The term 'Fax Predecessor' refers to two technologies that preceded the fax machine: Telex (5 letters) and Teletype (8 letters). Telex was a communication system developed in the 1930s that used teleprinters to send messages over telephone lines. Teletype was a brand of teleprinter developed in the 1920s that allowed users to send typed messages over telegraph lines. Both of these technologies were used extensively before the invention of the fax machine, and thus are considered its predecessors.