National Instruments NI 9871 - External Power Supply Requirements

NI 9871 Operating Instructions 8 ni.com
You must connect an external power supply to the NI 9871.
This power supply provides the power for the RS485/RS422
transceivers on the module. You can use the included female
four-position pigtail to connect to an external voltage source.
Figure 1 lists the connections between an external voltage source
(of +8 V to +28 V) and the NI 9871.
Figure 1. Four-Position External Power Connector
1V
SUP
2V
SUP
3 COM 4COM
1
3
4
2