Product Overview

The Woodward 9905-973 LINKnet 8-Channel Relay Output Module is a distributed digital output module used in compatible Woodward control systems. It provides eight relay output channels, allowing a controller to operate external devices through discrete switching signals rather than requiring every field connection to return directly to the main control cabinet.

In a turbine or engine control installation, the controller may need to operate auxiliary solenoid valves, signal external alarms, or switch interlock circuits as operating conditions change. The 9905-973 receives output commands through the LINKnet communication network and converts them into relay contact states for connected field circuits.

The module is part of Woodward’s LINKnet I/O family and is identified as the eight-channel relay output variant. It can be integrated into compatible control architectures, including systems using Woodward 723-series controls. Its function is distinct from that of a central controller: the controller executes the governing logic, while the relay module provides the physical switching interfaces needed to operate external equipment.

For maintenance engineers, the main selection considerations are the number of required relay outputs, contact ratings, network compatibility, and the electrical characteristics of the connected loads. The module must be installed and configured as part of a compatible LINKnet system rather than treated as a standalone programmable controller.

Technical Specifications

Product Features

• Eight relay output channels: Provides multiple discrete switching points for external control circuits.
• LINKnet communication: Receives output commands through the supported Woodward network architecture.
• Distributed I/O arrangement: Allows relay switching to be located near the equipment being controlled, where the system design permits.
• Controller integration: Works with compatible Woodward controllers that support LINKnet I/O modules.
• Field-circuit switching: Supports control applications involving suitable relay-operated devices and signal circuits.
• Separate control and field functions: Leaves control logic to the host controller while the module handles the relay output interface.
• Multi-channel control: Consolidates several discrete output functions within one module for organized panel wiring.

Working Principle

The 9905-973 receives digital output commands from a compatible Woodward controller over the LINKnet communication network. Based on the commands and module configuration, its relay channels change state to open or close the associated field circuits.

A typical control path is:

Woodward Controller → LINKnet Network → 9905-973 Relay Output Module → Field Devices

For example, when a controller’s operating logic calls for an auxiliary solenoid valve to energize, it sends the corresponding output command through LINKnet. The module switches the assigned relay contact, allowing the external circuit to operate the valve if the wiring and electrical ratings are appropriate.

The same arrangement can be used for alarm annunciation, permissive signals, and other discrete control functions. Each channel must be wired according to its intended circuit, including the required common, normally open, or normally closed contact arrangement where applicable.

The relay module does not independently determine when a valve or alarm should operate. The host controller supplies the logic and commands, while the module provides the physical switching function. Correct operation therefore depends on communication configuration, network wiring, channel assignment, external power, and suitable contact loading.

Relay contact ratings must be checked against the actual load. Inductive devices such as solenoids may require suitable suppression or interface components to manage switching transients and protect the contacts.

Role in the Woodward LINKnet Control Architecture

The 9905-973 occupies the discrete output layer of a distributed control system. It connects the controller’s digital commands to external relay-operated circuits, allowing field devices to be switched without assigning the relay module responsibility for the overall control sequence.

Woodward Controller → LINKnet Communication → 9905-973 → Relay Contacts → External Equipment

Industrial Applications

Installation and Maintenance

1. Verify the module reference: Confirm that the installed module is 9905-973 and that the control-system documentation identifies it as the required eight-channel relay output module.
2. Check controller compatibility: Verify that the host controller and its LINKnet interface support the module and the intended I/O configuration.
3. Confirm the network address: Set the module’s address switches to match the address assigned in the controller application.
4. Isolate the equipment: Follow the approved shutdown and electrical isolation procedure before working on the module or connected field circuits.
5. Inspect the mounting arrangement: Check the DIN rail, grounding block, and enclosure installation to ensure that the module is securely mounted.
6. Verify network wiring: Inspect the shielded twisted-pair communication cable, terminal connections, cable routing, and network termination arrangement.
7. Check the field wiring: Confirm that each relay channel is connected to its intended load and that the contact configuration matches the circuit design.
8. Verify electrical ratings: Check the voltage, current, and load characteristics of each connected device against the applicable relay contact ratings.
9. Inspect protective components: Verify any required fuses, suppression devices, and external circuit protection, particularly for inductive loads.
10. Check channel assignments: Compare the physical wiring with the controller application’s output mapping to prevent commands from operating the wrong equipment.
11. Test relay operation: During controlled commissioning, verify communication and test each output channel using the approved functional test procedure.
12. Record the configuration: Document the module reference, network address, channel assignments, field connections, and commissioning results for future maintenance.

Compatible System Components

Recommended Related Models

Key Advantages

• Provides eight relay outputs for discrete field-device control.
• Supports distributed I/O through a compatible LINKnet network.
• Allows relay-operated devices to be controlled by a host application.
• Supports integration with Woodward 723-series control architectures.
• Provides a dedicated switching interface for auxiliary equipment, alarms, and interlocks.

Technical FAQs

How many independent output channels does the 9905-973 provide?

The module provides eight relay output channels. Each channel must be assigned and wired according to the control application’s output mapping and the requirements of its connected circuit.

How is the module address configured within a LINKnet network?

The module uses rotary address switches that must match the address assigned in the controller application. An address mismatch can prevent the controller from communicating with the intended I/O module.

What network wiring is required for the 9905-973?

The LINKnet installation uses shielded twisted-pair wiring. The network must follow the specified cable, grounding, shielding, and termination arrangements, including the required termination network at the final module.

Can the 9905-973 be substituted directly with a LINKnet HT output module?

No direct substitution should be assumed. The original LINKnet and LINKnet HT systems use different network architectures, so a change requires verification of controller compatibility, communication hardware, application configuration, and wiring requirements.