Allen-Bradley ControlNet Modules: 1786-RG6F

Technical Dossier

Product Details And Specifications

Allen-Bradley ControlNet Series Technical Notes

The Allen-Bradley ControlNet platform is a deterministic, repeatable industrial network protocol developed by Rockwell Automation, operating at 5 Mbps over coaxial or fiber media. It has been deployed as a primary control backbone in continuous-process industries including petrochemical refineries, nuclear power generation facilities, offshore oil platforms, and large-scale chemical manufacturing plants. ControlNet's time-division multiple access (TDMA) scheduling mechanism guarantees deterministic data delivery for I/O and peer-to-peer messaging, making it a preferred architecture for safety-critical and high-availability control systems. Installations of ControlNet infrastructure remain active globally across tens of thousands of nodes, with many sites operating original hardware commissioned in the late 1990s and early 2000s. The 1786-RG6F is a RG-6 coaxial cable component within this ecosystem, used for trunk and drop wiring in ControlNet physical layer installations.

The Evolution of ControlNet Architecture

ControlNet was formally introduced by Allen-Bradley in 1995 as a successor to the proprietary Data Highway Plus (DH+) network, designed to bridge the gap between DeviceNet (device-level) and Ethernet/IP (information-level) networks in the Purdue Reference Model. The original physical layer specification mandated RG-6 coaxial cable with BNC connectors, supporting trunk segments up to 1,000 meters with up to 48 nodes per segment using repeaters.

In the early 2000s, Rockwell Automation introduced fiber-optic media options (1786-RPFRL, 1786-RPFRXL) to address electromagnetic interference (EMI) challenges in high-voltage switchgear environments and long-distance inter-building runs. The architecture remained backward-compatible across hardware generations, allowing 1747 SLC 500, 1756 ControlLogix, and 1771 PLC-5 platforms to coexist on the same ControlNet segment via their respective scanner and adapter modules.

By 2010, Rockwell Automation began transitioning new system designs toward EtherNet/IP, which offers higher bandwidth and IT infrastructure convergence. ControlNet was formally classified as a mature technology, with Rockwell committing to long-term spare parts availability but ceasing active feature development. Sites with existing ControlNet infrastructure face a strategic choice between costly migration to EtherNet/IP and extended lifecycle management of existing ControlNet assets — a gap that specialist distributors such as DriveKNMS are positioned to fill.

ControlNet Full Catalog & Functionalities (SKU List)

The following SKUs represent verified, commonly deployed components within the Allen-Bradley ControlNet ecosystem. Classifications follow standard I/O and network architecture categories.

Coaxial Cable & Physical Layer Media

1786-RG6F: RG-6 coaxial cable, bulk spool, for ControlNet trunk/drop wiring
1786-RG6: RG-6 coaxial cable, standard grade, non-plenum trunk media
1786-TPYR: Tap, 75-ohm, for ControlNet coax trunk tap connections
1786-TPYS: Tap, 75-ohm, short-body variant for space-constrained panel installations
1786-TPS: Terminator plug, 75-ohm, for ControlNet coax segment end termination

Repeaters & Media Converters

1786-RPT: ControlNet coax-to-coax repeater, extends segment length up to 1,000 m
1786-RPCD: ControlNet coax-to-coax repeater with diagnostics LED indicators
1786-RPFRL: ControlNet fiber repeater, multimode, for inter-segment fiber runs
1786-RPFRXL: ControlNet fiber repeater, extended range, single-mode fiber

ControlLogix ControlNet Scanner/Bridge Modules (1756 Platform)

1756-CNB: ControlNet bridge module for 1756 ControlLogix chassis, single port
1756-CNBR: ControlNet bridge module, redundant media, dual-port coax
1756-CN2: ControlNet bridge, Series B, enhanced diagnostics and throughput
1756-CN2R: ControlNet bridge, Series B, redundant media configuration

SLC 500 ControlNet Scanner (1747 Platform)

1747-KFC15: ControlNet interface module for SLC 500 chassis, 1 Mbps coax

PLC-5 ControlNet Scanner (1771 Platform)

1771-ACN15: ControlNet adapter module for 1771 I/O chassis, 1.5 Mbps
1771-ACNR15: ControlNet adapter, redundant media, for 1771 remote I/O chassis

Flex I/O ControlNet Adapter (1794 Platform)

1794-ACN15: ControlNet adapter for 1794 Flex I/O terminal base assemblies

Sourcing Hard-to-Find & Obsolete ControlNet Parts

A significant portion of the global ControlNet installed base consists of hardware that Rockwell Automation has classified as discontinued or end-of-life. Modules such as the 1756-CNB (Series A), 1771-ACN15, and 1747-KFC15 are no longer manufactured, yet they remain in active service at facilities where a full migration to EtherNet/IP is not economically or operationally feasible within current maintenance cycles.

DriveKNMS maintains a dedicated inventory of tested surplus and refurbished ControlNet components sourced from decommissioned plant assets, authorized channel partners, and controlled secondary market channels. Each unit undergoes functional verification before dispatch. For physical layer components such as the 1786-RG6F coaxial cable, DriveKNMS supplies cut-to-length and bulk spool formats to support both emergency replacement and planned maintenance shutdowns.

Quality Control for the ControlNet Range

ControlNet modules present specific test challenges due to their integrated backplane communication logic, TDMA scheduling firmware, and coaxial physical layer interfaces. DriveKNMS applies the following verification procedures to all ControlNet inventory:

For scanner and bridge modules (1756-CNB, 1756-CN2, 1756-CNBR series): units are installed in a live 1756 ControlLogix test chassis running RSLogix 5000 / Studio 5000. Network identity, node address assignment, scheduled and unscheduled bandwidth allocation, and I/O connection establishment are verified against a reference ControlNet segment. Firmware revision is documented and reported with each unit.

For repeaters (1786-RPT, 1786-RPCD): signal integrity is measured at input and output ports using a ControlNet network analyzer. Insertion loss, return loss, and TDMA frame pass-through are validated at 5 Mbps.

For coaxial cable and passive components (1786-RG6F, 1786-TPYR, 1786-TPS): impedance continuity (75-ohm ±3%) and connector integrity are verified. Cable assemblies are tested for shield continuity and center conductor resistance.