The ball is in and the game is on. After months and months of hype, digital television finally arrived in Britain yesterday with the launch of the BSkyB digital satellite system. But while its Irish launch is due soon, consumers are being advised to be patient as this is just the first step in the complete digitalisation of television.

Hot on Rupert Murdoch's heels, a rival digital terrestrial service will be launched next month, bringing digital pictures via small aerials. Not to be outdone, the British cable industry plans to launch its digital service next year. A similar transformation will take place here, but not as soon.

What does all this mean for viewers? Well, despite some confusion over supposedly "digital-ready" TV sets, the choice of which of the three delivery systems to opt for is more important than the choice of television set. With set-top boxes, all televisions will receive digital signals when they come (though widescreen is advisable).

In Britain, the first system on the market is digital satellite. Launched yesterday, BSkyB's service offers up to 140 channels, and costs £199.99 sterling for a dish, remote control and set-top box (£159.99 sterling for existing BSkyB customers). There is also a £25 sterling connection fee, and your phone must be connected to the set-top box to use interactive services such as video-on-demand. There will be Internet access, but limited to pre-approved sites.

The service is sold in packages, and includes six free-to-air channels: BBC1, BBC2, BBC Choice, BBC Education, Channel 4 and Channel 5 (ITV has remained out). The most basic package includes Sky One, Sky News, the QVC shopping channel, Bloomberg business channel and Discovery, and costs £6.99 sterling per month.

Other packages - costing up to £30 sterling per month - are grouped by genre, such as movie channels. BSkyB will have to encourage viewers to take them if it is to recoup its estimated £200 subsidy per installation, as profits from the basic package are estimated to be just £3 per month.

But if BSkyB is banking on the popularity of lots of channels, ONdigital is plugging simplicity instead. Owned by Carlton and Granada, its 30-channel digital terrestrial service goes live on November 15th, and also involves packages of channels starting from £7.99 sterling per month. The set-top box is expected to cost £200 sterling, but will cost more for viewers who only take the free-to-air channels.

With no dish or cable, ONdigital says it can break even with 1.7 million subscribers, making £100 million sterling profit with three million subscribers. Its chief executive, Mr Stephen Grabiner says its "pick and mix" channel packages offer more choice than BSkyB's packages which, he said, force subscribers to buy weaker channels.

ONdigital aims to be available in 70 per cent of Britain next month, rising to 90 per cent within a year, and is predicting tens of thousands of its set-top boxes will be in stores by Christmas.

Finally, in Britain the cable industry is planning to launch its own digital services next year. Cable and Wireless is expected to be first off, and is expected to be the only service which doesn't require users to purchase their set-top boxes. Like BSkyB it will offer up to hundreds of channels, including pay-per-view and interactive services.

The competition between the three camps has led to what has been dubbed a "box-war", with ONdigital opting for a set-top box which is not compatible with BSkyB's Electronic Programme Guide (or EPG, which is really a zapper with lots of handy features). Because of this, each service is determined to get viewers using its set-top boxes, in the hope that this will discourage them from turning over to rivals when initial one-year lock-in periods are up.

With this in mind, and with further advances likely in set-top box technology, the British Consumers' Association is advising people not to take the digital plunge yet. Rather than buying an inappropriate set-top box, it says, people should wait until the situation is clearer, which is exactly what the infant industry does not want.

In the Republic, with similar services planned, the advice is similar. Mr William Fagan, the Director of Consumer Affairs, says people should weigh up all the options, including the long-term options. "It is services, not more channels, people want," he says, adding that consumers should be asking suppliers about services such as video and music on demand, home banking, and Internet access, as well as costs.

The BSkyB service hasn't yet been launched in the Republic, amid what industry sources say is lobbying by the cable industry not to offer the British terrestrial services free to air. A BSkyB spokesman would not be drawn on what packages of channels will be available here, and would only say the service will be "available in autumn". Fees will be "roughly similar" to those in Britain. He said regulatory issues were still being sorted out, but sources suggested that with a shortage of set-top boxes in Britain, and no imminent competition from digital terrestrial or cable here, it's hard to see BSkyB actively promoting the service in the Republic until the boxes are more plentiful.

BSkyB's first competition here will come from the cable industry, with Cablelink expected to launch its service in the first half of next year. A spokeswoman said this will initially involve 30 to 40 channels, rising to about 200 channels by the following year. As with other services, channels will be offered in packages, while in keeping with the tradition in the cable industry, customers will lease rather than buy set-top boxes.

When the cable is upgraded (in three to five years, depending on the wishes of Cablelink's new owners), there will be interactive services including telephones, Internet, home shopping and banking. The company's Galway and Waterford cables are already more advanced than its Dublin equivalent.

This may prove a formidable opponent to BSkyB, as cable penetration here has always been much higher than in Britain (Dublin stands at about 80 per cent, while Britain has less than 30 per cent). However, RTE's plans for digital terrestrial may upset both apple carts.

RTE recently received Cabinet approval for a digital system which could be received by 70 per cent of the population using a set-top aerial and box. The remainder will need to use a rooftop aerial. Mr Peter Branagan, RTE's director of technology, says the system will support 50 channels.

Scheduled for launch in mid-2000, RTE and a yet-unnamed partner will provide a five-tiered service. The minimum offering will cost £75 per year, and will include five RTE channels (including one Oireachtas channel), two TV3 channels, at least one TnaG channel, as well as the five British terrestrial channels. There will also be pay-per-view services and interactive services.

Eoin Licken is at elicken@irish-times.ie