ine. voice-grade channel A channel with a frequency range of 4KHz. Also referred to as a tele- phone channel. Voice over Cable A technology for delivering cable-based IP telephony. voice-over-packet A technology for transporting real-time voice traffic over packet net- works. VoIP and VoFR are examples of voice-over-packet solutions. voice recognition A technology that allows spoken words in the form of human voice to provide input to a computer. voice synthesis Computer-generated sounds that simulate the human voice. VolP (Voice over IP) A technology for transporting integrated digital voice, video, and data over IP networks. VolP gateway A device that bridges the traditional circuit-switched PSTN and the packet- switched Internet. Glossary volatile storage volatile storage Memory that loses its contents when electrical power is removed. VoWLAN (Voice over Wireless Local Area Network) A local voice solution that VoIP and WLANs to marry the convenience of mobility with the cost-effectiveness of an IP PBX. VP (virtual path) A generic term for a collection of virtual channels that have the same endpoint. VPDN (virtual private dial network) A type of network that was developed for telecom- muters and road warriors who needed secure and convenient access to their enterprise servers. VPDNs have included the use of PPTP, L2TP, or IPsec. VPI (virtual path identifier) In ATM, the portion of a cell header that identifies the virtual path to which the cell belongs. Virtual paths are defined to permit groups of virtual channels to be manipulated as if they were a single channel. VPLS (Virtual Private LAN Services) A VPN technology that provides Ethernet-based multipoint-to-multipoint communication over IP-only networks. VPLS allows geographically dispersed sites to share an Ethernet broadcast domain by connecting sites through pseudo-wires. VPN (virtual private network) A software-defined network offered by telephone carriers for voice and data communications among multiple sites. A VPN provides the appearance of a private-