Digital TV: How Irish customers will get it

ADSL:

Asymetric Digital Subscriber Line technology is one of the hottest technologies to be developed in recent years.

It can be used to transmit digital information at very high speeds over ordinary copper phone lines that enter the home.

The technology works much better in urban areas than rural areas and is already being used to supply television in US and British cities.

Irish firms Eircom and Esat are testing the technology and are likely to provide high-speed Internet connections to customers from April.

A decision on whether they are allowed to carry television signals over there network will be made shortly by the telecoms regulator, Etain Doyle.

MMDS:

Multi-point Microwave Distribution System is already being used by several Irish companies to provide television services to customers.

This technology uses high-frequency microwave bands to deliver over distances of between 10 to 30 kilometres. Chorus is using this technology to supply digital TV in rural areas.

Unlike satellite or mobile phones, MMDS requires a direct line of sight between the transmitter and the viewer's receiving aerial to work effectively .

Small directional transmitters called "beambenders" are used to serve a terrace of houses if obstacles block the line of sight to a transmitter.

One drawback with MMDS is that it does not offer a return channel to enable a customer to use interactive multimedia services.

Cable:

Most Irish cities have cable systems that are currently being upgraded - you may have noticed all those traffic jams and pot holes - to enable them to carry digital television signals.

Cable is a stable platform from which to provide digital television services. But laying and upgrading cable requires road digs, which are slow and expensive.

NTL and Chorus budgeted to spend more than $400 million on these upgrades when they announced their digital services last year.

However, NTL is only able to offer 36,000 customers digital telephone services and has yet to offer a digital television service. Chorus has fewer than 5,000 digital TV customers.

DTT:

Digital Terrestrial Television will have the advantage of covering almost all the population. Access to the digital network is easier and less costly than hooking up to cable or satellite. Customers will be able to receive digital television signals simply by attaching a set-top box to their television.

However, the roll out of DTT in Ireland has been delayed due to disputes over who will run the service. It is unlikely customers will receive DTT until next year.

Satellite:

Soccer fans across the country will know that BSkyB beams English Premiership football over its satellite network directly into homes and pubs across the Republic.

Satellite communications can be cost effective, with short set-up times providing global access to the remotest of regions with the minimum of infrastructural requirements.

Sky was the first company to distribute digital television by satellite in the Republic - in late 1998. It currently has 4.7 million customers in Britain and Ireland.

However, as with MMDS services, satellite does not offer a return channel and BSkyB do not offer Internet services.