The Beckhoff KL6904 is a versatile Bus Terminal designed to combine safe communication with digital output control in one compact module. As part of Beckhoff’s TwinSAFE safety system, it offers a reliable and scalable solution for safety-critical applications in industrial automation, ensuring compliance, precision, and flexibility in managing safe input and output signals.

The KL6904 serves as a link unit between safe input devices—such as emergency stop buttons, light curtains, or protective switches—and connected output elements, including actuators or machine control circuits. It features four digital outputs, each rated for 24 V DC with a maximum output current of 0.5 A per channel (and a minimum of 20 mA). This makes it ideal for directly driving low-power actuators or interfacing with safety relays, while ensuring safe and reliable operation in compliance with modern functional safety requirements.

Central to its functionality is support for the TwinSAFE/Safety over EtherCAT protocol. This open, standardised protocol enables the integration of the KL6904 into Beckhoff’s TwinSAFE safety control environment, allowing it to be freely combined with other TwinSAFE components. Safety logic functions can be configured directly, giving engineers the flexibility to design and adapt safety systems to the unique needs of their machinery or plant.

The KL6904 also supports cycle times ranging from 4 to 100 ms, offering flexibility to balance system performance with safety requirements. Its fast and predictable response ensures timely safety actions, while its parameterisable watchdog provides configurable fault handling. In the event of a communication error or system fault, outputs are deactivated according to the defined watchdog time, minimising risk and ensuring compliance with safety standards.

Designed for ease of integration, the KL6904 uses straightforward 2-wire connection technology, simplifying wiring and reducing installation time. As part of the Bus Terminal system, it fits seamlessly into Beckhoff’s modular I/O architecture, allowing it to be used alongside both standard and safety terminals. This modularity supports cost-effective scaling of safety functionality without the need for separate, dedicated safety controllers.

The compact design of the KL6904 also conserves valuable control cabinet space, making it well suited for applications where both safety and efficiency are priorities. By combining safe communication and output functions into a single housing, it reduces hardware complexity and streamlines system architecture.

In summary, the Beckhoff KL6904 Bus Terminal is a powerful and flexible TwinSAFE logic module that integrates safety communication with four 24 V DC digital outputs. With its TwinSAFE/Safety over EtherCAT protocol support, configurable fault handling, and compact design, it offers a reliable solution for implementing functional safety in industrial automation. Whether applied in machine safety, process control, or plant automation, the KL6904 ensures that operators and systems are protected without compromising efficiency or scalability.