A feature of V.92 modems that allows users to connect to the Internet and switch to an incoming voice call when a call waiting signal is detected. When the voice call is terminated, the line is switched back to the Internet. There is a timeout period in which the user must end the voice call, otherwise the Internet connection is dropped.
If the user's modem is V.92, but the ISP supports only V.90 modems, this feature disconnects the Internet call and answers the voice call. Prior to V.92, when the user was online, a call waiting signal often dropped the Internet and voice connection. See V.92