When 2 digital devices are connected via AES/EBU or S/PDIF and recording in either direction, a common clock is required (For example: 1 device's clock must be slaved to the other's) If you are recording into Pro Tools via the AES/EBU or S/PDIF inputs (such as a DAT or any other digital device), the Sync Mode in the Hardware Setup window should be set to DIGITAL. Setup > Hardware > Sync Mode > Digital OR Windows > Show Session Setup > Sync Mode > DigitalWhen you are finished recording the digital signal, you should set your Sync Mode to Internal for Pro Tools playback.There are exceptions to these guidelines, especially when working with expanded systems, external synchronizers, and optical devices. Please refer to the appropriate installation guide when using expanded systems or additional devices.