Siemens SIMATIC S7-400H System Manual page 29

Power supply
You require one power supply module from the standard range of the S7-400 for each
fault-tolerant CPU, or to be more precise, for each of the two subsystems of the S7-400H.
The power supply modules available have rated input voltages of 24 V DC and 120/230 V AC,
at an output current of 10 and 20 A.
To increase availability of the power supply, you can also use two redundant power supplies
in each subsystem. For this configuration, you should use the PS 407 10 A R power supply
module for rated voltages of 120/230 V AC and an output current of 10 A.
Synchronization modules
The synchronization modules are used to link the two CPUs. They are installed in the CPUs
and interconnected by means of fiber-optic cables.
There are two types of synchronization modules: one for distances up to 10 meters, and one
for distances up to 10 km between the CPUs.
A fault-tolerant system requires 4 synchronization modules of the same type. For more
information on synchronization modules, refer to section Synchronization modules for S7-400H
(Page 249).
Fiber-optic cables
The fiber-optic cables are used to interconnect the synchronization modules for the redundant
link between the two central modules. They interconnect the upper and two lower pairs of
synchronization modules.
You will find the specifications of fiber-optic cables suitable for use in an S7-400H is in
section Selecting fiber-optic cables (Page 254).
S7-400H
System Manual, 09/2007, A5E00267695-03
S7-400H installation options
3.3 The S7-400H base system
29