Mayser SG-EFS 1X4/ZK2/1 (often specified as SG-EFS 104 ZK2/1 for 24V versions) is a single-fault-safe electronic control unit (safety relay) designed to monitor pressure-sensitive protection devices like safety edges, mats, and bumpers. Breakdown of the Code & Specifications

1. SG-EFS: Product series representing safety control units/electronics for pressure-sensitive safety guards.
2. 1X4 (or 104): Denotes the specific voltage/model variant—typically 24 VAC/VDC (whereas 114 represents 115V variants).
3. ZK2/1: Dual-channel redundant safety output configuration featuring force-guided relay monitoring (K1/K2).
4. Function: Monitors electrical resistance in the sensor circuit (e.g., 1.2 kΩ or 8.2 kΩ loops) to instantly cut safety outputs if an actuation or fault occurs.
5. Enclosure/Rating: Standard DIN-rail mount housing with an IP20 protection rating.