What are digital I/O?
Each digital I/O on a LabJack can be individually configured to one of 3 states: input, output-high, or output-low.
A digital input provides a voltage thresholding operation. If the voltage is higher than some value, the computer will detect the digital input as high/set/1. If the voltage is lower than some value, the computer will detect the digital input as low/clear/0.
A digital output allows you to control a voltage with a computer. If the computer instructs the output to be high, the output will produce a voltage (generally about 5 or 3.3 volts). If the computer instructs the output to be low, it is connected to ground and produces no voltage.
For LabJack-specific info on digital I/O, go to the user's guide or datasheet for the device of interest. Start at the main support page and go to the device of interest. For example, in the Section 2 of the U3, U6, or UE9 User's Guide, there is a Section about digital I/O, and Appendix A of each has electrical specs.
Thanks for all of your help.—Ian, USA