Porta Westfalica, November 2025 – The daisy chain from BERNSTEIN AG is growing: with the SLO ("Safety Lock OSSD"), a new blossom is joining the SMART Safety System. The new Safety switch with guard locking adds a function to the existing system that is indispensable in many machines: the safe locking of movable protective devices such as safety doors and flaps as long as there is still a risk.
Daisies that create safety
Since introducing its electronic RFID sensors (SRF) for monitoring protective devices, BERNSTEIN used to compare its SMART Safety System to a chain of daisies – a "daisy chain". Each sensor, each emergency stop device, each component joins the chain, picks up the safety signal, adds its own information and passes it on. This creates a continuous system – modular, reliable and space-saving. With the new SLO, a safety switch with guard locking is now being introduced into this chain of electronic components for the first time. A daisy that not only monitors the door, but also keeps it firmly closed – as long as there is still a danger.
Compact, powerful, safe
The SLO is an electromechanical safety switch with guard locking of type 4 in accordance with DIN EN ISO 14119 with RFID coding and safe interlock monitoring. Despite its compact design measuring just 30 × 30 × 135 mm, it offers a locking force of 3000 N and protection class IP69. Depending on the variant, door monitoring and interlock monitoring can each achieve up to Performance Level e (PL e), making them ideal for demanding applications. Thanks to variable coding levels (low, high, unique), tamper protection can be specifically adapted to the requirements of the application – without additional design effort.
A daisy with diagnostic talent
Like its sister blossom in the chain, the SLO is also fully integrated into the Daisy Chain Diagnostic (DCD). This means that each SLO transmits its status via the existing 4- or 5-pin cable. This includes a wide range of information, such as whether the door is closed, the guard locking is active or there is a fault – all information is available centrally.
The status data can be transferred to a smartphone via NFC using a diagnostic device, integrated into the control system using I/O-Link or forwarded to higher-level systems via Profinet or Ethernet using the BERNSTEIN SCR P and SCx modules. This saves time during commissioning, simplifies troubleshooting and enables predictive maintenance. Predictive maintenance offers a number of tangible advantages:
- Failure prevention – because unplanned downtime costs money
- Maintenance as needed instead of rigid maintenance cycle
- Longer machine service life: timely maintenance prevents consequential damage
- Higher plant availability: more production, less downtime
Systematic series connection
Like any daisy, the SLO can be connected in series. Whether with other SLOs, SRF sensors or SEU emergency stop devices: the series connection remains safe and also achieves up to PL e, Cat. 4 in combination. This reduces the wiring effort and at the same time maintains the diagnostic capability of each individual element.
Versatile
The SLO fulfils a key requirement of DIN EN ISO 14119: a safety door may only be opened once the hazard has been eliminated. This is precisely where the SLO comes into play – in packaging machines, woodworking, injection moulding systems or machine tools. Whether it's a door, flap or hood – wherever guard locking is required, the SLO can be flexibly adapted.
Conclusion: More flowers, more possibilities
With the SLO, BERNSTEIN is expanding its daisy chain with a function that is often needed in practice. Integration into the SMART Safety System with DCD diagnostics, flexible interface selection and comprehensive series connection capability makes the SLO a versatile addition to future-proof safety architectures.
Machines are becoming more complex – BERNSTEIN safety remains simple, modular and well thought-out. Or in other words: the daisy chain continues to flourish.
