Wiring the System
27
Siemens Building Technologies
Fire Safety & Security Products
09.2008
1
SPC Controller
2 - 4
Expanders
Fig. 8
Multi-Drop Configuration
The multi-drop configuration varies in that each Expander uses the same
communication channel as it wires onto the next Expander, with all Expanders
using the same input channel. See multi-drop configuration in Fig. 8.
A cable break in the X-BUS connection results in disconnection with the single
Expander on that cable. All other Expanders are unaffected as there are separate
communication paths. A short in the cable renders all Expanders disabled.
NOTE
On a Star wiring or Multi-Drop configuration, all Expanders should not have a jumper fitted (no
termination).
NOTE
Cable Shielding
The shielding terminals (SH) should only be used for cables types with shielding (e.g. Belden 9829). If
shielding is required (i.e. sites with high electric field interference) connect the cable shield to the SH
terminals on the SPC Controller and all networked Expanders. Earth the SH terminal on the Controller
ONLY. Do NOT earth the SH terminal on any of the Expanders.