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Chapter 5) 7SR17 Installation Guide
Section 6: Data Comms Connections
6.1
RS485 C
ONNECTION
The RS485 communication port is located on the rear of the relay and can be connected using a suitable RS485
120 screened twisted pair cable.
The RS485 electrical connection can be used in a single or multi-drop configuration. The RS485 master must support
and use the Auto Device Enable (ADE) feature.
The last device in the connection must be terminated correctly in accordance with the master driving the connection.
A terminating resistor is fitted in each relay, when required this is connected in circuit using an external wire loop
between terminals 18 and 20 of the power supply module.
Up to 64 relays can be connected to the RS485 bus.
The RS485 data communications link with a particular relay will be broken if the relay element is withdrawn from the
case, all other relays will still communicate.
Figure 6.1-1 RS485 Data Comms Connections Between Relays
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