To Acquire images from various sources (such as scanners, digital cameras, and others) first select the source in the Acquire dialog box.

The data source drivers list displays the Twain compatible drivers available in the system. To select a source, simply click it.
The list is not updated automatically, so if you have installed a new image acquisition device and it is not displayed in the list, click the Refresh List button. Be sure also you refresh the list if you have uninstalled a device driver.

You can also get the data source drivers list and select a source in the Select Source dialog box choosing the File > Select Source menu item.

Note: When more than one acquiring device is active i.e. you acquire an image (or images) from another Twain data source having left the previous one not closed, then you are prompted with an error message about software conflict. To avoid this, close currently opened dialog box or window first (if you started to acquire an image through dialog box). Then close the Twain data source window. Repeat acquiring again.

To acquire multiple images, check the Acquire multiple images box.
When checked, you can acquire multiple images from the same acquisition device driver dialog box.
When cleared, the device driver dialog box is closed automatically once you have acquired the image.
Make sure you close the dialog box of the acquiring device driver after acquiring multiple images.

Note that some acquiring devices do not support multiple images acquiring.