Description

Product Overview

The Allen‑Bradley 1757-SRM is a system redundancy module built for ControlLogix and ProcessLogix PLC chassis to deliver high-availability dual-chassis control. It occupies two slots in the ControlLogix rack and links primary and secondary controller chassis via multimode fiber cable, continuously synchronizing logic, tag data and online edits between the paired systems. This hardware eliminates costly unplanned shutdowns caused by CPU, power supply or chassis faults, enabling bumpless controller switchover without disrupting live process I/O. Automation control engineers and plant reliability teams rely on this module for critical production systems, with front-panel status LEDs and a fault relay contact to feed chassis health signals to external alarm systems. The fiber crosslink isolates the redundant chassis electrically, preventing ground loop noise and transient interference from corrupting synchronization data in high-noise industrial enclosures. Word count overview:174

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Technical Specifications

• Product Model: 1757-SRM
• Brand: Allen‑Bradley
• Warranty: One Year
• Input Voltage: Powered via ControlLogix backplane
• Operating Temperature: 0 °C to 60 °C
• Storage Temperature: -40 °C to 85 °C
• Response Time: Fast bumpless switchover <100 ms
• Protection Class: IP20 (cabinet mounting)
• Accuracy Class: Not applicable (redundancy sync module)
• Output Frequency: Not applicable
• Rated Current Range: 160 mA @24 V DC backplane draw
• Communication Interface: SC multimode fiber port; dry contact user relay
• Supported Protocols: Redundancy synchronization protocol for ControlLogix
• Overload Capacity: Backplane overcurrent protection, ESD protection
• Dimensions: Two-slot width for 1756 ControlLogix chassis

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Application Scenarios

• Refinery Continuous Process Control: This redundancy module pairs two ControlLogix chassis for crude distillation unit control. The 1757-SRM maintains full data synchronization between primary and backup controllers; if the primary chassis fails, automatic switchover preserves valve and transmitter control without tripping the process.
• Power Plant Boiler Safety Control: Installed in boiler main control cabinets, the module delivers redundant controller operation for fuel and air regulation. The built-in fault relay alerts SCADA operators immediately if synchronization is lost, allowing maintenance before a full controller outage occurs.
• Pharmaceutical Batch Manufacturing: The redundant system managed by this module maintains continuous control of sterilization and formulation batches. Seamless failover prevents batch loss and helps maintain compliance with regulated production records during controller hardware faults.

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Key Product Notes

This two-slot module requires a matched fiber cable between the primary and secondary chassis and is designed exclusively for ControlLogix / ProcessLogix redundant architectures. It automatically crossloads program edits, force values and runtime data to the standby chassis, with no extra programming required for basic redundancy. Allen‑Bradley has discontinued this module, so spare units are used to sustain legacy high-availability process control installations. Proper anti-static handling and fiber cable inspection are required during module replacement to avoid sync failures.