National Instruments NI USB-621x - Manual (Page 144)

Appendix A Device-Specific Information
NI USB-621x User Manual A-10 ni.com
Single-blink Operating normally. Connected to
USB Hi-Speed port. Refer to the
NI 621x Specifications for more
information.
Double-blink Connected to USB full speed port.
Device performance might be
affected. Refer to the NI 621x
Specifications for more
information.
Table A-6. PWR/ACT LED Status (Continued)
LED State Device Status