Telstar, Videotex and Communications
a Minitel Terminal, switches in a final translation layer at the point of rendering a frame. This translation layer converts Prestel type frames (CEPT3) to Minitel type frames (CEPT2), it should be a simple process but alas, it is not.
Telstar is a CEPT3 Prestel like system and cannot host CEPT2 type Minitel frames, it simply converts CEPT3 frames to CEPT2 frames on the fly at the point of rendering.
If for some reason Telstar fails to automatically detect the Minitel Terminal a single press of the Connection button (two presses will disconnect) should sort things out.