Siemens SIMATIC ET 200SP System Manual page 238

Technical specifications
14.3 Electromagnetic compatibility of fail-safe modules
The following figure shows an example configuration with fail-safe modules. Voltage is
supplied by 1 power supply unit. Note, however, that the total current of the modules fed by
the power supply unit must not exceed the permissible limits. You can also use multiple
power supply units.
Figure 14-1 External protective circuit (surge filter) for ET 200SP with fail-safe modules
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Distributed I/O system
System Manual, 12/2015, A5E03576849-AF