Grounding And Shielding; Figure 10: Location Of Ground Jumpers Rs485 Host Interface - Bosch AMC-4W Installation Manual

Access Controller AMC-4W
5.4.

Grounding and Shielding

All components of the access control system must be grounded. The grounding
points shall then be connected to an earth ground point. This insures that all
components are properly protected against shock hazard.
It is good practice to shield all wires carrying low level signals. You should
connect only one end of the shield, preferably the source end. Connecting both
ends of a shield will result in ground loops. It is recommended that the
unconnected end of the shield is insulated to prevent accidental connection.
The AMC-4W enables you to set up a central ground or shielding point, simply
by setting a couple of jumpers. Set these jumpers only if ground or shield is not
connected otherwise.
Warning! Risk of damaging equipment!
When using multiple AMC-4W devices, set the ground main jumper
only once to assure a central point star connection.

Figure 10: Location of ground jumpers RS485 host interface

Setting jumper 2 connects the internal ground of the AMC-4W to the ground of
the RS485 host interface. If the ground conductor of the RS485 interface
between the AMC-4W modules is connected, set Jumper 2 only at a single
Bosch Security Systems | V.3.1/2006-09 Installation Guide
Installing the AMC-4W
23