When troubleshooting BACnet connectivity for the Intesis 1 to 1 gateways, keep in mind that the terminals on the Intesis unit are simply labeled A B SG and DO NOT DENOTE POLARITY.
The manuals state that it is A+ B- and unfortunately this is the opposite for most building automation systems in north america. So, always watch for that, especially if the complaints are as follows:
“it brings down my whole MSTP trunk”
“there is no BACnet comms at all”