Britain's TV revolution starts today today

THE DIGITAL age starts today with the launch of BSkyB's digital satellite service of close to 200 television and music channels. The moment comes as a relief to a multibillion-pound industry that has spent years investing in, and promoting, a revolutionary form of television, but not selling it to anyone.

The launch will be celebrated by Sky tonight at a celebrity-studded party at Battersea power station in south London, while Dixons said its Oxford Street store would open at midnight and be the first store in Britain to sell digital equipment.

Sky signed up 20,000 customers for its first day of digital broadcasting, and is hoping to secure 200,000 subscribers by Christmas. "Today is the day that television changes," BSkyB's chief executive, Mark Booth, said. "It will revolutionise the way millions of people spend their leisure time."

Sir Christopher Bland, the chairman of the BBC, issued a warning about the digital revolution - urging broadcasters to protect viewers from "a tidal wave of cheap, acquired programming brought in to fill the airwaves with little regard for quality but with every consideration for cost per hour".

Appealing for the preservation of public service broadcasting, he said that in an environment of hundreds of channels and "deafening noise", audiences would be seeking names and channels that they trust.

The launch is the first stage of a process that could see the entire country switch to digital within 15 years. Chris Smith, Secretary of State for Culture, Media and Sport, has said he will monitor the situation closely and decide when to announce that current analogue television will be switched off entirely.

Nobody knows whether the public will quickly be won over to the attractions of digital, but an enormous advertising campaign is about to begin in an effort to secure fast take-up rates. Sky is to spend pounds 60m in the first three-month phase of its promotion, while its terrestrial rival ONdigital has promised an advertising budget of pounds 90m over the coming year. The BBC, meanwhile, is also betting on a digital future with a prominent "platform neutral" television campaign featuring Ruby Wax and Stephen Fry.

The message will be relentless, and is not likely to ease up in the year ahead. ONdigital will launch its 30-channel service on 15 November, and cable companies such as Cable & Wireless, Telewest and NTL are gearing up for launches next year.

Anyone wanting to subscribe to digital in the early stages will need one of the pounds 199 set-top boxes that go on sale today. Box manufacturer, PACE, said yesterday that the number of people who understand what digital television is has nearly doubled from 36 per cent to 62 per cent in the past year. It is a substantial increase, but still leaves more than one- third of the population in the dark over what digital television is about.

The first wave, which begins today, is essentially to introduce a huge range of channels to the public. The BBC, for instance, is busy launching more channels in one year than it has in the past 30. BBC Choice, the complementary channel to BBC1 and BBC2, is only the first in a wave of new channels that will include BBC Learning, an education channel, and UK Play, a joint-venture channel for teenagers mixing music and comedy. ITV will launch ITV2 to complement its analogue service, and Channel 4 will launch Film Four, a likely precursor to more niche channels from a horse-racing channel to a comedy channel.

The second wave of digital will come next year with "interactivity" - meaning that televisions will be used as two-way channels of communication. Apart from the set-top boxes, no extra equipment will be needed, but customers will be able to enter a world of television shopping, banking and e-mail.

The real breakthrough in interactivity, though, will come with the launch of cable services, which will provide access to a television version of the World Wide Web.