Allen-Bradley 1747-ASB vs 1747-L553

Understanding Two Important SLC 500 Components

The Allen-Bradley SLC 500 family has been widely used in industrial automation applications for many years.

Although many SLC 500 products share similar part numbering, different modules perform completely different roles within a control system.

Two commonly requested products are:

• Allen-Bradley 1747-ASB
• Allen-Bradley 1747-L553

Both belong to the SLC 500 platform, but they serve different purposes.

The 1747-L553 is a SLC 5/05 controller, while the 1747-ASB functions as a Remote I/O Adapter Module.

Quick Comparison Table

Allen-Bradley 1747-ASB Overview

The 1747-ASB is a Remote I/O Adapter Module designed for the Allen-Bradley SLC 500 platform.

It works as a communication interface between remote I/O chassis and PLC scanners, allowing distributed I/O devices to exchange data with the control processor.

Key Role

The main purpose of the 1747-ASB is:

(1) Remote I/O communication

(2) Data exchange between scanner and I/O modules

(3) Expansion of SLC 500 system architecture

(4) Support for distributed control applications

Product Page:

Allen-Bradley 1747-ASB

Allen-Bradley 1747-L553 Overview

The 1747-L553 belongs to the SLC 5/05 processor family.

It functions as the central processing unit of an SLC 500 control system, executing user programs and managing automation tasks.

Key Role

The 1747-L553 is mainly responsible for:

(1) Running PLC logic programs

(2) Processing control instructions

(3) Managing communication functions

(4) Controlling connected I/O modules

Product Page:

Allen-Bradley 1747-L553

1747-ASB vs 1747-L553: Main Differences

1. Function Difference

The biggest difference is their position within the control system.

2. System Position

A typical SLC 500 system may include:

	

		

			

				

					

						

							

								

								
								

									

										

											

												

PLC Processor
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1747-L553
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Remote I/O Network
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1747-ASB
      |
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I/O Modules
												
											
										
									
								
							
						
					
				
				

					

					
				
			
		
	

The processor handles control logic, while the ASB module manages communication with remote I/O.

When Do Customers Need 1747-ASB?

Customers usually search for 1747-ASB when:

• Maintaining existing SLC 500 remote I/O systems
• Replacing communication modules
• Supporting older production equipment
• Expanding existing I/O networks

When Do Customers Need 1747-L553?

The 1747-L553 is commonly required for:

• PLC processor replacement
• SLC 5/05 system maintenance
• Backup inventory preparation
• Legacy automation support

Why SLC 500 Spare Parts Are Still in Demand

Although newer PLC platforms are available, many factories continue operating SLC 500 systems because of:

(1) Existing machine configurations

(2) Long equipment lifecycle

(3) High migration costs

(4) Stable production requirements

For these users, sourcing compatible replacement modules is often the preferred maintenance approach.

Related Allen-Bradley Products

We also supply various Allen-Bradley automation products, including:

• SLC 500 Controllers
• 1746 I/O Modules
• 1747 Communication Modules
• PLC Processors
• Industrial Automation Spare Parts

Conclusion

The Allen-Bradley 1747-ASB and 1747-L553 are both important products within the SLC 500 platform, but they serve different purposes.

The 1747-L553 operates as the main PLC processor, while the 1747-ASB provides remote I/O communication support.

Understanding these differences helps maintenance teams and automation buyers select the correct replacement parts for existing systems.

Tags

Allen-Bradley

SLC 500

1747-ASB

1747-L553

PLC Modules

Industrial Automation

Remote I/O

PLC Spare Parts