Channels and Lines
After a device object is created, you must add channels or lines to it. You add channels to analog input and analog output objects, and you add lines to digital I/O objects. The channels added to a device object constitute a channel group, while the lines added to a device object constitute a line group. For example, to add two channels to the sound card object ai, issue the command
You can think of a device object as a channel or line container that reflects the common functionality of a particular device. The common functionality of a device applies to all channels or lines contained by it. For example, the sampling rate of an analog input object applies to all channels contained by that object. Therefore, the sampling rate is considered common functionality. In contrast, the channels and lines contained by the device object reflect the functionality only of a particular channel or line.
The relationship between an analog input object and the channels it contains is shown below.
For digital i/o objects, the diagram would look the same except that lines would be substituted for channels.
Note:
You cannot perform a data acquisition task with a device object that does not contain channels or lines. Similarly, you cannot perform a data acquisition task with channels or lines that are not contained by a device object.
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