The switching on of free digital television across the country has been hailed as a momentous step in Irish broadcasting.
The trial service will allow nine out of 10 viewers nationwide to tune into RTE One, RTE Two, TV3, TG4 and RTE News Now through the new technology.
The old analogue system of watching homegrown television stations through an outdoor or indoor aerial will be switched off in two years' time.
Communications Minister Eamon Ryan said the free-to-air digital service - called Saorview - based at 24 sites around the country will cover 90% of viewers.
"Digital television will improve the television experience for the viewer, with more channels, high-definition pictures, higher-quality sound, on-screen menus and digital teletext," he said.
Viewers will need an aerial and a special set-top box or digital-ready television set to tune in to the service.
More channels and radio services are to be added to the Saorview service as part of a national launch in spring next year. It is planned to be made available to the entire country by then.
Mr Ryan said switching off the old analogue system - currently viewed by more than one million people - would free up space on the airwaves for wireless broadband internet and new mobile services. "Television viewers and the country in general will benefit from this modernisation of our television service," he added.
RTE director general Cathal Goan said: "Saorview is a major step change in Irish broadcasting, offering viewers across the country more channels, high definition pictures, higher quality sound, on-screen programme menus and digital teletext - all free-to-air.
"When the full service is launched next year I believe it will be a very attractive proposition for TV viewers."