lution is based on MMW technology to deliver line-of-sight broadband. Also referred to as wireless fiber (WiFiber). VF (voice frequency) Any frequency within the part of the audio frequency range that is essential for the transmission of speech of commercial quality (i.e., 250Hz to 3,400Hz). Also called telephone frequency. VHF (very high frequency) The portion of the electromagnetic spectrum with frequen- cies between about 30MHz and 300MHz. VHF is the operating band for radio and television channels. video signal A signal in the frequencies normally required to transmit moving image information. videoconferencing A two-way communication between two or more parties that involves the exchange of images as well as voice. The images may or may not be in full motion. videotelephony Interactive communication between two parties involving the transmission and reception of images as well as voice. The degree to which the images are in full motion depends on the level of data compression used and on the available bandwidth. videotext A public or private telecommunications service that offers interactive browsing of a menu of textual and graphical information. The most widely used public videotext service is France Telecom's service, offered via Minitel terminals. virtual channel In ATM, the specific conversation path over which the cells from a given conversation flow from one ATM switch to another. virtual router An abstract representation that has the same mechanisms as a physical router and, therefore, can inherit all existing mechanisms and tools for configuration, deployment, operation, troubleshooting, monitoring, and accounting. Multiple virtual routers can exist in a single physical device, and virtual routers can be deployed in various VPN configurations. VISP (virtual Internet service provider) A provider that offers outsourced Internet ser- vice, running as a branded ISP. It is a turnkey ISP product aimed at affinity groups and mass mar- keters that want to add Internet access to their other products and serv