Internet Protocol, the language of most online communications, was supposed to have revolutionized the way we watch television by now, enabling a wide range of multimedia bells and whistles: from multiple camera angles to on-screen Web searches while viewing "Gilligan's Island" to see which actors are still living.

But just as the tech bubble's promise of ''IP'' telephone service over an Internet connection is only now becoming a widespread reality, IPTV finally appears to be on the verge of cracking the U.S. mainstream.

Not the cable TV establishment - which questions the technology and the demand for so much interactivity - but rather three Bell telephone companies are taking IPTV off the drawing board in the United States, much as telecom players in Asia and Europe have led the way abroad.

The extent of the Bells' plans vary considerably, but perhaps a dozen markets will see some form of IPTV starting later this year, and millions of homes may have the option by the end of 2006.

SBC Communications Inc., the dominant local phone company from the Midwest to California, is deploying a full-blown IPTV system which it plans to launch by year-end in at least a few undisclosed markets.

Verizon Communications Inc. plans to offer some interactive IP-based features on top of a conventional digital cable service.

The company also won't name its debut markets, though it has secured cable franchise licenses in certain suburbs of Dallas and Los Angeles.

While BellSouth Corp. has expressed doubt about whether a cable rollout makes financial sense, the company sees enough potential to trial IPTV technology in undisclosed markets.

The nation's dominant cable providers, busy introducing telephone service across the country, say there is no rush to introduce TV services much more interactive than video-on-demand and digital video recorders to pause, fast-forward and rewind.

The companies argue that both the IP technology and the telephone networks that the Bells are upgrading for video are unproven.

''They'll have some startup bugs. That's the nature of combining something new with something old,'' said Phil Leigh, president of Inside Digital MediaÂ, a research firm in TampaÂ, Fla.

''But if I was a cable company, I would not minimize what the Bells are doing. It's not just something they want to do because it's cool. It's something they are compelled to do to survive, and if somebody's survival is threatened, you'd better believe they're serious about what they're doing.''

So how does IPTV work, and what's the big deal?

IPTV converts a television signal into small packets of computer data like any other form of online traffic such as e-mail, a Web page or the Internet phone service known as VoIP, or Voice over Internet Protocol - making it easier to integrate the various services on a TV screen.

Using the home's high-speed Internet connection in both directions, a channel selection is transmitted from the set-top box to a local facility, which sends back only the packets of video and audio for the desired channel. The packets are reassembled into programming by software in the set-top box.

A conventional analog or digital cable signal uses far more bandwidth. Every single channel is sent all the way to the set-top box at all times. Each channel requires a separate stream, and there is only so much room on the wire.

That's why IPTV addresses a more pressing need for SBC, which is replacing its major copper phone cables with speedy optical fiber. SBC is not, however, replacing the local lines to every home, as Verizon is.

Copper can only carry a handful of channels at a time, so SBC is relying on IPTV to serve any home with multiple TVs.

Because the technology is relatively unproven, the Bells won't be attempting any of IPTV's more daring tricks in their customers' homes.

Instead, SBC and Verizon both plan to outdo the cable companies by offering a larger program selection, a competitive price, and a smattering of mildly futuristic features which remain a secret.

That secrecy doesn't prevent the Bells and other IPTV advocates from reciting a mantra of fanciful possibilities reminiscent of the early Web days with its visions of ''virtual assistants'' who would remember Mom's birthday and automatically send flowers.