0-9  A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z access The section of the network that connects the end user to the carrier. active component Active Component generates light (e.g., lasers and LEDS), dynamically manipulate it (modulators), amplify it, or detect the optical signal (detectors). active-matrix liquid crystal display A display that generates (rather than reflects) light using a matrix of tiny liquid crystals. active silicon optical circuit (ASOC) The trademark of Bookham's integrated components. add/drop multiplexer This is an optical network element that lets specific channels of a multi-channel optical transmission system be dropped and/or added without affecting the through signals (i.e., the signals that are to be transported through the network node). advanced mobile phone service (AMPS) The analog cellular mobile phone system used in North and South America and more than 35 other countries. Two cellular phone companies in each area or region share the spectrum allocated to AMPS. It uses frequency division multiple access (FDMA) transmission in the 800Mhz band. The first AMPS system in the United States was deployed in Chicago in 1983. Advanced Research Projects Agency Network (ARPANET) The networking precursor to the Internet, ARPANET was the first publicly displayed packet switching network. Funded by the Advanced Research Projects Agency (ARPA), it was launched in 1969. Over the following decade, ARPANET spawned other networks. In 1983, its protocols were changed to TCP/IP. As TCP/IP and gateway technologies matured, more disparate networks were connected, and the ARPANET became known as "the Internet." See TCP/IP. algorithm A procedure or formula for solving a problem or determining the likelihood of specific outcomes. all-optical network (AON) An all-optical network uses multiple-channel wavelengths rather than electronics for switching, routing, or distributing light. alphanumeric Alphanumeric systems use both alphabetical and numerical symbols. Two-way alphanumeric pagers enable users to send and receive email text messages. American National Standards Institute (ANSI) The United States government body responsible for approving US standards in many areas, including computers and communications. American Standard Code for Information Exchange (ASCII) A binary code for text that can be recognized by most minicomputers and personal computers. amortization Defined in two ways, with respect to debt and with respect to intangible assets. Related to debt, amortization refers to the retirement of debt through periodic payments. Related to intangible assets, amortization refers to the "systematic write-off of costs incurred to acquire an intangible asset, such as patents, copyrights, goodwill, organization, and expenses." (Barron's Business Guides, "Dictionary of Business Terms." Second Edition, 1994) In this case, amortization is performed to match the expense for the use of the intangible benefit over its life. This latter usage represents a non-cash item and is, therefore, excluded from consideration when securities analysts think about the operating cash flows or EBITDA from the business. amortization of cheap stock Describes the accounting pronouncement requiring companies to record compensation expense whenever options are granted below fair market value. When companies are private, independent auditors estimate the fair market value. If a company chooses to seek an initial public offering, the SEC may require the issuer to record an expense if estimations of fair market value are too low. This is an especially important accounting rule to technology companies, which commonly issue stock options as a part of the compensation package; the grant price of these options will have an impact on the income statement if the option strike price was below fair market value at the time of grant. Because these are non-cash charges, securities analysts sometimes place little weight on them or ignore these charges all together. amplitude The relative magnitude of a signal. analog A term used for any device, usually electronic, which represents values by a continuously variable physical property, such as voltage in an electronic circuit. An analog device can represent an infinite number of values within the range the device can handle. application layer (Layer 7) The seventh and highest level of the Open Systems Interconnection (OSI) data communications model. It supplies functions to applications or nodes. This allows them to communicate with other applications or nodes. File transfer and email work at this layer. application service provider (ASP) Service companies that host and manage applications for customers from a centrally managed facility, ensuring security and performance. The user can gain access to the application through the Internet, private lines, or the public network. application-specific integrated circuit (ASIC) A silicon chip custom-designed for a particular purpose. Many ASICs are actually designed to perform multiple, generalized tasks. For example, from the manufacturer's point of view, a microprocessor is an ASIC, though they can and are used for widely disparate purposes. Manufacturers use ASICs to consolidate many chips into a single package, thereby reducing system board size and power consumption. arrayed waveguide grating (AWG) A passive optical component that enables the multiplexing and de-multiplexing of optical signals of different wavelengths using optical waveguides such as silica (a type of planar lightwave circuit). asymmetric digital subscriber line (ADSL) Allows fast downstream (up to 8.192 Mbps) and upstream (up to 1.088 Mbps) date transmission with the ability to provide simultaneous voice service on a single phone line. asymmetrical A telecom channel that has more bandwidth in one direction than in the other. asynchronous An operation that proceeds independently of any timing mechanism such as a clock. An asynchronous network is driven by two different, independent clocks. asynchronous response mode (ARM) A communication mode in which two devices initiate transmission between each other and synchronize their respective data. asynchronous transfer mode (ATM) A protocol that segments digital information into 53-byte cells (5-byte header and 48-byte payload) that are switched throughout a network over virtual circuits. This protocol can accommodate many media (i.e., voice, video, data) at transmission rates ranging from 1.5 Mbps to 622 Mbps. ATM adaptation layer (AAL) The ATM adaptation layer converts data from the upper-layer format into the ATM layer. AAL 3 supports connection-oriented service. AAL 4 supports connectionless data service. ATM switch Wide area network (WAN) element that directs cell-based ATM traffic across service provider networks. attenuation The decrease in signal strength along a fiber-optic waveguide caused by absorption and scattering. Attenuation is usually expressed in decibels (dB) per kilometer. automated message accounting (AMA)   automatic protection switching (APS) The ability of a network element to detect a failed working line and switch the service to a spare (protection) line. 1+1 APS pairs a protection line with each working line. An APS provides one protection line for every working line. average revenue per user/unit (ARPU) available-to-promise A type of analysis used prinicipally by manufacturing firms that determines whether sufficient raw materials are on hand to produce and commit to a particular order.