© National Instruments Corporation xiii NI USB-621x User Manual
About This Manual
The NI USB-621x User Manual contains information about using the 
National Instruments USB-621x data acquisition (DAQ) devices with 
NI-DAQmx 8.9 and later. NI USB-6210, USB-6211, USB-6212, 
USB-6215, USB-6216, and USB-6218 devices feature up to 32 analog 
input (AI) channels, up to two analog output (AO) channels, two counters, 
and up to eight lines of digital input (DI) and up to eight lines of digital 
output (DO), or 32 bidirectional static DIO lines.
Conventions
The following conventions are used in this manual:
<> Angle brackets that contain numbers separated by an ellipsis represent 
a range of values associated with a bit or signal name—for example, 
AO <3..0>.
» The » symbol leads you through nested menu items and dialog box options 
to a final action. The sequence File»Page Setup»Options directs you to 
pull down the File menu, select the Page Setup item, and select Options 
from the last dialog box.
This icon denotes a note, which alerts you to important information.
This icon denotes a caution, which advises you of precau tions to take to 
avoid injury, data loss, or a system crash. When this symbol is marked on a 
product, refer to the Read Me First: Safety and Electromagnetic 
Compatibility document for information about precautions to take.
bold Bold text denotes items that you must select or click in the software, such 
as menu items and dialog box options. Bold text also denotes parameter 
names.
italic Italic text denotes variables, emphasis, a cross-reference, or an introduction 
to a key concept. Italic text also denotes text that is a placeholder for a word 
or value that you must supply.