Product Overview

The Allen-Bradley 440G-T27127​ is a sophisticated TLS-2 series safety interlock switch featuring an integrated Power-to-Lock​ solenoid locking mechanism, designed to provide the highest level of safety and control for machine guard access points. This device is a critical component in achieving compliance with international machine safety standards (such as ISO 14119, IEC 62061, and ISO 13849-1) by ensuring that a hazardous machine motion cannot be initiated while a guard door is open and, more importantly, that a guard door cannot be opened while a hazardous machine condition exists. The Allen-Bradley 440G-T27127 TLS-2 GD2​ switch operates on the “power-to-lock” principle, meaning electrical power must be continuously applied to the solenoid to keep the guard locked. Upon removal of power (a de-energization of the solenoid), the locking bolt is mechanically released, allowing the guard to be opened. This fail-safe design ensures that in the event of a control system failure or power loss, the guard unlocks, providing safe egress.As part of Rockwell Automation’s comprehensive Guardmaster safety component family, the 440G-T27127​ serves a dual function: it acts as a position switch to reliably detect the state of the safety gate (open/closed) through its positively driven actuator mechanism, and it provides a robust physical lock to prevent unauthorized or accidental access. The switch is rated at Safety Category 4 / PLe according to ISO 13849-1 and SIL 3 according to IEC 62061, making it suitable for protecting against the most severe risks. The “GD2” suffix in the model number often indicates a specific design variant, potentially related to the locking force or actuator type. The core value of the Allen-Bradley 440G-T27127​ lies in its ability to enforce safe machine operating procedures, enabling control modes like “safe standstill” or “safe limited speed” within a guarded area, and ensuring that maintenance personnel can safely enter only when all hazardous energy has been controlled and the lock is disengaged. It is an essential device for implementing control reliable safety circuits on presses, robots, plastic molding machines, and any automated equipment where access to a hazard must be strictly managed.

Technical Specifications

Main Features and Advantages

The Allen-Bradley 440G-T27127​ safety switch is engineered with features that prioritize safety, reliability, and resistance to tampering or defeat. Its most critical feature is the robust solenoid-operated locking mechanism. The “Power-to-Lock” design is inherently safe, as any loss of power to the solenoid (due to an E-Stop, safety controller trip, or power failure) will cause the lock to disengage, ensuring the guard can be opened for escape or access. The switch incorporates a high-security, uniquely coded actuator. This design prevents defeat by standard tools like screwdrivers and ensures that only the specifically mated actuator key can operate the switch, complying with standards that require protection against circumvention. The switch provides multiple, positively driven contacts: two normally open (NO) safety contacts wired in series into the safety circuit and a separate, dedicated monitoring contact for the lock’s status. This allows the safety controller to not only monitor guard position but also confirm the lock is physically engaged before allowing a hazardous machine function to start.Durability and environmental resistance are key advantages of the 440G-T27127. Its high IP67 enclosure rating ensures reliable operation in harsh industrial environments with exposure to coolants, dust, and washdowns. The mechanical construction is designed for high cycle life and can withstand significant mechanical stress. Integration is streamlined within the Allen-Bradley ecosystem; the switch can be directly monitored and controlled by Guardmaster safety relays or Compact/ControlLogix safety controllers using CIP Safety protocol. The ability to monitor the locking state provides a critical feedback loop for control systems, enabling sophisticated safe work procedures like Lockout/Tagout (LOTO) integration or controlled access for setup. The combination of a high safety integrity level (SIL 3, PLe), a fail-safe locking principle, high security against defeat, and rugged construction makes the Allen-Bradley 440G-T27127 TLS-2 GD2​ an indispensable component for creating reliable, standards-compliant, and worker-safe machine guarding solutions.