The Beckhoff KL1904 is a 4-channel digital input Bus Terminal developed for safety-related signal acquisition in automation systems. As part of the TwinSAFE product line, it provides secure input handling for devices such as emergency stop buttons, safety switches, light curtains, and other protective equipment, ensuring personnel and machinery remain safeguarded during operation.

Operating at 24 V DC, the KL1904 supports four independent digital input channels with 2-wire connection technology. This simplifies wiring and reduces installation effort while ensuring reliable signal acquisition from safety devices in the field. By consolidating multiple channels in a single terminal, the KL1904 saves valuable control cabinet space while providing flexibility in safety system design.

The terminal is fully integrated into Beckhoff’s TwinSAFE safety concept, supporting the Safety over EtherCAT (FSoE) protocol. This allows safe signals to be transmitted over standard EtherCAT networks, eliminating the need for dedicated safety wiring. With TwinSAFE, safety functions can be configured entirely in software, enabling engineers to adapt, expand, or reconfigure safety systems quickly and cost-effectively.

Response time is a key performance factor for safety terminals, and the KL1904 provides a typical input-to-K-bus transfer time of around 4 ms. This ensures timely detection of safety events and rapid communication with the higher-level safety controller. Additionally, the terminal includes a parameterisable watchdog, allowing system designers to define how the system should respond to faults. In the event of a communication failure or detected error, the KL1904 ensures that the safety function defaults to a safe state within the specified timeframe.

The KL1904 is designed for horizontal installation, aligning with typical control cabinet layouts. It consumes just 48 mA from the K-bus, supporting efficient system design and scalability. Its modular integration into Beckhoff’s I/O system ensures that safety channels can be seamlessly combined with standard I/O, allowing unified and compact control solutions.

Compliance with stringent functional safety standards ensures the KL1904 can be confidently applied in applications where safety integrity is critical. Whether used in machine tools, packaging systems, robotics, or material handling equipment, it delivers the reliability and assurance needed for SIL- and PL-rated safety systems.

In summary, the Beckhoff KL1904 is a compact and powerful 4-channel digital input terminal for safety applications. With its TwinSAFE/FSoE integration, fast response time, configurable watchdog, and simple wiring, it provides a flexible and reliable foundation for functional safety in industrial automation. By combining robust safety performance with modular scalability, the KL1904 supports safe, efficient, and future-proof system architectures.