Super Systems 3 Series - Manual (Page 12)

Operations Manual Series 3
12
2.13 Digital Communications
Optional.
Digital communications uses the Modbus protocol. The
interface comes standard as EIA485 (2-wire).
 Digital communications is not available if Remote
Setpoint is fitted

Cable screen should be grounded at one point only to
prevent earth loops.
• Isolated 240Vac CAT II.
EIA485 Connections
220Ω termination
resistor
* EIA232/EIA485 2-wire
communications converter eg
Type KD485
Daisy Chain to
further
controllers
Com
220Ω termination
resistor on last
controller in the line
Twisted pair
Tx Rx Com
Rx Tx Com
Screen
RxB/
TxB RxA/
TxA
*
Common
Rx A(+)
Tx B(-)
HD
HE
HF