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Description
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-CNBR |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | ControlNet Redundant Bridge Module |
| Series / Platform | 1756 ControlLogix |
| Network Ports | 2 × ControlNet BNC coaxial (Channel A / Channel B); 1 × NAP RJ45 |
| Transmission Rate | 5 Mbps (5000 kbps) |
| Maximum Nodes Supported | 99 nodes per ControlNet network |
| Logix Communication Connections | 40 to 48 (depending on revision and redundancy configuration) |
| Total Connections Supported | 64 maximum |
| ControlNet Cable | 1786-RG6 quad-shield RG6 coaxial |
| NAP Cable | 1786-CP |
| Current Draw | 970 mA @ 5.1V DC; 1.7 mA @ 24V DC |
| Power Dissipation | 5.1 W (17.4 BTU/hr) |
| Isolation Voltage | 30V continuous (basic insulation type, ControlNet A/B to backplane, ControlNet A to ControlNet B) |
| Slot Width | 1 ControlLogix slot |
| Module Location | Chassis based, any slot |
| Enclosure Type Rating | None (open-style) — ControlLogix chassis mounted |
| Dimensions | 140 × 40 × 118 mm (5.51 × 1.57 × 4.65 in) |
| Weight | 0.293 kg (0.64 lbs) |
| Operating Temperature | 0 °C to 60 °C (32 °F to 140 °F) |
| Storage Temperature | –40 °C to 85 °C (–40 °F to 185 °F) |
| Relative Humidity | 5% to 95% non-condensing |
| Vibration / Shock | 2 G @ 10–500 Hz vibration; 30 G operating / 50 G non-operating shock |
| EMC Immunity | ESD 6 kV contact / 8 kV air; EFT/B ±3 kV @ 5 kHz; Surge ±2 kV line-earth; Conducted RF 10V rms; Radiated RF 10 V/m |
| Emissions | CISPR 11 Class A |
| Temperature Code | T4A (North America) / T4 (IEC) |
| Certifications | UL Listed, c-UL-us, CE, ATEX, IECEx, China CCC, Australian RCM |
| Country of Origin | United States of America |
Main Features and Advantages
True Redundant Media Architecture: The defining capability of the 1756-CNBR is its dual ControlNet BNC port design, which allows simultaneous connection to two independent coaxial trunk lines (Channel A and Channel B). Should a tap, trunk cable, or connector on either channel fail — or be deliberately disconnected for maintenance — the module transitions seamlessly to the surviving channel with no loss of scheduled I/O or messaging traffic. This media-level redundancy eliminates the single greatest reliability weakness of standard ControlNet installations and underpins the high-availability architecture of redundant ControlLogix systems.rockwellautomation.com+1
Deterministic 5 Mbps ControlNet Communication: Operating at the full 5 Mbps ControlNet data rate, the 1756-CNBR delivers the precise, time-scheduled data delivery that distinguishes ControlNet from event-driven Ethernet architectures. When configured with the host Logix processor and RSNetWorx for ControlNet software, the module participates in a pre-computed network update time (NUT) that guarantees I/O data arrives within a fixed, predictable window — essential for coordinated motion, sequential batch control, and safety-adjacent interlocking.rockwellautomation.com+1
Substantial Connection Budget for Distributed Systems: With up to 64 total connections available (40–48 Logix communication connections depending on revision), the 1756-CNBR supports substantial multi-node deployments — a typical redundant system can comfortably host multiple remote I/O adapters, HMI stations, and controller-to-controller MSG paths simultaneously. Engineers managing connection budgets across large plants can plan system growth with confidence within this envelope.rockwellautomation.com+1
Integrated Network Access Port for Live Diagnostics: A dedicated RJ45 NAP port allows a programming laptop running RSNetWorx or RSLinx to connect directly to the ControlNet network via the 1786-CP cable without interrupting scheduled traffic. This makes commissioning, node addition, and network re-scheduling far faster and safer than approaches requiring temporary disconnection of a trunk line.rockwellautomation.com
Robust Industrial Design for Demanding Environments: Tested to 30 G operating shock, 2 G vibration across the 10–500 Hz band, and 5–95% non-condensing humidity, the 1756-CNBR withstands the electrical noise and mechanical stress typical of process-plant control rooms. Its Class A CISPR 11 emissions profile, 6 kV contact / 8 kV air ESD immunity, and ±3 kV EFT/B resilience on the ControlNet ports keep the module stable even in installations with extensive switching loads and long coaxial runs.rockwellautomation.com
Proven Legacy Platform Reliability: Having served as the ControlLogix ControlNet redundancy standard for nearly two decades, the 1756-CNBR benefits from an exceptionally mature firmware base, exhaustive field validation across every process industry, and extensive Rockwell knowledgebase documentation — making troubleshooting and module replacement straightforward for maintenance engineers encountering the platform for the first time.dosupply.com+1
