Siemens SINUMERIK 840D sl Function Manual page 182

Connecting sensors and actuators
8.1 Safety-related input/output signals
Example
2 inputs (to read-in the 2-channel sensor signals via SGE) and 2 standard test outputs (for the
forced checking procedure) are required for connecting a sensor in a failsafe fashion. The test
outputs are supplied from the two power supply voltages (VS1, VS2) of the safety input module.
For the connection concept with 4 terminals, both equivalence (NC contact/NC contact, NO
contact/NO contact) as well as non-equivalence (NC contact/NO contact) contact versions are
possible.
Note
Cross-circuit fault detection in the input module is not required. Measures against cross-circuit
faults are required only for equivalence contacts (NC contact/NC contact, NO contact/NO
contact) if the cable has been routed so that it is very exposed, e.g. for cables connecting
handheld terminals. This can be mechanically implemented in the cable, e.g. using the
appropriate shielding.
Figure 8-6
182
Sensor connection using the 4-terminal concept
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated