Allen-Bradley 1771-ALX PLC-5 Local I/O Adapter Module

Description

The Allen-Bradley 1771-ALX is a PLC-5 local I/O adapter module engineered to interface local I/O chassis within a 1771 I/O architecture. Designed for installation in the leftmost slot of an I/O chassis, this module manages communication across the local I/O bus and allows individual racks to be disconnected without requiring a complete system shutdown. Its hot-disconnect capability ensures that interconnect cables can be removed for maintenance without disrupting bus communication to downstream chassis in the system.

The module features onboard configuration switches that must be matched with backplane settings for the specific application. It supports standard interconnect cabling options—such as the 1771-CX1, 1771-CX2, and 1771-CX5 cables—and requires the 1771-CXT terminator plug on the final adapter of the bus chain. Operating reliably within standard industrial automation environments, the 1771-ALX provides robust backplane management for legacy PLC-5 control systems.

Features

• Designed for placement in the leftmost slot of a 1771 I/O chassis
• Enables disconnection of an individual I/O rack from the bus without shutting down the entire system
• Supports daisy-chaining up to 16 local I/O adapters on the communication bus
• Compatible with standard 1771 interconnect cables (1771-CX1, 1771-CX2, 1771-CX5)
• Requires Cat. No. 1771-CXT terminator plug on the final adapter in the bus sequence
• Configurable via integrated module switches matching backplane requirements
• Compatible with all Allen-Bradley 1771 external or slot power supplies

Applications

• Legacy Allen-Bradley PLC-5 industrial control systems
• Distributed local I/O chassis architectures
• Manufacturing and process automation lines requiring modular rack isolation
• Industrial plant retrofits and maintenance upgrades

Technical Specifications

Connections / Interfaces

The 1771-ALX module features physical ports for interconnect cabling to link adjacent 1771 I/O chassis. Front-panel connections accommodate standard 1771 series multi-conductor communication cables. Switch blocks on the module must be precisely configured to match chassis rack addressing and communication parameters.

Installation Guidelines

• Ensure all system power to the chassis is turned off before installing or removing the 1771-ALX module, unless performing authorized hot-disconnect procedures on isolated cabling.
• Install the adapter strictly in the leftmost slot of the designated 1771 I/O chassis.
• Verify that physical keying on the module connectors matches the backplane slot keying to prevent incorrect module insertion.
• Set the onboard configuration switches to correspond with your specific PLC-5 system architecture and rack addressing layout.
• Ensure the final adapter on the bus is properly terminated using the 1771-CXT terminator plug.