Siemens SINAMICS G120 Function Manual page 57

Figure 4-9
Additional installation options for the F-Switch and F-RSM modules are listed in the following
FAQ: FAQ (http://support.automation.siemens.com/WW/view/en/26694409).
Series-connected electromechanical sensors
You may connect Emergency Stop control devices in series if it can be ruled out that the
Emergency Stop command devices are simultaneously actuated. The simultaneous failure of
Emergency Stop control devices connected in series can generally be ruled out.
According to IEC 62061 (SIL) and EN ISO 13849-1 (PL), position switches of protective
doors may also connected in series.
Exception: If several protective doors are regularly opened at the same time, it is not
possible for faults to be detected, which means that the position switches must not be
connected in series.
If there is a risk of cross-circuits or short-circuits, the cables between the sensor and the
inverter must be protected, for example, by routing them in a steel tube.
Safety Integrated - SINAMICS G110M, G120, G120C, G120D and SIMATIC ET 200pro FC-2
Function Manual, 04/2014, FW V4.7, A5E34261271B AA
Directly controlling the safety functions in the ET 200pro FC-2 converter via the F-Switch
module
Installing
4.3 Activation via F-DI
57