loop. Lempel-Ziv-Welch LZW, a data compression method named after its compression developers. LZW techniques are founded on the notion that a given group of bytes can be compressed by substituting an index phrase. An optical device of one or more elements in an illuminating or image forming system such as the objective of a camera or projector. level The intensity of an electrical signal. A facility between a subscriber and a telecommunications carrier, generally a single analog communications path physically composed of twisted copper wire. line of sight Some spectrum-based transmission systems need an unobstructed path between the transmitter and receiver. The ability for the receiver to see the sender is described as having a clear line of sight. lipsynch The techniques used to maintain a precise coordination between the delivery of sound and the facial movements associated with speech. Lip synch is required because it takes much longer to process the video portion of a signal than the audio portion (the video part contains much more information and takes longer to compress). To mitigate the delay, a codec incorporates an adjustable audio delay circuit to delay-equalize sounds with faces, and allow talking-head images to look natural. LiveBoard LiveWork's group-oriented electronic whiteboard that allows users in different locations to interactively share information. A wireless pen is used to create documents or images viewed and edited in real-time over POTS lines. LiveBoard can also display full- motion color video and provide audio for mixed media applications. local loop In telephone networks, the lines that connect customer equipment to the switching system in the Glossary of Terms central office. local multipoint Broadband wireless local loop service that offers two- distribution service way digital broadcasting and interactive service over a (LMDS) special type of microwave. logarithm An exponential expression of the power to which a fixed number or base must be raised in order to produce a given number