The Schmersal group is launching new installation aids for securing complexing machine systems which allow quick and simple wiring of safety switchgear in series: the Schmersal safety installation systems.

The series connection significantly reduces the wiring involved. A particular benefit of this installation system is that different electronic safety switchgear systems, such as sensors and interlocks, can be mixed and connected in the relevant application. With larger systems, different machine areas often need to be secured using different safety switches. At the same time, the new system offers cost-optimised options for applications exclusively using electronic safety switchgear.

The safety installation systems also allow individual diagnosis of the safety switchgear connected. This means the operator can clearly identify which switch in the series has triggered a signal.  This means any errors can be fixed quickly and avoid machine downtime. The safety installation systems from Schmersal thus increase machine availability. 

Three alternatives for optimum personnel and production safety

Variants with a passive distributor module (PDM) or a passive fieldbox (PFB) are available for applications with exclusively electronic safety switchgear.  They allow mixed series connection with up to four different electronic safety switchgear units per module. Several modules can be connected to form larger systems.   

  • The passive distributor module (PDM) is small and compact, easy to install in existing terminal boxes and particularly suited to the heightened hygiene requirements for food and packaging machines.
  • The passive fieldbox (PFB) is a plug & play solution in a robust IP67 design for a range of applications.

The PDM and the PFB can be used to wire relatively large systems as wire cross sections of up to 1.5 mm² can be connected. The unique selling point of the two solutions is the individual securing of the safety switchgear devices with circuit breakers with self-returning fuses.


There is a third, active variant for safety switches and safety sensors.

  • For safe series connection of electromechanical safety switches or contact outputs or safety sensors with electronic OSSD outputs, an SRB-E range safety input expansion takes over active electronic signal evaluation. This solution also achieves a safety level of Cat. 4 / PL e / SIL 3 for the series connection of contacts.

The passive installation systems can also be fitted with an optional “Serial Diagnosis” (SD) interface for the transfer of non-secure data. Safety sensors and interlocks connected in series and fitted with an SD interface can transfer and visualise extensive diagnostics data via the SD gateway and a fieldbus to a controller, e.g. status data or error messages. For the MZM100-SD contactless magnetic solenoid interlock, this could be, for example diagnostics data or error messages such as “Error or cross-circuit on a safety output”, “Operating voltage too low” or “Actuator faulty”. This enables quick problem solving. Extended diagnostics functions will, in future, enable preventive maintenance and the avoidance of machine downtime.