Revision 6    HC900 Process & Safety Controller User and Installation Manual  21 
21 April 2017 
The HC900-expansion I/O link is a private network and the switch used for the interconnection of the 
HC900 Processor and Scanners must not be connected to any other LAN or WAN.  Likewise, no devices 
other than the HC900 components should be connected to the I/O link Switch.  Failure to comply will 
cause communication failures on the I/O link causing I/O modules to go in and out of their failsafe 
settings.