Asks to the opened source if she can support the automatic scan capability. 

This capability is intended to boost the performance of a Source. 

The fundamental assumption behind AutoScan is that the device is able to capture images without waiting for the Application to request the image transfers. 

The default behavior is undefined, because some high volume devices are capable of anything but TwainIsAutoScanAvailable() return value being equal to TRUE.

public Boolean TwainIsAutoScanAvailable();

Public Function TwainIsAutoScanAvailable() As Boolean

TRUE if support the automatic scan, FALSE otherwise -> Use TwainGetLastResultCode() and TwainGetLastConditionCode() functions for diagnosing the error.