Indicates trigger source terminal
When working with the session-based interface, the Source property indicates the device and terminal to which you added a trigger.
Create an clock external clock connection and view the connection properties.
Create a session and add a digital input channel.
Add an external scan clock connection.
ans = Scan Clock is provided externally and will be received by 'Dev1' at terminal 'PFI0'. Source: 'External' Destination: 'Dev1/PFI0' Type: ScanClock