ay) LCD (liquid crystal display) A graphic display on a terminal screen using an electrolumi- nescent technology to form symbols or shapes. LDAP (Lightweight Directory Access Protocol) The standard directory server technol- ogy for the Internet. LDAP allows retrieval of information from multivendor directories. LDP (Label Distribution Protocol) An MPLS signaling protocol. leased line A communications channel contracted for exclusive use from a common carrier, frequently referred to as a private line. LEC (local exchange carrier) The incumbent local telephone company. There was origi- nally no competition among LECs, but as soon as competition in the local loop picked up, LECs were segmented into ILECs, CLECs, and DCLECs. LED (light-emitting diode) A semiconductor junction diode that emits radiant energy and is used as a light source for fiber-optic communications, particularly for short-haul links. LEDs are also used in alphanumeric displays in electronic telephones, calculators, and other devices. LEO (low-earth-orbit) satellite A satellite that orbits at about 400 to 1,000 miles (640 to 1,600 km) above the earth. lightwave communications A term sometimes used in place of optical communications to avoid confusion with visual information and image transmission, such as facsimile or television. limited-distance modem A device that translates digital signals into analog signals (and vice versa) for transfers over limited distances. Some limited-distance modems operate at higher speeds than modems that are designed for use over analog telephone facilities. line (1) The communications path between two or more points, including a satellite or micro- wave channel, also referred to as the transmission line. (2) In data communications, a circuit that connects two or more devices. (3) The transmission path from a nonswitching subscriber termi- nal to a switching system. line hit Electrical interference that causes the introduction of undesirable signals on a circuit. line of sight (1) A characteristic of some open-air tra