Siemens SIMATIC NET PROFIBUS Owner's Manual page 258

Lightning and Surge Voltage Protection for LAN Cables Between Buildings
Underground cable,
potential equalization
cable
Figure B-1
B-4
PLC PLC
Fine protection close to
first nodes
Coarse protection at
entry to building
Lightning Protection Concept for LAN Cables Between Buildings
PLC PLC
Same protection
for further cable entry or
exit necessary
PROFIBUS Networks SIMATIC NET
6GK1970-5CA20-0AA1 Release 2 05/2000