Allen-Bradley 1771 Modules – 1771-IFE/C

Technical Dossier

Product Details And Specifications

Allen-Bradley 1771 Series Technical Notes

The Allen-Bradley 1771 series represents one of the most widely deployed programmable controller I/O platforms in global heavy industry. Engineered by Rockwell Automation under the Allen-Bradley brand, the 1771 platform has been installed across petrochemical refineries, nuclear power facilities, chemical processing plants, pulp and paper mills, and automotive assembly lines for over four decades. Its modular rack-based architecture — built around the 1771 I/O chassis — allows engineers to configure discrete, analog, and specialty I/O alongside processor modules within a single backplane. The 1771 system interfaces directly with the PLC-5 processor family, making it the backbone of legacy DCS and PLC infrastructure worldwide. Despite its end-of-life classification, the installed base remains enormous, and demand for spare parts, replacement modules, and lifecycle support continues to be significant across MRO (Maintenance, Repair & Operations) procurement channels globally.

The Evolution of 1771 Architecture

The 1771 I/O platform was introduced in the 1970s as part of Allen-Bradley's original PLC-2 and PLC-3 ecosystem, later becoming the standard I/O subsystem for the PLC-5 family. The architecture is built on a parallel backplane bus, with each 1771 chassis (available in 4-, 8-, 12-, and 16-slot configurations) supporting a mix of I/O and specialty modules. Early revisions used single-density I/O; later revisions introduced high-density discrete modules and expanded analog resolution. The 1771-IFE/C, for example, represents a mature revision of the analog input module line, offering enhanced noise immunity and improved calibration stability over earlier /A and /B revisions. As industry migrated toward ControlLogix (1756) and CompactLogix (1769) platforms through the 1990s and 2000s, the 1771 series entered a managed end-of-life phase. Rockwell Automation officially discontinued active production of most 1771 modules, but the platform remains in service at thousands of facilities where full DCS migration is cost-prohibitive. Compatibility between revisions is generally maintained at the chassis and backplane level, though firmware and adapter module versions must be verified for mixed-revision installations.

1771 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly sourced modules within the Allen-Bradley 1771 platform. Modules are classified by functional category.

Analog Input Modules

• 1771-IFE/C: 8-channel analog input, 12-bit resolution, current/voltage selectable per channel
• 1771-IFE/B: 8-channel analog input, earlier revision, 12-bit, voltage/current input
• 1771-IF: 4-channel analog input module, 12-bit, ±10V or 4–20mA input range
• 1771-IFM: 16-channel analog input, multiplexed, high-density configuration
• 1771-IFMS: 16-channel analog input with isolated channels, multiplexed scanning

Analog Output Modules

• 1771-OFE1: 4-channel analog output, 12-bit, current output 4–20mA
• 1771-OFE2: 4-channel analog output, 12-bit, voltage output ±10V
• 1771-OFE3: 4-channel analog output, 12-bit, combined current and voltage output
• 1771-OF: 2-channel analog output, 12-bit resolution, voltage or current selectable

Discrete Input Modules

• 1771-IA: 16-point discrete AC input module, 120VAC, single-density
• 1771-IB: 16-point discrete DC input module, 24VDC, sinking input
• 1771-IBD: 32-point discrete DC input, high-density, 24VDC
• 1771-IC: 16-point discrete AC input, 220VAC rated, single-density

Discrete Output Modules

• 1771-OA: 16-point discrete AC output, 120/240VAC, triac output
• 1771-OB: 16-point discrete DC output, 24VDC, sourcing transistor output
• 1771-OBD: 32-point discrete DC output, high-density, 24VDC sourcing
• 1771-OW: 16-point relay output module, isolated contacts, AC/DC compatible

Communication & Specialty Modules

• 1771-SDN: DeviceNet scanner module for 1771 chassis, supports up to 64 nodes
• 1771-ASB: Remote I/O adapter module, connects 1771 chassis to PLC-5 via RIO link
• 1771-KA: Data Highway adapter, connects 1771 I/O chassis to DH+ network