Siemens SIRIUS ACT 3SU1 System Manual page 40

Overview
4.5 Types of 3SU1 actuating elements and signaling elements
Mounting and stacking of the modules on a 4-slot holder
The figure below shows an example of the mounting and stacking of the modules on a 4-slot
holder.
It is not possible to mount an LED module on a 4-slot holder.
A
B1 / B2
D
40
4-slot holder
Contact module 1-pole
Contact module 2-pole
SIRIUS ACT 3SU1 pushbuttons and signaling devices
System Manual, 08/2018, A5E03457306020A/RS-AK/010