Specifications

7SR242 Duobias Installation Guide
©2010 Siemens Protection Devices Limited Chapter 5 Page 11 of 13
Section 6: Data Comms Connections
6.1 RS485 Connection
The RS485 communication port terminals are 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.
Each relay has an internal terminating resistor – this can be connected in circuit where necessary.
+ve
GND
-ve
Term.
14 16 18 20
+ve
GND
-ve
Term.
14 16 18 20
+ve
GND
-ve
Term.
14 16 18 20
Figure 6.1-1 RS485 Da Comms Connections
arrying IRIG-B time synchronisation signals. Ensure that the
ta
6.2 IRIG-B Connections
A BNC plug is provided to connect a co-axial cable c
stub length is minimised by connecting the tee-connector directly to the rear of the relay. A suitable co-axial cable
would be type RG 58 50ohms.