Dahua 42212TNI, System Installation Manual

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13
A surge suppressor is typically used with shielded Ethernet cable with the ground wire
connected to the metal structure, if any, at the MSDAU/Camera end and to a good
building or rod ground at the structure end. The MSDAU and Camera Mount enclosures
are non-metallic and thus isolate those electronics from ground. Thus, the MSDAU or
camera should not be directly tied to the mounting structure such as a metal tower. The
purpose of the surge suppressors is to shunt a voltage spike induced anywhere along
the Ethernet cable to ground rather than allow it to enter the outside or inside
electronics.
All four of the recommended cameras are PoE compatible meaning that a single
Ethernet cable provides the communication signals as well as power over otherwise
unused wire pairs. The single-port and 4-port power “injectors” derive approximately
56VDC from the AC line and provide it to each port. The cable from an MSDAU and/or
camera plugs into one of the POE ports and the LAN port is connected to the local
router or computer via a short cable.