Advant Fieldbus AF100 is it RS485 or what? What's the bitrate?
From the manual:
Advant Fieldbus 100 is a high performance fieldbus which is used for communication between
Advant Controllers, S800 I/O Stations, AdvaSoft for Windows and equipment developed and
sold by other ABB companies
The media could be twisted pair, coaxial, or optical. Depends of the media, it supports different line lenghts and number of nodes. Usually own ABB modems/transmitters are used.
Physically it is based on RS485. In case twisted pair cable is used:
The modems are able to drive a 750 meter (2500 ft.) of 150 ohms twisted pair cable with 32 AF 100 Stations connected.
For details look in specialized manuals, e.g.