The Line Seiki SM1-301 is a 23mm ultra-compact emergency stop safety relay engineered for single/dual-channel monitoring of emergency stop buttons and limit switches. Its defining characteristic is an exceptionally narrow footprint—just 23mm wide—achieved without compromising safety integrity. The device is certified to the highest functional safety standards, including PLe / Safety Category 4 (ISO 13849-1) and SIL 3 (IEC 61508), with a Mean Time to Dangerous Failure (MTTFd) exceeding 100 years. This combination of extreme compactness and maximum safety certification makes the SM1-301 an ideal choice for machine builders facing severe panel space constraints while requiring uncompromised safety performance.

At the heart of the SM1-301's reliability is its force-guided contact technology and dual-channel monitoring architecture. The unit provides three independent normally open (NO) safety outputs (13-14, 23-24, 33-34) and one normally closed (NC) auxiliary output (41-42). The force-guided design ensures that a welded safety contact will be detected via the auxiliary contact, preventing the system from being reset and maintaining safety function integrity. Two independent input channels (S11-S12 and S21-S22) continuously monitor the connected safety devices. When a safety demand or fault is detected, the redundant safety outputs de-energize within 20 milliseconds. The device also features short-circuit protection via an internal electronic fuse.

The SM1-301 offers flexible integration options. A rear-mounted changeover switch allows selection between automatic reset and manually monitored reset modes. In manual reset mode, a deliberate reset action via terminals S33-S34 is required after safety inputs are restored—a critical feature for preventing unexpected machine restart. Front-panel LEDs provide clear visual diagnostics, with indicators for power supply and the state of both internal relays (K1 and K2). The device is powered by a 24V AC/DC supply with wide tolerance (-15%/+10%) and consumes just 5VA (AC) or 2.5W (DC), making it compatible with standard industrial control power architectures.

Installation is straightforward on a standard 35mm DIN rail. The compact housing measures 100mm high, 23mm wide, and 114mm deep, with a weight of 180g. The device carries an IP20 protection rating and operates reliably across an ambient temperature range of -20°C to 60°C. It complies with a comprehensive suite of international standards, including ISO 13849-1, IEC 60204-1, IEC 61508, IEC 62061, UL 60947-1, UL 60947-5-1, CSA C22.2 No. 60947-1, CSA C22.2 No. 60947-5-1, and carries CE and RoHS marks. When paired with Line Seiki's SS4 series non-contact safety switches, up to 25 switches can be connected in series while still maintaining PLe / Category 4 compliance. With its combination of ultra-compact dimensions, certified high-level safety integrity, and robust electrical specifications, the Line Seiki SM1-301 is an ideal safety core for packaging machinery, small machine tools, robotic work cells, conveyor systems, and woodworking equipment where panel space is at a premium.

Technical Specifications