RS-485 bias switches - Facility Explorer - Part No. 24-10143-861 - Supervisory Device - FX Supervisory Controller

FX80 Supervisory Controller Installation Instructions

Facility Explorer
Product name
FX Supervisory Controller
Document type
Installation Guide
Document number
Part No. 24-10143-861
Document revision
Revision date
Each RS-485 port has an adjacent 3-position biasing switch, with these settings:
  • BIA - (Default, middle) Controller provides RS485 biasing, but without a termination resistor.
  • END - Both RS485 biasing and a termination resistor are provided by the controller.
  • MID - No RS485 biasing or termination resistor is provided by the controller.

Often, adding RS-485 biasing can improve communications by eliminating indeterminate idle states.

Note: FX-PC controllers implement biasing. When using RS485 for BACnet MS/TP with FX-PC controllers, we recommend using the MID position (with FX-PC controllers at the ends of the trunks with their EOLs set). The BIA position is not required for an all FX-PC controller trunks. For more information, refer to the FX-PC Series Controllers MS/TP Communications Bus Technical Bulletin (LIT-12011670).