iSMA-B-LP Room Panel/Modbus
version 1.3
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2.4
Connecting more Room Panels in the network
It is possible to connect more Room Panels into the one network in a very simple way.
Additional RJ12 socket can be used to connect another Room Panel by using one single
cable. Every panel can exchange information within the network. The solution can be
applied in large areas when more than one Room Panels are needed. Maximal number of
devices connected in one network is 128.
WARNING! First and last device in the network need to have termination activated (see
RS485 network termination)
Max. 128
RJ12
*** RJ12
First Room Panel in the network Last Room Panel in the network
Figure 7 Several Room Panels connection
2.5
RS485 network termination
The transmission line effects often present a problem on data communication networks.
These problems include reflections and signal attenuation.
To eliminate the presence of reflections from cable ends, the cable must be terminated at
both ends with a resistor across the line equal to its characteristic impedance. Both ends
must be terminated since the direction of propagation is bidirectional. In case of a RS485
twisted pair cable this termination is
typically 120 Ω.
Each panel has in-built termination resistor which can be added to the network by setting
switch no. 2 in the DIP-switch to ON position. The last and first Room Panels in the
network need to have termination activated.
Figure 8 Connecting termination resistor by Switch no. 2
