Neither telex nor fax have any relevance in an Internet world.
Telex has been obsolete since about 1995 and, while there are some good business reasons for using fax, most of us can accomplish the same thing with a PC and a scanner.
Incidentally, I worked with one of the very early faxes about 1960. The quality was very poor at that time, but they soon improved and were a major resource for businesses for the next 40 years. Now, like snail mail, they're still used but have really been surpassed.