Allen-Bradley 1747-BSN Backup Scanner Module

Configured for SLC 500 redundant scanner coordination in 1746 backplane architectures, the Allen-Bradley 1747-BSN, (1747-BSN Backup Scanner Module) provides direct physical/electrical execution of backup scanning and controller switchover management across SLC 5/02 through SLC 5/05 processor networks.

Suffix Breakdown & Model Matrix

The 1747-BSN identifier is a fixed catalog designation within the SLC 500 backup and remote I/O scanner family. No functional suffix segmentation or option coding is defined in the model structure.

Hardware Specifications

Backplane Scan Arbitration and Redundant Control Transfer

The module implements SLC 500 backup scanning logic through synchronized 1746 backplane communication cycles. Scan data is mirrored between primary and secondary scanner paths, enabling deterministic switchover behavior during processor or communication fault conditions. DH+ and RS-232 channels are mapped into the scanner pipeline for remote I/O and supervisory link monitoring. The backup scanner maintains state alignment through cyclic update windows tied to backplane scan execution, ensuring controlled handoff without discontinuity in I/O image table synchronization.

Frequently Asked Questions

Q: Does the 1747-BSN participate in direct I/O execution or only scanning functions?
A: The module functions as a backup scanner and does not execute direct I/O control logic; it mirrors scan data between primary and backup paths.

Q: What is the impact of backplane current consumption on chassis design?
A: The module draws 800 mA at 5 VDC from the backplane and must be included in total chassis power budget to avoid undervoltage conditions.

Q: Can the module operate with SLC processors outside the listed compatibility range?
A: Operation is limited to SLC 5/02, 5/03, 5/04, and 5/05 processor families; other processor types are not supported by the scan synchronization protocol.

Field Installation Guidelines

• Install the module in a compatible 1746 chassis with verified backplane integrity.

• Ensure processor compatibility is validated before system integration.

• Use Belden 9463 cable for DH+ and remote I/O communication paths.

• Maintain separation between RS-232 and high-noise switching conductors.

• Verify connector seating on the 6-pin Phoenix terminal block before energization.

• Confirm backup/primary scanner configuration alignment prior to system start-up.