User manual
Chapter Three Operation
Page 23 © January 2011
Module S and T are configured with group address 1 (only one group address as it is not
configured as a repeater). When S transmits a message, T and A will receive it and output the
data. If module X can hear the message, it will not output it as module X is configured with
group address 2.
Repeater A will re-transmit the radio message, but on group address 2. Module S and T will
receive the re-transmitted message, but will not output the message as the group address is now
wrong. Module X will receive the message and will output the message as the group address is
now correct.
Repeater B will also receive the re-transmitted message from A, and will output the data as well
as re-transmit on group address 3.
The only other module which is also on group address 3 is repeater C. It will accept the message
and re-transmit it on group address 4 - to module Z.
Note that when a message is transmitted from a remote module, the repeaters will only transmit
a message in one direction. For example :
When X transmits a message, repeater A will receive the message on group address 2. Repeater
A will not output the data as the group address is not the repeater’s first group address. Repeater
A will re-transmit on group address 1 to modules S and T. But repeater B will not accept the re-
transmitted message on group address 1.
If repeater B is able to hear the original message from module X (on group address 2), then it
will re-transmit it on. But if it cannot, then the message will not be transmitted on to module Z.
3.6 Controlled Mode
In controlled mode, data is only transferred between two modules (that is, a point to point link).
One of the modules is configured as a “master” unit and the other as a “slave” unit. There can
also be up to five intermediate repeaters in the link. Each 905U-D unit is configured with a unit
address - only the unit with an address matching the destination address of the radio message
will process the message and output the serial data.
A
B
C
Group Address
First 1 2 3
Second 2 3 4
S
T
X
Z
Repeaters
Remote
Modules
Group Address 1 2 4