RADIUS
Product
Description
PDR 121
iom_pdr121_04_r02.doc
Rev 02
Page 16 (67)
7.4 Communication
The PDR 121 can act as a master or a slave/repeater in the system. The routing information, RTU
addresses, radio identities and repeater paths, are configured in each radio unit.
When the connected control system transmits a telegram to the master, the master reads the
telegram address, i.e. the destination. The master compares the address to the configured network
routing table to check if there is a (slave) radio ID tied to the telegram address. If there is, the
master checks if the telegram shall be transmitted via any repeaters Finally the master radio
transmits the telegram to the slave via repeaters, if any. A reply back to the master is performed in
the same manner.
Figure 1. Example of signalling procedure.
Master
Slave 3
Slave 6
Slave 7
Slave 5
Slave 4
Slave 2
Slave 1
The master
receives a
telegram from the
connected control
system
The master
transmits the
telegram via radio
Repeater 1
receives and
transmits the
telegram via radio
Repeater 2
receives and
transmits the
telegram via radio
Repeater 3
receives and
transmits the
telegram via radio
Repeater 4
receives and
transmits the
telegram via radio
Slave 7 receives the
telegram and
transmits it to the
connected device
Example 2: Telegram from master to Slave 5 via the repeaters 1, 2, 3 and 4
The master
receives a
telegram from the
connected control
system
The master
transmits the
telegram via radio
Slave 7 receives the
telegram and
transmits it to the
control led system
(RTU or IED)
Example 1: Telegram from master to slave 7