National Instruments NI 9871 Getting Started Guide

RS485 Transceiver Control
Refer to Table 3 for a listing of TX and RX enable conditions for
the different RS485 transceiver control modes.
Table 3. Transceiver Control Pin Conditions
Enable 4-Wire
2-Wire
DTR/Echo DTR/No Echo Auto
TX On DTR DTR TX
RX On On DTR# TX#
NI 9871 Hardware Overview
The NI 9871 has four independent RS485/RS422 ports that are
isolated from the other modules in the system. Each port is fully
compatible with the ANSI/EIA/TIA-485 standard.
14 | ni.com | NI 9871 Getting Started Guide

National Instruments NI 9871 Specifications

General

Brand	National Instruments
Model	NI 9871
Category	Control Unit
Language	English