Product Overview

The 033-59-20-99G​ is a specialized PCLF (Process Control Link Fieldbus) interface board developed by Foxboro—now operating under the Honeywell portfolio—as a core communications component within the renowned 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 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 refurbished or surplus 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.