I have memories from around 1980 of visiting some friends of my parents who had a television with teletext. The television had a remote control and when you pressed a certain button the picture vanished and was replaced by a screen filled with text. Entering in a number using the remote control would bring up another page of text about something else. There were pages for all sorts of things ranging from weather reports to airline flights to international news. It was amazing. I would spend hours looking at the pages of Ceefax and Oracle.
Televisions with teletext were an expensive luxury in 1980. My family had to make do with a Sony portable with knobs and buttons on the front panel and no remote control. Teletext was an option on many early 80's televisions that added around ?100 to the price. Only in the late 80's were teletext decoders included as standard in most televisions.
Not many people know this but teletext will die when analogue broadcasts are switched off.