Siemens SIMATIC ET 200M Operating Instructions Manual page 66

Installation
4.2 Installation
Rail for active bus module
The figure below shows the dimensioned drawing of the rail with active bus module, S7-300
module and explosion-proof partition. The rail is 482.6 mm or 530 mm long.
①
②
③
④
Plugging in Output Modules During Operation of an ET 200M Installation
When you insert output modules, uncontrolled system states may occur.
This also applies if you insert input / output modules tilted on the bus module.
When you insert an output module, the outputs set by the user program immediately
become active.
We recommend that you set the outputs in the user program to "0" when you remove an
output module.
If modules are removed and inserted incorrectly, neighboring modules may be affected via
the backplane bus.
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Explosion-proof partition
S7-300 module
active bus module
Mounting rail for the "Insertion and Removal" function
WARNING
Operating Instructions, 04/2022, EWA-4NEB7806006-09
ET 200M