What's the story with High Definition TV? High definition television has arrived. After months of hype Sky Television finally unveiled its new service to its 400,000 Irish satellite subscribers last week.

Timed to coincide with the beginning of the World Cup, the roll-out wasn't entirely problem-free and Sky was forced to admit that 17,000 customers in Ireland and Britain who signed up to its service had to have their set-top box installation dates rescheduled because of strong demand and "an unforeseen and very late hold-up in the manufacturing process".

Another unforeseen hiccup which may have dampened enthusiasm for HDTV here has been the Republic of Ireland's failure to qualify for the World Cup. If the Irish soccer team had qualified, TV sales would have jumped by as much as 40 per cent in the run-up to the tournament, industry sources say. Despite the on-field disappointment, however, TV sales are still brisk, something attributed to maturing SSIA schemes and the promise of enormously improved picture quality offered by HDTV.

From launch, Sky has been offering nine HDTV channels covering entertainment, sports, movies and both the Discovery and National Geographic channels. US dramas such as 24 and CSI, which are shot with high-definition cameras, will be available and the BBC is to broadcast several World Cup matches and Wimbledon in high definition through Sky's set-top boxes. It has also filmed a number of dramas using HD cameras.

While Ntl and Chorus are committed to develping HDTV products, they have yet to give a launch date. For its part, RTÉ has placed HDTV on its agenda, but has no timeframe for a roll-out. "It is happening and we have to be involved," a spokeswoman says. She expresses optimism that the national broadcaster will be in a position to offer some HDTV transmissions within 18 months but says a "huge upgrade" of everything from cameras to studio make-up - the ragged edges of traditional TV make-up can be visible on HDTV - is needed before RTÉ can shoot in high definition.

So how does HDTV work? It's all in the lines. While a standard television picture uses 576 visible lines to make up the picture, HDTV uses 720 or 1,080 lines per image, bringing up to four times more sharpness. To benefit from this increased clarity, a HD-ready television is needed as is a subscription to Sky's satellite service and a new set-top box.

It is "one product which does not need an explanation. People who come in to the shop can see the difference with their own eyes," according to Shane O'Connor, the general manager of O'Connor's TV and Hi-Fi in Galway. He says HDTV sales are steady and there is a "very high level of awareness" of the concept.

"Over the last six months we have seen a dramatic increase in the numbers of customers checking that the TV they're about to buy is HD ready" he says. With this increased awareness, the traditional cathode ray tube (CRT) market has all but collapsed and now amounts to less than 20 per cent of sales.

Future proofing is difficult when it comes to emerging technologies but consumers dithering over a TV purchase today can at least take solace in the fact that HD-ready TVs do not cost a great deal more than standard models. A 26-inch HD ready, flat screen TV from Philips for example costs €879 while a 32-inch model costs €1,299.

Consumers do need to guard against salesman's sophistry. While they sound similar there is a world of difference between HD-ready and HD-compatible models. The former is the official industry-wide term used to declare that a product will receive a full HDTV signal. The latter just means a TV can get a signal from a HD set-top box, but will not display the highest quality picture.

Similarly, industry sources say, consumers should be wary of salesmen pushing HD formats with just 780 on-screen lines when a superior 1,080 line model can be bought for not very much more (and sometimes no more at all).

The good news for couch potatoes is that, unlike virtually every other sector, prices are falling. "The television market is one of the very few consumer sectors where prices have collapsed in recent years," says O'Connor. History supports his claim.

In the 1970s a standard 25-inch colour TV cost three months' salary in Ireland. Now, for under €2,000 you can pick up a top-of-the-range 42-inch flat screen HD-ready TV while a 20-inch model can be bought for about €500.

It's not all good news, however, and people attempting to sign up before the World Cup will almost certainly be disappointed. Anyone who has ever waited in vain for a Sky repairman to call will appreciate the irony of last week's announcement from the company that its turn to be let down had finally come.

Installations of the set-top boxes in the UK and Ireland had to be delayed last week because the necessary hardware had not been delivered to the company on time.

"We ordered more than enough boxes to meet demand and we're ready to install them but they're not arriving from our supplier as fast as we agreed," the company was forced to admit.