Impulse 2202 - Manual (Page 9)

Configuration
Sealevel Systems SeaPORT+2/485 Page 6
Switch Examples
Figure 2: RS422/485 Interface Configuration
485
Mode Selection
OFF : 422 Mode
The transmitter lines TX+ and TX- are always driven
ON : 485 Mode
The transmitter lines TX+ and TX- are switched to high
impedance when the device is not actively transmitting data
NE 485 option, OFF for 422
OFF : The receiver is always enabled. In a two-wire setup the
receiver will echo back all transmitted data.
ON : The receiver is disabled when the transmitter is enabled. In a
two-wire setup the receiver will not echo back transmitted
data.
Note: Switch positions 1 and 2 are for port 1 and switch positions 3 and 4 for
port 2.
ON
12
3
4
OF
F
485 1
NE 1
485 2
NE 2
SW3