FAX machines actually have nothing to do with the AT command set. The AT command set is for controlling a modem. Some modems have the capability to operate as a FAX transponder and these units may or may not use extensions of the AT command set to put them into and out of FAX mode.

As far as sending ASCII data via FAX. This is a complex subject to say the least. At the Group 3 FAX level the data for FAXing is sent as a graphics image as pixels in a very specific format. Group 4 and later technologies actually have extended modes for sending data in non graphics formats which are meant for end to end file transfer and not necessarily to instruct the target device to "print" anything on its paper.

It is HIGHLY unlikely that there will be a single scrap of information in a FAX machine manual or a FAX modem manual that describes the protocol or data formats used by Group 3 or Group 4 FAX transmissions. You would have to become a Googler to locate certain information on the WEB or find the web sites of standards bodies which are the sources for specifications to which FAX machine and FAX modem manufacturers build their equipment.

Michael Karas