Product Overview

The Foxboro 033-59-20-99G​ (also referenced as 033-059-20-99G) is a specialized PCLF (Process Control Link Fieldbus) interface board developed by Foxboro—now part of Honeywell Process Solutions—and serves as a core communications component within the legendary Foxboro I/A Series Distributed Control System (DCS). While it does not directly process temperature or pressure signals, the 033-59-20-99G​ sits at the very heart of the system’s “neural network,” acting as the indispensable bridge through which all data flowing to and from the field-mounted Field Bus Modules (FBM) must pass. In essence, this board functions as a highly reliable, purpose-built network switch, but one that speaks the proprietary F-Bus protocol native to the I/A Series architecture.Installed within the Nodebus unit or the Field Bus Processor (FBP) rack, the 033-59-20-99G​ performs the critical task of protocol conversion and signal conditioning between the Nodebus—the high-speed link connecting to the Control Processor (CP)—and the multiple F-Bus segments that drive field I/O. It translates messages from the control layer into the fieldbus protocol understood by FBM201, FBM202, FBM203, FBM204, FBM206, and other series I/O modules, while simultaneously managing and driving multiple fieldbus channels. This message-routing intelligence ensures that every control command reaches its intended actuator and every field measurement returns to the controller without collision or delay.The 033-59-20-99G​ is engineered for maximum availability in mission-critical process environments. It supports 1:1 redundancy, allowing two identical PCLF boards to operate in a paired configuration so that the failure of one board does not interrupt communications with the field. Multiple onboard LED indicators provide at-a-glance visibility into power status, communication health, and fault conditions. Although the 033-59-20-99G​ has been out of production for many years and now circulates primarily as new-surplus or tested take-out stock, it remains an absolutely essential spare part for the vast installed base of Foxboro I/A Series systems worldwide. When specifying a replacement, strict attention must be paid to hardware revision compatibility with the existing CP type, FBM type, and system software version, as version mismatch can lead to communication interruption.

Technical Specifications