The bolt pin mechanically guides the actuator when it is retracted into the safety switch. The BRÜHL-RI® bolt system has an integrated random safety device; a pressure spring moves the bolt tongue into the "bolt closed" position without any actuation. Aluminum plugs serve as tamper protection. This system is very robust, low-maintenance and low-cleaning and has proven itself over 30 years in the industrial environment. The BRÜHL-RI® add-on system can be easily combined with safety switches of type 2 (with or without solenoid interlock) from the manufacturers Bernstein, Euchner, Honeywell, Leuze electronic, Pilz, Rockwell Automation, Schmersal, Telemecanique Sensors, Sick and Siemens.