The big amount of strongpoints and resistence nests also needed a big communication network.
A fortress telephone network linked all the major strongpoints, and from there on lines went to
the smaller resistence nests.
The major line went through the middle of the island to keep it fairly safe from (air)attacks.
Four 617 bunkers were built at network junction points. A fifth fortress communication
bunker was built at Stp Tannenberg, this being on two floors. It served the Festungkommandant
and 319th infantery division. The 617 Nz E at Les Canus, St Sampson isn't visible.
21 Kabelschaltbrünnen served as switching points to the strongpoints. Most of them are very
hard to find because of their small size.
After the war a big part of the telephone network was used for civil purposes. Until the eighties
some of the bunkers were still in use which explains why they're still in such a good shape.
All the bunkers are on private property so ask permission first before visiting them.