A connection of devices of this type will usually be admissible for all multifunctional safety relay modules of type series PROTECT-SRB, but under consideration of the limit value specified in the data sheets for voltages and current (refer in this respect to data sheet information). The circuitry of the respective modules contains a current and voltage limitation which is essential for safety reasons if devices are connected with NC contacts (in order to counter the risk of contact welding). In the case of devices with NC/NO combinations the current and voltage limitation will be an advantage of availability.

Safety solenoid-operated switches are frequently offered as (certified) subsystem, consisting of sensor and analysis unit (from K.A. Schmersal GmbH as "BNS/AES combinations"). This is associated with the advantage that the "sensor/analysis unit" interface is already tested. In the case of a separate structure (see above) the interface responsibility will be with the user.