Siemens Simatic S7-400 - Manual (Page 190)

Digital Modules
4-68
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
Note
If the power supply is switched on by means of a mechanical contact, a voltage
pulse may occur at the outputs. The transient pulse lasts a maximum of 0.5 ms.
Changing Fuses
!
Warning
This can result in injury.
If you change a fuse without removing the front connector of the module, you could
be injured by an electric shock.
Consequently, always remove the front connector before you change the fuse.