[albertkoz]

Teletext is still popular in the some European countries. e.g. in prisons to send one way messages from families. For small amount of money you can buy an ad in the teletext and most of the prisoners here got access to the tv.

[anthk]

And to smuggle stuff into prisons and to secretly communicate with the outside.

The put fake adverts/dates/sales and such on the Teletext to chat 'in code words'.

I think it happened in some Spanish prison.