Additional Information
There are 3.3 V devices that are 5 V tolerant. For those devices, you can directly connect the digital output without any bus transceiver. Also, both
NI R Series and
NI HSDIO Series products support 3.3 V natively.
The PXI form factor for the NI 6509 directly pulls the 5V
from the VCC on the chassis backplane. This VCC is not user selectable because of which, the PXI 6509 can only output 5V signals.