Intel Corp yesterday unveiled Intercast, a Windows personal computer board that turns the machine into a television receiver and enables broadcasters to deliver data with their television programs over the flyback and blanking lines, some of which are currently used for Teletext services. Using the blanking lines means that broadcasters can transmit data at almost four times the speed of the fastest available modems. Data will be delivered in the form of World Wide Web pages, providing the capability for interactivity through conventional Internet access. It all sounds extremely clumsy, but Packard Bell Electronics Inc and Gateway 2000 Inc both plan to include the hardware to receive Intercast signals in their computers from next year. Broadcasters NBC and Cable News Network, plus QVC Inc and WGBH, the Boston public broadcasting station are also in on it, as are cable operators Viacom Inc and Comcast Corp, on-line service provider America Online Inc and software developers Asymetrix Inc, En Technology Corp and Netscape Communications Corp. The PCI analogue-to-digital converter board and tuner will be $150.