When Coax Runs Out of Road: The 1786-RPFRL Story
A Gulf Coast refinery expanded its tank farm two kilometers past the existing ControlNet trunk. Coaxial cable could not carry the deterministic 5 Mbps signal that far without repeaters and ground-loop problems. The engineering team needed a fiber bridge that kept the network schedule intact. The Allen-Bradley 1786-RPFRL solved that problem by converting electrical ControlNet signals to optical signals for long-distance, noise-immune ring topologies.
This fiber ring long-distance repeater belongs to the ControlNet / Bulletin 1786 family from Allen-Bradley (Rockwell Automation). It provides ground-loop isolation and extends ControlNet reach well beyond coaxial limits. Status LEDs and a fault relay contact support practical diagnostics in the field.
Important Lifecycle Notice
The 1786-RPFRL is discontinued. The discontinuation date was 2022-09-30. Rockwell Automation lists an engineering replacement path toward the 1786-RPFRXL or other ControlNet fiber ring alternatives. Please verify current lifecycle status and availability with Oil AutoTech before ordering.
Technical Specifications That Matter
Three parameters define what this repeater can do in a real plant.
Optical Reach and Media
The unit uses multimode fiber at 820 nm with ST connectors. Each segment reaches up to 3 km. A full ring can span up to 20 km with a 15 dB loss limit. This reach lets engineers link remote process areas, loading terminals, or pipeline stations that coax simply cannot cover.
Ports and Network Role
The module carries 2x BNC coax ports and 2x ST fiber ports. That combination lets it sit between existing coaxial trunk sections and new fiber spans. The repeater regenerates the ControlNet signal, so the deterministic 5 Mbps schedule continues across the optical link.
Power and Isolation
The repeater runs from a 24V DC supply and draws 570mA at 5V DC, which equals 3.02W. It provides 50V isolation. That isolation helps break ground loops between buildings or between electrically noisy process areas.
Environmental and Mounting Data
The operating range is 0-60 C. The enclosure carries an IP20 rating, so it belongs inside a control cabinet or protected enclosure. The series family supports ambient operating temperatures up to 60 C, with storage from -40 to 85 C.
Where the 1786-RPFRL Earns Its Keep
Oil and Gas Tank Farms
Long tank farms often separate the control room from remote manifolds. Fiber segments of up to 3 km let the ControlNet ring reach those manifolds without signal degradation. The 50V isolation also reduces ground-loop risk between structures.
Redundant Ring Topologies
ControlNet supports redundant media with Trunk A and Trunk B. The 1786-RPFRL fits ring designs where one path stays available if the other suffers damage. The fault relay contact gives maintenance teams a clear diagnostic signal.
Legacy System Extension
Plants with existing Bulletin 1786 coax infrastructure can add fiber spans instead of replacing the whole network. This approach protects prior investment while extending reach. For discontinued units, Oil AutoTech helps buyers compare the 1786-RPFRXL and other ControlNet fiber ring alternatives.
Installation and Setup Guidance
Mount the repeater inside a protected enclosure that meets the IP20 rating. Keep the 24V DC supply within the stated range and confirm the 570mA at 5V DC load budget. Use quad-shielded RG-6 coax (75 ohm) with BNC connectors on the coaxial side. Use multimode fiber at 820 nm with ST connectors on the optical side.
Plan the fiber budget carefully. The 15 dB loss limit applies across the ring, so every connector and splice consumes part of that margin. Verify segment lengths stay within the 3 km per-segment limit and the 20 km ring limit. Follow the manufacturer’s installation manual for wiring and configuration details.
Maintenance and Reliability
Inspect the unit periodically. Check ST and BNC connections for contamination, looseness, or mechanical stress. Confirm the status LEDs and fault relay contact behave as expected during scheduled network checks. Keep the cabinet clean and within the 0-60 C operating range.
Because the product is discontinued, spare-unit planning matters. A ready-to-ship spare reduces downtime risk when a legacy ControlNet ring depends on this repeater. Fast dispatch, worldwide, keeps oil, gas, and industrial sites running while migration plans develop.
Compatibility and Integration
The 1786-RPFRL operates within ControlNet networks running at 5 Mbps. It works with coaxial trunk media using quad-shielded RG-6 coax (75 ohm) and BNC connectors. It also supports fiber links using multimode fiber at 820 nm with ST connectors.
Integration Note
Wiring into ControlNet networks may require specific cables, connectors, or connection modules. Confirm cable types, fiber patch cords, and any gateway needs with Oil AutoTech or the manufacturer before installation.
Selection Guide: What to Verify Before Buying
Check the network media first. Confirm whether the site uses coax, fiber, or a mix. Verify the required segment distance against the 3 km per-segment limit and the 20 km ring limit. Confirm the 15 dB loss budget fits the planned fiber route.
Check power availability. The unit needs a 24V DC supply and draws 570mA at 5V DC (3.02W). Confirm cabinet space and the IP20 environment. For discontinued units, ask about the 1786-RPFRXL and other ControlNet fiber ring alternatives. Oil AutoTech provides hands-on technical selection help and fast-dispatch spares for oil, gas, and industrial automation applications.
Frequently Asked Questions
Is the 1786-RPFRL still in production?
No. Rockwell Automation discontinued this model on 2022-09-30. The listed engineering replacement path points to the 1786-RPFRXL or other ControlNet fiber ring alternatives. Contact Oil AutoTech to confirm current availability.
What fiber type does the 1786-RPFRL use?
The repeater uses multimode fiber at 820 nm with ST connectors. Each segment supports up to 3 km, and a ring can reach up to 20 km with a 15 dB loss limit.
How much power does the module require?
It runs from a 24V DC supply and draws 570mA at 5V DC, which equals 3.02W. It also provides 50V isolation.
Can I mix coax and fiber on the same network?
Yes. The unit provides 2x BNC coax ports and 2x ST fiber ports, so it can bridge existing coaxial trunk sections and fiber spans within a ControlNet ring.
What should I check before ordering a replacement?
Verify your segment distances, fiber loss budget, power supply, and cabinet environment. Then contact Oil AutoTech today for pricing and availability.
