Honeywell ERX 350 - Serial Connections: RS-232 or RS-485

7 Serial Connections via RS-232 or RS-485
Connections to the ERX 350 serial communication interface are shown in the image below. Interface
options at TB4 on the I/O Board allow for RS-232 or RS-485 (2-wire).
RS-232 Connections:
TXD is at TB4 pin 1
RXD is at TB4 pin 2
GND is at TB4 pin
RS-485 Connections (2-wire):
‘A’ is made at TB4 pin 1 (TXD)
‘B’ is made at TB4 pin 2 (RXD)
Jumpers: JP1 and JP2 positions:
RS-232: Jumpers on pins: B-C
RS-485: Jumpers on pins: A-B
Ensure Item 1220 (Serial Interface Type) is configured for the appropriate serial interface type:
RS-232 or RS-485
7 Serial Connections via RS-232 or RS-485
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