Product Overview
Downtime in a ControlLogix redundant controller system often traces back to one missing part: the fiber optic link between redundancy modules. The Allen-Bradley 1756-RMC1 solves that problem directly. This one-meter (3.28 ft) fiber optic communication cable connects ControlLogix redundancy modules in standard and extreme-environment chassis. It belongs to the Bulletin 1756-RMCx cable series, which offers multiple lengths for different panel layouts. At one meter, the 1756-RMC1 is the shortest option in that family. That makes it the practical choice when modules sit close together and excess cable would only create clutter inside the enclosure.
Key Parameters That Matter
Length and Routing
At 3.28 feet (1 meter), this cable keeps the signal path short and the cabinet tidy. Short runs reduce the chance of sharp bends, which matter because the cable contains optical fibers. A clean, direct route also simplifies maintenance access later.
Fiber Optic Construction
The 1756-RMC1 uses fiber optic technology with a 20 AWG wire size. Fiber eliminates the electrical noise concerns that plague copper links in heavy industrial environments. It connects at the bottom of the module in a downward orientation, so plan your cable path before mounting hardware.
Temperature Range
The cable operates from 32 to 140 degrees Fahrenheit (0 to 60 degrees Celsius). This covers most control room and enclosure conditions. For extreme-environment modules, the same cable applies, which simplifies spare-part stocking across a facility.
Single-Channel Design
The 1756-RMC1 carries one channel. A redundant fiber cable system tolerates a single fault on one channel. If faults occur on both channels, network operation becomes unpredictable. This is why correct cable count and routing matter from day one.
Where the 1756-RMC1 Fits
Redundant ControlLogix Systems
Building a ControlLogix redundant controller system requires one or two of these cables. They pair with the 1756-RM2 and 1756-RM2K redundancy modules. Because modules and chassis do not ship with these connectors, buyers must order them separately before system assembly. Missing this step delays commissioning and pushes back production schedules.
Upgrade and Replacement Projects
When an existing redundancy link fails or a panel gets rebuilt, the 1756-RMC1 restores communication fast. Its one-meter length suits tight layouts where longer cables would need coiling or strain relief. Keeping a spare on the shelf shortens mean time to repair significantly.
Extreme-Environment Installations
The cable works with both standard and extreme-environment modules. That flexibility means one part number covers more of your installed base, reducing the number of line items in your spares inventory.
Installation Notes
Remove the protective caps before connecting the cable. Route it away from areas where it could be run over, abraded, cut, or otherwise damaged. Avoid sharp bends at all times. An LC connector coupler can hold the cable in a safe curve and allows easy connection or disconnection without removing the module from the chassis. The cable connects at the bottom of the module, pointing downward. Plan the route before you start, and leave enough slack for service access without creating loops.
Reliability and Maintenance
Inspect the cable periodically for abrasion, kinks, or connector contamination. Fiber optic links are sensitive to physical damage, so visual checks during scheduled downtime are worthwhile. Keep spare cables on hand. A failed link in a redundant pair may not stop production immediately, but it removes your fault tolerance. Replacing a damaged cable quickly restores full redundancy. Store spares in a clean, dry location with caps in place.
Compatibility Check Before You Buy
Confirm your redundancy modules are the 1756-RM2 or 1756-RM2K. Verify the distance between modules fits a one-meter run. If your layout needs more length, other cables in the Bulletin 1756-RMCx series may suit better. Check that your chassis supports the modules you plan to link. Please verify current lifecycle status and availability with SpareTechPLC before ordering.
Frequently Asked Questions
What does the 1756-RMC1 connect?
It connects ControlLogix redundancy modules, specifically the 1756-RM2 and 1756-RM2K, in redundant controller systems.
How long is this cable?
It measures 1 meter, or 3.28 feet. It is the shortest cable available for these modules.
Can I use it with extreme-environment modules?
Yes. The cable is compatible with both standard and extreme-environment modules.
How many cables does a redundant system need?
Building a ControlLogix redundant controller system requires one or two of these cables, depending on your configuration.
What should I check before installing?
Remove the protective caps, avoid sharp bends, and route the cable away from areas where it could be damaged.
