ight Amplification by the Stimulated Emission of Radiation. A device that produces optical radiation both in the range of visible light wavelengths and outside this range. Lasers are used in optical fiber networks to transmit signals through a process of oscillation. Local Access and Transport Areas. The areas within which the Bell Operating and independent telephone companies can provide transport services. The Telecommunications Deregulation Act of 1996 is changing this distinction as sufficient competition in local access is achieved. The FCC is gradually allowing RBOCs and IXCs to compete outside of their historic constraints. latency Latency refers to the transmission delays encountered in a packet-switched network. Latency refers to the tendency of packet-switched networks to slow down when they become congested. It is lethal for data types such as voice and video that require constant bit rates to ensure that these time-sensitive data types arrive with minimal and predictable delays. lavaliere microphone A small clip-on microphone, popular because it is unobtrusive and maintains a fixed distance to the speaker's mouth. layer Layering is an approach taken in the process of developing protocols for compatibility between dissimilar products, services and applications. In the seven-layer OSI model, layering breaks each step of a transmission between two devices into a discrete set of functions. These functions are grouped within a layer according to what they are intended to accomplish. Each layer communicates with its counterpart through header-defined interfaces. The flexibility offered through the layering approach allows products and services to evolve while accommodating changes made at the layer level. leased line A transmission facility reserved from a communications carrier for the exclusive use of a Video Communication: the Whole Picture subscriber. See private line. Local Exchange Carrier. LECs include the Bell Operating Companies and independent telephone companies that provide the subscriber local 