Teiliteacs is a videotex service which allows access to various categories of services, such as a phone directory (which is free), mail-order retail companies, airship or ferry ticket purchases, information services, databases and message boards. It was launched in Ireland by P7T (the Department of Post and Telegraphs), but found its greatest success in Armorican Isles, where it is known as Bycopel.
The system comes in two forms. The services can be accessed through a dumb terminal which looks something like a computer with a keyboard, a small screen and an integrated modem. Alternatively, it can delivered over the airwaves (similarly to teletext *here*, or some elements of the Sky Digital system *here*), but this service requires a specially chipped television receiver and only offers a read-only view of the free services, but providing closed-captioning for broadcasts. The variation with the greatest popularity is the terminal, but modern televisions now come prechipped to decode teiliteacs.
At first graphics on the screen were notably primitive being purely character-based, but in recent years have become more and more sophisticated, starting with character block graphics and now simple vector graphics (like the abortive NAPLPS, and the BBC Model B's VDU 25 command *here*).
This technology has been succeeded by the internetwork, but it remains in common use today as a cheaper and more established alternative.