation of the ITU-T specification for ISDN basic rate interface (BRI), also known as basic rate access (BRA). BRI supports two bearer (B) channels and one data (D) channel. Intended for applications that do not require an information-bearing channel for voice or data transmission, 0B+D supports zero bearer (B) channels and one data (D) channel.The D channel is designated for signalling and control purposes, but also can be used for low-speed packet data applications such as transaction processing, credit card verification, and telemetry. See also 1B+D, BRI, and ISDN.

1-Pair Gas Lightning Protector - Used in Siecor telephone network interfaces.

1-persistent carrier sense multiple access (1-Persistent CSMA) - See CSMA.

1-Persistent CSMA (1-Persistent Carrier Sense Multiple Access) - See CSMA.

1.5-way paging - A variation of two-way paging, which supports guaranteed message delivery, as the network does not attempt to download messages until such time as the pager is within range, turned on, and has enough memory to support the download. The general location of the pager is communicated upstream, so the messages can be downloaded to the system antennas supporting that particular geographic area, rather than being broadcast across the entire paging network. Once downloaded successfully, the pager acknowledges to the network the receipt of the page. See also antenna, download, two-way paging, and upstream.

1/3 FEC - A type of forward error correction (FEC) used in Bluetooth networks.The Bluetooth packet header is 16 bits in length, but is repeated three times to ensure that there are no errors in header transmission.As a result, the header consumes a total of 54 bits.This approach is overhead-intensive, but reliable. See also Bluetooth, FEC, header, overhead, and packet.

1+ Dialing - Synonymous with Direct Distance Dialing (DDD). See DDD.

1+ WATS - See Virtual WATS.

10 Gigabit Attachment Unit Interface (XAUI) - See XAUI.

10 Gigabit Ethernet (10GbE) - Standardized by the IEEE as 802.3ae, 10GbE uses the same frame format and medium access control (MAC) layer as predecessor Ethernets. 10GbE runs only in full-duplex (FDX) mode, which makes collision control unnecessary.The primary line coding technique used in both 10GbE and GbE is 8B/10B, which carries a 25 percent overhead penalty, thereby forcing the system to run at a signaling rate of 125 Gbps. Some 10GbE systems use the more recently developed 64B/66B line coding, which is similar but much more efficient.Although the signaling rates discourage the use of copper transmission media, 802.3ae currently specifies 10GBase-T for short distances using Cat 6 and Cat 7 twisted pair. Fiber optic systems are preferable, however, and 802.3ae specifies a number of options, including 10GBase-SR, SW; 10GBase-LR, LW; 10GBase-ER, EW; and 10GBase-LX4. 10GbE has application in the backbones of very bandwidth intensive local area networks (LANs) and metropolitan area networks (MANs). See also 10GBase-CX4; 10GBase-SR, SW; 10GBase-LR, LW; 10GBase-ER, EW; 10GBase-LX4; 64B/66B; 802.3ae; 8B/10B; Cat 6; Cat 7; IEEE; LAN, line coding; MAC; MAN; overhead; and signaling rate.

10/100 (Ten/One-Hundred) - A reference to the newer family of Ethernet as a whole. 10BaseT is 10 Mbps, 100BaseT is 100 Mbps, and 10BaseF is 100 Mbps over fiber optic. It is also referred to as 802, 10/100. Because the 10BaseT and 100BaseT can interconnect, the network as a whole is frequently called Ten-One Hundred network. For a diagram of the IEEE 802 Ethernet family, see IEEE 802 Ethernet.

100-Pair Cable UTP - Telephone twisted copper pair commonly used in building horizontal distribution or in riser systems, (connectivity between floors). The cable is 100 UTP (Unshielded Twisted Pair) plenum.

1000Base-LX (1000 Mbps; Baseband; Long range) - The IEEE 802.3z media specifications for Gigabit Ethernet (GbE) transmission over multimode fiber (MMF) and single-mode fiber (SMF), using a wavelength of 1300 nm and 1310 nm, respectively.The modal bandwidth for the MMF options ranges from 400 MHz/km to 500 MHz/km, and maximum distance is 550 meters.The letter X indicates that 8B/10B signal encoding technique is used. See 802.3z for comparisons. See also 8B/10B,IEEE,MMF,modal bandwidth, and wavelength.

1000Base-SX (1000 Mbps; Baseband; Short range) - The IEEE 802.3z media specifications for Gigabit Ethernet (GbE) transmission over multimode fiber (MMF) with a core diameter of either 50µ or 62.5µ, using a wavelength of 850 nm.The modal bandwidth ranges from 160 MHz/km to 500 Mhz/km, and maximum distance ranges from 220 meters to 550 meters.The letter X indicates that 8B/10B signal encoding technique is used. See 802.3z for comparisons. See also 8B/10B, IEEE, MMF, modal bandwidth, and wavelength.

1000Base-T (1000 Mbps; Baseband;Twisted pair) - An IEEE standard (802.3ab, 1999) similar in concept to the predecessor 10/100Base-T, 1000Base-T translates to 1000 Mbps (theoretical transmission rate) Baseband (one transmission at a time over a single, shared channel), over Twisted pair media.The original specifications called for Cat 5 cable to support Gigabit Ethernet (GbE) over four pairs and distances up to 100 meters. Cat 6 cabling specifications include unshielded twisted pair (UTP), shielded twisted pair (STP), and screened twisted pair (ScTP) rated at 250 MHz over distances up to 220 meters. See also 10Base-T, 100Base-T, baseband, Cat 5, Cat 6, channel, Ethernet, GbE, hub, IEEE, repeater, ScTP, standard, STP, transmission rate, and UTP.

100Base-T4 - A 100Base-T extension that specifies Cat 3 or better unshielded twisted pair (UTP), operating in either half-duplex (HDX) or full duplex (FDX) over distances up to 100 meters. See also 100Base-T, Cat 3, FDX, HDX, and UTP.

100BaseFX - A 100-Mbps baseband (single channel) Fast Ethernet specification using two strands of multimode fiber-optic per link. To guarantee proper signal timing, a 100BaseFX link cannot exceed 1312 feet (400 meters) in length. It is based on the IEEE 802.3 standard. See also 100BaseX, Fast Ethernet, and IEEE 802.3.

100BaseT - 802.3 ethernet 100Mb/s LAN standard. See Ethernet. 100BaseT4 A 100-Mbps baseband (single channel) Fast Ethernet specification using four pairs of Category 3, 4, or 5 UTP wiring. To guarantee proper signal timing, a 100BaseT4 segment cannot exceed 328 feet (100 meters) in length. It is based on the IEEE 802.3 standard. See also Fast Ethernet and IEEE 802.3. For a diagram of the IEEE Ethernet family, see IEEE 802 Ethernet.

100BaseTX - A 100-Mbps baseband (single channel) Fast Ethernet specification using two pairs of either UTP or STP wiring. The first pair of wires is used to receive data; the second pair is used to transmit. To guarantee proper signal timing, a 100BaseTX segment cannot exceed 328 feet (100 meters) in length. It is based on the IEEE 802.3 standard. See also 100BaseX, Fast Ethernet, and IEEE 802.3.

100BaseX - 100-Mbps baseband Fast Ethernet specification that refers to the 100BaseFX and 100BaseTX standards for Fast Ethernet over fiber optic cabling. Based on the IEEE 802.3 standard. See also 100BaseFX, 100BaseTX, Fast Ethernet, and IEEE 802.3.

100VG - (AnyLAN) 100-Mbps Fast Ethernet and token-ring media technology using four pairs of Category 3, 4, or 5 UTP cabling. This transport technology, developed by Hewlett-Packard, can operate on existing 10BaseT Ethernet networks. Based on the IEEE 802.12 standard. See also IEEE 802.12.

1010XXX - The number format in the United States for accessing an interexchange carrier (IXC) for casual callers without a presubscription agreement with an IXC and for dial-around purposes in the event that the presubscribed carrier is suffering from network congestion or a failure.The format originally was 10XXX, but competition encouraged the formation of so many IXCs that the format had to be expanded. See also IXC and presubscription.

101B Closure - A closure/housing used to protect service wire splices and inside wiring splices.

10Base2 (10 Mbps; Baseband; 200 meters) - The IEEE standard (1986) for relatively thin coaxial cable in support of Ethernet transmission. Also known as ThinNet (Thin EtherNet), 10Base2 translates to 10 Mbps (theoretical transmission rate), Baseband (one transmission at a time over a single, shared channel), and 200 meters maximum segment length (actually 185 meters, rounded up). The thinner cable is less costly to acquire and deploy than earlier 10Base5, although its performance is less in terms of transmission distance due to increased attenuation. See also 10Base2, attenuation, baseband, channel, coaxial cable, Ethernet, IEEE, and transmission rate.

10Base5 (10 Mbps; Baseband; 500 meters) - The IEEE standard (1983) for coaxial cable assemblies in support of Ethernet transmission.Also known as ThickNet (Thick EtherNet), 10Base5 specifies traditional thick coaxial cable, often known affectionately as goldenrod, referring to its high cost, high value, and the yellow cable sheath used by some manufacturers. Other manufacturers used orange cable sheaths for thick coax, giving rise to the term orange hose. 10Base5 translates to 10 Mbps (theoretical transmission rate), Baseband (one transmission at a time over a single, shared channel), and 500 meters maximum segment length. See also 10Base2, baseband, channel, coaxial cable, Ethernet, IEEE, and transmission rate.

10BaseF - A 10-Mbps Ethernet specification that has three subcategories, or accessories; 10BaseFB, 10BaseFL, and 10BaseFP. These standards are for Ethernet over fiber-optic cabling. See also 10BaseFB, 10BaseFL, 10BaseFP, and Ethernet.

10BaseFB - An accessory to the 10-Mbps Ethernet specification 10BaseFP that uses fiber-optic cabling. 10BaseFB is part of the IEEE 10BaseF specification. It is not used to connect user stations, but instead provides a synchronous signaling backbone that allows additional segments and repeaters to be connected to the network. 10BaseFB segments can be up to 1.24 miles (2000 meters) long. See also 10BaseF and Ethernet.

10BaseFL - A 10-Mbps Ethernet specification using fiber-optic cabling. 10BaseFL is part of the IEEE 10BaseF specification and, although able to interoperate with FOIRL, it is designed to replace the FOIRL specification. 10BaseFL segments can be up to 3280 feet (1000 meters) long if used in conjunction with FOIRL, and up to 1.24 miles (2000 meters) if 10BaseFL is used exclusively. See also 10BaseF, Ethernet, and FOIRL.

10BaseFP - A 10-Mbps fiber-passive baseband (single channel) Ethernet specification using fiber-optic cabling. 10BaseFP is part of the IEEE 10BaseF specification. It organizes a number of computers into a star topology without the use of repeaters. 10BaseFP segments can be up to 1640 feet (500 meters) long. See also 10BaseF and Ethernet.

10BaseT - 802.3 ethernet 10Mb/s LAN standard. See Ethernet, and IEEE 802 Ethernet.

10Broad36 (10 Mbps, Broadband, 3600 meters) - The IEEE standard for a broadband LAN, 10Broad36 derives multiple channels through frequency division multiplexing (FDM). The aggregate bandwidth is 550 MHz and the FDM channels are 14 MHz wide, with 4 MHz guardbands.The modulation technique is differential phase shift keying (DPSK).The total span is a maximum of 3600 meters, and can be divided into multiple segments, each with a maximum distance of 1800 meters. 10Broad36 is considered obsolete. See also bandwidth, broadband, channel, DPSK, FDM, guard band, IEEE, LAN, and modulation.

10GBase-CX4 (802.3ak) - An IEEE standard for twinaxial cable patch cord assemblies in support of 10G Ethernet over distances of up to 50 feet.The standard specifies the same connectors used in 4X InfiniBand and the XAIU (10 Gigabit Attachment Unit Interface) specified in 802.3ae, spreading the 10 Gbps datastream over four paired transmitters and receivers, with each pair operating differentially over a thin twinaxial cable. As the 10 Gbps is spread over the twinax bundle, each cable supports a data rate of 2.5 Gbps over a 3.125 GHz channel with 8B10B coding.This approach requires four differential pairs in each direction, for a total of eight twinax cables per assembly. The tight operating tolerances require that the cable assemblies be factory-terminated. Also, and in consideration of the impact of resistance on signal attenuation, the diameter of the center conductors is sensitive to cable length.At a distance of 20 feet, the outside diameter a CX-4 cable is approximately the same as that of a Cat 5e cable. See also 8B/10B, InfiniBand, twinaxial cable, and XAUI.

10GBase-ER, EW (10 Gbps; Baseband; Extended Range, Long Wavelength) - The IEEE 802.3ae media specification for 10 Gbps Ethernet (10GbE) transmission over single-mode fiber (SMF) with a core diameter of 8.3µ, 9µ, or 10µ; using a wavelength of 1550 nm; and a maximum distance of 40 kilometers. The letter R indicates that 64B/66B signal encoding is used.The W refers to the WAN Interface Sublayer (WIS) that enables compatibility between 10GbE equipment and SONET long haul equipment in a LAN-to-WAN interface scenario. See also 64B/66B, 802.3ae, IEEE, SMF, and wavelength.

10GBase-LR, LW (10 Gbps; Baseband; Long Range, Long Wavelength) - The IEEE 802.3ae media specification for 10 Gbps Ethernet transmission over single-mode fiber (SMF) with a core diameter of 8.3µ, 9µ, or 10µ; using a wavelength of 1310 nm; and a maximum distance of 10 kilometers.The letter R indicates that 64B/66B signal encoding is used. See also 64B/66B, 802.3ae, IEEE, SMF, and wavelength.

10GBase-LX4 (10 Gbps; Baseband; Long range times 4 wavelengths) - The IEEE 802.3ae media specifications for 10 Gbps Ethernet (10GbE) transmission over optical fiber, multiplexing four wavelengths through coarse wavelength division multiplexing (CWDM).There are two specifications, one of which is for multimode fiber (MMF) with a core diameter of 50µ or 62.5µ, using a wavelength of 1310 nm, with a modal bandwidth of 500 MHz/km; using a wavelength of 1550 nm; and a maximum distance of 40 kilometers.The second specification is for single-mode fiber (SMF) with a core diameter of 10µ, using a wavelength of 1310 nm, and with a maximum distance of 10 kilometers. See also 802.3ae, CWDM, IEEE, MMF, modal bandwidth, SMF, and wavelength.

10GBase-SR, SW (10 Gbps; Baseband; Short Range, Short Wavelength) - The IEEE 802.3ae media specification for 10 Gbps Ethernet (10GbE) transmission over multimode fiber (MMF) with a core diameter of 62.5 Ì, using a wavelength of 850 nm, with a modal bandwidth of 160 MHz/km, and a maximum distance of 160 meters.The letter R indicates that 64B/66B signal encoding is used.The W refers to the WAN Interface Sublayer (WIS) that enables compatibility between 10GbE equipment and SONET long haul equipment in a LAN-to-WAN interface scenario. See also 64B/66B, 802.3ae, IEEE, MMF, modal bandwidth, and wavelength.

10GBase-T - An IEEE standard (802.3an, 2006) for 10 Gigabit Ethernet (10GbE). 10GBase-T translates to 10 Gbps (theoretical transmission rate), Baseband (one transmission at a time over a single, shared channel), over Twisted pair media. Specifically, 10GBase-T specifies Cat 6 cable for distances up to at least 55 meters, although distances generally can be extended to 100 meters. Cat 7 cable is expected to extend those distances even farther. See also baseband, Cat 6, Cat 7, channel, Ethernet, IEEE, standard, STP, and transmission rate.

10GbE (10 Gbps Ethernet) - See 10 Gigabit Ethernet.

10GigE (10 Gbps Ethernet) - See 10 Gbps Ethernet.

10XXX - See 1010XXX.

110 Punch Tool - A tool used to terminate solid twisted-pair copper wire on AT&T 100 termination blocks.

110 Termination Block - Also called AT&T 110 (“one-ten”) blocks. Devices used to mount twisted-pair wire so that different devices in a network can be cross connected easily.

128-QAM - A variation on the quadrature amplitude modulation (QAM) signal modulation scheme. 128-QAM yields 128 possible signal combinations, with each symbol representing seven bits (2⁷= 128). The yield of this complex modulation scheme is that the transmission rate is seven times the signaling rate. See also amplitude, bit, modulation, QAM, signal, signaling rate, symbol, and transmission rate.

1394 - The IEEE specification for a data transport bus between a host computer and peripherals, such as high-density storage devices and high-resolution still and video cameras, and is designed to eliminate the bottleneck at the serial port of a LAN-attached PC. 1394 increases the speed of the Small Computer System Interface (SCSI) to100, 200, and 400 Mbps to support take full advantage of high speed LANs. A single 1394 port can support up to 63 peripherals over a six-conductor cable up to 4.5 meters in length, and as many as 16 cables can be daisy-chained to extend the total length to as much as 72 meters. IEEE 1394 is known as FireWire in Apple Computer terminology. See also bus, daisy chain, host, LAN, PC, peripheral, and SCSI.

145A Test Set - An analog telephone cable test set that measures the length of twisted pairs, and tests for grounds and shorts. This test set can also send a tone.

16-QAM - A variation on the quadrature amplitude modulation (QAM) signal modulation scheme that splits the carrier into two waveforms that are 90° out of phase, and specifies two possible amplitude values for each of eight phase shifts separated by 45° (0°, 45°, 90°, 135°, 180°, 225°, 270°, and 315°).Thereby, each symbol carries one of 16 possible signal combinations and represents four bits (2⁴= 16).At a signaling rate of 2400 baud, for example, this quadbit modulation scheme yields a transmission rate of 9600 bps. 16-QAM is specified in the ITU-T V.29 Recommendation and the IEEE 802.11a (Wi-Fi5) standard. See also 802.11a, amplitude, carrier, ITU-T,modulation, QAM, quadbit, signal, signaling rate, symbol, transmission rate, V series, and waveform.

16-QPSK - A variation on the quadrature phase shift keying (QPSK) signal modulation scheme, 16-QPSK is a quadbit technique that impresses four bits on a baud by defining 16 phase shifts. See also baud, bit, modulation, phase, QPSK, and signal.

1A - The first key telephone system (KTS), the 1A was a hardwired system comprising components physically wired together by hand. Developed by the Bell System and first marketed in 1938, the 1A was an electromechanical system. See also 1A1, 1A2, and KTS.

1A1 - The A hardwired electromechanical key telephone system (KTS) comprising components physically wired together by hand. Developed by the Bell System and first marketed in 1953, 1A1 systems superseded the 1A systems, adding a few features, including line status lamps that lit steadily to indicate a line in use and flashed to indicate a line on hold. 1A1 systems were superseded, in turn, by 1A2 systems. See also 1A, 1A2, and KTS.

1A2 - A modular electromechanical key telephone system (KTS) comprising hardwired circuit packs that plugged into a pre-built chassis that included cable connectors for attaching station equipment. Developed by the Bell System and first marketed in 1963, 1A2 systems were an improvement over earlier 1A and 1A1 systems, as they allowed the addition of a limited number of enhanced features through common control cards in the form of circuit packs. Electronic common control (ECC) systems made 1A2 systems obsolete long ago. See also 1A, 1A1, ECC, and KTS.

1B+D - Referring to a variation of the ITU-T specification for ISDN basic rate interface (BRI), also known as basic rate access (BRA). BRI supports two bearer (B) channels and one data (D) channel. Intended for applications that require only one information-bearing channel, perhaps for voice or datatran smission, 1B+D supports one bearer (B) channel and one data (D) channel.The D channel is designated for signalling and control purposes, but also can be used for low-speed packet data applications such as transaction processing, credit card verification, and telemetry. See also 0B+D, BRI, and ISDN.

1Base5 (1 Mbps; Baseband; 500 meters) - The IEEE standard (mid-1980s) for Ethernet transmission over Cat 3, Cat 4, or Cat 5 unshielded twisted pair (UTP) cable. 1Base5 translates to 1 Mbps (theoretical transmission rate), Baseband (one transmission at a time over a single, shared channel), and 500 meters maximum segment length.The predecessor to 10Base-T, 1Base5 is considered obsolete. See also 10Base-T, baseband, Cat 3, Cat 4, Cat 5, channel, Ethernet, IEEE, and transmission rate.

1FB - A service code that defines a flat-rate business telephone line. A line where a subscriber can make unlimited local calls and not be billed extra, regardless of the number of calls or their duration.

1FR - A service code that defines a flat-rate residential telephone line. A line where a subscriber can make unlimited local calls and not be billed extra, regardless of the number of calls or their duration.

1G (1st Generation) - In cellular radio, referring to analog systems such as Advanced Mobile Phone System (AMPS), Narrowband AMPS (N-AMPS), Nordic Mobile Telephone (NMT), and Total Access Communications System (TACS). See also 2G, 2.5G, 3G, AMPS, analog, cellular radio, N-AMPS, NMT, and TACS.

1MB - A service code that defines a measured-rate business telephone line. A line where the subscriber is billed either for the number of calls made or by the minute.

1MR - A service code that defines a measured-rate business telephone line. A line where the subscriber is billed either for the number of calls made or by the minute.

1xEV-DO (one carrier EVolution-Data Optimized) - A high data rate (HDR) version of Code Division Multiple Access 2000 (CDMA2000) that employs 16-QPSK modulation in support of a peak data rate of 2.4 Mbps on the downlink and 153 kbps on the uplink. In a fully loaded cell, 1xEV-DO supports average aggregate throughput of 4.1 Mbps on the downlinks and 660 kbps on the uplinks.1xEV-DO can run in any band and can coexist in any type of network. See also 16-QPSK, CDMA2000, downlink, modulation, throughput, and uplink.

1xRTT (one times Radio Transmission Technology) - The initial version of CDMA2000, with one times referring to standard channel width). See CDMA2000.

2 Binary 1 Quaternary (2B1Q) - See 2B1Q.

2-Line Network Interface - Old style with interchangeable lightning protectors. The white paint on the tops of the protectors indicates “gas type,” rather than the carbon type.

2.5G (Two point Five Generation) - In cellular radio, referring to digital systems and standards that are midway, or transitional, between 2G and 3G. Such systems include Enhanced Data rates for GSM Evolution (EDGE), General Packet Radio Service (GPRS), High-Speed Circuit Switched Data (HSCSD), and Universal Mobile Telecommunications System (UMTS). See also 2G, 3G, cellular radio, digital, EDGE, GPRS, and HSCSD.

2001: A Space Odyssey - The movie script was written by Arthur C. Clarke and Stanley Kubrick, and based on Clarke’s short story “The Sentinel.” In telecommunications circles, Clarke is better known as the inventor of communications satellites. He publicly unveiled the concept in an article entitled “ExtraTerrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage,” published in Wireless World in February 1945. See also Clarke, Sir Arthur C.

218–219 MHz Service - In the United States, a short distance, interactive licensed communications service for the transmission of information, product, and service offerings.The service is licensed in two blocks, with Block A operating in the 218.0–218.5 MHz band and Block B in the 218.5–219.0 Mhz band. A system comprises one or more cell transmitter stations (CTSs) and response transmitter units (RTSs).Anticipated applications include ordering goods and services offered by television services, viewer polling, remote meter reading, vending machine inventory control, and cable television theft deterrence. The Federal Communications Commission (FCC) includes the service in the family of personal radio services.The service formerly was known as Interactive Video and Data Services (IVDS), although the bandwidth is insufficient for video transmission. See also bandwidth, FCC, and personal radio services.

23B+D - Synonymous with primary rate interface (PRI). Referring to the ITU-T specification for an ISDN interface supporting 23 bearer (B) channels and 1 data (D) channel. 23B+D is compatible with T1 and J-1, and is used in North America and Japan. See also ISDN and PRI.

25-Pair Modular Splice - Used in a modular splice tool to splice PIC telephone cable.

2500 Set - A frequently referred to telephone because it is known to be “noncordless,” to have a switch-hook that is not built into the handset, and to have a mechanical bell ringer equivalence between 0.8 and 1. The 2500 was the Western Electric model number of this once most widely used telephone set. A “2500 telephone” is also a reference to a traditional analog telephone.

256-QAM - A variation on the quadrature amplitude modulation (QAM) signal modulation scheme. 256-QAM yields 256 possible signal combinations, with each symbol representing eight bits (2⁸= 256). The yield of this complex modulation scheme is that the transmission rate is eight times the signaling rate. In the United States, 256-QAM is used in digital CATV applications. See also amplitude, bit, modulation, QAM, signal, signaling rate, symbol, and transmission rate.

258A Adapter - Adapter used to connect 25-pair Amphenol cables to RJ45 patch cords.

25PR Connector - Also called an Amphenol, Amp connector, P connector (male), or C connector (female).

25PR PVC - Common telephone cabling used for horizontal and vertical wiring in buildings.

267A Adapter- Also called a one-line splitter. This is a simple “T” adapter that splits a single jack into two.

267C Adapter - Also called a two-line splitter. This adapter is frequently confused with a 267A adapter, which is a one-line splitter. The 267C unit is designed to split two separate lines (with two separate phone numbers) out of one RJ-11 jack. See also 267A.

2B+D - Synonymous with basic rate interface (BRI) and basic rate access (BRA). Referring to the ITU-T specification for an ISDN interface supporting two bearer (B) channels and one data (D) channel. See also ISDN and BRI.

2B1Q (2 Binary 1 Quaternary) - A line coding technique, with echo cancellation, used in North America for ISDN basic rate interface (BRI). 2B1Q is a form of pulse amplitude modulation (PAM) that uses four (i.e., quaternary) levels of amplitude (i.e., voltage), each of which represents two adjacent bits in a bit stream, and is accomplished by varying the voltage at nominal levels of ±1 (actually 0.833) and ±3 (actually 2.5) volts, as illustrated in the accompanying figure. As 2B1Q impresses two bits on each baud, the baud rate is halved, and a baud rate of 80 kilobaud will support a signaling rate of 160 kbps. Because statistics force the line voltage to be positive half the time and negative half the time, on average, the signal power lies at a frequency of 40 kHz, which is half the baud rate. 2B1Q also is the electrical line coding technique used in high-bit-rate digital subscriber line (HDSL). 2B1Q also is known as 4-level pulse amplitude modulation (4 PAM). In European and many other countries, the line coding technique employed is 4 Binary 3 Ternary (4B3T). See also 4B3T, baud rate, bit rate, BRI, echo cancellation, HDSL, ISDN, and PAM.

2FR - A service code for a flat-rate party line with two subscribers. For more info, see Selective Ringing Module and Party Line.

2G (2nd Generation) - In cellular radio, referring to systems based on the first digital standards, including Digital-AMPS (D-AMPS), Global System for Mobile Communications (GSM), Personal Digital Cellular (PDC), and Personal Communications System (PCS). See also cellular radio, D-AMPS, digital, GSM, PDC, and PDH.

30B+D - Synonymous with primary rate access (PRA). Referring to the ITU-T specification for an ISDN interface supporting 30 bearer (B) channels and one data (D) channel. 30B+D is compatible with E-1, and is used outside of North America and Japan. See also ISDN and PRA.

3720 - A common reference for an IBM 3720 communications controller. For more information and a diagram, see Communications Controller.

3725 - A common reference for an IBM 3725 communications controller. For more information and a diagram, see Communications Controller.

3745 - A common reference for an IBM 3745 communications controller. For more information and a diagram, see Communications Controller.

3746 - A common reference for an IBM 3746 communications controller. For more information and a diagram, see Communications Controller.

3FR - A service code for a flat-rate party line with three subscribers. For more information, see Selective Ringing Module and Party Line.

3G (3rd Generation) - Referring to digital cellular radio systems and standards that fit under the umbrella of International Mobile Telecommunications-2000 (IMT-2000), an ITU initiative for a twentyfirst century wireless network architecture. Specifications include 128/144 kbps for high-mobility applications, 384 kbps for pedestrian speed (i.e., walking speed) applications, and 2.048 Mbps for both fixed WLL (Wireless Local Loop) and in-building applications such as WLANs (Wireless LANs). 3G systems include Universal Mobile Telecommunications System (UMTS), also known as Wideband CDMA (W-CDMA), Code Division Multiple Access 2000 (CDMA2000), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). See also CDMA2000, cellular radio, IMT-2000, ITU-T, TDSCDMA, UMTS, W-CDMA, WLAN, and WLL.

3GPP (3rd Generation Partnership Project) - A collaboration that brings together a number of national standards parties to develop 3G mobile systems based on evolved Global System for Mobile Communication (GSM) core technologies and standards.The scope includes maintenance and development of General Packet Radio Service (GPRS), Enhanced Data rates for GSM Evolution (EDGE), and Universal Mobile Telecommunications System (UMTS). For contact information, see Appendix A. See also 3G, EDGE, GPRS, GSM, standards, and UMTS.

3rd Generation Partnership Project (3GPP) - See 3GPP.

3x - In cellular radio systems, also known as IS-2000-A.An enhancement to CDMA2000 that uses three cdmaOne carriers for total bandwidth of 3.75 MHz. See also bandwidth, carrier, cellular radio, CDMA2000, and cdmaOne.

4 Binary 3 Ternary (4B3T) - See 4B3T.

4 Pair - Is 4-pair, PVC (Polyvinyl Chloride Jacketed) UTP (Unshielded Twisted Pair).

4 PAM (4-level Pulse Amplitude Modulation) - More commonly known as 2 Binary 1 Quaternary (2B1Q). See 2B1Q.

4-level pulse amplitude modulation (4 PAM) - More commonly known as 2 Binary 1 Quaternary (2B1Q). See 2B1Q.

419 Advance Fee Fraud - Also known as the Nigerian Connection or Nigerian Scam. Named after a formerly relevant section of the Criminal Code of Nigeria, where the scam originated and where most activity still originates.The target receives an unsolicited e-mail (i.e., spam) indicating something along the lines that some member of a previous government or royal family of Nigeria or some other West African nation (or now some country in the Middle East or some other exotic place) has had substantial funds frozen by the current government and cannot access or expatriate those funds.The recipient of the e-mail can help by wiring $5,000 or so as an advance fee, transfer fee, or performance bond, for which the target will receive a much larger sum of money. Sometimes the offer is for the target to accept a cashier’s check for $100,000 and return $75,000 of that via wire transfer, but keep the rest as a fee. The $100,000 cashier’s check is bogus, of course, while the $75,000 wire transfer is real. Sometimes the scam involves alleged overinvoicing or double-invoicing, with the party receiving the fake cashier’s check asked to cash it and wire the overage back to the scam artist, less a handsome fee for the inconvenience, of course.This sort of fraudulent activity has gone on at least since the 1970s through the postal service and via fax machines, but is much more prevalent these days due to the widespread reach and ease of use of Internet e-mail.There are endless variations on the scam, and not all originate in Nigeria, although many originate in West African countries. See also e-mail, Internet, and spam.

49A Ready Access Terminal - A common terminal found in an outdoor aerial copper telephone plant. These terminals will soon be very uncommon because better splice closures and weatherproof access devices have come to market. The 49A is a ready-access pic terminal, which means that the copper pairs are not pre-spliced to binding posts within the cover. To install service from one of these terminals, a technician splices directly into the pair. These older terminals have been a mainstay for telephone companies for decades because they are inexpensive and flexible in making service changes.

4B/5B (4 Bits/5 Bits) - A line coding technique used in 100Base-TX, 100Base-FX, and Fiber Distributed Data Interface (FDDI) LANs. 4B/5B refers to the fact that every nibble of 4 Bits of data is encoded into 5 Bits of signal. Specified by the American National Standards Institute (ANSI) X3T9.5 committee recommendation for FDDI, 4B/5B is sometimes referred to as block coding, as a block of data bits is mapped into a block of signaling bits.This approach increases the number of bit patterns from 16 (2⁴= 16) to 32 (2⁵ = 32), which means that each five-bit signal block includes enough clocking pulses and signal transitions to synchronize the network. 4B5B also provides some level of error detection. So, the signaling rate must be 125 MHz to support a unipolar code (such as that used with classic 10 Mbps Ethernet) with a signaling rate of 125 Mbps, which, in turn, supports a data rate of 100 Mbps.To address this issue, 100Base-TX uses an intermediate step known as multi-level transition (MLT) that reduces the carrier frequency to only 31.25 MHz. See also 100Base-TX, 100Base-FX, 8B/10B, ANSI, block coding, carrier, FDDI, LAN, MLT, quadbit, synchronize, and unipolar.

4B/5B Coding (4-Bit/5-Bit Coding) - A physical layer coding/compression method used by the FDDI (Fiber-Distributed Data Interface) for 100-Mbps physical layer applications. In applications where the ATM cell format is transmitted over 4B/5B FDDI, an additional byte of overhead results from the encoding and cell delimiting method. However, the net transmission rate remains the same because of the compression. The mechanics of this compression method are the same (yet a smaller version) of 8B/10B coding. See also 8B/10B Coding.

4B3T (4 Binary 3 Ternary) - A line coding technique used in European and many other countries outside North America for ISDN basic rate access (BRA). 4B3T combines four bits to represent one ternary signal state. Therefore, the baud rate is three-fourths of the signaling rate, and ISDN BRA at 160 kbps requires a baud rate of 120 KBaud. 4B3T yields shorter ISDN transmission distances than 2B1Q, but distances in Europe and elsewhere often are much shorter between the central office exchange (COE) and the customer premises. See also 2B1Q, baud rate, BRI, COE, ISDN, and signaling rate.

4FR - A service code for a flat-rate party line with four subscribers. For more information, see Selective Ringing Module and Party Line.

500 Service - In the North American Numbering Plan (NANP), 500 service is intended to support premium follow-me personal communications services, which are defined as a set of capabilities that allows some combination of personal mobility, terminal mobility, and service profile management. 500 service is designed to allow the subscriber to select from a menu of services and to initiate or receive calls at any terminal, fixed or mobile, across networks, regardless of geographic carrier. 500 numbers can be protected by the personal identification number (PIN) for network and feature access.As 500 numbers are not locationspecific and are transportable across carriers and carrier domains, one number theoretically can be retained for life. 500 service numbers are in the format 500-NXX-XXXX. See also NANP.

512-QAM - A variation on the quadrature amplitude modulation (QAM) signal modulation scheme. 512-QAM yields 512 possible signal combinations, with each symbol representing nine bits (2⁹= 512). The yield of this complex modulation scheme is that the transmission rate is nine times the signaling rate. See also amplitude, bit, modulation, QAM, signal, signaling rate, symbol, and transmission rate.

6-Pair Can - A termination or splicing enclosure designed especially for 6-pair aerial or buried service wire. 6-pair cans are available with lightning protectors (protected 6-pair can).

64-QAM - A variation on the quadrature amplitude modulation (QAM) signal modulation scheme. 64-QAM yields 64 possible signal combinations, with each symbol representing six bits (2⁶= 64). The yield of this complex modulation scheme is that the transmission rate is six times the signaling rate. In the United States, 64-QAM is used in digital CATV applications and is specified in the IEEE 802.11a (Wi-Fi5) standard. See also 802.11a, amplitude, bit, CATV, modulation, QAM, signal, signaling rate, symbol, and transmission rate.

64B/66B - A block line coding technique in which 8 data octets comprising 64 data bits is encoded into a block of 66 signaling bits prior to transmission.The data are scrambled in a self-synchronous scrambler function that is intended to even the distribution of 1s and 0s and thereby both achieve DC balance on the line and prevent intersymbol interference. See also balance, bit, block coding, line coding, DC, intersymbol interference, octet, and synchronize.

66 Block - The 66M150 termination block is used to terminate twisted-pair wire on distribution frames and any other solid 22 to 24 wiring application.

8-level vestigial sideband (8-VSB) - See 8-VSB.

8-Phase Shift Keying (8-PSK) - See 8-PSK.

8-PSK (8-Phase Shift Keying) - A signal modulation technique that involves eight levels of phase shift and, therefore, supports three bits per symbol. 8-PSK is specified in Enhanced General Packet Radio Service (EGPRS), the packet-switched transmission mode of Enhanced Data rates for GSM Evolution (EDGE), a 2.5G cellular radio standard. See also 2.5G, bit, cellular radio, EDGE, EGPRS, modulation, phase, PSK, signal, and symbol.

8-VSB (8-level vestigial sideband) - A radio frequency (RF) modulation technique specified by the Advanced Television Systems Committee (ATSC) for use in digital television (DTV), including both high definition television (HDTV) and standard definition television (SDTV). 8-VSB employs 8 levels of amplitude modulation (AM) to achieve a bit rate of 19.28 Mbps over a 6 MHz terrestrial broadcast channel. See also AM, ATSC, bit rate, broadcast, channel, DTV, HDTV, RF, SDTV, and VSB.

80/20 Rule - See Pareto principle.

800 Service - The original area code prefix for toll free long distance services in the United States was 800.As the service gained in popularity during the 1990s, the numbering scheme was expanded to include 866, 877, and 888 area codes. See also area code and toll free service.

802.1 - The IEEE Working Group that concerns itself with standards and recommendations in the areas of architecture and internetworking of local area networks (LANs) and metropolitan area networks (MANs), security, network management, and protocol issues above the Data Link Layer. See also Data Link Layer, IEEE, LAN, and MAN.

802.10 - The IEEE standards for Interoperable LAN/MAN Security (SILS).This standard was withdrawn in 2004, and the working group is currently inactive. Security for wireless networks is being addressed in 802.11i.VLAN security is addressed in 802.11q. See also security and VLAN.

802.11 - The family of IEEE standards describing the over-the-air interfaces for a number of wireless local area networks (WLANs).Variously referred to in the vernacular as Wi-Fi (Wireless Fidelity) and Wireless Ethernet (the Ethernet CSMA/CA protocol is used in 802.11), 802.11 standards include infrared (IR) and radio frequency (RF) solutions, although there currently appear to be no practical applications for IR.The RF standards fall into the 2.4 GHz and 5 GHz ISM bands and offer theoretical bandwidth up to 54 Mbps. The original 802.11 standard (1997) operated in the 2.4 GHz band and supported theoretical data rates up to 2 Mbps. This early standard included a great number of options, which made interoperability of products difficult, or at least uncertain. As a result, 802.11 never gained any real traction in the market. Soon afterward, however, much improved extensions to 802.11 were finalized, and WLANs quickly gained in popularity. Current extensions include 802.11a, 802.11b, and 802.11g. Still under development is 802.11n. See also 802.11a, 802.11b, 802.11g, 802.11n, CSMA/CA,Ethernet,IEEE,ISM,RF,Wi-Fi,Wi-Fi5, and WLAN.

802.11a - Also known as Wi-Fi5 (Wireless Fidelity 5 GHz). The IEEE standard for an 802.11 wireless local area network (WLAN) operating in the 5-GHz range. 802.11a uses coded orthogonal frequency division multiplexing (COFDM), which sends a stream of data symbols in a massively parallel fashion across multiple subcarriers, each of which is 20 MHz wide and is subdivided into 52 subcarrier channels, each of which is approximately 300 KHz wide. Of those subcarrier channels, 48 are used for data transmission, and the remaining 4 for error control.The specific modulation scheme depends on link quality, with the highest link quality employing the most complex technique, which yields the greatest signaling rate. As the link quality deteriorates, the modulation technique ratchets down to the least capable. In order of complexity and yield, those techniques are as follows:

• Binary phase-shift keying (BPSK) at 125 kbps per channel for a total of 6 Mbps (125 kbps × 48 channels= 6 Mbps), and 187.5 kbps for a total of 9 Mbps

• Quadrature phase-shift keying (QPSK) at 250 kbps per channel for a total of 12 Mbps, and 375 kbps per channel for a total of 18 Mbps

• 16-level quadrature amplitude modulation (16-QAM) at 500 kbps per channel for a total of 24 Mbps, and 750 kbps per channel for a total of 36 Mbps

• 64-level quadrature amplitude modulation (64-QAM) at 1 Mbps per channel for a total of 48 Mbps, and 1.125 Mbps per channel for a total of 54 Mbps

In Europe, 802.11a competes for spectrum with HiperLAN, the standard developed and promoted by the European Telecommunications Standards Institute (ETSI). ETSI requires that two additional protocols be used in conjunction with 802.11a in order to protect incumbent applications and systems running over previously allocated shared spectrum. Dynamic frequency selection (DFS) allows the 802.11a system to dynamically shift frequency channels, and transmission power control (TPC) reduces the power level. In combination, these protocols serve to eliminate interference issues with incumbent signals. See also 16-QAM, 64-QAM, 802.11, BPSK, channel, ETSI, IEEE, modulation, QAM, QPSK, protocol, signaling rate, subcarrier, symbol, and WLAN.

802.11b - Also known as Wi-Fi (Wireless Fidelity).The IEEE standard for an 802.11 wireless local area network (WLAN) operating in the 2.4-GHz band. 802.11b transmission options include infrared (IR), which is rarely used, and radio frequency (RF). 802.11b uses direct sequence spread spectrum (DSSS) modulation. DSSS involves the transmission of a bit stream that is modulated with the Barker code chipping sequence. Each bit is encoded into a redundant 11-bit Barker code (e.g., 10110111000), with each resulting data object forming a chip. The chip is put on a carrier frequency in the 2.4 GHz range (2.4–2.483 GHz) and the waveform is modulated using one of several modulation schemes, depending on link quality.The highest link quality employs the most complex technique, which yields the greatest signaling rate. As the link quality deteriorates, the modulation technique ratchets down to the least capable. In order of complexity and yield, those techniques are as follows:

• Binary phase-shift keying (BPSK) at 1 Mbps.

• Quadrature phase-shift keying (QPSK) at 2 Mbps.

• Complementary code keying (CCK) at 5.5 and 11 Mbps.

Radio link quality is always uncertain, especially when using unlicensed frequencies due to the potential for mutual interference with other systems.At the lowest rate, however, 802.11b link quality generally is acceptable at distances of up to 100 meters or so. 802.11b divides the available spectrum into 14 channels, each of which has a width of 25 MHz. In the United States, the FCC allows the use of 11 channels. Four channels are available in France, 13 in the rest of Europe, and only 1 in Japan.There also is overlap between adjacent channels as each has a width of 25 MHz and all share a band that is only 83 Mhz (2.4–2.483 GHz) wide. See also 802.11, Barker code, BPSK, carrier, CCK, DSSS, frequency, IR, modulation, QPSK, RF, and WLAN.

802.11e - The IEEE standard (2005) for wireless LAN (WLAN) quality of service (QoS) based on access priority classes. 802.11e introduces a coordination function that provides a station with high priority traffic such as voice with more frequent network access than a station with low priority traffic such as e-mail. The station with the high priority traffic also is granted a longer transmit opportunity, or window, in which to transmit as many frames as possible. In all, 802.11e defines four access priority classes, which the Wi-Fi Alliance terms Wi-Fi MultiMedia Extensions (WMMs, or WMEs).Those classes are as follows:

• Voice Priority, the highest level, is defined in support of low latency voice.

• Video Priority, the second highest level, prioritizes video relative to other data traffic. One 802.11a/b channel can support three-to-four standard definition television (SDTV) datastreams or one high definition television (HDTV) datastream.

• Best Effort Priority is intended to support traffic from legacy devices and from applications or devices that lack QoS capabilities.Web browsing is an example of best effort traffic.

• Background Priority is defined in support of low priority traffic without strict latency and throughput requirements.

Examples cited include file downloads and print jobs. 802.11e is critical to the successful implementation of voice over Wi-Fi (VoWiFi). See also 802.11a, 802.11b, frame, HDTV, latency, SDTV, throughput, VoWiFi, Wi-Fi Alliance, and WLAN.

802.11g - Also known as Wi-Fi (Wireless Fidelity).The IEEE standard (June 2003) for an 802.11 wireless local area network (WLAN) operating in the 2.4-GHz band at a signaling speed of up to 54 Mbps. Backward-compatible with 802.11b, 802.11g divides the available radio frequency (RF) spectrum into 14 channels, each of which has a width of 25 MHz. In the United States, the FCC allows the use of 11 channels, only three of which can be used in a confined area at any given time without overlap. Four channels are available in France, 13 in the rest of Europe, and only 1 in Japan. Like 802.11a, 802.11g uses orthogonal frequency division multiplexing (OFDM) at data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbps, with the attainable speed being highly sensitive to distance and line of sight (LOS).At 5.5 Mbps and 11 Mbps, the modulation technique reverts to complementary code keying (CCK), which also is used in 802.11b. At 2 Mbps, it reverts to direct sequence spread spectrum (DSSS) and quadrature phase-shift keying (QPSK), and at 1 Mbps to DSSS and binary phase-shift keying (BPSK), again defaulting to the 802.11a specification.Tri-mode components allow 802.11a/b/g-equipped terminals and access points (APs) to interoperate, although supporting multiple simultaneous protocols affects performance negatively. See also 802.11, 802.11a, 802.11b,AP,BPSK, CCK, channel,DSSS, FCC,IEEE, LOS,modulation,OFDM,QPSK,RF,spectrum, and WLAN.

802.11i - The IEEE standard (June 2004) for 802.11 wireless LAN (WLAN) security mechanisms. The standard is more commonly known as WPA2 (Wi-Fi Protected Access version 2), which is the fully compliant mechanism developed and promoted by the Wi-Fi Alliance. See also 802.11, IEEE, Wi-Fi Alliance, WLAN, and WPA.

802.11n - The developing IEEE standard (estimated March 2009) for an 802.11 wireless local area network (WLAN) operating in the 2.4-GHz band and operating at a signaling speed of up to 108 Mbps, with an option to increase speed to as much as 600 Mbps. 802.11n will be backward-compatible with 802.11a/b/g, building on them by introducing antenna technology known as multiple-input multipleoutput (MIMO), which is based on the concept of spatial diversity.The transmitter splits the signal among multiple transmit antennas separated by some amount of space, but operating on the same frequency at the same time.The multiple receive antennas gather the signal, which has suffered from the effects of multipath propagation. Some signal elements will be stronger than others and will arrive ahead of others. Sophisticated signal processing software combines and correlates many signal elements arriving at different times into one linear combination of a stronger, synchronized, intelligible signal derived from each of the receive antennas and reconstitutes the original data stream. See also 802.11a, 802.11b, 802.11g, IEEE, frequency, MIMO, multipath propagation, and spatial diversity.

802.12 - The IEEE standards for 100+ Mbps LANs using demand priority access. The focus was on 100VG-AnyLAN, a standard that is considered obsolete.

802.14 - The IEEE standards initiative for Broadband Cable Access Method and Physical Layer Specification in Local and Metropolitan Networks.The standard was withdrawn.

802.15 - The IEEE medium access control (MAC) and Physical Layer (PHY) specifications for wireless personal area networks (WPANs). Bluetooth is formalized in 802.15.1 (2002). 802.15.4 is the specification for a low-data-rate WPAN comprising devices of very low complexity transmitting at very low power levels and very long battery life. ZigBee is based on 802.15.4. See also Bluetooth, MAC, PAN, and ZigBee.

802.16 - The IEEE specification entitled Air Interface for Fixed Broadband Wireless Access (BWA) Systems.The 802.16 Working Group was formed to develop a set of specifications to standardize Local Multipoint Distribution Service (LMDS) and Multichannel Multipoint Distribution Services (MMDS), once promising BWA technologies that proved too costly and unreliable.The 802.16 specifications evolved over a number of years, as follows:

• 802.16 (2001) standardized LMDS, focusing on fixed wireless solutions in both point-to-point and point-to-multipoint configurations, operating at frequencies in the 10–66 GHz range, and requiring line of sight (LOS).

• 802.16a (2003) was based on MMDS and the European HiperMAN system.This extension includes both point-to-point and point-to-multipoint configurations, operates in the 2–11 GHz range, and does not require LOS in the lower bands.

• 802.16d, aka 802.16-2004 (2004), is a compilation and modification of previous versions and amendments. 802.16d specifies frequencies in the 2–11GHz range, and includes point-to-point, point-tomultipoint, and mesh topologies.This specification recommends, but does not require, LOS, and includes support for indoor CPE.

• 802.16e (October 2005), formally known as Mobile WirelessMAN, adds hand-off capability, thereby supporting portability and pedestrian-speed mobility for users of laptop, tablet, and handheld computers. Operating in the 2–6 GHz range, it is designed for point-to-multipoint applications and does not require LOS.

See WiMAX for more technical detail. See also BWA, CPE, hand-off, HiperMAN, LMDS, LOS, mesh, MMDS, point-to-point, point-to-multipoint, portability, and WLL.

802.17 - The IEEE Working Group on Resilient Packet Ring (RPR) Access Method and Physical Layer Specifications. RPR standards address the resilient and efficient transfer of data packets over fiber optic local, metropolitan and wide area networks (LANs, MANs, and WANs) at rates scalable to many Gbps. See also RPR.

802.1p - The IEEE specification (September 1998) that enables LAN switches and other devices (e.g., bridges and hubs) to prioritize traffic into one of eight classes. Class 7, the highest priority, is reserved for network control data such as Open Shortest Path First (OSPF) and Routing Information Protocol (RIP) table updates. Classes 6 and 5 can be used for voice, video, and other delay-sensitive traffic. Classes 4 through 1 address streaming data applications through loss-tolerant traffic such as File Transfer Protocol (FTP). Class 0, the default class, is a best effort class. In conjunction with the 802.1q specification for VLAN tagging, 802.1p paved the way for standards-based multivendor grade of service (GoS). See also FTP, GoS, IEEE, LAN, OSPF, RIP, and VLAN.

802.1q - The IEEE specification that defines a virtual LAN (VLAN), which allows multiple logical LANs to share the same physical infrastructure. 802.1q defines a 32-bit tag that is added to the frame header to identify the specific VLAN and provide for priority indication. See also frame, IEEE, header, LAN, logical, physical, and VLAN.

802.2 - The IEEE Working Group that develops standards for Logical Link Control (LLC), which corresponds to the upper sublayer of the Data Link Layer in the OSI Reference Model.The LLC sublayer is concerned with issues of multiplexing, flow control, and detection and retransmission of dropped frames. See also Data Link Layer, flow control, IEEE, LLC, multiplexer, and OSI Reference Model.

802.22 - The IEEE Working Group on Wireless Regional Area Networks (WRANs). 802.22 is an initiative directed toward the development of a cognitive radio air interface for use by license-exempt radios on a non-interfering basis in spectrum currently allocated to television broadcast service. See also cognitive radio, IEEE, and spectrum.

802.3 - The IEEE standard that defines the carrier sense multiple access (CSMA) method of medium access control (MAC), and Physical Layer specifications.Although the term is commonly used interchangeably with Ethernet, 802.3 actually is a variation on the original Ethernet standard. (Note: Project 802 took its name from the fact that it was established in the year 1980, and the month 2, i.e., February.) See also, CSMA, Ethernet, IEEE, LAN, MAC, and standard.

802.3ab - The IEEE standard for 1000Base-T. See 1000Base-T.

802.3ae - The IEEE media specifications for 10 Gigabit Ethernet (10GigE).Those specifications address both multimode (MMF) and single-mode (SMF) optical fiber, core diameter, wavelength, modal bandwidth (MMF), and distance limitations.

Standard	Fiber Type	Core Diameter	Wavelength	Modal Bandwidth (MHz/hm)	Distance (Maximum)
10GBase-SR, SW	MMF	62.5µ	850 nm	160	300 m
10GBase-LR, LW	SMF	8.3µ, 9µ, 10µ	1310 nm	Not Applicable	10 km
10GBase-ER, EW	SMF	8.3µ, 9µ, 10µ	1550 nm	Not Applicable	40 km
10GBase-LX4	MMF	50µ, 62.5µ	1310 nm	500	300 m
10GBase-LX4	SMF	10µ	1310 nm	Not Applicable	10 km

10 Gigabit Ethernet (IEEE 802.3ae) Media Specifications

802.3af - The IEEE standard (June 2003) for power over Ethernet (PoE). See PoE.

802.3ak - The IEEE standard for 10GBase-CX4. See 10GBase-CX4.

802.3an - The IEEE standard for 10GBase-T. See 10GBase-T.

802.3u - The IEEE standard for 100Base-T. See 100Base-T.

802.3z - The IEEE media specifications for Gigabit Ethernet (GbE, or GigE).Those specifications address both multimode (MMF) and single-mode (SMF) optical fiber, core diameter, wavelength, modal bandwidth (MMF), and distance limitations.

Standard	Fiber Type	Core Diameter	Wavelength	Modal Bandwidth (MHz/hm)	Distance (Maximum)
1000Base-SX	MMF	62.5 µ	850 nm	160	220 m
1000Base-SX	MMF	62.5 µ	850 nm	200	275 m
1000Base-SX	MMF	50.0 µ	850 nm	400	500 m
1000Base-SX	MMF	50.0 µ	850 nm	500	550 m
1000Base-LX	MMF	62.5 µ	1300 nm	500	550 m
1000Base-LX	MMF	50.0 µ	1300 nm	400	550 m
1000Base-LX	MMF	50.0 µ	1300 nm	500	550 m
1000Base-LX	SMF	9 µ	1310 nm	Not Applicable	5 km

Gigabit Ethernet (IEEE 802.3z) Media Specifications

802.4 - The IEEE standard for Token Bus, a local area network (LAN) token passing protocol based on a physical bus topology.Token Bus is considered an orphaned standard, as the 802.4 committee disbanded in 2004 due to lack of interest. See also bus, Ethernet, IEEE, LAN, and token passing.

802.5 - The IEEE standard for token-passing ring access method and Physical Layer specifications. The 802.5 recommendations include Token Ring. See also IEEE, Physical Layer, token passing, and Token Ring.

802.6 - The IEEE standard for metropolitan area network (MAN) access method and Physical Layer specifications. Distributed Queue Dual Bus (DQDB) is defined here. Switched Multimegabit Data Service (SMDS) was derived from 802.6.This standard has been withdrawn. See also IEEE, DQDB, MAN, Physical Layer, and SMDS.

802.7 - The IEEE Broadband Technical Advisory Group, chartered to develop standards for definition of a broadband cable plant design and establish guidelines for LAN construction within a physical facility such as a building.This standard has been withdrawn.

802.8 - The IEEE Fiber Optic Technical Advisory Group, established to assess impact of fiber optics and to recommend standards.

802.9 - The IEEE Integrated Services LAN (ISLAN) design for the integration of voice and data networks, both within the LAN domain and interfacing to publicly and privately administered networks running protocols such as FDDI and ISDN. The 802.9 Working Group developed the Isochronous Ethernet (IsoEthernet or IsoEnet) standard, which has been withdrawn.

802 - The IEEE 802 LAN/MAN Standards Committee develops local area network (LAN) standards and metropolitan area network (MAN) standards.The most widely used standards are for the Ethernet family, Token Ring (TR), wireless LAN (WLAN), bridging and virtual bridged LANs. An individual Working Group (WG) provides the focus for each area. See also bridge, Ethernet, IEEE, LAN, MAN, standard, Token Ring, and WLAN.

850 Band - The wavelength band defined by the ITU-T window as 810–890 nm. See also window.

866 - An area code prefix for toll free services in the United States. See also 800 Service, area code, and toll free service.

877 - An area code prefix for toll free services in the United States. See also 800 Service, area code, and toll free service.

888 - An area code prefix for toll free services in the United States. See also 800 Service, area code, and toll free service.

89B Bracket - The bracket that is used to attach 66M150 blocks to back boards in telephone closets or distribution frames.

8B/10B (8 Bits/10 Bits) - A line coding technique that maps eight data bits into a 10-bit symbol, or character.The eight-bit data octet is divided into two groups.The three most significant bits, or leftmost bits, are encoded into a four-bit group (3B/4B).The five least significant bits, or rightmost bits, are encoded into a six-bit group (5B/6B).The two groups are then concatenated, or joined together, and placed on the line.As eight bits yields 256 possible bit combinations (2⁸ = 256) and 10 bits yields 1,024 (2¹⁰ = 1024) bit combinations, each eight-bit data octet can be phrased two different ways, with one being the bit-wise inverse of the other. For example, a data octet of 11001010 might be expressed the first time as 1000100111, and the second time as 0111011000.That encoding scheme yields direct current (DC) electrical balance on the line, as the number of 1s and 0s will be equal in the long term.This approach also ensures proper clocking as there is sufficient ones density. 8B/10B also provides an additional embedded error control mechanism similar to that discussed in 4B/5B, which is used in 100Base-TX. On the downside, 8B/10B adds 25 percent overhead (10/8 = 1.25) to the serial datastream. Note: The 10B format also provides for a number of control characters. 8B/10B is used in 10 Gigabit Ethernet (10GbE or 10GigE), Gigabit Ethernet (GbE or GigE), ESCON and Fibre Channel Storage Area Networks (SANs). See also 10 Gigabit Ethernet, 4B/5B, 64B/66B, balanced, DC, encode, ESCON, Fibre Channel, GigE, ones density, and line coding.

8B/10B Coding (8-Bit/10-Bit Coding) -A physical-layer compression method developed by Fiber Channel that is used to transfer ATM transmissions from OC-3 SONET to STS-3 twisted pair. This is an ATM LAN application that is recommended up to 100 meters. The 8B/10B coding technique combines overhead with data. With the 10 bit/baud, 1024 symbols can be transmitted (0000000000 to 1111111111). Because payload data is based on 8 bits, which, in turn, enables 256 different symbols, 768 spare symbols remain that can represent a combination data-character/overhead-information. If a user is transporting ATM over SONET OC-3, that transmission can be directly transferred to a twisted pair with no buffering and no delay, so long as 8B/10B coding is used.

8FR - A service code for a flat-rate party line with eight subscribers. For more information, see Selective Ringing Module and Party Line.

900 Service - In the North American Numbering Plan (NANP), 900/976 numbers are used to access premium information services that carry either a flat cost per call or a cost per minute determined by the called party, or sponsoring party.The revenues are divided among the sponsoring party receiving the call and the various carriers involved. 900/976 service was originally intended for applications such as telethons and informational services, and was used widely by companies offering technical support on a per-call and per-minute basis. Subsequently, the service gained a bad reputation as many providers of telephone sex and other questionable services make extensive use of them. Fraud schemes actively use 900/976 numbers. In such a scheme, a caller will leave a message asking for a return call to a 900/976 number, with the call carrying an exorbitant charge.As a result, 900/976 services have fallen out of favor and are no longer widely used. 900 numbers are in the format 900-NXX-XXXX. See also NANP.

900 - A dial prefix for toll free services in some countries. See also 800, area code, and toll free service.

911 - The dialing sequence used in the United States for calls for emergency assistance from police, fire, and ambulance services. Calls to 911 are routed to a public safety access point (PSAP). Enhanced 911 (E911) provides caller location information to the PSAP. See also E911 and PSAP.