455U-D Radio Modem
User Manual
Page
46
©
Jan 2016
If configuraing using Hayes commands the Dual Redundancy is set via the AT#O command
(“Control digital I/O function”).
Force a changeover from primary to secondary, use command AT#O5.
Force a changeover from secondary to primary, use the command AT#O6.
Status of the Dual Redundant system is displayed in register S33.
S33 Value
Dual Redundant State
2
Active Primary
3
Active Secondary
4
Active Primary – no secondary detected
5
Inactive Primary
6
Inactive Secondary
3.8.1 Single Host Device
If the 455U redundant pair are connected to a single host device, they should be connected via
RS485 - both 455U units will hear all data messages, but only the active 455U unit will send
messages.
3.8.2 Redundant Host Pair
If the host device is duplicated as a redundant pair, with an individual host connected to an
individual 455U, then RS232 should be used - the 455U will receive and send serial
messages, however only the active 455U will transmit via the radio.
RS232
RS232
RS485
REDUNDANT PAIR WITH SINGLE HOST
REDUNDANT PAIR WITH REDUNDANT HOSTS
USING RS485
USING RS232
