PRODUCT INFORMATION
Product Overview
The Allen-Bradley 1791-8BR is a Block I/O 1791 Relay Block Module designed for distributed industrial control. This combination unit features eight 24V DC discrete inputs and eight normally open contact outputs. It includes an integrated power supply, signal conditioning circuits, and a Remote I/O communication interface. The rackless housing mounts directly onto a standard DIN rail or panel surface.
The module operates as a standalone distributed station positioned near field sensors and actuators. Distributed placement minimizes field wiring distances across industrial control architectures. Communication links use the Allen-Bradley Remote I/O network protocol across discrete automation systems. The hardware interfaces directly with PLC-2, PLC-3, and PLC-5 remote scanner modules. Each output group provides isolated relay switching for external DC and AC circuits.
TECHNICAL DATA
Technical Specifications
| Parameter | Specification |
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| Category | PLCs |
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| UPC | 612598126224 |
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| Weight | 1.88 lbs (0.85 kg) |
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| Input Off-state Voltage | 5V dc max. |
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| Input On-state Current | 11mA @ 30V max. |
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| Input Off-state Current | 1.5mA min. |
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| Compatible Controllers | PLC-2, PLC-3, PLC-5/20, and PLC-5 |
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| Module Type | Block I/O combination module |
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| Module power | 24VDC |
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| No. of Inputs | Eight (8) |
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| Input On-state voltage | 10-30VDC |
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| Output voltage | 20-30V dc @ 1A resistive, max. |
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| Mounting orientation | Vertical and Horizontal |
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| Voltage | 24V dc |
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| Inputs per Block | 8 |
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| Input On-state Voltage Range | 10-30V dc |
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| Outputs per Block | 8 |
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| Output Voltage Range | 20-30V dc @ 1A resistive max. |
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| External Power | 19.2-30V dc |
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| Product Lifecycle Status* | Discontinued/Obsolete |
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TECHNICAL INFORMATION
Features
- Combination design integrates eight 24V DC inputs and eight normally open relay outputs.
- Direct compatibility with Remote I/O networks for distributed Allen-Bradley PLC architectures.
- Rackless housing supports direct panel mounting or standard DIN rail installation.
- Input circuitry supports 10 to 30V DC operating ranges.
- Relay contact outputs switch resistive loads up to 1A at 20 to 30V DC.
- Integrated internal power supply operates from an external 19.2 to 30V DC supply.
TECHNICAL INFORMATION
Applications
- Distributed machine interface near field switches and solenoid valves.
- Remote digital status sensing and actuator control on PLC-5 networks.
- Field point expansion for legacy Allen-Bradley PLC-2 and PLC-3 installations.
TECHNICAL INFORMATION
Connections / Interfaces
- Incoming external DC power connects to terminals +24 (1), GND (2), and RET +24 (3).
- Remote I/O network wiring attaches to terminals BLU (6), SHD (7), and CLR (8).
- Field inputs accept standard binary devices such as proximity switches, limit switches, and pushbuttons.
- Relay output contacts interface directly with motor starters, solenoids, and resistive loads.
- Wiring terminations require 14-gauge stranded conductors with up to 3/64-inch insulation thickness.
TECHNICAL INFORMATION
Installation Guidelines
- Mount the unit in either vertical or horizontal orientation on a panel or DIN rail.
- Install external fusing because the module does not provide internal surge-limiting protection.
- Never connect relay output channels in parallel to avoid reducing overall circuit resistance.
TECHNICAL INFORMATION
Compatibility
- Compatible with Allen-Bradley PLC-5 scanners including 1771-SN and PLC-5VME 6008-LTV modules.
- Integrates with PLC-2 family communication modules including 1772-SD and 1772-SD2 scanners.
- Supports PLC-3 systems through 1775-S5 and 1775-SR5 Remote I/O scanner hardware.
TECHNICAL INFORMATION
Lifecycle / Replacement Information
- Rockwell Automation lists the 1791-8BR as discontinued and obsolete.
- Aituos Controls supplies tested replacement units to maintain existing field installations.
TECHNICAL RESOURCES
Documentation
COMPATIBILITY
Compatibility & Replacement
COMPATIBLE MODELSCompatible with Allen-Bradley PLC-5 scanners including 1771-SN and PLC-5VME 6008-LTV modules. Integrates with PLC-2 family communication modules including 1772-SD and 1772-SD2 scanners. Supports PLC-3 systems through 1775-S5 and 1775-SR5 Remote I/O scanner hardware.
Verify compatibility against the exact Part Number, revision and manufacturer documentation before ordering.
PART VERIFICATION
Before You Order
Industrial automation parts can share similar model names, suffixes and revisions. Confirm the complete manufacturer Part Number before purchase.
01Check Part NumberMatch the complete ordering code on the existing unit.
02Confirm RevisionCheck suffix, hardware or firmware when applicable.
03Send a Label PhotoWe can review a clear label photo when identification is uncertain.
ORDERING PROCESS
From RFQ to Dispatch
1Submit Part Number2Verify Product Identity3Confirm Stock & Condition4Issue Quotation5Dispatch & Tracking
PRODUCT FAQ
Frequently Asked Questions
What is the primary function of the Allen-Bradley 1791-8BR module?
The 1791-8BR is a compact Block I/O module with eight 24V DC inputs and eight relay outputs.
What network protocol does the 1791-8BR support?
It communicates across Allen-Bradley Remote I/O (RIO) links to PLC-2, PLC-3, and PLC-5 controllers.
Does the 1791-8BR contain internal output protection against surge currents?
No, the unit lacks internal output fuses, so users must install external circuit protection.
What is the market reference price for the 1791-8BR?
Observed market reference pricing ranges from $1,854.80 to $3,076.29 depending on condition. These figures represent indicative market reference pricing only and are not a final quotation.
