Product Overview

The Allen-Bradley 1747-C20 Programming/Communication Cable is an industrial communication accessory designed for use with Allen-Bradley SLC 500 automation systems. With a cable length of 20 feet (approximately 6.1 meters), it provides an extended connection between compatible SLC 500 system components and peripheral communication equipment.

In industrial automation, programming and communication cables are essential for connecting controllers, programming interfaces, and network accessories. They allow maintenance engineers to access controller data, configure system parameters, troubleshoot communication problems, and support routine PLC maintenance.

The 1747-C20 is associated with the SLC 500 DH-485 communication architecture. It can be used in applications where a peripheral device needs to be connected over a distance greater than the standard 6-foot cable length. When used with the appropriate 1747-AIC Isolated Link Coupler and compatible interface equipment, it supports communication connections within the SLC 500 system.

Its 20-foot length provides additional installation flexibility in industrial control cabinets, maintenance stations, and distributed equipment arrangements. This can be useful when the programming device or peripheral interface cannot be positioned directly beside the controller.

The cable is particularly relevant to facilities maintaining existing SLC 500 installations. Since the 1747-C20 has been discontinued, replacement procurement should involve checking the complete part number, connector configuration, and intended communication arrangement before ordering.

Technical Specifications

Note: The 3 kg figure is the supplied shipping weight, not a verified cable-only weight. Confirm the connector arrangement and intended use against the original cable documentation before purchasing.

Function and Working Principle

The 1747-C20 provides a physical communication connection between compatible SLC 500 system equipment. Its function is to carry communication signals between the connected devices as part of the configured control-system architecture.

1. DH-485 Communication Connection

DH-485 is a communication protocol used in Allen-Bradley SLC 500 automation systems. It allows compatible controllers and peripheral devices to exchange information within an industrial control environment.

The 1747-C20 provides an extended cable connection for supported DH-485 arrangements. It is useful when a programming interface or peripheral device must be positioned farther from the controller or isolated link coupler than a shorter cable allows.

2. Extended Connection Distance

The 20-foot cable length provides additional flexibility compared with shorter connection cables.

In a maintenance environment, the programming computer or interface equipment may need to be placed outside the control cabinet or at a nearby service position. The extended cable helps accommodate this arrangement without requiring the peripheral device to be positioned directly beside the controller.

The actual permitted communication distance depends on the complete network architecture, interface devices, and installation requirements.

3. Controller Programming Access

When used with compatible interface equipment, the cable supports the connection needed for PLC programming and maintenance activities.

Engineers can use the appropriate programming interface and software to access controller information, review operating parameters, make authorized configuration changes, and troubleshoot system issues.

The cable itself does not perform programming or protocol conversion. Those functions depend on the connected interface equipment and software.

4. Peripheral Device Connectivity

The 1747-C20 can be used in supported SLC 500 configurations involving peripheral devices such as the 1747-PIC Personal Interface Converter and 1747-DTAM-E Data Table Access Module.

The exact connection arrangement should follow the applicable SLC 500 hardware documentation. Different cables in the 1747 family have different purposes, even when their product descriptions appear similar.

Role in Industrial Control Systems

The 1747-C20 is a supporting component within the SLC 500 communication and maintenance environment. Although it does not execute control logic or process I/O signals, it provides a physical connection that helps engineers access and maintain the automation system.

PLC Programming and Maintenance

A programming connection allows engineers to communicate with a controller during commissioning, troubleshooting, and routine maintenance.

The 1747-C20 can support an appropriate SLC 500 programming arrangement when used with compatible interface equipment. This is particularly useful in older installations where the original communication architecture remains in service.

DH-485 Network Connectivity

The cable can be used as part of a DH-485 connection arrangement involving the 1747-AIC Isolated Link Coupler.

The coupler provides the required network interface and isolation functions within the system. The cable provides the physical connection between compatible devices.

Maintenance Station Access

Industrial facilities often position maintenance computers and programming interfaces at locations convenient for engineers. A longer cable can provide additional flexibility when the controller is installed inside a cabinet or machine enclosure.

This arrangement can reduce the need to move equipment during routine diagnostic work, provided the installation remains within the supported cable and network specifications.

Support for Legacy Automation Systems

Many manufacturing facilities continue to operate SLC 500 controllers as part of established production systems. Replacing an individual communication accessory can help maintain the existing architecture without requiring an immediate controller upgrade.

The 1747-C20 is therefore relevant to spare-parts inventories and maintenance projects involving legacy Allen-Bradley equipment.

Industrial Applications

1. SLC 500 PLC Maintenance

The cable can support communication connections used during SLC 500 controller maintenance. Engineers may use compatible interface equipment to access controller information and perform troubleshooting.

2. Industrial Control Cabinets

In installations where the controller and maintenance interface are not positioned close together, the 20-foot cable provides additional connection reach.

3. Manufacturing Production Lines

Production lines often contain multiple control cabinets and machine stations. A suitable communication cable can support maintenance access to existing SLC 500 equipment without changing the controller hardware.

4. Packaging and Material Handling Systems

SLC 500 controllers may be used in packaging machinery, conveyor systems, and material-handling equipment. The 1747-C20 can support the associated programming and communication arrangements where the specified interface configuration is used.

5. Process Automation Facilities

Older process-control installations may rely on SLC 500 controllers for auxiliary machine functions, equipment sequencing, and local automation. Maintaining the correct communication accessories helps preserve access to these systems.

6. Industrial Equipment Repair and Refurbishment

Repair workshops and automation service providers may require original communication cables when testing or maintaining SLC 500 equipment. The 1747-C20 can be useful where the original DH-485 connection arrangement is retained.

Installation and System Integration

Correct cable selection and connection are important for stable communication and reliable maintenance access.

1. Confirm the Communication Architecture

Before installation, identify the controller model and the intended communication interface. Confirm whether the application uses a DH-485 connection involving the 1747-AIC Isolated Link Coupler.

Do not assume that every SLC 500 programming port uses the same cable. The 1747-C20 should not be confused with other SLC 500 cables that support different communication channels or connector arrangements.

2. Check Connector Compatibility

Inspect both cable ends and compare their connector types with the corresponding equipment ports. Check for bent contacts, damaged locking features, contamination, or loose connections.

Never force a connector into a port. A connector that appears physically similar may have a different pin arrangement or intended application.

3. Plan Cable Routing

Route the communication cable away from high-current power conductors, motor leads, and other potential sources of electrical interference where practical.

Avoid sharp bends, excessive pulling force, and locations where the cable may be crushed by cabinet doors or machinery. Maintain suitable separation from moving mechanical components.

4. Connect the Appropriate Interface Equipment

Install the cable according to the SLC 500 communication arrangement. Where an isolated link coupler is required, confirm that the coupler is correctly powered and connected.

The 1747-C20 is a cable, not a standalone communication converter. It does not independently convert USB, RS-232, or other interface signals.

5. Verify Communication

After connection, check that the programming device or peripheral equipment can communicate with the intended controller.

If communication fails, inspect the cable, connectors, interface equipment, controller configuration, and network wiring. Verify that the correct cable type has been selected for the specific communication channel.

6. Handle and Store Correctly

Keep the cable away from moisture, oil contamination, excessive heat, and mechanical damage. When removing it, hold the connector body rather than pulling the cable itself.

For spare-parts storage, label the cable with its complete catalog number and intended application to reduce the risk of incorrect substitution.

Compatible System Components

The 1747-C20 is associated with the Allen-Bradley SLC 500 communication environment. The following components may be relevant to a compatible installation.

Compatibility depends on the exact controller, interface device, and connection arrangement. The cable should not be treated as a universal programming cable for every Allen-Bradley PLC.

Alternative Models and Replacement Considerations

The 1747-C20 is discontinued, so replacement selection requires careful comparison of its original function and communication arrangement.

These models are not automatically interchangeable. A replacement must be selected according to the controller port, communication protocol, connector arrangement, and intended connection distance.

Before purchasing a substitute, verify:

• The complete original catalog number.
• The controller model and communication channel.
• The required communication protocol.
• The connector type at both ends.
• The connection arrangement involving the 1747-AIC, where applicable.
• The required cable length.
• Whether the replacement is an original Rockwell Automation product or a third-party equivalent.

Key Advantages

Extended 20-Foot Cable Length

The 20-foot length provides additional flexibility when connecting supported peripheral equipment to an SLC 500 communication arrangement.

Support for Legacy SLC 500 Installations

The cable is relevant to facilities that continue to maintain Allen-Bradley SLC 500 controllers and their original communication architecture.

Programming and Maintenance Connectivity

When used with compatible interface equipment, the cable supports access for controller programming, diagnostics, and maintenance activities.

Flexible Equipment Positioning

Its extended length can make it easier to position a programming interface or peripheral device at a convenient service location.

Compatibility with Established DH-485 Equipment

The 1747-C20 is associated with the DH-485 communication environment and can be used in supported arrangements involving SLC 500 interface accessories.

Useful for Spare-Parts Management

Keeping the correct cable available can help maintenance teams avoid unnecessary delays when servicing older automation systems.

Technical FAQs

1. What is the Allen-Bradley 1747-C20?

The 1747-C20 is a programming and communication cable associated with Allen-Bradley SLC 500 systems. It is used in supported communication arrangements involving compatible controller and peripheral interface equipment.

2. What is the cable length?

The cable length is 20 feet, approximately 6.1 meters.

3. Which PLC family is it designed for?

It is associated with the Allen-Bradley SLC 500 family. Compatibility should be checked against the controller model and the intended communication arrangement.

4. Can the 1747-C20 be used with DH-485 equipment?

Yes. SLC 500 documentation identifies the 1747-C20 for supported DH-485 peripheral connection arrangements involving the 1747-AIC Isolated Link Coupler.

5. What is the function of the 1747-AIC?

The 1747-AIC Isolated Link Coupler provides a connection to the DH-485 network and incorporates electrical isolation between the communication network and connected equipment.

6. Does the 1747-C20 convert USB to DH-485?

No. The 1747-C20 is a communication cable, not a USB converter. A compatible interface device is required when connecting a modern computer to an older DH-485 system.

7. Can it replace the 1747-C10?

Not automatically. Although both models are associated with SLC 500 communication applications, they have different cable lengths and intended connection arrangements. Check the system documentation before substitution.

8. Is the 1747-C20 still manufactured?

Rockwell Automation lists the product as discontinued, with a discontinuation date of December 31, 2022. It may still be available through industrial spare-parts suppliers.

9. What should be checked before purchasing?

Verify the full catalog number, cable length, connector condition, connector arrangement, and intended communication application. For used products, inspect the cable jacket and connector contacts for damage.

10. Is the listed 3 kg weight the actual cable weight?

The 3 kg figure supplied for this product is identified as shipping weight. It should not be treated as the verified weight of the cable alone. Confirm the packed shipment weight with the supplier before arranging transportation.

Procurement and Maintenance Recommendations

When purchasing the Allen-Bradley 1747-C20, begin by confirming that the existing installation requires this exact cable type. SLC 500 systems use several communication cables, and selecting a similar-looking model may result in an incompatible connection.

For discontinued products, request clear photographs of both connectors and the cable identification label. Confirm whether the unit is new, unused surplus, refurbished, or used. If the cable is intended for a critical production system, request an appropriate continuity and communication test before installation.

For international shipments, confirm the packaged dimensions and shipping weight separately from the cable’s nominal specifications. The supplied 3 kg value should be treated as a shipping parameter until verified.

During maintenance, inspect the cable jacket and connectors regularly. Avoid pulling the cable during disconnection, protect it from mechanical damage, and store it in a clean, dry location.

Conclusion

The Allen-Bradley 1747-C20 Programming/Communication Cable is a 20-foot communication accessory associated with the SLC 500 automation platform. It supports specified DH-485 connection arrangements and provides additional reach for connecting compatible peripheral equipment and programming interfaces.

For facilities maintaining legacy SLC 500 controllers, the correct communication cable remains important for programming access, diagnostics, and equipment maintenance. Since the 1747-C20 has been discontinued, confirming the catalog number, connector arrangement, and intended application is essential when sourcing replacement stock.