Once television was an innocent handful of channels. Some soaps, news, sitcoms, sports.

But that innocent period faded long ago. Somehow television received license to go forth and multiply.The handful of UHF and VHF channels has doubled, tripled, quadrupled, gotten cabled, dished, downlinked and uplinked.

We are in the Age of Three Digit TV, 150 channels in many homes, each channel spinning out around the clock. Clearly, this is potentially the most significant giant step in the yellow-brick passage of television from innocence to dominance.

Before exhaustion sets in, take a break and consider what is happening:

-Massive Time Warner, which among other things operates five cable systems in New York, said earlier this month that it will convert its franchise in the Queens and Brooklyn boroughs into a 150-channel operation by year's end. The present 75 channels won't do. Full up. Nationally, only one-fourth of cable's 54 million subscribers have choices beyond 50. If 150 channels makes you feel inadequate, you are not alone.

-CableLabs, the research and development technicians of the cable industry, is also thinking big: a digital transmission system that would deliver 100 to 150 channels with an important plus - high-definition pictures for those new sets heading toward these shores. Demonstrations of these new systems are scheduled for this fall.

-MCA, Paramount and a company called TVN Entertainment Corp. last week said that they would be able to deliver to certain home dish users as many as 10 pay-per-view channels next month, quintupling what it could do earlier in the year.

That noise you just heard? It is the electronic slam-dunk machine moving through the paint and crashing the rim.

Three-digit TV has to be more than just more-of-the-same, although a lot of that will still be around. But the promises are for so much more. How the promises will be delivered will be the make-or-break point for these new technologies and these expanded channels. If the program providers can truly deliver on their promises - more choices, more variety, more services - then a major social and cultural change is under way. Viewers will gain in expanded menus. Hometown Hollywood's producers will see greater values for their film and television products. More writers, directors, actors and craftspeople will contribute. If the promises are fulfilled.

Time Warner's New York City Cable Group may very well be a model of how we will live with television in the '90s and beyond. Its 75 channels were reformed to state-of-the-art technologies only five years ago. But it has reached capacity. In addition to the traditional cable load of pay movie channels, broadcast networks and local stations, it has eight foreign-language channels (three in Spanish, one each in Chinese, Korean, Hindi, Greek, Hebrew) and a ninth (TeleColombia) on the way, four education channels, four pay-per-view channels for movies, sports and special events.

But what do you put on 75 new channels? The future is already forming. Time Warner officials talk about choices. One executive said there would be a channel devoted to narrowcasting only, sort of an electronic community newspaper. This channel will be engineered to broadcast only news of certain specific neighborhoods, the meetings, the police blotter activity, the community events. Change your neighborhood and the same channel delivers that neighborhood's news.

Richard Aurelio, president of the Time Warner New York system, also stresses choice: "With more channels we will be better able to satisfy all the communities and the smaller markets. Smaller systems don't bother with narrow, specialized interests. If we have greater capacity, why not offer more? Give people more chances on what they want to learn or be entertained with.

"We have 350,000 subscribers in Queens. Thirty-thousand subscribe to our various language broadcasts. If we can get these first-generation people and their children interested in cable, they will also have access to the educational shows, even MTV and all the rest."

Choices? A 24-hour New York news station is in the planners' minds. As is an additional education channel. Such new cable offerings as Court TV and a 24-hour international news channel from the Christian Science Monitor are being considered, plus whatever else springs from the fertile minds of Hollywood's dreamers.

By redoing its system with fiber-optics technology this year, the Queens system will not only double itself but also will become more interactive - more movies and concerts to order up, more shopping to do, more new schemes. Possibly travel ticketing via television. Banking, maybe.

More choices, especially from that money cow pay-per-view.

But even choices are limited and have their price. Half of the new 75 channels will end up selling movies through pay-per-view. The reason: Each pay-per-view movie will start on the half hour. A two-hour movie would require four channels. Ten movies: 40 channels. With a movie only a half an hour away, the idea of choice takes on a whole new meaning. "A huge theater available 24 hours," Aurelio said.

Almost everybody in Three-Digit TV calls it something else. To one programmer it is a home video store where you get the latest along with some standard movies without changing shoes.

Others call it home multiplex, a replacement for the neighborhood movie house. Order up and just add popcorn.

Another calls it a magazine rack. Something for everyone in one place. General interest. Special interests. Plain-wrap choices. Showier choices.

John Malone, president of the largest cable delivery company in the United States, has likened it to "a Chinese menu of services." You pay for what you pick.

Whatever it will end up being compared to, the introduction of this new technology may result in one good deed. Somebody at Time Warner came up with a new name for the clumsy and suggestively silly pay per view.

Henceforth it will be known more seriously as Home Theater.