Ireland's analogue television network has been replaced by a digital signal in line with the rest of Europe.
The free-to-air television service, known as Saorview, will provide consumers with a greater choice of channels, better quality pictures and sound and digital Aertel.
Minister for Communications Pat Rabbitte said the switchover "heralds the dawn of the digital broadcasting era" in Ireland.
He said the closure of the analogue TV network frees up "space for mobile broadband services".
To receive Saorview, viewers will need to have purchased a set-top box or a Saorview-approved television.
Retailers around the country have reported a significant late surge in business.
For those who have not made the switch, their screens went blank at 10am.
Analogue Aertel will continue to be broadcast on UPC, and for Sky customers who are currently able to receive the signal.
Following today's switchover, Aertel will be available on Saorview and online in a new digital format on www.rte.ie/aertel.
For mobile users it is available as usual on m.rte.ie/aertel.
Saorview queries – 1890-222-012 or www.saorview.ie
Aertel has over 1.2m users on a weekly basis and around 5m page impressions online a month on www.rte.ie/aertel and m.rte.ie/aertel.
Director of Production and Operations at RTÉ Digital Tom Grealis said Aertel has an emotive appeal to teletext users who have grown up with the service.
"We've taken the best of the service and modernised it on www.rte.ie, while keeping a familiar look and feel that appeals to our traditional users," he said.