ices. VLAN (virtual local area network) VLAN (virtual local area network) A network of computers that behave as if they are con- nected to the same wire even though they may actually be physically located on different seg- ments of a LAN. VLANs are configured through software rather than hardware, which makes them extremely flexible. A big advantage of VLANs is that when a computer is physically moved to another location, it can stay on the same VLAN without any hardware reconfiguration. VLF (very low frequency) Frequencies below 30KHz. VoATM (Voice ATM) A technology for transporting integrated digital voice, video, and data over ATM networks. vocoders (voice coder/decoder) A device used for compression of voice traffic. High- bit-rate vocoders are used by PCS, wireless local loops, and wireless office telecommunication systems applications. Low-bit-rate vocoders are used in cellular systems that deal with vehicular traffic, where there are large cells and a need to facilitate a large number of conversations. VOD (video-on-demand) A service whereby a subscriber can order and almost immedi- ately view films and other entertainment from a television set. In true VOD, the film can be paused, rewound, and fast-forwarded. In "near" VOD, these functions are not possible. VOD Metadata A project established by CableLabs that is pertinent to the future of interac- tive services. The initial efforts of VOD Metadata are focused on creating specifications for VOD and subscription VOD (SVOD) applications. VoDSL (Voice over DSL) A technology for delivering voice transmissions over DSL lines. VoDSL enables service providers to deliver high-speed data access and up to 16 telephone lines over 1 DSL line. VoFR (Voice over Frame Relay) A technology for transporting integrated digital voice, video, and data over Frame Relay networks. voice digitization Conversion of an analog voice into digital symbols for storage or transmission. voice grade A telecommunications link with a bandwidth (about 4KHz) appropriate to an audio telephone l