Product Overview

The ABB 663636IAI​ is an I/O Assignment Interface (IAI) printed circuit board — sometimes called an I/O distribution or termination board — designed for use in ABB Bailey MCS (Modular Control System) racks that host INFI 90 and Net 90 Distributed Control System (DCS) I/O modules such as the IC03 (analog input), IMDSI (digital input), IMCPI (counter/pulse input), IMFEC (analog output), and others. Physically, the 663636IAI​ occupies a dedicated IAI slot at the front of the MCS rack (typically just behind or integrated with the field‑wiring compartment) and provides a set of screw‑terminal blocks or pin‑header fields that accept field instrument wiring — 4–20 mA analog loops, 24/48/120 VAC/DC discrete signals, thermocouple/millivolt leads (when used with appropriate I/O module front‑end), and 24 VDC loop power returns. These field connections are routed through the board’s gold‑finger edge connector to the mating I/O module plugged into the rack’s module slots, completing the signal path between the plant floor and the DCS processor (IMFCI / INICT01 / INNIS01 etc.) via the INFI 90 I/O bus.Unlike smart I/O modules that contain active electronics, the ABB 663636IAI​ is primarily a passive signal‑distribution vehicle — a high‑quality multilayer FR4 PCB with gold‑plated edge fingers, keyed mechanical slots to prevent mis‑mating with incompatible boards, and clearly silk‑screened terminal designations that correspond to the I/O module’s channel map. Some IAI variants include onboard passive components (RC filters, cold‑junction reference pads for TC inputs when used with an AI module, or loop‑power distribution terminals) but contain no microprocessor or active signal‑conditioning ICs — their role is purely to present a rugged, serviceable field‑wiring interface that can be replaced independently of the I/O module itself. In a Bailey INFI 90 rack the IAI board is the point of contact between the instrument technician and the DCS: removing or swapping an I/O module does not disturb field wiring; conversely, replacing a damaged 663636IAI​ does not require re‑seating the I/O electronics.Because the INFI 90 platform remains in continuous operation across thousands of power‑generation units, oil refineries, and large‑scale process plants worldwide, the ABB 663636IAI​ is a strategically important legacy spare. Authentic boards are required to maintain original impedance characteristics, terminal layout, and keying — generic third‑party reproductions can introduce wiring mismatches, signal‑reflection issues on high‑speed digital I/O, or mechanical fit problems in the tightly toleranced MCS rack. Specifying a genuine 663636IAI​ ensures continued compliance with the plant’s original DCS design documentation and loop diagrams.

Technical Specifications

Main Features and Advantages

Field‑wiring independence from I/O module: The most operationally significant feature of the 663636IAI​ is that field cables terminate on the IAI board, not on the I/O module itself. When an I/O module (e.g., IMDSI02 digital input card) fails and must be replaced, the technician extracts the module from the rack — the 663636IAI​ with all field wires remains undisturbed. Conversely, if a terminal clamp fatigues or a board trace is damaged, the IAI alone is swapped without touching the expensive I/O electronics. This separation of concerns reduces mean time to repair (MTTR) and minimizes the risk of accidentally loosening or mis‑wiring a field instrument lead during module change‑out.Original impedance and signal‑integrity preservation: Bailey INFI 90 analog input modules (IC03 / IMFEC) are specified with particular input impedance and common‑mode rejection characteristics that assume the IAI board’s trace geometry, ground‑plane layout, and terminal contact resistance fall within tight tolerances. The genuine 663636IAI​ replicates the original PCB artwork — controlled trace widths, ground‑return routing, and gold‑plated edge fingers — ensuring that thermocouple micro‑voltage signals, 4–20 mA loops, and high‑speed digital discrete inputs see the same electrical environment as when the system was commissioned. Substituting an unverified copy board can introduce small resistances or crosstalk that manifest as measurement drift or intermittent channel noise on sensitive analog loops.