Siemens SIMATIC S7 - Applications 9 and 10: 1 Oo2 Evaluation of 4-Wire Non-Equivalent Sensor Circuit

Fail-Safe signal module (SM) applications
3.1 Digital input applications
S7-1200 Functional Safety Manual
Manual, 02/2015, A5E03470344-AA
73
3.1.6
Applications 9 and 10: 1oo2 evaluation of 4-wire non-equivalent sensor circuit
S0 and S8 can be dual contacts of a single sensor.
Figure 3-9 F-DI Application mode 9: Internal sensor supply
Figure 3-10 F-DI Application mode 10: External sensor supply