The cFP-DI-330 has 8 Discrete inputs that can be used with input signals that range from 5 - 250 V AC or DC. The threshold level (the level at which an "On" signal is seen) will vary with the frequency. More information on the input levels can be found in the Operating Instructions for the module at the following link:
http://digital.ni.com/manuals.nsf/websearch/CAF2D6498AE91BA386256C620079544D?OpenDocument&node=132100_US
Regards,
Aaron
LabVIEW Champion, CLA, CPI