Siemens SCALANCE X-400 Operating Instructions Manual page 103

Connectors of the signaling contact and grounding strap (X2)
The signaling contact is connected by contacts MK1 and MK2 on the 4-pin connector to the
rear terminal block on the power module.
Figure 5-2
By inserting a strap between protective earth GND and M3, IE Switches X-400 can be
operated with grounded reference potential.
When the device ships, no strap is fitted (non-grounded reference potential).
Conn. 2
SCALANCE X-400
Operating Instructions, 06/2015, C79000-G8976-C186-12
Pins of connector X2
MK1 Floating signaling contact relay connector 1
M3 Ground
GND Protective earth
MK2 Floating signaling contact relay connector 2
Connecting
5.2 Ports
103