22    HC900 Process & Safety Controller User and Installation Manual  Revision 6 
    21 April 2017 
Table 2 – Descriptions of Major Redundancy Components 
Includes: Rack, 2 Power Supplies, 2 C75 
Controllers, 1 Redundancy Switch Module (RSM) 
Includes: 1 Scanner 2 module, 1 Power Supply, and 
up to 4, 8, or 12 I/O modules. Optional second 
Power Supply and Power Status Module (PSM) on 
8- and 12-slot I/O racks. 
900 Control Station operator interface 
communicates via Ethernet or RS-485 serial link 
PC 
Configuration 
Tool (Serial 
Interface 
option) 
  For legacy system- The PC configuration tool 
connects from the RS-232 serial port of the 
Controller Module to a serial port on the PC 
  For new system – The PC Configuration tool 
connects from the galvanically isolated RS-485 
port of the Controller Module using an external 
Honeywell qualified RS-485 to USB converter.  
PC is from third-party 
supplier. Configuration 
software is from 
Honeywell. RS-485 to 
USB converter is a third 
party device available 
from Honeywell. 
HMI (Human-
Machine 
Interface) 
(Optional) PC link to Ethernet network, which may 
include other HMIs, other HC900 Controllers, and 
other networks (including Internet).   
Typically includes HMI operating software.  
May also include Designer Software (configuration 
tool and utility software). 
PC is from third-party 
supplier.   
HMI software is 
available from 
Honeywell (Experion 
HS or SpecView32) or 
from third-party 
supplier. 
Qualifies un-
managed 
Ethernet 
100Base-T 
Switch  
Required if using 2 or more I/O Expansion racks. 
Provides connection of the I/O Ethernet 100Base-T 
port on a Controller Module to the Scanner 
modules. Switch not required for connection to a 
single I/O rack.  
Qualified third party 
devices available from 
Honeywell 
Ethernet 
10/100Base-T  
Switch or 
Router/Firewall 
Enables inter-connection of several 10/100Base-T 
Ethernet devices in an Ethernet network.  Devices 
include other HC900 Controllers, HMIs, and can 
also include routers, servers, and other devices in 
wider networks. Use of a properly configured firewall 
provides a more robust network limiting exposure to 
uncontrolled network traffic. 
Honeywell or third-party 
suppliers. 
Ethernet CAT5 
shielded cable 
Connects I/O expansion racks to controllers and/or 
to 10/100baseT Ethernet switches. It also connects 
to 900 Control Stations and PC SCADA software 
applications. 
Third-party suppliers or 
Honeywell 
For legacy system, Null modem cable, up to 50’ 
(15.24m) (PC modem cable if used with Modems.) 
For new systems, RS-485 to USB converter, 
connects galvanically isolated RS-485 port to USB 
port. 
Third-party suppliers or 
Honeywell