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Description
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1747-BSN |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | Backup Scanner Module / Remote I/O Redundancy Module |
| Parent System | Allen-Bradley SLC 500 Programmable Controller Family |
| Compatible Processors | SLC 5/02, SLC 5/03, SLC 5/04, SLC 5/05 |
| Backplane Current | 800 mA @ 5V DC |
| RIO Baud Rates | 57.6 K, 115.2 K, 230.4 Kbaud (DIP switch selectable) |
| Remote I/O Capacity | Up to 4 logical racks (32 input + 32 output image words) |
| RIO Cable | Belden 9463 (Blue Hose) twisted pair, shielded |
| Maximum RIO Link Distance | 3,048 m (10,000 ft) at 57.6 Kbaud; 1,524 m at 115.2 K; 762 m at 230.4 K |
| M0/M1 File Size | 5,548 words (RSLogix 500 v5.50+); 5,547 words (earlier versions) |
| Block Transfer Support | Up to 64 words per transfer, 32 buffers via M0/M1 files |
| Operating Temperature | 0°C to +60°C (32°F to 140°F) |
| Storage Temperature | -40°C to +85°C (-40°F to 185°F) |
| Humidity | 5% to 95% non-condensing |
| Noise Immunity | NEMA Standard ICS 2-230 |
| Mounting | Any slot of local 1746 SLC chassis except slot 0 |
| Agency Certification | UL Listed, CSA Certified, Class I Division 2 Groups A/B/C/D, CE marked |
| LED Indicators | FAULT (red) and COMM (green) status LEDs |
Main Features and Advantages
Genuine Hot-Standby Redundancy: The Allen-Bradley 1747-BSN is engineered specifically for paired operation, where two scanners — one in the primary chassis and one in the backup chassis — continuously cross-synchronise their RIO image data. If the primary processor, the primary scanner or the primary RIO link fails, the backup 1747-BSN assumes control of the remote I/O link automatically, and the remote adapters continue scanning without the output glitch, communication loss or manual intervention that a cold restart would require. This switchover capability is the defining reason critical SLC 500 installations were specified with paired 1747-BSN modules from the outset.
Full Functional Equivalence to the 1747-SN Scanner: Beyond its redundancy role, the 1747-BSN performs every duty of the standard 1747-SN Remote I/O Scanner. It scans up to four logical racks of discrete remote I/O, supports quarter, half, three-quarter and full logical rack device configurations, executes block transfers through its M0 and M1 buffers, and communicates with the full range of RIO-compatible devices including 1747-ASB adapters, PanelView terminals, RediPANEL operator interfaces, Dataliner displays and 1336/1395 drive adapters. This equivalence means a 1747-BSN can serve in a single-scanner application where system standardisation on one part number is preferred.
Automatic Fault Detection and Diagnostics: Two front-panel status LEDs — FAULT and COMM — give maintenance technicians immediate visual confirmation of scanner health and RIO link condition. Detailed fault codes are reported to the SLC processor status file, distinguishing between G-file configuration errors, duplicate node detection, hardware faults and communication failures, allowing the fault source to be isolated quickly during troubleshooting rather than through trial-and-error module substitution.
Seamless Integration with the SLC 500 Ecosystem: The Allen-Bradley 1747-BSN uses the same RSLogix 500 G-file configuration workflow as the 1747-SN, and its M0/M1 file sizing requirements (5,548 words for RSLogix 500 version 5.50 and later) are documented in the same Rockwell literature set. Programming technicians already familiar with the SLC 500 platform require no additional training to configure, commission or troubleshoot the 1747-BSN, and all existing SLC 500 system documentation, I/O maps and block transfer routines remain valid when the module is installed.
Lifecycle and Spares Strategy Value: Because the SLC 500 family is now in Rockwell’s mature/legacy lifecycle status and the 1747-BSN is no longer in active production, every verified unit in the supply chain represents preserved redundancy capability for an operating plant. Holding tested spares of this module ensures that a hot-backup system retains its designed availability, and provides the schedule cushion needed to plan an orderly migration toward ControlLogix or CompactLogix redundancy architectures rather than an unplanned emergency conversion.
Simple Slot Installation and Baud Configuration: The 1747-BSN occupies any slot of a local 1746 chassis except slot 0, requires no special wiring beyond the Belden 9463 RIO link and the backup interconnect cable, and is configured through a two-position baud DIP switch and the RSLogix 500 G-file. Commissioning a replacement module in an existing redundancy pair is a matter of matching the DIP setting, downloading the existing program, and confirming LED status — a task well within the capability of a plant’s instrument and electrical team.
