KL6904 Beckhoff
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MPN: KL6904-0000
The Beckhoff KL6904 is part of the KL Analog Input Modules series and supports TwinSAFE/Safety over EtherCAT protocol. This module features four outputs, a nominal supply voltage of 24 V DC, and a maximum output current of 500 mA. The device has a protection rating of IP20 and measures 24 by 100 by 68 mm.
Internal Product Review
The KL6904 is a Beckhoff safety module for TwinSAFE/Safety over EtherCAT architectures with 4 outputs. Support for up to 1024 TwinSAFE devices and a 24 V DC nominal supply make the module especially appealing for scalable machine safety integration. A strong choice for compact safety control with impressive network capacity.
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Product Description:
The KL6904 safety terminal is produced by Beckhoff within the KL Analog Input Modules series. It is an I/O slice used in industrial automation to connect safety-related field circuits to an EtherCAT controller, so status information and shutdown commands can move through the same bus as standard process data. By occupying one slot on a modular rail, the terminal adds safety functions to a compact control system without requiring a separate backplane. It is commonly used where machine signals must be processed together with standard I/O inside a single terminal assembly.
Electrically, the KL6904 uses 2-wire field connections, which let connected devices share a common supply conductor and reduce cabinet wiring. The four output channels can source up to 500 mA in total, while the internal K-bus may draw as much as 250 mA from the neighboring power feed. Signals can be routed over installation cables up to 100 m long, provided each conductor is at least 0.75 mm². For insulation integrity, the device withstands 500 V DC. The housing measures 24 × 100 × 68 mm, which allows the terminal to align neatly with other KL modules in a compact panel layout. Its narrow width also helps preserve rail space when several terminals are grouped in one station.
The safety function relies on the TwinSAFE protocol layer over Safety over EtherCAT frames. Through this link, the terminal can establish up to 15 logical TwinSAFE connections and participate in networks that include as many as 1024 certified TwinSAFE devices. Operation is referenced to a 24 V DC supply delivered through the power contacts on the Bus Coupler. With an enclosure rated at IP20, the module is intended for closed control cabinets where no direct water exposure occurs. The four semiconductor outputs deliver the configured safety response to field actuators, and their status is transmitted over the protocol so the controller can monitor shutdown chains without hardwired feedback loops. This arrangement allows safety-related switching states to remain visible within the same control architecture as the rest of the terminal station.
