Minitel is now history. Since June the 30th, 2012, the minitel doesn't work any longer. All minitel services were shut down officially that day, and are now available on the internet.
This small device was used in France only. It was born a long time ago, when internet was not yet available to public. You may consider it as a -very- low resolution internet, with almost no graphic display ability. But as long as what you wanted was alpha numerical, you were OK. And precisely, METARs, TAFs and text can be displayed on a MINITEL.
To use it, you dialed first a 4 digits phone number depending on the service you wanted to use, on a telephone linked to the minitel (For exemple 3615). When you hear a tone much alike a fax one, you pushed the "Connexion/fin" button on the minitel. Then you typed the name of the service (for exemple METAR) on the keyboard, and pressed the "envoi" button (return key). You were now linked to the service, and just had to follow the instructions.
When you had got what you wanted, you should not forget to press again two times the "Connexion/fin" button to end the communication.
I was asked to add a few details concerning Minitel. Instructions given on the screen depend on the minitel site you're connected to.
On a Minitel, though, you will always find the same keys: