The Allen-Bradley 1756-RM2/A, also cataloged as the 1756-RM2 ControlLogix Redundancy Enhanced Module, provides single-channel fiber-optic communication between redundant ControlLogix chassis for redundancy link transmission and reception.

Model Identification

The 1756-RM2 is an enhanced ControlLogix redundancy module configured with one transmit fiber interface and one receive fiber interface. The supplied model information identifies 1756-RM2/A as a spare model designation.

Hardware Specifications

Fiber-Optic Redundancy Link

The 1756-RM2 uses a dedicated transmit and receive fiber pair for communication between redundant ControlLogix systems. The specified interface supports 8.5/125 micron single-mode fiber and a maximum stated transmission distance of 10 km.

The optical interface is specified for operation at a 1310 nm wavelength with a maximum transmission rate of 1000 Mbps. Fiber selection, connector condition, routing, and optical loss must remain within the limits of the installed redundancy system.

Ordering Information

• 1 x Allen-Bradley 1756-RM2 ControlLogix Redundancy Enhanced Module
• 1 x Fiber-optic redundancy module interface assembly
• 1 x Manufacturer model designation: 1756-RM2/A where applicable
• Fiber-optic cables are not included unless specifically listed with the supplied configuration.

Installation Considerations

• Install the module in a compatible ControlLogix chassis according to the applicable Rockwell Automation installation documentation.
• Use 8.5/125 micron single-mode fiber for the specified optical link.
• Route fiber cables separately from high-voltage power conductors and high-current switching wiring where practical.
• Maintain the minimum bend radius specified by the selected fiber cable manufacturer.
• Keep optical connectors clean and protected from dust during installation.
• Verify transmit and receive fiber orientation before commissioning the redundancy link.
• Do not apply copper shielding or grounding methods to the optical fiber itself.
• Confirm chassis configuration and firmware compatibility before placing redundant controllers into service.

Frequently Asked Questions

• What fiber type does the 1756-RM2 use?

  The supplied specification identifies 8.5/125 micron single-mode fiber as the required fiber type for the redundancy communication link.

• How many fiber connections are provided?

  The module uses a single transmit fiber and a single receive fiber, forming a dedicated two-fiber optical communication path.

• What is the maximum stated transmission distance?

  The supplied product data specifies a maximum transmission distance of up to 10 km for the supported single-mode fiber link.

• What optical wavelength is specified?

  The supplied specification identifies 1310 nm as the operating optical wavelength for the 1756-RM2 fiber interface.

• What is the maximum transmission rate?

  The listed maximum transmission rate is 1000 Mbps. Actual system performance depends on the complete redundancy-link configuration.

• Can the 1756-RM2 be used in SIL2 applications?

  The supplied product information states that the 1756-RM2 can be used in ControlLogix SIL2 applications. System-level safety requirements must still be verified.

• Is the operating temperature specified?

  No operating-temperature value was included in the supplied product data. The applicable installation documentation should be consulted before environmental qualification.

• Is power consumption specified?

  No power-consumption value was included in the supplied data. The actual chassis backplane load should be verified against the applicable ControlLogix hardware documentation.