Fiber Optics Illustrated Dictionary Audion Basic Electronic Concepts February 1998.AICE studies the social consequences of information technology, with its theoretical and practical ramifications. Australian Resource Information and Environ- mentSatellite ARIES. A low Earth orbit (LEO) sun- synchronous satellite project for deploying a hyperspectral sensor capable of identifying details of the Earth's surface that cannot be sensed by other types of instruments. Thus, resource, agricultural, and enviornmental products using reflected visible and infrared light gathered through about 96 spectral bands can be provided to commercial markets. The CSIRO Division of Exploration and Mining has been coordinating the collaborative project. After years of planning and feasibility studies, ARIES re- ceived the go-ahead in 1995, and a time line was es- tablished for it to become operational in 2001 (since delayed to 2002). A vertical tracking spatial resolu- tion of 30 x 30 meters is possible on the system, which can be increased by viewing sideways or im- proved when resolving certain high-contrast objects. http://www.eoc.csiro.au/aries/ Australian Speech Science and Technology Asso- ciation Incorporated ASSTA. A nonprofit scientific association seeking to advance research and under- standing of speech science and its application in speech technologies for the benefit of Australia. authenticate To establish the identity and authori- zation status ofa user, device, process, or data seek- ing entry to a system or seeking to negotiate a trans- action. Authentication is used at network access points, such as gateways and firewalls, in electronic transactions, such as purchases or contracts, and at password prompts to systems, servers, and applica- tions. Data is often authenticated to see whether it has been altered during transmission, and email messages may be authenticated before being sent or received. See certificate, Challenge-Handshake Authentication Protocol, Clipper Chip, encryption, Pretty Good Pri- vacy. authentication, authorization, and accounting AAA. A network security approach for restricting, controlling, and recording remote access to network resources on an individual user and resource basis while maintaining an audit trail for system adminis- tration and billing. authentication, basic access A basic authentication scheme for users accessing Internet services speci- fied in the original HTTP protocol. This system is only minimally secure, as the usemame and password are transmitted as text that can potentially be captured and read. See authenticate; authentication, digest ac- cess; RFC 2617. authentication, digest access A means to provide improved security for HTTP user authentication over basic access authentication. See authenticate, RFC 2069. authenticator In packet networking, the end of the link that requires authentication, and specifies the authentication protocol to be used in the link estab- lishment phase. See Challenge-Handshake Authen- tication Protocol. I III~ .~. "#19~' • , tllII.t~ FI& I-alN.HECTIONB amMa TWO WALUU or .u.a C'L-~T 1:} " i it .rnA &-coNJlKCTIUNI TO OIt.':lUO- QU.R promotes self-regulation within the industry. The ACA was established under the Australian Commu- nications Authority Act 1997 and is empowered un- der the Telecommunications Act 1997 and the Radio- communications Act 1992. It falls within the Com- munications, Information Technology and the Arts portfolio. http://www.aca.gov.au/ Lee de Forest invented the Audion through trial and error and didn tfully understand why it worked; thus, it was difficult to commercially manufacture consis- tently reliable tubes. Edwin H. Armstrongsexplana- tion of the workings of the Audion, published in Elec- trical World in 1914, provided the theoretical back- groundneeded to improve manufacturingconsistency and hencepractical applications of this important in- vention. See Audion. rm. ! (X)NNICTIOHI nl OIl8BRV- IJiG 0 CU'IR.ItNT AHD Gam rorranIAL Australian Computer Society see computer societ- ies, national. Australian Institute of Computer Ethics AlCE. A national organization to provide research and education to the public and advice and expertise to leadership bodies in computer ethics in Australia, established in 82 © 2003 by CRC Press LLC authoring The process of using authoring systems to create computer software or multimedia presenta- tions without a large expenditure in time in learning to program. The rationale for authoring is to free the creator from technicalities to concentrate on content and flow. Authoring involves developing a scenario, providing content, and putting them together in an interactive environment according to how the author wishes the user to interact with the software or pre- sentation. Some authoring languages are very simi- lar to English or BASIC. Others use graphical inter- faces to allow the user to create the scenarios, and interrelate the program building blocks with a mini- mum of programming or text entry. authoringsystem, authoringlanguageA high-level computer programming language designed to be quickly and easily learned and used such that profes- sionals (e.g., teachers) with expertise in their specific subject fields, but without programming experience, can develop computer software such as courseware and multimedia presentations. authorization Pennission to use a product or service or to gain entry to an area or structure. More and more, computerized means are being used to assign, track, and administrate access to secure areas or within cor- porate premises. Authorization can be monitored through video systems, magnetic cards, retina or fin- gerprint scanning, visual recognition of faces, pass- words, and voice recognition. authorization code A code that must be entered into a telecommunications system to gain access to the service or specific features of the service, or to gen- erate statistical records of use. It is used for security or efficiency monitoring, frequently on touchtone phone systems to pennit long-distance calls or gather departmental data. When used for security, the code is often typed before the desired number, although in cases of departmental billing or monitoring, it might be required after the number has been dialed. Authorization Code Table ACT. A lookup table for detennining whether a phone call is authorized on the list and should be permitted to ring through. Ifa num- ber is not found on the list, it is called an unmatched call and may be rejected or fOlWarded to someone in authority. authorized agent A person authorized to resell, re- lease, or represent the product or services ofa com- pany in a somewhat cooperative, independent man- ner with state restrictions. It is common for large tele- phone carriers, both landline and wireless, to pennit authorized agents to resell or repackage phone ser- vices such as long-distance services. In some cases, the agent is a software developer or Internet Services Provider (ISP) who works with the phone company to provide digital value-added services. authorized userA person or entity authorized by the company or provider to use a service, system, or spe- cific application or data file. This concept is impor- tant in communications security. auto answer The capability ofa telecommunications receiving device to automatically detect and respond to an incoming transmission. Facsimile machines, BBS modems, and answering machines are examples of devices with auto answer capabilities. Modems typically include the AutoAnswer command as part of their command set. Sophisticated telephone sys- tems can be configured to automatically answer a voice call and, by using Caller ill, to display the person's file on a computer monitor. See Caller ID, Caller Name, bulletin board system, auto dial. auto attendant, automated attendantAn automated voice system, designed to provide a 24-hour a day substitute for an operator or receptionist, that answers incoming calls and plays a recorded message to the caller providing a number of touchtone options or selections from a touchtone-activated menu. Differ- ent systems can transfer calls to humans or voice-mail systems, perform transactions, provide information, initiate a faxback transmission, or initiate a fax tone for those with manual fax machines. The better sys- tems allow you to go to submenus without waiting for the current recording to end and will give you an easy way to return to the main menu. Auto attendants are used by banks, mail order companies, informa- tion service companies, and others. See voice mail, Automatic Call Distribution. Auto Busy RedialA surcharge phone service, multi- line subscriber feature, or consumer phone feature in which the last number called can be redialed continu- ously until a connection is made. The system recog- nizes a busy signal, hangs up, and redials. There is a similar feature in most telecommunications software that is used to connect to BBS or Internet services which can cycle through a list of numbers, trying each one in tum, or which continuously attempts to con- nect with a specific number. The software can often further be configured to dial at specific intervals or for a specific duration of time. The Auto Busy Re- dial service is useful when combined with auto dial for voice communications. See auto dial. auto dial, speed dial A phone feature in which a short code has been assigned to a longer number to allow the number to be dialed automatically with fewer keystrokes. See abbreviated dialing. auto dial capability A softwarelhardware applica- tions feature for dialing a phone number through a modem and setting it up for voice rather than data communication. It's very handy for dialing from a laptop, acellular laptop link, or from a database on a desktop computer. Some phone solicitors use auto dial in conjunction with phone listings to maximize the number of call connects. Be aware that there are strict regulations governing the use of automated pro- cedures for phone solicitations. See auto answer. auto discovery, auto mountAn automated process whereby a network server is alerted to a new device on the system and can gain sufficient information about its operating characteristics to bring it online and make it available to users. Device tables and da- tabases are sometimes used to make this possible, and manufacturers are creating more devices that signal their presence and include electronically accessible information about the brand, model, capacity, and attributes. 83 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary auto start 1. The capability of an emergency power system to detect when electricity falls below a cer- tain crucial level and start up standby generators to provide continuous service. 2. The capability of a computer system to restart or reboot after a power outage or power fluctuation sufficient to take down the system. auto-negotiation In communications between two or more entities, the process of setting up parameters for intercommunication that are acceptable to both par- ties. Auto-negotiation commonly involves selecting the communications rate, though many other aspects may be auto-negotiated. For example, in the early days of modem communications, a user had to find out the communications parameters for the other party and match them on his or her system before at- tempting to make a connection. By the early 1980s, "autobaud" modems were being installed by bulle- tin board service (BBS) providers to automatically negotiate an acceptable connection speed (you still had to set some of the other parameters such as par- ity, stop bits, etc.), thus simplifying the process for busy or less technical users. In traditional telephone modems, auto-negotiating a speed usually involves the autobaud modem (e.g., at the ISP) sending out a series of modem signal tones from the highest to the lowest available speeds until the user modem responds. By going from high to low, the fastest possible negotiation is chosen. In other words, if the ISP can provide connections at speeds up to 9600 bps and the user dials into the service at 2400 bps, the ISP's modem would start sending a tone signal for 9600 bps, if there is no response, the next tone might be 5600 bps, then 3300 bps, until it reaches 2400 bps at which point the user's modem should respond and the connection is negotiated. Sometimes the autobaud modem will go through the sequence a couple of times before abandoning the call, in case there was interference on the line that altered the signal. Auto-negotiation is now an integral aspect of many communications networks. For example, ports on an Ethemetwork auto-negotiate during the linking phase ofa connection (the same general idea as two mo- dems negotiating a transmission speed for connect- ing over phone lines). The capability is now com- monly built into hubs and network interface cards (NICs) as part of the 1 OOBASE- TX and other stan- dards (it is optional in the 100BASE-SX standard). Auto-negotiation pulses are transmitted in pairs, with a clock pulse and a data pulse and repeated at inter- vals. Since fiber standards did not originally include auto-negotation in the sense of the 1 OOBASE- TX standard, an emulation system for a link pulse was devised for fiber-based transmissions, with adjust- ments for the different timing needs of fiber loss ver- sus twisted pair. See handshake. autoanswer See auto answer. autobaud The capability of a modem to detect the incoming baud rate and adjust its transmission speed and handshaking to match the rate in order to estab- lish a connection. Useful in 24-hour a day, unattended 84 services like BBSs and on systems that may be serv- ing a variety of types ofcomputers and modems. autobaud rate Early modems had to be individually matched to the same baud rate in order to communi- cate successfully with one another, but since the mid- 1980s, when 1200 baud transmissions were common, most modems have incorporated autobaud capabili- ties in which the called modem and the calling mo- dem negotiate a common speed and then commence with user communications. Autobaud capabilities have been a great boon to bulletin board systems (BBSs) and Internet Service Providers (ISPs) as they must accommodate users calling in on a variety of types ofcomputers and modems. autodialing recorded message player ARMP. An automatic dialer which plays a recording to the per- son who answers the phone to keep him or her on the line until an agent can take the call. ADRMP systems are disliked by many callees who consider it intru- sive to pick up the phone and be connected to a re- corded message and asked to wait. Nonetheless, they are used by telephone solicitors and collection agen- cies to increase dialing and caller connect efficiency. AUTODIN Automatic Digital Network. A global communications network of the U.S. Department of Defense. Autoplex The first commercially significant semi- automatic telegraph key, jointly developed by Horace G. Martin and Walter Polk Phillips (developer of the Phillips telegraph code). The device was patented in 1902 by Martin. See 73, Phillips code. Automated Attendant See Auto Attendant. Automated Attendant Billing System AABS. In telephony, a system in which the caller dials collect and long-distance calls with the aid of an automated voice prompting system that seeks authorization from the called party, connects or rejects the call, and bills accordingly. Most telephone services in North America have become automated in this way with the use of speech recognition and synthesized operator- assist voices. automated voice response systemA VRS. A system designed to respond to voice commands without the intervention ofa human operator. This type of sys- tem is often used over telephones by banks and mail order companies. It is sometimes used for security purposes and building access. It is applicable to visi- tor information systems installed in kiosks in amuse- ment parks and other tourist attractions. See speech recognition, voice recognition. Automated DirectoryAssistance CanCompletion ADACC. Atelephone directory call completion ser- vice made commercially available to telephone ser- vice carriers which automatically directs a call with information provided by the caller. In some areas it has superseded the familar Directory Assistance (DA) service. The service is usually billed to subscribers on an as-used basis. See Automated Directory Assis- tance Service. Automated DirectoryAssistance Service ADAS. A commercial telephone service in which a speech rec- ognition system is used to get information from a © 2003 by CRC Press LLC caller who has requested directory assistance. It re- quests the location and name and then either provides the phone number or compresses out pauses and patches the call to an operator who provides the phone number. Ifacaller is tentative or repetitious, the au- tomated service can reprompt and then pass on only relevant information for the operator. Automated Interchange of Technical Information MIL-STD-1840x. A data interchange standard. automated loop test ALT. An automated system for testing traditional telephone service lines. Cables can be scanned for excessive noise, aberrations, water faults, or outright failure and traffic routed through a backup loop until the fault is corrected. Loop tests may be run on aregular basis (e.g., once a day), usu- ally during low traffic times. Automated Maritime/Marine Telecommunica- tions System AMTS. The AMTS is a specialized network of public coast stations providing commu- nications over inland waterways and ocean coastlines. Public coast stations (marine operators) are desig- nated as common telephone carriers; they provide a means to connect marine radio transmissions to the public switched telephone network (PSTN). In Spring 2000, Mobex Communications Inc. ac- quired Regionet Wireless, which had licenses for more than 3900 channels in the AMTS system serv- ing the west and east coasts. This announcement came soon after the Mobex announcement of intent to ac- quire Waterway Communications System LLC, a holder of licenses for over 4000 channels serving the Gulf Coast and Ohio River barge industry. Thus, Mobex became a significant provider of marine mo- bile radio services in North America. AutomatedMessage Handling System AMHS. An interface between an automatic digital network and a local area network intended to facilitate the delivery of messages to a user's desktop station. AMHS was developed by NASAlJPL with funding from the u.S. Department of Defense and subsequently transferred to the Telos Corporation for servicing requests. Automated Packet Recognition/Translation APaRT. A Cisco Systems technology that allows au- tomatic. network configuration and translation, e.g., Ethernet clients and a CDDI or FDDI server, so that workstations or switches do not have to be individu- ally configured. APaRT recognizes and, if necessary, translates specific data link layer encapsulation packet types. automatic alternate routing AAR. 1. A telephony service for placing calls that will be automatically routed through the most economical path available at the time. It is spelled with capitals when referring to a subscriber service specifically offered by a phone company. 2. A network service for obtaining a con- nection through an alternate route, if the primary route is unavailable, without user intervention. Automatic Call Distribution ACD. A multiline phone capability or service that automatically man- ages and routes incoming calls to assigned lines. If there are no available lines at the moment the call is received, it is placed on hold, and may be configured to playarecording such as "Your call is important to us, please stay on the line and your call will be an- swered in the order received." ACD systems can put the party on hold and playa recording, or they can be quite sophisticated, performing significant traffic direction and business transactions. Mail-order companies, airlines, and other high phone- traffic businesses utilize ACD systems, although smaller companies are starting to use them as they become less expensive. An ACD system detects and answers incoming calls, searches a database for in- structions on how to handle the call, responds to the call (as with a recording), and reroutes it appropri- ately as human operators become available. The rout- ing itself can be programmed to the subscriber's needs, with a number of options available: Uniform distributes calls evenly, Top-down distributes the calls according to a list in the same order each time, so that calls go to the top of the list first, and work their way down, and Specialty distributes calls acco~ding to the callee who most appropriately can handle the call. ACDs can also be used to gather statistical data on the number of calls received, and how they are handled in order to fine-tune the system, and to re- spond to the business needs of the subscriber to im- prove call handling or change it as the need arises. See Centrex, private branch exchange. automatic call gapping ACG. A scheme to help con- trol system congestion at the call establishment stage in wireless intelligent networks (WINs). ACG intro- duces a minimum time gap between call attempts and permits a maximum number of attempts per defined unit of time if call volume is high. Implementations vary, but gaps of about a second are common. In the late 1990s, ACG was tested for performance improve- ments in a number of simulated and real networks, including A-link loads. Prouskas et al. have more recently proposed a multi- agent system for controlling network load that may give better performance results for load control of network components than ACG. automatic callback A subscriber option usually found on private branches in which a caller can key in a code or press a button for automatic callback if she or he has encountered a busy signal on an exten- sion line. When the line is freed, the caller's phone and the callee's phone both ring so that the connec- tion can be made. automatic calling unit ACU. A device used to auto- matically dial numbers (a modem and the appropri- ate software can also do this) in order to save a hu- man operator the time and inconvenience of dialing a lot of calls. This type of system is used by fundraisers, telemarketers, researchers, and others who make frequent calls to a predetermined list of numbers. On computer systems, ACU software is sometimes coupled with database directory programs or address books. Automatic Circuit Assurance ACA. Acircuit ef- ficiency feature available to private branch exchange (PBX) telephone subscribers. ACA evaluates and re- ports on phone trunk usage or malfunctions. Trunks 85 ~. . :.~ ••. ;.: •. : .•. ; •.•. 1 • ~ •• :~ .•. :. . ,~1 • © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary are typically evaluated on whether they are in use or locked, and whether holding times are long or short. ACA can also be used to chart unusual patterns to facilitate troubleshooting. When apotential problem is detected, an attendant is notified. Automatic Data Capture Association ADCA. An Australian association of companies involved in manufacturing, distribution, and consulting for the data capture industry. ADCA promotes the develop- ment and maintenance of standards and education in data capture. Some specific data capture areas include radio communications, vision systems, optical char- acter recognition, barcode interpretation, mobile pen computing, scanning, and others. http://www.adca.com.au/ automatic dialer, autodialer A timesaving device enabling a user to program and store a short sequence of characters to represent a long number. When the short sequence is entered, the phone checks memory and, if the sequence is found, it automatically dials the corresponding long number. See speed dialing. automatic direction finder ADF. An antenna that usually rotates or arcs back and fOlWard and continu- ously monitors signals until it finds a strong one or one with specified desired characteristics. It then locks onto that signal or provides the direction or fre- quency information on some type of output device such as a monitor or dial. Automatic Electric Company Ahistoric telephone technology vendor supplying automatic switching systems based on Strowger technology, co-founded in 1901 by Almon B. Strowger, a mortician who re- portedly wanted an automatic exchange because hu- man operators were diverting business to his com- petition. This company was able to compete by in- stalling working systems quickly, according to cus- tomer specifications, and was the largest company supported by telephone company independents. It was directed by Alexander E. Keith. Originally most of the Automatic Electric systems were three-wire systems which used two wires plus the Earth as the third return-path conductor for the transmission. Later, they developed a two-wire sys- tem.1n 1955, the company was merged into General Telephone and Electronics (GTE). See Strowger switch. automatic exchange A central telephone switching office in which calls from subscribers are automati- cally routed to the callee through mechanical, elec- tromechanical, or electronic switching. There are still a few operator-assisted exchanges around, mostly in remote locations or third-world countries, but auto- matic exchanges are found in most developed nations. The history of automated exchanges is interesting. Besides the economic motivation of not having to pay wages to operators, one of the early switching sys- tems was designed by a mortician because he was apparently concerned that operators were channeling calls to his competition. automatic exclusion Once a call has been answered, subsequent stations, nodes, or consoles are excluded from having access to the line. 86 automaticfrequency control AFC. 1. Periodic sam- pling ofa frequency modulated (FM) signal to focus the receiver on the approximate center of the trans- mission band. This came into widespread use in the 1930s. 2. A device that can seek aparticular frequency or monitor the incoming frequency to keep the tun- ing accurate. AFC is common on FM receivers and other devices that must maintain operations within a very narrow range. automatic gain control, automatic volume control AVC. Acircuit designed to sense the level of incom- ing sounds and adjust their volume. It can serve two common purposes: to increase the dynamic range of the sound by making quiet sounds quieter and loud ones louder; or to condition the sound by making the volume more consistent (e.g., by quieting down the loudest sounds and strengthening the quietest sounds) when incoming signals are fluctuating more than is desired. Volume conditioning is widely incorporated into sound receivers with tuners, as the signal com- ing through an antenna can vary significantly due to varying broadcast characteristics and weather. automatic hold A convenience in which the opera- tor ofa multiline telephone console or switchboard can switch between active call lines without having to push a hold button. This saves operator time and prevents caller frustration as the operator can't un- intentionally disconnect the caller by forgetting to press the hold button. automatic identification technology AlT. A general category of technological tools for facilitating and automating recognition of goods, processes, or indi- viduals. There are software programs for automati- cally recognizing individuals by biometric data such as voice prints, fingerprints, facial features, retina scans, etc. Bar codes and radio frequency tags are used for recognition of goods in shipping and inven- tory management systems in many distribution and retail businesses. In March 2001, the U. S. Defense Logistics Agency published the Defense Logistics Agency Automatic Identification Technology Imple- mentation Plan which details the integration ofAlT into its business processes for collecting source data and asset information. Used wisely, AIT has the potential to reduce repeti- tive work and manual label-reading and -processing. It can also be practical for surveillance and security applications, provided people's privacy rights are taken into consideration. Automatic Identified Outward Dialing AlOD. A multiline phone option that records the extension number of the originating phone in order to facilitate billing. AlOD is especially common for the identifi- cation oflong-distance calls. AlOD leads are termi- nal leads used to transmit this information to the phone carrier. automatic level control See automatic gain control. automatic light controlA feature on many different types of cameras, in which the camera will adjust the settings to changes in lighting without manual me- tering or intervention by the user. This feature is par- ticularly prevalent on small automatic cameras and © 2003 by CRC Press LLC many camcorders. Sometimes backlighting, high contrast, and other lighting situations can be preset with buttons so that a general ambience is made known to the camera, but the final settings are still automated. Professionals prefer automatic systems only if they also have a manual over-ride for tricky lighting situations. Automatic Line Insulation Testing ALIT. Test equipment used by telephone companies to identify and test faulty outside cables, when not in use, by seeking below-threshold leakage resistance. Results can be communicated by various means to an atten- dant or test facility. ALIT testing is quick and is typi- cally conducted during low traffic hours in order not to tie up the system. automatic line hold See automatic hold. automatic link establishment ALE. In radio com- munications and computer networking, the capabil- ity ofa system to negotiate automatically a connec- tion between two or more stations. Handshaking, identification, and authentication may be part of the process. In radio communications, ALE systems sometimes require a table or list of frequencies that are likely to result in a successful connection. In com- puter modem links, a record of communication pa- rameters and modem speeds (if not autobaud) may be maintained to facilitate automatic connections. Au- tomatic link establishment is now common and al- most taken for granted, but until the mid-1990s, in computer communications especially, automatic con- nection was in no way guaranteed and, in many cases, not even possible. automatic location identification, automatic loca- tion information ALI. A feature of enhanced 911 emergency systems that automatically provides in- formation on the source of the call from a database. automatic loop protection switching ALPS. A net- work flow protection mechanism that protects data flow by switching to a redundant or other backup sys- tem to continue service until corrections can be made to the faulty circuit. In a loop system, the backup sys- tem provides a different physical path for the data. This type of system is suitable for localized computer networks as opposed to public distributed networks. In telephony, there are similar systems for switching to a backup loop if the main loop is faulty. Automatic Network Dialing AND. Also called Au- tomatic Dialing (AD), AND is a means of using ap- plications to dial a telephone number on a digital net- work or from various electronic peripheral devices on a network (e.g., a facsimile machine). For ex- ample, a database of phone numbers can be accessed by a computer-based dialing utility to dial the num- bers in succession until a call is answered, to dial a single number repeatedly, or to dial specific numbers on a programmed schedule. The Telephony Applica- tion Programming Interface (TAPI) is one of the soft- ware programming tools that facilitates the develop- ment of applications to communicate over phone lines, using computers to handle the routine dialing tasks. AND is widely used by businesses that seek to automate their customer call-backs or telemarketing calls. With Internet phone and Voice over IP becom- ing increasingly prevalent, AND is gaining in impor- tance. See war dialer. ~~:~%:~;~~;:;:se~h~~:.::a:~~:~ ~~~tt:~. provided the callee has the service and equipment to display the information. It was historically distin- guished from Caller ill by the number of rings within which the information was sent to the caller, but that distinction is disappearing. See Caller 10, Signaling System 7. 2. A multi frequency signaling parameter by which a long-distance carrier receives the caller's number from the local carrier for billing purposes. automatic privacyA feature on some multiline sys- tems that automatically locks out the ability of other people who pick up a phone to select the line already in use. These systems may also include a 'release' button that allows others to pick up the line and join the conversation. Automatic Protection Switching APS. A network switching technique which varies from system to sys- tem. In some, it is a device that automatically switches from a primary to a secondary circuit if excessive er- ror conditions are detected on the primary circuit. For Synchronous Optical Networks (SONETs), APS is defined in ANSI Tl.105-1995. In SONET,APS car- ries the signaling bytes associated with establishing and releasing the protection of the optical facility. Automatic Recall AR. A subscriber telephone ser- vice that allows a callee to dial automatically to the number that most recently tried to reach the callee. It allows the callees to reach the caller that they missed picking up or that they missed as a Call Waiting while they were already on the line. If the automatically dialed line is busy, the automatic dialing can continue for up to half an hour. Ifa connection is made, a ring alerts the user to the completed connection. automatic recovery If there is a power outage or other problem that interrupts a phone system, bulle- tin board system, network, etc., automatic recovery is the capability of that system to power up to oper- ating status and to recover as many of the original operating parameters and files as possible, as well as to recover or recreate the information that was con- tained in memory that is of importance to continued operations. Automatic Redial A surcharge phone service that allows a caller to recall the most recent previously dialed number and dial it again by inputting a short code instead of rekeying the whole number. It is handy if the line was busy the first time it was called. Many business and consumer phones now have a re- dial button, thus decreasing demand for this service. automatic rerouting The capability ofa system to route a transmission through another leg, hop, or path when the original or expected path is not available. Dynamic routing in large systems often works this way. Large distributed systems where the physical and virtual pathways change constantly usually func- tion with automatic rerouting. In some systems, such as Fiber Distributed Data Interface (FOOl), alternate routing is supplied in a dual ring system in which the 87 © 2003 by CRC Press LLC AUUG Australian Unix User Group. AUXBC auxiliary broadcasting. signed to carry out many of the transaction activities (usually financial) that have historically been handled by human bank tellers. Typical ATM functions in- clude deposits, withdrawals, payments, transfers, and balance inquiries. ATMs are intended to provide ser- vices 24 hours a day or an option to those who prefer automated services. ATMs are networked to a central system, if free- standing or off-site, or they may be directly linked to the local network when attached to the building with which it is associated. automatic volume control AVC. Acircuit in a radio receiver designed to prevent loud blasts from strong transmitting stations when the user moves the dial through the various stations. It can be disconcerting to tune through several weak stations and then hit a strong one that assaults your ear drums. AVe was designed in the 1930s to prevent these sudden gains and dramatic volume changes, and most systems now incorporate this feature. automatic wakeup A timing device that creates an alarm or other alert to wake up a person. These can include a clock radio, alarm clock, bell, computer pro- grammed sound file, or telephone signal. Automation Tooling Systems ATS. A leading inter- national provider of automation systems integration. ATS designs and manufactures factory automation systems, custom automation equipment, and high- volume precision components. The company has been developing custom automation solutions for fi- ber optics, optoelectronics, and photonics industries since 1994. autonomous built-in self test ABIST. The capabil- ity ofa system to automatically run built-in diagnos- tic routines. autonomous switching A Cisco Systems router fea- ture that enables the ciscoBus to switch packets in- dependently, without interrupting the system proces- sor, to provide faster packet processing. Autonomous System Number ASN. A common administrative routing setup identifier, that is, rout- ing through acollective numbered common domain. The ASN designates a system under common opera- tions control, using common routing protocols, with the various routing tables dynamically maintained. AVV, AVV bit ATM User-to-User bit. A payload type identifier (PTI) field bit used with AAL5 to in- dicate the end ofa higher protocol packet (e.g., the IF packet). The PTI is defined for all AAL types with regard to AUU as shown in the chart. signal condition AUU bit Fiber Optics Illustrated Dictionary port adaptor and various ports are quickly reconfig- ured to the secondary systems to prevent loss of data and connectivity. automatic retransmit request, automatic repeat request ARQ. In its simplest form, as in CB radio, a verbal request for the sender to repeat a message that did not come through clearly or completely. More standardized, automated ARQ systems exist, including one in which characters are sent in groups ofa set length, and the sender waits for an acknowl- edged (ACK) or not acknowledged (NAK) signal (or no response) before retransmitting or continuing. In some systems, such as amateur radio communica- tions, ARQ is called mode A. In high-speed data transmission, error-detection fields are built into the data and used as check fields by the recipient. As in broadcast ARQ systems, an acknowl- edge (ACK) or not acknowledge (NAK) is transmit- ted to the sender and the sender responds accordingly. Automatic Route Selection A phone service that automatically seeks and selects the desired circuit from available options (usually the least expensive carrier) for the path of an outgoing call. See Least Cost Routing. Automatic Scheduled Testing AST. A form of tele- phone testing in which the telephone carrier provides test lines with associated responders for conducting loss and noise tests on a scheduled basis. Additional testing may be requested at an extra charge from the central provider. Test results are logged for each trunk line and provided to the carrier. Automatic Sequence Controlled Calculator (ASCC). See Harvard Mark I. automatic sounder A historic telegraph device that created audible clicks of the incoming transmission that could be heard and interpreted by the telegraph receiving operator. The term was also applied to a sounding device used for the teaching of telegraphic sending and receiving skills. When contact was made between the arm and the stop, the sounder's circuit was closed. See sounder. Automatic Speech Recognition ASR. A term in te- lephony services for the capability to interpret auser's verbal response to prompts in order to facilitate call direction or other handling. automatic switching system Various types of me- chanical and electrical telephone switching systems became prevalent after the invention of the historic Strowger telephone switching system. These auto- matic systems enabled telephone circuitry to be con- trolled so that a call was connected by dialing a code rather than by asking a human operator to manually patch through the call. A number of large and small telephone switching manufacturers, including AT&T / Bell and the Lorimer brothers, created automatic switching equipment in the early 1900s, a trend that continued until the 1970s. By the 1980s, very few manual systems were in use except in rural or spe- cialized situations, as they had been superseded by electronic switching systems. Automated TeUerlTransaction Machine ATM. Any automated walk-up or drive-up console system de- 88 no congestion no congestion congestion congestion AUUO AUUl AUUO AUU 1 bit pattern 000 001 010 011 © 2003 by CRC Press LLC availability 1. The amount of time during which a telephone or network system is available for handling calls. It is expressed as the ratio of denied calls to at- tempted calls. See reliability. 2. In Global Position- ing Service (GPS), the period of time during which a particuhtt location, within angle of elevation param- eters, has sufficient satellites to make a position fix. Available BitRate ABR. InATM networking, a layer service category related to flow control that may change subsequent to establishing the connection. ABR is related to Best Effort service. It is a class of service (CoS) defined by the ATM Forum that uti- lizes bandwidth on an availability basis for the trans- port of bursty data traffic. It is designed to approxi- mate the traffic characteristics ofexisting local area network (LAN) protocols. In network implementa- tions, there is generally an Available Bit Rate (ABR) command that facilitates the configuration ofpeak and minimum cell rates in kilobits per second. See cell rate, constant bit rate, variable bit rate. available bit rate ABR. avalanche diode A diode in which there is a break- down region in the reverse bias that is triggered at a certain voltage. This makes them useful as voltage regulating components. See diode; zener diode; pho- todiode, avalanche. avalanche noise In semiconductor junctions, a situ- ation in which sufficient high-voltage energy is gen- erated by some carriers such that others are physi- cally impacted. avatar 1. An embodiment in human form. 2. An elec- tronic image or other embodiment of an individual that is computer-generated and holds some essence or presence ofindividuality or actuality beyond that of a photographic image or scan. This concept is prevalent in the imaginary world ofcomputer gam- ing (and Internet chat areas), especially in virtual re- ality simulations. AVD See alternate voice data. average busy hour The hour in a day during which the most traffic is carried on a system. This informa- tion is important for configuring and tuning computer and telephone networks to handle traffic efficiently. Average Delay in Queue ADQ. A measure of the average time a caller waits before a telephone call is processed or handled by an agent. It is important to keep this time as short as possible, to discourage the caller from hanging up or negatively perceiving the service. average line utilization ALD. A telephony admin- istrative statistic describing average bandwidth usage over a specified period of time. The information is useful in managing bandwidth in a multichannel system. average speed ofanswer ASA. Atelephony admin- istrative statistic describing the average time it takes for an operator or automated system to answer a call, usually measured in seconds. ASA is used for sys- tem configuration, statistical, and staff training and management purposes. AVHRR See advanced very high resolution radi- ometer. aviation channelsA set ofbroadcast frequencies set aside for aviation communications and aviation-re- lated signaling/sensing purposes (e.g., radar). AVIOS See American Voice Input/Output Society. AVRS See automated voice response system. AVSSeS See AudioNisual Service Specific Conver- gence Sublayer. AWA See Antique Wireless Association. AWACS SeeATMWirelessAccess Communication System. Awe See Association for Women in Computing. AWG 1. See American Wire Gauge. 2. Association for Women Geoscientists. 3. Association of Washing- ton Geographers. awk An interpreted computer language common on Unix systems, developed by Aho, Weinberger, and Kernighan (who is also an author of C). It has a C-like syntax. See Perl. AX.25 A communications protocol designed for packet radio communications that operates at the link layer level. It is based on the ISO Open Systems In- terconnection Reference Model (OSI-RM). Since its introduction, it has generally been superseded by NETIROM, a more flexible means of transmission. See Open Systems Interconnection. axial leads Leads on a component that are arranged to protrude along a linear axis in a common plane. In other words, they stick out the ends rather than out the sides. axial ratioIn elliptically polarizedradiant energy, the ratio of the major axis to the minor axis. axial ray See axis ray. axicon An optical imaging element commercially manufactured as a conical lens (rotationally symmet- ric prism) with the capability ofconverting a beam of coherent light into a ring with anondiffracting cen- tral region. Diffractive axicons, with very long focal lines, may be applied to 3D imaging technologies and have been demonstrated for generating Bessel beams for manipulating particles. Holographic axicons may be used as tools for generating volume intensity dis- tributions. Collimation of atomic beams was accomplished with axicons in the late 1980s and wider commercial dis- tribution of ax icons increased in the late 1990s and early 2000s. Commercial axicon components have conical polished surfaces, come in a number of stan- dard types, and may be used in conjunction with fo- cusing lenses. Axicon lens cone angles are typically about 160 o ±20°. Bessel beams may be generated through axicon lenses in the micrometer- and milli- meter-wave ranges. See Bessel beam, laser. axis 1. A reference, orientation, or vector in a coor- dinate system, typically depicted as a line when graphed. See normal. 2. Aprimary direction or line of motion. 3. An imaginary or implied line around which other elements appear to be oriented as, for ex- ample, the vertical axis ofa tree trunk or the hori- zontal axis ofa sea/skyscape. 4. A drawn line, usu- ally straight, used as a reference in a graph or chart. 5. The longitudinal center or cross-sectional diameter of a wire or cable, commonly referenced for size. 89 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary axis ofrotation A straight line around which a body or representation is symmetrically aligned or around which it rotates. axis parabolic, axis paraboloidal See off-axis para- bolic, on-axis parabolic. axis ray, axial ray In fiber optic networks, a light beam or ray, from a laser source, that travels along a path in the waveguide that is coincident with the axis (longitudinal center) of symmetry of the light-guid- ing fiber. See fiber optic cable, waveguide. AZERTYA designation for a computer keyboard or typewriter keyboard used in some European countries such as France. The letters represent the fITst six top left letters directly below the number/symbol keys. The layout is essentially an adaptation ofa QWERTY keyboard with slight changes to accommodate some of the alphabetic differences in European languages (e.g., extra letters). See QWERTY. azimuth 1. A geometric arc used in navigation and astronomy which is calculated, for example, between a fIXed point on the horizon, and clockwise through to the center ofa specified object. 2. A horizontal di- rection calculated from the angular distance between the direction ofa fixed point, such as a navigational heading, and the direction of the object (boat, space- craft, etc.). 3. A specific arc described in relation to a fIXed point and a moving object or radiating trans- mission such as a rotating storage medium (drive, tape, etc.), or antenna. 4. The horizontal direction of a celestial point from a reference terrestrial point, expressed as an angular distance. Ayrton, Hertha Marks (nee Phoebe Sarah Marks 1854-1923)ABritish physicist, inventor, and author who investigated electricity, particularly electric arcs. She became the fITst female member of the Institu- tion of Electrical Engineers (lEE). Ayrton was the author of The Electric Arc, published by Van Nostrand in 1902, which became a standard textbook on the subject. In 1906 she was awarded the Hughes medal for her work on electric arcs and on 90 sand ripples. Ayrton was awarded a patent for the in- vention of an instrument that was used for dividing a line into any number of equal parts. E. Sharp pub- lished a memoir of Ayrton in 1926. Hertha Marks Ayrton - Physicist, Inventor Hertha Marks Ayrton was an intelligentandversa- tile observer, inventor, and author interested in the physics andapplications of electricity. [ca. 1899 pho- tograph courtesy of the Archives of the Institution of Electrical Engineers (lEE), London.] azimuth-elevation mount A common type of an- tenna mount that facilitates two types of rotation, for adjusting both horizontal orientation (azimuth) and elevation (height). This type of mount is frequently used with parabolic antennas that work best when fo- cused precisely toward highly directional beams. See parabolic antenna, microwave antenna, polar mount. © 2003 by CRC Press LLC ~ symb. Greek letter beta, often used in geometric drawings to denote a specific angle. May also repre- sent phase constant in electrical equations. B 1. symb. magnetic flux. 2. abbrev. brightness, as a computer monitor or TV picture tube setting. 3. symb. byte, a unit of data commonly consisting of eight bits. See byte. Historic Dry and Wet B Batteries Older wet B batteries (right), with the individual battery cells connected in series, were cumbersome and awkward to handle. Historic wet cells were su- perseded by more convenientdrybatteries (left). These examples arefrom the American Radio Museum col- lection. [Classic Concepts; usedwith permission.] BbatteryA low-voltage source of direct current (DC) power, historically used to provide power to the plate, or anode, in electron tubes, or to relays in a communi- cations circuit. Bbatteries ranged from about 22.5 to 130 volts, with 48 volts common in communications circuits. The early B batteries were wet cells, often consisting of a matrix of 1.5-volt cells combined. Later dry cells, with two leads, replaced the more cumbersome wet cells. Most had snap connectors, but some had 4-pin plugs. While B batteries are no longer common, there are still a few commercially available, ranging from 22.5 to 67.5 volts. Antique radio buffs will sometimes wire up aseries ofcommercial9-volt batteries to produce the functionality of an old-time B battery. See battery. B Block A Federal Communications Commission (FCC) designation for a Personal Communications Services (peS) license granted to a telephone com- pany serving a Major Trading Area (MTA). It grants permission to operate at certain FCC-specified frequencies. In 1994/95, the FCC auctioned Broad- band PCS A and B blocks to 18 winning bidders for total revenues exceeding $7 billion. See A Block for a chart ofdesignated frequencies for Blocks A to F. B CarrierA local wire line cellular telephone com- munications carrier. It is the designation for the local phone company, although the cellular system may be sold offafter initial licensing by the local carrier. B Carriers are permitted to operate in four stipulated frequency ranges between 835 and 894 MHz. See A Carrier. B channell. In a stereo system, the designation for the right audio channel, typically connected to the right speaker, often color-coded as red. 2. bearer chan- nel. A channel in a circuit-switched ISDN connec- tion with bidirectional data transmission capability. For a fuller description, see ISDN. B interface An interface used in Cellular Digital Packet Data (CDPD) which is deployed over AMPS. The B interface connects the Mobile Data Interme- diate System (MD-IS) to the Mobile Data Base Sys- tem (MDBS). See Ainterface, C interface, Cellular Digital Packet Data, D, E, and I interface. B minus, B- A negative terminal on a B battery. A negative polarity in avacuum tube anode. Bplus, B+ Apositive terminal on aB battery. A posi- tive polarity in a vacuum tube anode or voltage source in an electronic transistor. See B battery. B port In a Class A, dual-attachment (dual ring) Fi- ber Distributed Data Interface (FDDI) token-passing network, there are two physical ports, designated PHY A and PHY B. Each of these ports is connected to both the primary and the secondary ring to act as a receiver for one, and atransmitter for the other. Thus, the B port is a transmitter for the primary ring and a receiver for the secondary ring. The dual ring system is configured to provide fault tolerance for the net- work. FDDI ports can be connected to either single mode or multimode fiber optic media, providing half du- plex transmissions. LEDs are commonly used on port adaptors as status indicators. Optical bypass switches may in tum be attached to the port adaptors. Optical bypasses are provided to avoid segmentation which might occur ifthere is a failure in the system, and a station is temporarily eliminated. See dual attachment 91 © 2003 by CRC Press LLC . interface cards (NICs) as part of the 1 OOBASE- TX and other stan- dards (it is optional in the 100 BASE-SX standard). Auto-negotiation pulses are transmitted in pairs, with a clock pulse and a data pulse and repeated at inter- vals. Since fiber standards did not originally include auto-negotation in the sense. interface cards (NICs) as part of the 1 OOBASE- TX and other stan- dards (it is optional in the 100 BASE-SX standard). Auto-negotiation pulses are transmitted in pairs, with a clock pulse and a data pulse and repeated at inter- vals. Since fiber standards did not originally include auto-negotation in the sense of the 1 OOBASE- TX standard, an emulation system for a link pulse was devised for fiber- based transmissions, with adjust- ments for the different timing needs of fiber loss ver- sus twisted pair. See handshake. autoanswer See auto answer. autobaud The capability of a modem to detect the incoming baud rate and adjust its transmission speed and handshaking to match the rate in order to estab- lish a connection. Useful in 24-hour a day, unattended 84 services like BBSs and on systems that may be serv- ing a. model, capacity, and attributes. 83 © 2003 by CRC Press LLC Fiber Optics Illustrated Dictionary auto start 1. The capability of an emergency power system to detect when electricity falls below a cer- tain crucial level and start up standby generators to provide continuous service. 2. The capability