Siemens SIMATIC S7-400 Configuration And Use Manual page 32

CPUs of the S7-400
Redundant Digital Output Modules
The fault-tolerant control of an actuator can be achieved by connecting two outputs
of two digital output modules in parallel
Redundant Analog Output Modules
You can redundantly operate analog output modules with power outputs.
The value to be output is halved and each module outputs one half of the value. If
one of the modules fails, this is detected and the remaining module outputs the full
value. This reduces any current surge to the output module when an error occurs.
Single Operation
You can also use an H CPU in a standard SIMATIC-400 station.
This allows you to use the following applications that cannot be used with the
standard CPUs from the S7-400 range:
• Use of fault-tolerant connections
• Configuration of the S7-400F/FH fail-safe automation system
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Automation System S7-400 Configuration and Use
A5E00442711-02