User's Manual

Chapter Two Installation
Man_905UD_2.0.doc Page 15
2.3 Power Supply
The 905U-D module may be powered by either a 12VDC or a 24VDC supply.
The negative side of the supply is connected to "COM" and may be connected to “ground”.
The supply negative is connected to the “GND” terminal internally. The positive side of the
supply must not be connected to earth. The DC supply may be a floating supply or
negatively grounded.
The 12V supply is suitable for an unregulated DC supply. Where battery backup is required,
a 12V battery charger may be used to supply the 905U-D module as well as charging the
battery.
The power requirements of the 905U-D units is 155mA at 12VDC or 100mA at 24VDC. The
supply is protected by an internal 1A fuse, accessible at the bottom of the unit.
2.4 Serial Connections
2.4.1 RS232 Serial Port
The serial port is a 9 pin DB9 female and provides for connection to a host device as well as
a PC terminal for configuration, field testing and for factory testing. This port is internally
shared with the RS485 - ensure that the RS485 is disconnected before attempting to use the
RS232 port. Communication is via standard RS232 signals. The 905U-D is configured as
DCE equipment with the pinout detailed below.